Source file src/go/types/api_test.go

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package types_test
     6  
     7  import (
     8  	"errors"
     9  	"fmt"
    10  	"go/ast"
    11  	"go/importer"
    12  	"go/parser"
    13  	"go/token"
    14  	"internal/goversion"
    15  	"internal/testenv"
    16  	"slices"
    17  	"sort"
    18  	"strings"
    19  	"sync"
    20  	"testing"
    21  
    22  	. "go/types"
    23  	"runtime"
    24  )
    25  
    26  // nopos indicates an unknown position
    27  var nopos token.Pos
    28  
    29  func defaultImporter(fset *token.FileSet) Importer {
    30  	return importer.ForCompiler(fset, runtime.Compiler, nil)
    31  }
    32  
    33  func mustParse(fset *token.FileSet, src string) *ast.File {
    34  	f, err := parser.ParseFile(fset, pkgName(src), src, parser.ParseComments)
    35  	if err != nil {
    36  		panic(err) // so we don't need to pass *testing.T
    37  	}
    38  	return f
    39  }
    40  
    41  func typecheck(src string, conf *Config, info *Info) (*Package, error) {
    42  	// TODO(adonovan): plumb this from caller.
    43  	fset := token.NewFileSet()
    44  	f := mustParse(fset, src)
    45  	if conf == nil {
    46  		conf = &Config{
    47  			Error:    func(err error) {}, // collect all errors
    48  			Importer: defaultImporter(fset),
    49  		}
    50  	}
    51  	return conf.Check(f.Name.Name, fset, []*ast.File{f}, info)
    52  }
    53  
    54  func mustTypecheck(src string, conf *Config, info *Info) *Package {
    55  	pkg, err := typecheck(src, conf, info)
    56  	if err != nil {
    57  		panic(err) // so we don't need to pass *testing.T
    58  	}
    59  	return pkg
    60  }
    61  
    62  // pkgName extracts the package name from src, which must contain a package header.
    63  func pkgName(src string) string {
    64  	const kw = "package "
    65  	if i := strings.Index(src, kw); i >= 0 {
    66  		after := src[i+len(kw):]
    67  		n := len(after)
    68  		if i := strings.IndexAny(after, "\n\t ;/"); i >= 0 {
    69  			n = i
    70  		}
    71  		return after[:n]
    72  	}
    73  	panic("missing package header: " + src)
    74  }
    75  
    76  func TestValuesInfo(t *testing.T) {
    77  	var tests = []struct {
    78  		src  string
    79  		expr string // constant expression
    80  		typ  string // constant type
    81  		val  string // constant value
    82  	}{
    83  		{`package a0; const _ = false`, `false`, `untyped bool`, `false`},
    84  		{`package a1; const _ = 0`, `0`, `untyped int`, `0`},
    85  		{`package a2; const _ = 'A'`, `'A'`, `untyped rune`, `65`},
    86  		{`package a3; const _ = 0.`, `0.`, `untyped float`, `0`},
    87  		{`package a4; const _ = 0i`, `0i`, `untyped complex`, `(0 + 0i)`},
    88  		{`package a5; const _ = "foo"`, `"foo"`, `untyped string`, `"foo"`},
    89  
    90  		{`package b0; var _ = false`, `false`, `bool`, `false`},
    91  		{`package b1; var _ = 0`, `0`, `int`, `0`},
    92  		{`package b2; var _ = 'A'`, `'A'`, `rune`, `65`},
    93  		{`package b3; var _ = 0.`, `0.`, `float64`, `0`},
    94  		{`package b4; var _ = 0i`, `0i`, `complex128`, `(0 + 0i)`},
    95  		{`package b5; var _ = "foo"`, `"foo"`, `string`, `"foo"`},
    96  
    97  		{`package c0a; var _ = bool(false)`, `false`, `bool`, `false`},
    98  		{`package c0b; var _ = bool(false)`, `bool(false)`, `bool`, `false`},
    99  		{`package c0c; type T bool; var _ = T(false)`, `T(false)`, `c0c.T`, `false`},
   100  
   101  		{`package c1a; var _ = int(0)`, `0`, `int`, `0`},
   102  		{`package c1b; var _ = int(0)`, `int(0)`, `int`, `0`},
   103  		{`package c1c; type T int; var _ = T(0)`, `T(0)`, `c1c.T`, `0`},
   104  
   105  		{`package c2a; var _ = rune('A')`, `'A'`, `rune`, `65`},
   106  		{`package c2b; var _ = rune('A')`, `rune('A')`, `rune`, `65`},
   107  		{`package c2c; type T rune; var _ = T('A')`, `T('A')`, `c2c.T`, `65`},
   108  
   109  		{`package c3a; var _ = float32(0.)`, `0.`, `float32`, `0`},
   110  		{`package c3b; var _ = float32(0.)`, `float32(0.)`, `float32`, `0`},
   111  		{`package c3c; type T float32; var _ = T(0.)`, `T(0.)`, `c3c.T`, `0`},
   112  
   113  		{`package c4a; var _ = complex64(0i)`, `0i`, `complex64`, `(0 + 0i)`},
   114  		{`package c4b; var _ = complex64(0i)`, `complex64(0i)`, `complex64`, `(0 + 0i)`},
   115  		{`package c4c; type T complex64; var _ = T(0i)`, `T(0i)`, `c4c.T`, `(0 + 0i)`},
   116  
   117  		{`package c5a; var _ = string("foo")`, `"foo"`, `string`, `"foo"`},
   118  		{`package c5b; var _ = string("foo")`, `string("foo")`, `string`, `"foo"`},
   119  		{`package c5c; type T string; var _ = T("foo")`, `T("foo")`, `c5c.T`, `"foo"`},
   120  		{`package c5d; var _ = string(65)`, `65`, `untyped int`, `65`},
   121  		{`package c5e; var _ = string('A')`, `'A'`, `untyped rune`, `65`},
   122  		{`package c5f; type T string; var _ = T('A')`, `'A'`, `untyped rune`, `65`},
   123  
   124  		{`package d0; var _ = []byte("foo")`, `"foo"`, `string`, `"foo"`},
   125  		{`package d1; var _ = []byte(string("foo"))`, `"foo"`, `string`, `"foo"`},
   126  		{`package d2; var _ = []byte(string("foo"))`, `string("foo")`, `string`, `"foo"`},
   127  		{`package d3; type T []byte; var _ = T("foo")`, `"foo"`, `string`, `"foo"`},
   128  
   129  		{`package e0; const _ = float32( 1e-200)`, `float32(1e-200)`, `float32`, `0`},
   130  		{`package e1; const _ = float32(-1e-200)`, `float32(-1e-200)`, `float32`, `0`},
   131  		{`package e2; const _ = float64( 1e-2000)`, `float64(1e-2000)`, `float64`, `0`},
   132  		{`package e3; const _ = float64(-1e-2000)`, `float64(-1e-2000)`, `float64`, `0`},
   133  		{`package e4; const _ = complex64( 1e-200)`, `complex64(1e-200)`, `complex64`, `(0 + 0i)`},
   134  		{`package e5; const _ = complex64(-1e-200)`, `complex64(-1e-200)`, `complex64`, `(0 + 0i)`},
   135  		{`package e6; const _ = complex128( 1e-2000)`, `complex128(1e-2000)`, `complex128`, `(0 + 0i)`},
   136  		{`package e7; const _ = complex128(-1e-2000)`, `complex128(-1e-2000)`, `complex128`, `(0 + 0i)`},
   137  
   138  		{`package f0 ; var _ float32 =  1e-200`, `1e-200`, `float32`, `0`},
   139  		{`package f1 ; var _ float32 = -1e-200`, `-1e-200`, `float32`, `0`},
   140  		{`package f2a; var _ float64 =  1e-2000`, `1e-2000`, `float64`, `0`},
   141  		{`package f3a; var _ float64 = -1e-2000`, `-1e-2000`, `float64`, `0`},
   142  		{`package f2b; var _         =  1e-2000`, `1e-2000`, `float64`, `0`},
   143  		{`package f3b; var _         = -1e-2000`, `-1e-2000`, `float64`, `0`},
   144  		{`package f4 ; var _ complex64  =  1e-200 `, `1e-200`, `complex64`, `(0 + 0i)`},
   145  		{`package f5 ; var _ complex64  = -1e-200 `, `-1e-200`, `complex64`, `(0 + 0i)`},
   146  		{`package f6a; var _ complex128 =  1e-2000i`, `1e-2000i`, `complex128`, `(0 + 0i)`},
   147  		{`package f7a; var _ complex128 = -1e-2000i`, `-1e-2000i`, `complex128`, `(0 + 0i)`},
   148  		{`package f6b; var _            =  1e-2000i`, `1e-2000i`, `complex128`, `(0 + 0i)`},
   149  		{`package f7b; var _            = -1e-2000i`, `-1e-2000i`, `complex128`, `(0 + 0i)`},
   150  
   151  		{`package g0; const (a = len([iota]int{}); b; c); const _ = c`, `c`, `int`, `2`}, // go.dev/issue/22341
   152  		{`package g1; var(j int32; s int; n = 1.0<<s == j)`, `1.0`, `int32`, `1`},        // go.dev/issue/48422
   153  	}
   154  
   155  	for _, test := range tests {
   156  		info := Info{
   157  			Types: make(map[ast.Expr]TypeAndValue),
   158  		}
   159  		name := mustTypecheck(test.src, nil, &info).Name()
   160  
   161  		// look for expression
   162  		var expr ast.Expr
   163  		for e := range info.Types {
   164  			if ExprString(e) == test.expr {
   165  				expr = e
   166  				break
   167  			}
   168  		}
   169  		if expr == nil {
   170  			t.Errorf("package %s: no expression found for %s", name, test.expr)
   171  			continue
   172  		}
   173  		tv := info.Types[expr]
   174  
   175  		// check that type is correct
   176  		if got := tv.Type.String(); got != test.typ {
   177  			t.Errorf("package %s: got type %s; want %s", name, got, test.typ)
   178  			continue
   179  		}
   180  
   181  		// if we have a constant, check that value is correct
   182  		if tv.Value != nil {
   183  			if got := tv.Value.ExactString(); got != test.val {
   184  				t.Errorf("package %s: got value %s; want %s", name, got, test.val)
   185  			}
   186  		} else {
   187  			if test.val != "" {
   188  				t.Errorf("package %s: no constant found; want %s", name, test.val)
   189  			}
   190  		}
   191  	}
   192  }
   193  
   194  func TestTypesInfo(t *testing.T) {
   195  	// Test sources that are not expected to typecheck must start with the broken prefix.
   196  	const broken = "package broken_"
   197  
   198  	var tests = []struct {
   199  		src  string
   200  		expr string // expression
   201  		typ  string // value type
   202  	}{
   203  		// single-valued expressions of untyped constants
   204  		{`package b0; var x interface{} = false`, `false`, `bool`},
   205  		{`package b1; var x interface{} = 0`, `0`, `int`},
   206  		{`package b2; var x interface{} = 0.`, `0.`, `float64`},
   207  		{`package b3; var x interface{} = 0i`, `0i`, `complex128`},
   208  		{`package b4; var x interface{} = "foo"`, `"foo"`, `string`},
   209  
   210  		// uses of nil
   211  		{`package n0; var _ *int = nil`, `nil`, `untyped nil`},
   212  		{`package n1; var _ func() = nil`, `nil`, `untyped nil`},
   213  		{`package n2; var _ []byte = nil`, `nil`, `untyped nil`},
   214  		{`package n3; var _ map[int]int = nil`, `nil`, `untyped nil`},
   215  		{`package n4; var _ chan int = nil`, `nil`, `untyped nil`},
   216  		{`package n5; var _ interface{} = nil`, `nil`, `untyped nil`},
   217  		{`package n6; import "unsafe"; var _ unsafe.Pointer = nil`, `nil`, `untyped nil`},
   218  
   219  		{`package n10; var (x *int; _ = x == nil)`, `nil`, `untyped nil`},
   220  		{`package n11; var (x func(); _ = x == nil)`, `nil`, `untyped nil`},
   221  		{`package n12; var (x []byte; _ = x == nil)`, `nil`, `untyped nil`},
   222  		{`package n13; var (x map[int]int; _ = x == nil)`, `nil`, `untyped nil`},
   223  		{`package n14; var (x chan int; _ = x == nil)`, `nil`, `untyped nil`},
   224  		{`package n15; var (x interface{}; _ = x == nil)`, `nil`, `untyped nil`},
   225  		{`package n15; import "unsafe"; var (x unsafe.Pointer; _ = x == nil)`, `nil`, `untyped nil`},
   226  
   227  		{`package n20; var _ = (*int)(nil)`, `nil`, `untyped nil`},
   228  		{`package n21; var _ = (func())(nil)`, `nil`, `untyped nil`},
   229  		{`package n22; var _ = ([]byte)(nil)`, `nil`, `untyped nil`},
   230  		{`package n23; var _ = (map[int]int)(nil)`, `nil`, `untyped nil`},
   231  		{`package n24; var _ = (chan int)(nil)`, `nil`, `untyped nil`},
   232  		{`package n25; var _ = (interface{})(nil)`, `nil`, `untyped nil`},
   233  		{`package n26; import "unsafe"; var _ = unsafe.Pointer(nil)`, `nil`, `untyped nil`},
   234  
   235  		{`package n30; func f(*int) { f(nil) }`, `nil`, `untyped nil`},
   236  		{`package n31; func f(func()) { f(nil) }`, `nil`, `untyped nil`},
   237  		{`package n32; func f([]byte) { f(nil) }`, `nil`, `untyped nil`},
   238  		{`package n33; func f(map[int]int) { f(nil) }`, `nil`, `untyped nil`},
   239  		{`package n34; func f(chan int) { f(nil) }`, `nil`, `untyped nil`},
   240  		{`package n35; func f(interface{}) { f(nil) }`, `nil`, `untyped nil`},
   241  		{`package n35; import "unsafe"; func f(unsafe.Pointer) { f(nil) }`, `nil`, `untyped nil`},
   242  
   243  		// comma-ok expressions
   244  		{`package p0; var x interface{}; var _, _ = x.(int)`,
   245  			`x.(int)`,
   246  			`(int, bool)`,
   247  		},
   248  		{`package p1; var x interface{}; func _() { _, _ = x.(int) }`,
   249  			`x.(int)`,
   250  			`(int, bool)`,
   251  		},
   252  		{`package p2a; type mybool bool; var m map[string]complex128; var b mybool; func _() { _, b = m["foo"] }`,
   253  			`m["foo"]`,
   254  			`(complex128, p2a.mybool)`,
   255  		},
   256  		{`package p2b; var m map[string]complex128; var b bool; func _() { _, b = m["foo"] }`,
   257  			`m["foo"]`,
   258  			`(complex128, bool)`,
   259  		},
   260  		{`package p3; var c chan string; var _, _ = <-c`,
   261  			`<-c`,
   262  			`(string, bool)`,
   263  		},
   264  
   265  		// go.dev/issue/6796
   266  		{`package issue6796_a; var x interface{}; var _, _ = (x.(int))`,
   267  			`x.(int)`,
   268  			`(int, bool)`,
   269  		},
   270  		{`package issue6796_b; var c chan string; var _, _ = (<-c)`,
   271  			`(<-c)`,
   272  			`(string, bool)`,
   273  		},
   274  		{`package issue6796_c; var c chan string; var _, _ = (<-c)`,
   275  			`<-c`,
   276  			`(string, bool)`,
   277  		},
   278  		{`package issue6796_d; var c chan string; var _, _ = ((<-c))`,
   279  			`(<-c)`,
   280  			`(string, bool)`,
   281  		},
   282  		{`package issue6796_e; func f(c chan string) { _, _ = ((<-c)) }`,
   283  			`(<-c)`,
   284  			`(string, bool)`,
   285  		},
   286  
   287  		// go.dev/issue/7060
   288  		{`package issue7060_a; var ( m map[int]string; x, ok = m[0] )`,
   289  			`m[0]`,
   290  			`(string, bool)`,
   291  		},
   292  		{`package issue7060_b; var ( m map[int]string; x, ok interface{} = m[0] )`,
   293  			`m[0]`,
   294  			`(string, bool)`,
   295  		},
   296  		{`package issue7060_c; func f(x interface{}, ok bool, m map[int]string) { x, ok = m[0] }`,
   297  			`m[0]`,
   298  			`(string, bool)`,
   299  		},
   300  		{`package issue7060_d; var ( ch chan string; x, ok = <-ch )`,
   301  			`<-ch`,
   302  			`(string, bool)`,
   303  		},
   304  		{`package issue7060_e; var ( ch chan string; x, ok interface{} = <-ch )`,
   305  			`<-ch`,
   306  			`(string, bool)`,
   307  		},
   308  		{`package issue7060_f; func f(x interface{}, ok bool, ch chan string) { x, ok = <-ch }`,
   309  			`<-ch`,
   310  			`(string, bool)`,
   311  		},
   312  
   313  		// go.dev/issue/28277
   314  		{`package issue28277_a; func f(...int)`,
   315  			`...int`,
   316  			`[]int`,
   317  		},
   318  		{`package issue28277_b; func f(a, b int, c ...[]struct{})`,
   319  			`...[]struct{}`,
   320  			`[][]struct{}`,
   321  		},
   322  
   323  		// go.dev/issue/47243
   324  		{`package issue47243_a; var x int32; var _ = x << 3`, `3`, `untyped int`},
   325  		{`package issue47243_b; var x int32; var _ = x << 3.`, `3.`, `untyped float`},
   326  		{`package issue47243_c; var x int32; var _ = 1 << x`, `1 << x`, `int`},
   327  		{`package issue47243_d; var x int32; var _ = 1 << x`, `1`, `int`},
   328  		{`package issue47243_e; var x int32; var _ = 1 << 2`, `1`, `untyped int`},
   329  		{`package issue47243_f; var x int32; var _ = 1 << 2`, `2`, `untyped int`},
   330  		{`package issue47243_g; var x int32; var _ = int(1) << 2`, `2`, `untyped int`},
   331  		{`package issue47243_h; var x int32; var _ = 1 << (2 << x)`, `1`, `int`},
   332  		{`package issue47243_i; var x int32; var _ = 1 << (2 << x)`, `(2 << x)`, `untyped int`},
   333  		{`package issue47243_j; var x int32; var _ = 1 << (2 << x)`, `2`, `untyped int`},
   334  
   335  		// tests for broken code that doesn't type-check
   336  		{broken + `x0; func _() { var x struct {f string}; x.f := 0 }`, `x.f`, `string`},
   337  		{broken + `x1; func _() { var z string; type x struct {f string}; y := &x{q: z}}`, `z`, `string`},
   338  		{broken + `x2; func _() { var a, b string; type x struct {f string}; z := &x{f: a, f: b,}}`, `b`, `string`},
   339  		{broken + `x3; var x = panic("");`, `panic`, `func(interface{})`},
   340  		{`package x4; func _() { panic("") }`, `panic`, `func(interface{})`},
   341  		{broken + `x5; func _() { var x map[string][...]int; x = map[string][...]int{"": {1,2,3}} }`, `x`, `map[string]invalid type`},
   342  
   343  		// parameterized functions
   344  		{`package p0; func f[T any](T) {}; var _ = f[int]`, `f`, `func[T any](T)`},
   345  		{`package p1; func f[T any](T) {}; var _ = f[int]`, `f[int]`, `func(int)`},
   346  		{`package p2; func f[T any](T) {}; func _() { f(42) }`, `f`, `func(int)`},
   347  		{`package p3; func f[T any](T) {}; func _() { f[int](42) }`, `f[int]`, `func(int)`},
   348  		{`package p4; func f[T any](T) {}; func _() { f[int](42) }`, `f`, `func[T any](T)`},
   349  		{`package p5; func f[T any](T) {}; func _() { f(42) }`, `f(42)`, `()`},
   350  
   351  		// type parameters
   352  		{`package t0; type t[] int; var _ t`, `t`, `t0.t`}, // t[] is a syntax error that is ignored in this test in favor of t
   353  		{`package t1; type t[P any] int; var _ t[int]`, `t`, `t1.t[P any]`},
   354  		{`package t2; type t[P interface{}] int; var _ t[int]`, `t`, `t2.t[P interface{}]`},
   355  		{`package t3; type t[P, Q interface{}] int; var _ t[int, int]`, `t`, `t3.t[P, Q interface{}]`},
   356  		{broken + `t4; type t[P, Q interface{ m() }] int; var _ t[int, int]`, `t`, `broken_t4.t[P, Q interface{m()}]`},
   357  
   358  		// instantiated types must be sanitized
   359  		{`package g0; type t[P any] int; var x struct{ f t[int] }; var _ = x.f`, `x.f`, `g0.t[int]`},
   360  
   361  		// go.dev/issue/45096
   362  		{`package issue45096; func _[T interface{ ~int8 | ~int16 | ~int32  }](x T) { _ = x < 0 }`, `0`, `T`},
   363  
   364  		// go.dev/issue/47895
   365  		{`package p; import "unsafe"; type S struct { f int }; var s S; var _ = unsafe.Offsetof(s.f)`, `s.f`, `int`},
   366  
   367  		// go.dev/issue/74303. Note that interface field types are synthetic, so
   368  		// even though `func()` doesn't appear in the source, it appears in the
   369  		// syntax tree.
   370  		{`package p; type T interface { M(int) }`, `func(int)`, `func(int)`},
   371  
   372  		// go.dev/issue/50093
   373  		{`package u0a; func _[_ interface{int}]() {}`, `int`, `int`},
   374  		{`package u1a; func _[_ interface{~int}]() {}`, `~int`, `~int`},
   375  		{`package u2a; func _[_ interface{int | string}]() {}`, `int | string`, `int | string`},
   376  		{`package u3a; func _[_ interface{int | string | ~bool}]() {}`, `int | string | ~bool`, `int | string | ~bool`},
   377  		{`package u3a; func _[_ interface{int | string | ~bool}]() {}`, `int | string`, `int | string`},
   378  		{`package u3a; func _[_ interface{int | string | ~bool}]() {}`, `~bool`, `~bool`},
   379  		{`package u3a; func _[_ interface{int | string | ~float64|~bool}]() {}`, `int | string | ~float64`, `int | string | ~float64`},
   380  
   381  		{`package u0b; func _[_ int]() {}`, `int`, `int`},
   382  		{`package u1b; func _[_ ~int]() {}`, `~int`, `~int`},
   383  		{`package u2b; func _[_ int | string]() {}`, `int | string`, `int | string`},
   384  		{`package u3b; func _[_ int | string | ~bool]() {}`, `int | string | ~bool`, `int | string | ~bool`},
   385  		{`package u3b; func _[_ int | string | ~bool]() {}`, `int | string`, `int | string`},
   386  		{`package u3b; func _[_ int | string | ~bool]() {}`, `~bool`, `~bool`},
   387  		{`package u3b; func _[_ int | string | ~float64|~bool]() {}`, `int | string | ~float64`, `int | string | ~float64`},
   388  
   389  		{`package u0c; type _ interface{int}`, `int`, `int`},
   390  		{`package u1c; type _ interface{~int}`, `~int`, `~int`},
   391  		{`package u2c; type _ interface{int | string}`, `int | string`, `int | string`},
   392  		{`package u3c; type _ interface{int | string | ~bool}`, `int | string | ~bool`, `int | string | ~bool`},
   393  		{`package u3c; type _ interface{int | string | ~bool}`, `int | string`, `int | string`},
   394  		{`package u3c; type _ interface{int | string | ~bool}`, `~bool`, `~bool`},
   395  		{`package u3c; type _ interface{int | string | ~float64|~bool}`, `int | string | ~float64`, `int | string | ~float64`},
   396  
   397  		// reverse type inference
   398  		{`package r1; var _ func(int) = g; func g[P any](P) {}`, `g`, `func(int)`},
   399  		{`package r2; var _ func(int) = g[int]; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
   400  		{`package r3; var _ func(int) = g[int]; func g[P any](P) {}`, `g[int]`, `func(int)`},
   401  		{`package r4; var _ func(int, string) = g; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
   402  		{`package r5; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
   403  		{`package r6; var _ func(int, string) = g[int]; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
   404  
   405  		{`package s1; func _() { f(g) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func(int)`},
   406  		{`package s2; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g`, `func[P any](P)`}, // go.dev/issues/60212
   407  		{`package s3; func _() { f(g[int]) }; func f(func(int)) {}; func g[P any](P) {}`, `g[int]`, `func(int)`},
   408  		{`package s4; func _() { f(g) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func(int, string)`},
   409  		{`package s5; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
   410  		{`package s6; func _() { f(g[int]) }; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}`, `g[int]`, `func(int, string)`},
   411  
   412  		{`package s7; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `g`, `func(int, int)`},
   413  		{`package s8; func _() { f(g, h) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func(int, string)`},
   414  		{`package s9; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h`, `func[P, Q any](P, Q)`}, // go.dev/issues/60212
   415  		{`package s10; func _() { f(g, h[int]) }; func f[P any](func(int, P), func(P, string)) {}; func g[P any](P, P) {}; func h[P, Q any](P, Q) {}`, `h[int]`, `func(int, string)`},
   416  
   417  		// go.dev/issue/68639
   418  		// parenthesized and pointer type expressions in various positions
   419  		// - as variable type, not generic
   420  		{`package qa1; type T int; var x T`, `T`, `qa1.T`},
   421  		{`package qa2; type T int; var x (T)`, `T`, `qa2.T`},
   422  		{`package qa3; type T int; var x (T)`, `(T)`, `qa3.T`},
   423  		{`package qa4; type T int; var x ((T))`, `T`, `qa4.T`},
   424  		{`package qa5; type T int; var x ((T))`, `(T)`, `qa5.T`},
   425  		{`package qa6; type T int; var x ((T))`, `((T))`, `qa6.T`},
   426  		{`package qa7; type T int; var x *T`, `T`, `qa7.T`},
   427  		{`package qa8; type T int; var x *T`, `*T`, `*qa8.T`},
   428  		{`package qa9; type T int; var x (*T)`, `T`, `qa9.T`},
   429  		{`package qa10; type T int; var x (*T)`, `*T`, `*qa10.T`},
   430  		{`package qa11; type T int; var x *(T)`, `T`, `qa11.T`},
   431  		{`package qa12; type T int; var x *(T)`, `(T)`, `qa12.T`},
   432  		{`package qa13; type T int; var x *(T)`, `*(T)`, `*qa13.T`},
   433  		{`package qa14; type T int; var x (*(T))`, `(T)`, `qa14.T`},
   434  		{`package qa15; type T int; var x (*(T))`, `*(T)`, `*qa15.T`},
   435  		{`package qa16; type T int; var x (*(T))`, `(*(T))`, `*qa16.T`},
   436  
   437  		// - as ordinary function parameter, not generic
   438  		{`package qb1; type T int; func _(T)`, `T`, `qb1.T`},
   439  		{`package qb2; type T int; func _((T))`, `T`, `qb2.T`},
   440  		{`package qb3; type T int; func _((T))`, `(T)`, `qb3.T`},
   441  		{`package qb4; type T int; func _(((T)))`, `T`, `qb4.T`},
   442  		{`package qb5; type T int; func _(((T)))`, `(T)`, `qb5.T`},
   443  		{`package qb6; type T int; func _(((T)))`, `((T))`, `qb6.T`},
   444  		{`package qb7; type T int; func _(*T)`, `T`, `qb7.T`},
   445  		{`package qb8; type T int; func _(*T)`, `*T`, `*qb8.T`},
   446  		{`package qb9; type T int; func _((*T))`, `T`, `qb9.T`},
   447  		{`package qb10; type T int; func _((*T))`, `*T`, `*qb10.T`},
   448  		{`package qb11; type T int; func _(*(T))`, `T`, `qb11.T`},
   449  		{`package qb12; type T int; func _(*(T))`, `(T)`, `qb12.T`},
   450  		{`package qb13; type T int; func _(*(T))`, `*(T)`, `*qb13.T`},
   451  		{`package qb14; type T int; func _((*(T)))`, `(T)`, `qb14.T`},
   452  		{`package qb15; type T int; func _((*(T)))`, `*(T)`, `*qb15.T`},
   453  		{`package qb16; type T int; func _((*(T)))`, `(*(T))`, `*qb16.T`},
   454  
   455  		// - as method receiver, not generic
   456  		{`package qc1; type T int; func (T) _() {}`, `T`, `qc1.T`},
   457  		{`package qc2; type T int; func ((T)) _() {}`, `T`, `qc2.T`},
   458  		{`package qc3; type T int; func ((T)) _() {}`, `(T)`, `qc3.T`},
   459  		{`package qc4; type T int; func (((T))) _() {}`, `T`, `qc4.T`},
   460  		{`package qc5; type T int; func (((T))) _() {}`, `(T)`, `qc5.T`},
   461  		{`package qc6; type T int; func (((T))) _() {}`, `((T))`, `qc6.T`},
   462  		{`package qc7; type T int; func (*T) _() {}`, `T`, `qc7.T`},
   463  		{`package qc8; type T int; func (*T) _() {}`, `*T`, `*qc8.T`},
   464  		{`package qc9; type T int; func ((*T)) _() {}`, `T`, `qc9.T`},
   465  		{`package qc10; type T int; func ((*T)) _() {}`, `*T`, `*qc10.T`},
   466  		{`package qc11; type T int; func (*(T)) _() {}`, `T`, `qc11.T`},
   467  		{`package qc12; type T int; func (*(T)) _() {}`, `(T)`, `qc12.T`},
   468  		{`package qc13; type T int; func (*(T)) _() {}`, `*(T)`, `*qc13.T`},
   469  		{`package qc14; type T int; func ((*(T))) _() {}`, `(T)`, `qc14.T`},
   470  		{`package qc15; type T int; func ((*(T))) _() {}`, `*(T)`, `*qc15.T`},
   471  		{`package qc16; type T int; func ((*(T))) _() {}`, `(*(T))`, `*qc16.T`},
   472  
   473  		// - as variable type, generic
   474  		{`package qd1; type T[_ any] int; var x T[int]`, `T`, `qd1.T[_ any]`},
   475  		{`package qd2; type T[_ any] int; var x (T[int])`, `T[int]`, `qd2.T[int]`},
   476  		{`package qd3; type T[_ any] int; var x (T[int])`, `(T[int])`, `qd3.T[int]`},
   477  		{`package qd4; type T[_ any] int; var x ((T[int]))`, `T`, `qd4.T[_ any]`},
   478  		{`package qd5; type T[_ any] int; var x ((T[int]))`, `(T[int])`, `qd5.T[int]`},
   479  		{`package qd6; type T[_ any] int; var x ((T[int]))`, `((T[int]))`, `qd6.T[int]`},
   480  		{`package qd7; type T[_ any] int; var x *T[int]`, `T`, `qd7.T[_ any]`},
   481  		{`package qd8; type T[_ any] int; var x *T[int]`, `*T[int]`, `*qd8.T[int]`},
   482  		{`package qd9; type T[_ any] int; var x (*T[int])`, `T`, `qd9.T[_ any]`},
   483  		{`package qd10; type T[_ any] int; var x (*T[int])`, `*T[int]`, `*qd10.T[int]`},
   484  		{`package qd11; type T[_ any] int; var x *(T[int])`, `T[int]`, `qd11.T[int]`},
   485  		{`package qd12; type T[_ any] int; var x *(T[int])`, `(T[int])`, `qd12.T[int]`},
   486  		{`package qd13; type T[_ any] int; var x *(T[int])`, `*(T[int])`, `*qd13.T[int]`},
   487  		{`package qd14; type T[_ any] int; var x (*(T[int]))`, `(T[int])`, `qd14.T[int]`},
   488  		{`package qd15; type T[_ any] int; var x (*(T[int]))`, `*(T[int])`, `*qd15.T[int]`},
   489  		{`package qd16; type T[_ any] int; var x (*(T[int]))`, `(*(T[int]))`, `*qd16.T[int]`},
   490  
   491  		// - as ordinary function parameter, generic
   492  		{`package qe1; type T[_ any] int; func _(T[int])`, `T`, `qe1.T[_ any]`},
   493  		{`package qe2; type T[_ any] int; func _((T[int]))`, `T[int]`, `qe2.T[int]`},
   494  		{`package qe3; type T[_ any] int; func _((T[int]))`, `(T[int])`, `qe3.T[int]`},
   495  		{`package qe4; type T[_ any] int; func _(((T[int])))`, `T`, `qe4.T[_ any]`},
   496  		{`package qe5; type T[_ any] int; func _(((T[int])))`, `(T[int])`, `qe5.T[int]`},
   497  		{`package qe6; type T[_ any] int; func _(((T[int])))`, `((T[int]))`, `qe6.T[int]`},
   498  		{`package qe7; type T[_ any] int; func _(*T[int])`, `T`, `qe7.T[_ any]`},
   499  		{`package qe8; type T[_ any] int; func _(*T[int])`, `*T[int]`, `*qe8.T[int]`},
   500  		{`package qe9; type T[_ any] int; func _((*T[int]))`, `T`, `qe9.T[_ any]`},
   501  		{`package qe10; type T[_ any] int; func _((*T[int]))`, `*T[int]`, `*qe10.T[int]`},
   502  		{`package qe11; type T[_ any] int; func _(*(T[int]))`, `T[int]`, `qe11.T[int]`},
   503  		{`package qe12; type T[_ any] int; func _(*(T[int]))`, `(T[int])`, `qe12.T[int]`},
   504  		{`package qe13; type T[_ any] int; func _(*(T[int]))`, `*(T[int])`, `*qe13.T[int]`},
   505  		{`package qe14; type T[_ any] int; func _((*(T[int])))`, `(T[int])`, `qe14.T[int]`},
   506  		{`package qe15; type T[_ any] int; func _((*(T[int])))`, `*(T[int])`, `*qe15.T[int]`},
   507  		{`package qe16; type T[_ any] int; func _((*(T[int])))`, `(*(T[int]))`, `*qe16.T[int]`},
   508  
   509  		// - as method receiver, generic
   510  		{`package qf1; type T[_ any] int; func (T[_]) _() {}`, `T`, `qf1.T[_ any]`},
   511  		{`package qf2; type T[_ any] int; func ((T[_])) _() {}`, `T[_]`, `qf2.T[_]`},
   512  		{`package qf3; type T[_ any] int; func ((T[_])) _() {}`, `(T[_])`, `qf3.T[_]`},
   513  		{`package qf4; type T[_ any] int; func (((T[_]))) _() {}`, `T`, `qf4.T[_ any]`},
   514  		{`package qf5; type T[_ any] int; func (((T[_]))) _() {}`, `(T[_])`, `qf5.T[_]`},
   515  		{`package qf6; type T[_ any] int; func (((T[_]))) _() {}`, `((T[_]))`, `qf6.T[_]`},
   516  		{`package qf7; type T[_ any] int; func (*T[_]) _() {}`, `T`, `qf7.T[_ any]`},
   517  		{`package qf8; type T[_ any] int; func (*T[_]) _() {}`, `*T[_]`, `*qf8.T[_]`},
   518  		{`package qf9; type T[_ any] int; func ((*T[_])) _() {}`, `T`, `qf9.T[_ any]`},
   519  		{`package qf10; type T[_ any] int; func ((*T[_])) _() {}`, `*T[_]`, `*qf10.T[_]`},
   520  		{`package qf11; type T[_ any] int; func (*(T[_])) _() {}`, `T[_]`, `qf11.T[_]`},
   521  		{`package qf12; type T[_ any] int; func (*(T[_])) _() {}`, `(T[_])`, `qf12.T[_]`},
   522  		{`package qf13; type T[_ any] int; func (*(T[_])) _() {}`, `*(T[_])`, `*qf13.T[_]`},
   523  		{`package qf14; type T[_ any] int; func ((*(T[_]))) _() {}`, `(T[_])`, `qf14.T[_]`},
   524  		{`package qf15; type T[_ any] int; func ((*(T[_]))) _() {}`, `*(T[_])`, `*qf15.T[_]`},
   525  		{`package qf16; type T[_ any] int; func ((*(T[_]))) _() {}`, `(*(T[_]))`, `*qf16.T[_]`},
   526  
   527  		// For historic reasons, type parameters in receiver type expressions
   528  		// are considered both definitions and uses and thus also show up in
   529  		// the Info.Types map (see go.dev/issue/68670).
   530  		{`package t1; type T[_ any] int; func (T[P]) _() {}`, `P`, `P`},
   531  		{`package t2; type T[_, _ any] int; func (T[P, Q]) _() {}`, `P`, `P`},
   532  		{`package t3; type T[_, _ any] int; func (T[P, Q]) _() {}`, `Q`, `Q`},
   533  	}
   534  
   535  	for _, test := range tests {
   536  		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
   537  		var name string
   538  		if strings.HasPrefix(test.src, broken) {
   539  			pkg, err := typecheck(test.src, nil, &info)
   540  			if err == nil {
   541  				t.Errorf("package %s: expected to fail but passed", pkg.Name())
   542  				continue
   543  			}
   544  			if pkg != nil {
   545  				name = pkg.Name()
   546  			}
   547  		} else {
   548  			name = mustTypecheck(test.src, nil, &info).Name()
   549  		}
   550  
   551  		// look for expression type
   552  		var typ Type
   553  		for e, tv := range info.Types {
   554  			if ExprString(e) == test.expr {
   555  				typ = tv.Type
   556  				break
   557  			}
   558  		}
   559  		if typ == nil {
   560  			t.Errorf("package %s: no type found for %s", name, test.expr)
   561  			continue
   562  		}
   563  
   564  		// check that type is correct
   565  		if got := typ.String(); got != test.typ {
   566  			t.Errorf("package %s: expr = %s: got %s; want %s", name, test.expr, got, test.typ)
   567  		}
   568  	}
   569  }
   570  
   571  func TestInstanceInfo(t *testing.T) {
   572  	const lib = `package lib
   573  
   574  func F[P any](P) {}
   575  
   576  type T[P any] []P
   577  `
   578  
   579  	type testInst struct {
   580  		name  string
   581  		targs []string
   582  		typ   string
   583  	}
   584  
   585  	var tests = []struct {
   586  		src       string
   587  		instances []testInst // recorded instances in source order
   588  	}{
   589  		{`package p0; func f[T any](T) {}; func _() { f(42) }`,
   590  			[]testInst{{`f`, []string{`int`}, `func(int)`}},
   591  		},
   592  		{`package p1; func f[T any](T) T { panic(0) }; func _() { f('@') }`,
   593  			[]testInst{{`f`, []string{`rune`}, `func(rune) rune`}},
   594  		},
   595  		{`package p2; func f[T any](...T) T { panic(0) }; func _() { f(0i) }`,
   596  			[]testInst{{`f`, []string{`complex128`}, `func(...complex128) complex128`}},
   597  		},
   598  		{`package p3; func f[A, B, C any](A, *B, []C) {}; func _() { f(1.2, new(string), []byte{}) }`,
   599  			[]testInst{{`f`, []string{`float64`, `string`, `byte`}, `func(float64, *string, []byte)`}},
   600  		},
   601  		{`package p4; func f[A, B any](A, *B, ...[]B) {}; func _() { f(1.2, new(byte)) }`,
   602  			[]testInst{{`f`, []string{`float64`, `byte`}, `func(float64, *byte, ...[]byte)`}},
   603  		},
   604  
   605  		{`package s1; func f[T any, P interface{*T}](x T) {}; func _(x string) { f(x) }`,
   606  			[]testInst{{`f`, []string{`string`, `*string`}, `func(x string)`}},
   607  		},
   608  		{`package s2; func f[T any, P interface{*T}](x []T) {}; func _(x []int) { f(x) }`,
   609  			[]testInst{{`f`, []string{`int`, `*int`}, `func(x []int)`}},
   610  		},
   611  		{`package s3; type C[T any] interface{chan<- T}; func f[T any, P C[T]](x []T) {}; func _(x []int) { f(x) }`,
   612  			[]testInst{
   613  				{`C`, []string{`T`}, `interface{chan<- T}`},
   614  				{`f`, []string{`int`, `chan<- int`}, `func(x []int)`},
   615  			},
   616  		},
   617  		{`package s4; type C[T any] interface{chan<- T}; func f[T any, P C[T], Q C[[]*P]](x []T) {}; func _(x []int) { f(x) }`,
   618  			[]testInst{
   619  				{`C`, []string{`T`}, `interface{chan<- T}`},
   620  				{`C`, []string{`[]*P`}, `interface{chan<- []*P}`},
   621  				{`f`, []string{`int`, `chan<- int`, `chan<- []*chan<- int`}, `func(x []int)`},
   622  			},
   623  		},
   624  
   625  		{`package t1; func f[T any, P interface{*T}]() T { panic(0) }; func _() { _ = f[string] }`,
   626  			[]testInst{{`f`, []string{`string`, `*string`}, `func() string`}},
   627  		},
   628  		{`package t2; func f[T any, P interface{*T}]() T { panic(0) }; func _() { _ = (f[string]) }`,
   629  			[]testInst{{`f`, []string{`string`, `*string`}, `func() string`}},
   630  		},
   631  		{`package t3; type C[T any] interface{chan<- T}; func f[T any, P C[T], Q C[[]*P]]() []T { return nil }; func _() { _ = f[int] }`,
   632  			[]testInst{
   633  				{`C`, []string{`T`}, `interface{chan<- T}`},
   634  				{`C`, []string{`[]*P`}, `interface{chan<- []*P}`},
   635  				{`f`, []string{`int`, `chan<- int`, `chan<- []*chan<- int`}, `func() []int`},
   636  			},
   637  		},
   638  		{`package t4; type C[T any] interface{chan<- T}; func f[T any, P C[T], Q C[[]*P]]() []T { return nil }; func _() { _ = (f[int]) }`,
   639  			[]testInst{
   640  				{`C`, []string{`T`}, `interface{chan<- T}`},
   641  				{`C`, []string{`[]*P`}, `interface{chan<- []*P}`},
   642  				{`f`, []string{`int`, `chan<- int`, `chan<- []*chan<- int`}, `func() []int`},
   643  			},
   644  		},
   645  		{`package i0; import "lib"; func _() { lib.F(42) }`,
   646  			[]testInst{{`F`, []string{`int`}, `func(int)`}},
   647  		},
   648  
   649  		{`package duplfunc0; func f[T any](T) {}; func _() { f(42); f("foo"); f[int](3) }`,
   650  			[]testInst{
   651  				{`f`, []string{`int`}, `func(int)`},
   652  				{`f`, []string{`string`}, `func(string)`},
   653  				{`f`, []string{`int`}, `func(int)`},
   654  			},
   655  		},
   656  		{`package duplfunc1; import "lib"; func _() { lib.F(42); lib.F("foo"); lib.F(3) }`,
   657  			[]testInst{
   658  				{`F`, []string{`int`}, `func(int)`},
   659  				{`F`, []string{`string`}, `func(string)`},
   660  				{`F`, []string{`int`}, `func(int)`},
   661  			},
   662  		},
   663  
   664  		{`package type0; type T[P interface{~int}] struct{ x P }; var _ T[int]`,
   665  			[]testInst{{`T`, []string{`int`}, `struct{x int}`}},
   666  		},
   667  		{`package type1; type T[P interface{~int}] struct{ x P }; var _ (T[int])`,
   668  			[]testInst{{`T`, []string{`int`}, `struct{x int}`}},
   669  		},
   670  		{`package type2; type T[P interface{~int}] struct{ x P }; var _ T[(int)]`,
   671  			[]testInst{{`T`, []string{`int`}, `struct{x int}`}},
   672  		},
   673  		{`package type3; type T[P1 interface{~[]P2}, P2 any] struct{ x P1; y P2 }; var _ T[[]int, int]`,
   674  			[]testInst{{`T`, []string{`[]int`, `int`}, `struct{x []int; y int}`}},
   675  		},
   676  		{`package type4; import "lib"; var _ lib.T[int]`,
   677  			[]testInst{{`T`, []string{`int`}, `[]int`}},
   678  		},
   679  
   680  		{`package dupltype0; type T[P interface{~int}] struct{ x P }; var x T[int]; var y T[int]`,
   681  			[]testInst{
   682  				{`T`, []string{`int`}, `struct{x int}`},
   683  				{`T`, []string{`int`}, `struct{x int}`},
   684  			},
   685  		},
   686  		{`package dupltype1; type T[P ~int] struct{ x P }; func (r *T[Q]) add(z T[Q]) { r.x += z.x }`,
   687  			[]testInst{
   688  				{`T`, []string{`Q`}, `struct{x Q}`},
   689  				{`T`, []string{`Q`}, `struct{x Q}`},
   690  			},
   691  		},
   692  		{`package dupltype1; import "lib"; var x lib.T[int]; var y lib.T[int]; var z lib.T[string]`,
   693  			[]testInst{
   694  				{`T`, []string{`int`}, `[]int`},
   695  				{`T`, []string{`int`}, `[]int`},
   696  				{`T`, []string{`string`}, `[]string`},
   697  			},
   698  		},
   699  		{`package issue51803; func foo[T any](T) {}; func _() { foo[int]( /* leave arg away on purpose */ ) }`,
   700  			[]testInst{{`foo`, []string{`int`}, `func(int)`}},
   701  		},
   702  
   703  		// reverse type inference
   704  		{`package reverse1a; var f func(int) = g; func g[P any](P) {}`,
   705  			[]testInst{{`g`, []string{`int`}, `func(int)`}},
   706  		},
   707  		{`package reverse1b; func f(func(int)) {}; func g[P any](P) {}; func _() { f(g) }`,
   708  			[]testInst{{`g`, []string{`int`}, `func(int)`}},
   709  		},
   710  		{`package reverse2a; var f func(int, string) = g; func g[P, Q any](P, Q) {}`,
   711  			[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
   712  		},
   713  		{`package reverse2b; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g) }`,
   714  			[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
   715  		},
   716  		{`package reverse2c; func f(func(int, string)) {}; func g[P, Q any](P, Q) {}; func _() { f(g[int]) }`,
   717  			[]testInst{{`g`, []string{`int`, `string`}, `func(int, string)`}},
   718  		},
   719  		// reverse3a not possible (cannot assign to generic function outside of argument passing)
   720  		{`package reverse3b; func f[R any](func(int) R) {}; func g[P any](P) string { return "" }; func _() { f(g) }`,
   721  			[]testInst{
   722  				{`f`, []string{`string`}, `func(func(int) string)`},
   723  				{`g`, []string{`int`}, `func(int) string`},
   724  			},
   725  		},
   726  		{`package reverse4a; var _, _ func([]int, *float32) = g, h; func g[P, Q any]([]P, *Q) {}; func h[R any]([]R, *float32) {}`,
   727  			[]testInst{
   728  				{`g`, []string{`int`, `float32`}, `func([]int, *float32)`},
   729  				{`h`, []string{`int`}, `func([]int, *float32)`},
   730  			},
   731  		},
   732  		{`package reverse4b; func f(_, _ func([]int, *float32)) {}; func g[P, Q any]([]P, *Q) {}; func h[R any]([]R, *float32) {}; func _() { f(g, h) }`,
   733  			[]testInst{
   734  				{`g`, []string{`int`, `float32`}, `func([]int, *float32)`},
   735  				{`h`, []string{`int`}, `func([]int, *float32)`},
   736  			},
   737  		},
   738  		{`package issue59956; func f(func(int), func(string), func(bool)) {}; func g[P any](P) {}; func _() { f(g, g, g) }`,
   739  			[]testInst{
   740  				{`g`, []string{`int`}, `func(int)`},
   741  				{`g`, []string{`string`}, `func(string)`},
   742  				{`g`, []string{`bool`}, `func(bool)`},
   743  			},
   744  		},
   745  	}
   746  
   747  	for _, test := range tests {
   748  		imports := make(testImporter)
   749  		conf := Config{Importer: imports}
   750  		instMap := make(map[*ast.Ident]Instance)
   751  		useMap := make(map[*ast.Ident]Object)
   752  		makePkg := func(src string) *Package {
   753  			pkg, err := typecheck(src, &conf, &Info{Instances: instMap, Uses: useMap})
   754  			// allow error for issue51803
   755  			if err != nil && (pkg == nil || pkg.Name() != "issue51803") {
   756  				t.Fatal(err)
   757  			}
   758  			imports[pkg.Name()] = pkg
   759  			return pkg
   760  		}
   761  		makePkg(lib)
   762  		pkg := makePkg(test.src)
   763  
   764  		t.Run(pkg.Name(), func(t *testing.T) {
   765  			// Sort instances in source order for stability.
   766  			instances := sortedInstances(instMap)
   767  			if got, want := len(instances), len(test.instances); got != want {
   768  				t.Fatalf("got %d instances, want %d", got, want)
   769  			}
   770  
   771  			// Pairwise compare with the expected instances.
   772  			for ii, inst := range instances {
   773  				var targs []Type
   774  				for i := 0; i < inst.Inst.TypeArgs.Len(); i++ {
   775  					targs = append(targs, inst.Inst.TypeArgs.At(i))
   776  				}
   777  				typ := inst.Inst.Type
   778  
   779  				testInst := test.instances[ii]
   780  				if got := inst.Ident.Name; got != testInst.name {
   781  					t.Fatalf("got name %s, want %s", got, testInst.name)
   782  				}
   783  				if len(targs) != len(testInst.targs) {
   784  					t.Fatalf("got %d type arguments; want %d", len(targs), len(testInst.targs))
   785  				}
   786  				for i, targ := range targs {
   787  					if got := targ.String(); got != testInst.targs[i] {
   788  						t.Errorf("type argument %d: got %s; want %s", i, got, testInst.targs[i])
   789  					}
   790  				}
   791  				if got := typ.Underlying().String(); got != testInst.typ {
   792  					t.Errorf("package %s: got %s; want %s", pkg.Name(), got, testInst.typ)
   793  				}
   794  
   795  				// Verify the invariant that re-instantiating the corresponding generic
   796  				// type with TypeArgs results in an identical instance.
   797  				ptype := useMap[inst.Ident].Type()
   798  				lister, _ := ptype.(interface{ TypeParams() *TypeParamList })
   799  				if lister == nil || lister.TypeParams().Len() == 0 {
   800  					t.Fatalf("info.Types[%v] = %v, want parameterized type", inst.Ident, ptype)
   801  				}
   802  				inst2, err := Instantiate(nil, ptype, targs, true)
   803  				if err != nil {
   804  					t.Errorf("Instantiate(%v, %v) failed: %v", ptype, targs, err)
   805  				}
   806  				if !Identical(inst.Inst.Type, inst2) {
   807  					t.Errorf("%v and %v are not identical", inst.Inst.Type, inst2)
   808  				}
   809  			}
   810  		})
   811  	}
   812  }
   813  
   814  type recordedInstance struct {
   815  	Ident *ast.Ident
   816  	Inst  Instance
   817  }
   818  
   819  func sortedInstances(m map[*ast.Ident]Instance) (instances []recordedInstance) {
   820  	for id, inst := range m {
   821  		instances = append(instances, recordedInstance{id, inst})
   822  	}
   823  	slices.SortFunc(instances, func(a, b recordedInstance) int {
   824  		return CmpPos(a.Ident.Pos(), b.Ident.Pos())
   825  	})
   826  	return instances
   827  }
   828  
   829  func TestDefsInfo(t *testing.T) {
   830  	var tests = []struct {
   831  		src  string
   832  		obj  string
   833  		want string
   834  	}{
   835  		{`package p0; const x = 42`, `x`, `const p0.x untyped int`},
   836  		{`package p1; const x int = 42`, `x`, `const p1.x int`},
   837  		{`package p2; var x int`, `x`, `var p2.x int`},
   838  		{`package p3; type x int`, `x`, `type p3.x int`},
   839  		{`package p4; func f()`, `f`, `func p4.f()`},
   840  		{`package p5; func f() int { x, _ := 1, 2; return x }`, `_`, `var _ int`},
   841  
   842  		// Tests using generics.
   843  		{`package g0; type x[T any] int`, `x`, `type g0.x[T any] int`},
   844  		{`package g1; func f[T any]() {}`, `f`, `func g1.f[T any]()`},
   845  		{`package g2; type x[T any] int; func (*x[_]) m() {}`, `m`, `func (*g2.x[_]).m()`},
   846  
   847  		// Type parameters in receiver type expressions are definitions.
   848  		{`package r0; type T[_ any] int; func (T[P]) _() {}`, `P`, `type parameter P any`},
   849  		{`package r1; type T[_, _ any] int; func (T[P, Q]) _() {}`, `P`, `type parameter P any`},
   850  		{`package r2; type T[_, _ any] int; func (T[P, Q]) _() {}`, `Q`, `type parameter Q any`},
   851  	}
   852  
   853  	for _, test := range tests {
   854  		info := Info{
   855  			Defs: make(map[*ast.Ident]Object),
   856  		}
   857  		name := mustTypecheck(test.src, nil, &info).Name()
   858  
   859  		// find object
   860  		var def Object
   861  		for id, obj := range info.Defs {
   862  			if id.Name == test.obj {
   863  				def = obj
   864  				break
   865  			}
   866  		}
   867  		if def == nil {
   868  			t.Errorf("package %s: %s not found", name, test.obj)
   869  			continue
   870  		}
   871  
   872  		if got := def.String(); got != test.want {
   873  			t.Errorf("package %s: got %s; want %s", name, got, test.want)
   874  		}
   875  	}
   876  }
   877  
   878  func TestUsesInfo(t *testing.T) {
   879  	var tests = []struct {
   880  		src  string
   881  		obj  string
   882  		want string
   883  	}{
   884  		{`package p0; func _() { _ = x }; const x = 42`, `x`, `const p0.x untyped int`},
   885  		{`package p1; func _() { _ = x }; const x int = 42`, `x`, `const p1.x int`},
   886  		{`package p2; func _() { _ = x }; var x int`, `x`, `var p2.x int`},
   887  		{`package p3; func _() { type _ x }; type x int`, `x`, `type p3.x int`},
   888  		{`package p4; func _() { _ = f }; func f()`, `f`, `func p4.f()`},
   889  
   890  		// Tests using generics.
   891  		{`package g0; func _[T any]() { _ = x }; const x = 42`, `x`, `const g0.x untyped int`},
   892  		{`package g1; func _[T any](x T) { }`, `T`, `type parameter T any`},
   893  		{`package g2; type N[A any] int; var _ N[int]`, `N`, `type g2.N[A any] int`},
   894  		{`package g3; type N[A any] int; func (N[_]) m() {}`, `N`, `type g3.N[A any] int`},
   895  
   896  		// Uses of fields are instantiated.
   897  		{`package s1; type N[A any] struct{ a A }; var f = N[int]{}.a`, `a`, `field a int`},
   898  		{`package s2; type N[A any] struct{ a A }; func (r N[B]) m(b B) { r.a = b }`, `a`, `field a B`},
   899  
   900  		// Uses of methods are uses of the instantiated method.
   901  		{`package m0; type N[A any] int; func (r N[B]) m() { r.n() }; func (N[C]) n() {}`, `n`, `func (m0.N[B]).n()`},
   902  		{`package m1; type N[A any] int; func (r N[B]) m() { }; var f = N[int].m`, `m`, `func (m1.N[int]).m()`},
   903  		{`package m2; func _[A any](v interface{ m() A }) { v.m() }`, `m`, `func (interface).m() A`},
   904  		{`package m3; func f[A any]() interface{ m() A } { return nil }; var _ = f[int]().m()`, `m`, `func (interface).m() int`},
   905  		{`package m4; type T[A any] func() interface{ m() A }; var x T[int]; var y = x().m`, `m`, `func (interface).m() int`},
   906  		{`package m5; type T[A any] interface{ m() A }; func _[B any](t T[B]) { t.m() }`, `m`, `func (m5.T[B]).m() B`},
   907  		{`package m6; type T[A any] interface{ m() }; func _[B any](t T[B]) { t.m() }`, `m`, `func (m6.T[B]).m()`},
   908  		{`package m7; type T[A any] interface{ m() A }; func _(t T[int]) { t.m() }`, `m`, `func (m7.T[int]).m() int`},
   909  		{`package m8; type T[A any] interface{ m() }; func _(t T[int]) { t.m() }`, `m`, `func (m8.T[int]).m()`},
   910  		{`package m9; type T[A any] interface{ m() }; func _(t T[int]) { _ = t.m }`, `m`, `func (m9.T[int]).m()`},
   911  		{
   912  			`package m10; type E[A any] interface{ m() }; type T[B any] interface{ E[B]; n() }; func _(t T[int]) { t.m() }`,
   913  			`m`,
   914  			`func (m10.E[int]).m()`,
   915  		},
   916  		{`package m11; type T[A any] interface{ m(); n() }; func _(t1 T[int], t2 T[string]) { t1.m(); t2.n() }`, `m`, `func (m11.T[int]).m()`},
   917  		{`package m12; type T[A any] interface{ m(); n() }; func _(t1 T[int], t2 T[string]) { t1.m(); t2.n() }`, `n`, `func (m12.T[string]).n()`},
   918  
   919  		// For historic reasons, type parameters in receiver type expressions
   920  		// are considered both definitions and uses (see go.dev/issue/68670).
   921  		{`package r0; type T[_ any] int; func (T[P]) _() {}`, `P`, `type parameter P any`},
   922  		{`package r1; type T[_, _ any] int; func (T[P, Q]) _() {}`, `P`, `type parameter P any`},
   923  		{`package r2; type T[_, _ any] int; func (T[P, Q]) _() {}`, `Q`, `type parameter Q any`},
   924  	}
   925  
   926  	for _, test := range tests {
   927  		info := Info{
   928  			Uses: make(map[*ast.Ident]Object),
   929  		}
   930  		name := mustTypecheck(test.src, nil, &info).Name()
   931  
   932  		// find object
   933  		var use Object
   934  		for id, obj := range info.Uses {
   935  			if id.Name == test.obj {
   936  				if use != nil {
   937  					panic(fmt.Sprintf("multiple uses of %q", id.Name))
   938  				}
   939  				use = obj
   940  			}
   941  		}
   942  		if use == nil {
   943  			t.Errorf("package %s: %s not found", name, test.obj)
   944  			continue
   945  		}
   946  
   947  		if got := use.String(); got != test.want {
   948  			t.Errorf("package %s: got %s; want %s", name, got, test.want)
   949  		}
   950  	}
   951  }
   952  
   953  func TestGenericMethodInfo(t *testing.T) {
   954  	src := `package p
   955  
   956  type N[A any] int
   957  
   958  func (r N[B]) m() { r.m(); r.n() }
   959  
   960  func (r *N[C]) n() {  }
   961  `
   962  	fset := token.NewFileSet()
   963  	f := mustParse(fset, src)
   964  	info := Info{
   965  		Defs:       make(map[*ast.Ident]Object),
   966  		Uses:       make(map[*ast.Ident]Object),
   967  		Selections: make(map[*ast.SelectorExpr]*Selection),
   968  	}
   969  	var conf Config
   970  	pkg, err := conf.Check("p", fset, []*ast.File{f}, &info)
   971  	if err != nil {
   972  		t.Fatal(err)
   973  	}
   974  
   975  	N := pkg.Scope().Lookup("N").Type().(*Named)
   976  
   977  	// Find the generic methods stored on N.
   978  	gm, gn := N.Method(0), N.Method(1)
   979  	if gm.Name() == "n" {
   980  		gm, gn = gn, gm
   981  	}
   982  
   983  	// Collect objects from info.
   984  	var dm, dn *Func   // the declared methods
   985  	var dmm, dmn *Func // the methods used in the body of m
   986  	for _, decl := range f.Decls {
   987  		fdecl, ok := decl.(*ast.FuncDecl)
   988  		if !ok {
   989  			continue
   990  		}
   991  		def := info.Defs[fdecl.Name].(*Func)
   992  		switch fdecl.Name.Name {
   993  		case "m":
   994  			dm = def
   995  			ast.Inspect(fdecl.Body, func(n ast.Node) bool {
   996  				if call, ok := n.(*ast.CallExpr); ok {
   997  					sel := call.Fun.(*ast.SelectorExpr)
   998  					use := info.Uses[sel.Sel].(*Func)
   999  					selection := info.Selections[sel]
  1000  					if selection.Kind() != MethodVal {
  1001  						t.Errorf("Selection kind = %v, want %v", selection.Kind(), MethodVal)
  1002  					}
  1003  					if selection.Obj() != use {
  1004  						t.Errorf("info.Selections contains %v, want %v", selection.Obj(), use)
  1005  					}
  1006  					switch sel.Sel.Name {
  1007  					case "m":
  1008  						dmm = use
  1009  					case "n":
  1010  						dmn = use
  1011  					}
  1012  				}
  1013  				return true
  1014  			})
  1015  		case "n":
  1016  			dn = def
  1017  		}
  1018  	}
  1019  
  1020  	if gm != dm {
  1021  		t.Errorf(`N.Method(...) returns %v for "m", but Info.Defs has %v`, gm, dm)
  1022  	}
  1023  	if gn != dn {
  1024  		t.Errorf(`N.Method(...) returns %v for "m", but Info.Defs has %v`, gm, dm)
  1025  	}
  1026  	if dmm != dm {
  1027  		t.Errorf(`Inside "m", r.m uses %v, want the defined func %v`, dmm, dm)
  1028  	}
  1029  	if dmn == dn {
  1030  		t.Errorf(`Inside "m", r.n uses %v, want a func distinct from %v`, dmm, dm)
  1031  	}
  1032  }
  1033  
  1034  func TestImplicitsInfo(t *testing.T) {
  1035  	testenv.MustHaveGoBuild(t)
  1036  
  1037  	var tests = []struct {
  1038  		src  string
  1039  		want string
  1040  	}{
  1041  		{`package p2; import . "fmt"; var _ = Println`, ""},           // no Implicits entry
  1042  		{`package p0; import local "fmt"; var _ = local.Println`, ""}, // no Implicits entry
  1043  		{`package p1; import "fmt"; var _ = fmt.Println`, "importSpec: package fmt"},
  1044  
  1045  		{`package p3; func f(x interface{}) { switch x.(type) { case int: } }`, ""}, // no Implicits entry
  1046  		{`package p4; func f(x interface{}) { switch t := x.(type) { case int: _ = t } }`, "caseClause: var t int"},
  1047  		{`package p5; func f(x interface{}) { switch t := x.(type) { case int, uint: _ = t } }`, "caseClause: var t interface{}"},
  1048  		{`package p6; func f(x interface{}) { switch t := x.(type) { default: _ = t } }`, "caseClause: var t interface{}"},
  1049  
  1050  		{`package p7; func f(x int) {}`, ""}, // no Implicits entry
  1051  		{`package p8; func f(int) {}`, "field: var  int"},
  1052  		{`package p9; func f() (complex64) { return 0 }`, "field: var  complex64"},
  1053  		{`package p10; type T struct{}; func (*T) f() {}`, "field: var  *p10.T"},
  1054  
  1055  		// Tests using generics.
  1056  		{`package f0; func f[T any](x int) {}`, ""}, // no Implicits entry
  1057  		{`package f1; func f[T any](int) {}`, "field: var  int"},
  1058  		{`package f2; func f[T any](T) {}`, "field: var  T"},
  1059  		{`package f3; func f[T any]() (complex64) { return 0 }`, "field: var  complex64"},
  1060  		{`package f4; func f[T any](t T) (T) { return t }`, "field: var  T"},
  1061  		{`package t0; type T[A any] struct{}; func (*T[_]) f() {}`, "field: var  *t0.T[_]"},
  1062  		{`package t1; type T[A any] struct{}; func _(x interface{}) { switch t := x.(type) { case T[int]: _ = t } }`, "caseClause: var t t1.T[int]"},
  1063  		{`package t2; type T[A any] struct{}; func _[P any](x interface{}) { switch t := x.(type) { case T[P]: _ = t } }`, "caseClause: var t t2.T[P]"},
  1064  		{`package t3; func _[P any](x interface{}) { switch t := x.(type) { case P: _ = t } }`, "caseClause: var t P"},
  1065  	}
  1066  
  1067  	for _, test := range tests {
  1068  		info := Info{
  1069  			Implicits: make(map[ast.Node]Object),
  1070  		}
  1071  		name := mustTypecheck(test.src, nil, &info).Name()
  1072  
  1073  		// the test cases expect at most one Implicits entry
  1074  		if len(info.Implicits) > 1 {
  1075  			t.Errorf("package %s: %d Implicits entries found", name, len(info.Implicits))
  1076  			continue
  1077  		}
  1078  
  1079  		// extract Implicits entry, if any
  1080  		var got string
  1081  		for n, obj := range info.Implicits {
  1082  			switch x := n.(type) {
  1083  			case *ast.ImportSpec:
  1084  				got = "importSpec"
  1085  			case *ast.CaseClause:
  1086  				got = "caseClause"
  1087  			case *ast.Field:
  1088  				got = "field"
  1089  			default:
  1090  				t.Fatalf("package %s: unexpected %T", name, x)
  1091  			}
  1092  			got += ": " + obj.String()
  1093  		}
  1094  
  1095  		// verify entry
  1096  		if got != test.want {
  1097  			t.Errorf("package %s: got %q; want %q", name, got, test.want)
  1098  		}
  1099  	}
  1100  }
  1101  
  1102  func TestPkgNameOf(t *testing.T) {
  1103  	testenv.MustHaveGoBuild(t)
  1104  
  1105  	const src = `
  1106  package p
  1107  
  1108  import (
  1109  	. "os"
  1110  	_ "io"
  1111  	"math"
  1112  	"path/filepath"
  1113  	snort "sort"
  1114  )
  1115  
  1116  // avoid imported and not used errors
  1117  var (
  1118  	_ = Open // os.Open
  1119  	_ = math.Sin
  1120  	_ = filepath.Abs
  1121  	_ = snort.Ints
  1122  )
  1123  `
  1124  
  1125  	var tests = []struct {
  1126  		path string // path string enclosed in "'s
  1127  		want string
  1128  	}{
  1129  		{`"os"`, "."},
  1130  		{`"io"`, "_"},
  1131  		{`"math"`, "math"},
  1132  		{`"path/filepath"`, "filepath"},
  1133  		{`"sort"`, "snort"},
  1134  	}
  1135  
  1136  	fset := token.NewFileSet()
  1137  	f := mustParse(fset, src)
  1138  	info := Info{
  1139  		Defs:      make(map[*ast.Ident]Object),
  1140  		Implicits: make(map[ast.Node]Object),
  1141  	}
  1142  	var conf Config
  1143  	conf.Importer = defaultImporter(fset)
  1144  	_, err := conf.Check("p", fset, []*ast.File{f}, &info)
  1145  	if err != nil {
  1146  		t.Fatal(err)
  1147  	}
  1148  
  1149  	// map import paths to importDecl
  1150  	imports := make(map[string]*ast.ImportSpec)
  1151  	for _, s := range f.Decls[0].(*ast.GenDecl).Specs {
  1152  		if imp, _ := s.(*ast.ImportSpec); imp != nil {
  1153  			imports[imp.Path.Value] = imp
  1154  		}
  1155  	}
  1156  
  1157  	for _, test := range tests {
  1158  		imp := imports[test.path]
  1159  		if imp == nil {
  1160  			t.Fatalf("invalid test case: import path %s not found", test.path)
  1161  		}
  1162  		got := info.PkgNameOf(imp)
  1163  		if got == nil {
  1164  			t.Fatalf("import %s: package name not found", test.path)
  1165  		}
  1166  		if got.Name() != test.want {
  1167  			t.Errorf("import %s: got %s; want %s", test.path, got.Name(), test.want)
  1168  		}
  1169  	}
  1170  
  1171  	// test non-existing importDecl
  1172  	if got := info.PkgNameOf(new(ast.ImportSpec)); got != nil {
  1173  		t.Errorf("got %s for non-existing import declaration", got.Name())
  1174  	}
  1175  }
  1176  
  1177  func predString(tv TypeAndValue) string {
  1178  	var buf strings.Builder
  1179  	pred := func(b bool, s string) {
  1180  		if b {
  1181  			if buf.Len() > 0 {
  1182  				buf.WriteString(", ")
  1183  			}
  1184  			buf.WriteString(s)
  1185  		}
  1186  	}
  1187  
  1188  	pred(tv.IsVoid(), "void")
  1189  	pred(tv.IsType(), "type")
  1190  	pred(tv.IsBuiltin(), "builtin")
  1191  	pred(tv.IsValue() && tv.Value != nil, "const")
  1192  	pred(tv.IsValue() && tv.Value == nil, "value")
  1193  	pred(tv.IsNil(), "nil")
  1194  	pred(tv.Addressable(), "addressable")
  1195  	pred(tv.Assignable(), "assignable")
  1196  	pred(tv.HasOk(), "hasOk")
  1197  
  1198  	if buf.Len() == 0 {
  1199  		return "invalid"
  1200  	}
  1201  	return buf.String()
  1202  }
  1203  
  1204  func TestPredicatesInfo(t *testing.T) {
  1205  	testenv.MustHaveGoBuild(t)
  1206  
  1207  	var tests = []struct {
  1208  		src  string
  1209  		expr string
  1210  		pred string
  1211  	}{
  1212  		// void
  1213  		{`package n0; func f() { f() }`, `f()`, `void`},
  1214  
  1215  		// types
  1216  		{`package t0; type _ int`, `int`, `type`},
  1217  		{`package t1; type _ []int`, `[]int`, `type`},
  1218  		{`package t2; type _ func()`, `func()`, `type`},
  1219  		{`package t3; type _ func(int)`, `int`, `type`},
  1220  		{`package t3; type _ func(...int)`, `...int`, `type`},
  1221  
  1222  		// built-ins
  1223  		{`package b0; var _ = len("")`, `len`, `builtin`},
  1224  		{`package b1; var _ = (len)("")`, `(len)`, `builtin`},
  1225  
  1226  		// constants
  1227  		{`package c0; var _ = 42`, `42`, `const`},
  1228  		{`package c1; var _ = "foo" + "bar"`, `"foo" + "bar"`, `const`},
  1229  		{`package c2; const (i = 1i; _ = i)`, `i`, `const`},
  1230  
  1231  		// values
  1232  		{`package v0; var (a, b int; _ = a + b)`, `a + b`, `value`},
  1233  		{`package v1; var _ = &[]int{1}`, `[]int{…}`, `value`},
  1234  		{`package v2; var _ = func(){}`, `(func() literal)`, `value`},
  1235  		{`package v4; func f() { _ = f }`, `f`, `value`},
  1236  		{`package v3; var _ *int = nil`, `nil`, `value, nil`},
  1237  		{`package v3; var _ *int = (nil)`, `(nil)`, `value, nil`},
  1238  
  1239  		// addressable (and thus assignable) operands
  1240  		{`package a0; var (x int; _ = x)`, `x`, `value, addressable, assignable`},
  1241  		{`package a1; var (p *int; _ = *p)`, `*p`, `value, addressable, assignable`},
  1242  		{`package a2; var (s []int; _ = s[0])`, `s[0]`, `value, addressable, assignable`},
  1243  		{`package a3; var (s struct{f int}; _ = s.f)`, `s.f`, `value, addressable, assignable`},
  1244  		{`package a4; var (a [10]int; _ = a[0])`, `a[0]`, `value, addressable, assignable`},
  1245  		{`package a5; func _(x int) { _ = x }`, `x`, `value, addressable, assignable`},
  1246  		{`package a6; func _()(x int) { _ = x; return }`, `x`, `value, addressable, assignable`},
  1247  		{`package a7; type T int; func (x T) _() { _ = x }`, `x`, `value, addressable, assignable`},
  1248  		// composite literals are not addressable
  1249  
  1250  		// assignable but not addressable values
  1251  		{`package s0; var (m map[int]int; _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
  1252  		{`package s1; var (m map[int]int; _, _ = m[0])`, `m[0]`, `value, assignable, hasOk`},
  1253  
  1254  		// hasOk expressions
  1255  		{`package k0; var (ch chan int; _ = <-ch)`, `<-ch`, `value, hasOk`},
  1256  		{`package k1; var (ch chan int; _, _ = <-ch)`, `<-ch`, `value, hasOk`},
  1257  
  1258  		// missing entries
  1259  		// - package names are collected in the Uses map
  1260  		// - identifiers being declared are collected in the Defs map
  1261  		{`package m0; import "os"; func _() { _ = os.Stdout }`, `os`, `<missing>`},
  1262  		{`package m1; import p "os"; func _() { _ = p.Stdout }`, `p`, `<missing>`},
  1263  		{`package m2; const c = 0`, `c`, `<missing>`},
  1264  		{`package m3; type T int`, `T`, `<missing>`},
  1265  		{`package m4; var v int`, `v`, `<missing>`},
  1266  		{`package m5; func f() {}`, `f`, `<missing>`},
  1267  		{`package m6; func _(x int) {}`, `x`, `<missing>`},
  1268  		{`package m6; func _()(x int) { return }`, `x`, `<missing>`},
  1269  		{`package m6; type T int; func (x T) _() {}`, `x`, `<missing>`},
  1270  	}
  1271  
  1272  	for _, test := range tests {
  1273  		info := Info{Types: make(map[ast.Expr]TypeAndValue)}
  1274  		name := mustTypecheck(test.src, nil, &info).Name()
  1275  
  1276  		// look for expression predicates
  1277  		got := "<missing>"
  1278  		for e, tv := range info.Types {
  1279  			//println(name, ExprString(e))
  1280  			if ExprString(e) == test.expr {
  1281  				got = predString(tv)
  1282  				break
  1283  			}
  1284  		}
  1285  
  1286  		if got != test.pred {
  1287  			t.Errorf("package %s: got %s; want %s", name, got, test.pred)
  1288  		}
  1289  	}
  1290  }
  1291  
  1292  func TestScopesInfo(t *testing.T) {
  1293  	testenv.MustHaveGoBuild(t)
  1294  
  1295  	var tests = []struct {
  1296  		src    string
  1297  		scopes []string // list of scope descriptors of the form kind:varlist
  1298  	}{
  1299  		{`package p0`, []string{
  1300  			"file:",
  1301  		}},
  1302  		{`package p1; import ( "fmt"; m "math"; _ "os" ); var ( _ = fmt.Println; _ = m.Pi )`, []string{
  1303  			"file:fmt m",
  1304  		}},
  1305  		{`package p2; func _() {}`, []string{
  1306  			"file:", "func:",
  1307  		}},
  1308  		{`package p3; func _(x, y int) {}`, []string{
  1309  			"file:", "func:x y",
  1310  		}},
  1311  		{`package p4; func _(x, y int) { x, z := 1, 2; _ = z }`, []string{
  1312  			"file:", "func:x y z", // redeclaration of x
  1313  		}},
  1314  		{`package p5; func _(x, y int) (u, _ int) { return }`, []string{
  1315  			"file:", "func:u x y",
  1316  		}},
  1317  		{`package p6; func _() { { var x int; _ = x } }`, []string{
  1318  			"file:", "func:", "block:x",
  1319  		}},
  1320  		{`package p7; func _() { if true {} }`, []string{
  1321  			"file:", "func:", "if:", "block:",
  1322  		}},
  1323  		{`package p8; func _() { if x := 0; x < 0 { y := x; _ = y } }`, []string{
  1324  			"file:", "func:", "if:x", "block:y",
  1325  		}},
  1326  		{`package p9; func _() { switch x := 0; x {} }`, []string{
  1327  			"file:", "func:", "switch:x",
  1328  		}},
  1329  		{`package p10; func _() { switch x := 0; x { case 1: y := x; _ = y; default: }}`, []string{
  1330  			"file:", "func:", "switch:x", "case:y", "case:",
  1331  		}},
  1332  		{`package p11; func _(t interface{}) { switch t.(type) {} }`, []string{
  1333  			"file:", "func:t", "type switch:",
  1334  		}},
  1335  		{`package p12; func _(t interface{}) { switch t := t; t.(type) {} }`, []string{
  1336  			"file:", "func:t", "type switch:t",
  1337  		}},
  1338  		{`package p13; func _(t interface{}) { switch x := t.(type) { case int: _ = x } }`, []string{
  1339  			"file:", "func:t", "type switch:", "case:x", // x implicitly declared
  1340  		}},
  1341  		{`package p14; func _() { select{} }`, []string{
  1342  			"file:", "func:",
  1343  		}},
  1344  		{`package p15; func _(c chan int) { select{ case <-c: } }`, []string{
  1345  			"file:", "func:c", "comm:",
  1346  		}},
  1347  		{`package p16; func _(c chan int) { select{ case i := <-c: x := i; _ = x} }`, []string{
  1348  			"file:", "func:c", "comm:i x",
  1349  		}},
  1350  		{`package p17; func _() { for{} }`, []string{
  1351  			"file:", "func:", "for:", "block:",
  1352  		}},
  1353  		{`package p18; func _(n int) { for i := 0; i < n; i++ { _ = i } }`, []string{
  1354  			"file:", "func:n", "for:i", "block:",
  1355  		}},
  1356  		{`package p19; func _(a []int) { for i := range a { _ = i} }`, []string{
  1357  			"file:", "func:a", "range:i", "block:",
  1358  		}},
  1359  		{`package p20; var s int; func _(a []int) { for i, x := range a { s += x; _ = i } }`, []string{
  1360  			"file:", "func:a", "range:i x", "block:",
  1361  		}},
  1362  	}
  1363  
  1364  	for _, test := range tests {
  1365  		info := Info{Scopes: make(map[ast.Node]*Scope)}
  1366  		name := mustTypecheck(test.src, nil, &info).Name()
  1367  
  1368  		// number of scopes must match
  1369  		if len(info.Scopes) != len(test.scopes) {
  1370  			t.Errorf("package %s: got %d scopes; want %d", name, len(info.Scopes), len(test.scopes))
  1371  		}
  1372  
  1373  		// scope descriptions must match
  1374  		for node, scope := range info.Scopes {
  1375  			kind := "<unknown node kind>"
  1376  			switch node.(type) {
  1377  			case *ast.File:
  1378  				kind = "file"
  1379  			case *ast.FuncType:
  1380  				kind = "func"
  1381  			case *ast.BlockStmt:
  1382  				kind = "block"
  1383  			case *ast.IfStmt:
  1384  				kind = "if"
  1385  			case *ast.SwitchStmt:
  1386  				kind = "switch"
  1387  			case *ast.TypeSwitchStmt:
  1388  				kind = "type switch"
  1389  			case *ast.CaseClause:
  1390  				kind = "case"
  1391  			case *ast.CommClause:
  1392  				kind = "comm"
  1393  			case *ast.ForStmt:
  1394  				kind = "for"
  1395  			case *ast.RangeStmt:
  1396  				kind = "range"
  1397  			}
  1398  
  1399  			// look for matching scope description
  1400  			desc := kind + ":" + strings.Join(scope.Names(), " ")
  1401  			if !slices.Contains(test.scopes, desc) {
  1402  				t.Errorf("package %s: no matching scope found for %s", name, desc)
  1403  			}
  1404  		}
  1405  	}
  1406  }
  1407  
  1408  func TestInitOrderInfo(t *testing.T) {
  1409  	var tests = []struct {
  1410  		src   string
  1411  		inits []string
  1412  	}{
  1413  		{`package p0; var (x = 1; y = x)`, []string{
  1414  			"x = 1", "y = x",
  1415  		}},
  1416  		{`package p1; var (a = 1; b = 2; c = 3)`, []string{
  1417  			"a = 1", "b = 2", "c = 3",
  1418  		}},
  1419  		{`package p2; var (a, b, c = 1, 2, 3)`, []string{
  1420  			"a = 1", "b = 2", "c = 3",
  1421  		}},
  1422  		{`package p3; var _ = f(); func f() int { return 1 }`, []string{
  1423  			"_ = f()", // blank var
  1424  		}},
  1425  		{`package p4; var (a = 0; x = y; y = z; z = 0)`, []string{
  1426  			"a = 0", "z = 0", "y = z", "x = y",
  1427  		}},
  1428  		{`package p5; var (a, _ = m[0]; m map[int]string)`, []string{
  1429  			"a, _ = m[0]", // blank var
  1430  		}},
  1431  		{`package p6; var a, b = f(); func f() (_, _ int) { return z, z }; var z = 0`, []string{
  1432  			"z = 0", "a, b = f()",
  1433  		}},
  1434  		{`package p7; var (a = func() int { return b }(); b = 1)`, []string{
  1435  			"b = 1", "a = (func() int literal)()",
  1436  		}},
  1437  		{`package p8; var (a, b = func() (_, _ int) { return c, c }(); c = 1)`, []string{
  1438  			"c = 1", "a, b = (func() (_, _ int) literal)()",
  1439  		}},
  1440  		{`package p9; type T struct{}; func (T) m() int { _ = y; return 0 }; var x, y = T.m, 1`, []string{
  1441  			"y = 1", "x = T.m",
  1442  		}},
  1443  		{`package p10; var (d = c + b; a = 0; b = 0; c = 0)`, []string{
  1444  			"a = 0", "b = 0", "c = 0", "d = c + b",
  1445  		}},
  1446  		{`package p11; var (a = e + c; b = d + c; c = 0; d = 0; e = 0)`, []string{
  1447  			"c = 0", "d = 0", "b = d + c", "e = 0", "a = e + c",
  1448  		}},
  1449  		// emit an initializer for n:1 initializations only once (not for each node
  1450  		// on the lhs which may appear in different order in the dependency graph)
  1451  		{`package p12; var (a = x; b = 0; x, y = m[0]; m map[int]int)`, []string{
  1452  			"b = 0", "x, y = m[0]", "a = x",
  1453  		}},
  1454  		// test case from spec section on package initialization
  1455  		{`package p12
  1456  
  1457  		var (
  1458  			a = c + b
  1459  			b = f()
  1460  			c = f()
  1461  			d = 3
  1462  		)
  1463  
  1464  		func f() int {
  1465  			d++
  1466  			return d
  1467  		}`, []string{
  1468  			"d = 3", "b = f()", "c = f()", "a = c + b",
  1469  		}},
  1470  		// test case for go.dev/issue/7131
  1471  		{`package main
  1472  
  1473  		var counter int
  1474  		func next() int { counter++; return counter }
  1475  
  1476  		var _ = makeOrder()
  1477  		func makeOrder() []int { return []int{f, b, d, e, c, a} }
  1478  
  1479  		var a       = next()
  1480  		var b, c    = next(), next()
  1481  		var d, e, f = next(), next(), next()
  1482  		`, []string{
  1483  			"a = next()", "b = next()", "c = next()", "d = next()", "e = next()", "f = next()", "_ = makeOrder()",
  1484  		}},
  1485  		// test case for go.dev/issue/10709
  1486  		{`package p13
  1487  
  1488  		var (
  1489  		    v = t.m()
  1490  		    t = makeT(0)
  1491  		)
  1492  
  1493  		type T struct{}
  1494  
  1495  		func (T) m() int { return 0 }
  1496  
  1497  		func makeT(n int) T {
  1498  		    if n > 0 {
  1499  		        return makeT(n-1)
  1500  		    }
  1501  		    return T{}
  1502  		}`, []string{
  1503  			"t = makeT(0)", "v = t.m()",
  1504  		}},
  1505  		// test case for go.dev/issue/10709: same as test before, but variable decls swapped
  1506  		{`package p14
  1507  
  1508  		var (
  1509  		    t = makeT(0)
  1510  		    v = t.m()
  1511  		)
  1512  
  1513  		type T struct{}
  1514  
  1515  		func (T) m() int { return 0 }
  1516  
  1517  		func makeT(n int) T {
  1518  		    if n > 0 {
  1519  		        return makeT(n-1)
  1520  		    }
  1521  		    return T{}
  1522  		}`, []string{
  1523  			"t = makeT(0)", "v = t.m()",
  1524  		}},
  1525  		// another candidate possibly causing problems with go.dev/issue/10709
  1526  		{`package p15
  1527  
  1528  		var y1 = f1()
  1529  
  1530  		func f1() int { return g1() }
  1531  		func g1() int { f1(); return x1 }
  1532  
  1533  		var x1 = 0
  1534  
  1535  		var y2 = f2()
  1536  
  1537  		func f2() int { return g2() }
  1538  		func g2() int { return x2 }
  1539  
  1540  		var x2 = 0`, []string{
  1541  			"x1 = 0", "y1 = f1()", "x2 = 0", "y2 = f2()",
  1542  		}},
  1543  	}
  1544  
  1545  	for _, test := range tests {
  1546  		info := Info{}
  1547  		name := mustTypecheck(test.src, nil, &info).Name()
  1548  
  1549  		// number of initializers must match
  1550  		if len(info.InitOrder) != len(test.inits) {
  1551  			t.Errorf("package %s: got %d initializers; want %d", name, len(info.InitOrder), len(test.inits))
  1552  			continue
  1553  		}
  1554  
  1555  		// initializers must match
  1556  		for i, want := range test.inits {
  1557  			got := info.InitOrder[i].String()
  1558  			if got != want {
  1559  				t.Errorf("package %s, init %d: got %s; want %s", name, i, got, want)
  1560  				continue
  1561  			}
  1562  		}
  1563  	}
  1564  }
  1565  
  1566  func TestMultiFileInitOrder(t *testing.T) {
  1567  	fset := token.NewFileSet()
  1568  	fileA := mustParse(fset, `package main; var a = 1`)
  1569  	fileB := mustParse(fset, `package main; var b = 2`)
  1570  
  1571  	// The initialization order must not depend on the parse
  1572  	// order of the files, only on the presentation order to
  1573  	// the type-checker.
  1574  	for _, test := range []struct {
  1575  		files []*ast.File
  1576  		want  string
  1577  	}{
  1578  		{[]*ast.File{fileA, fileB}, "[a = 1 b = 2]"},
  1579  		{[]*ast.File{fileB, fileA}, "[b = 2 a = 1]"},
  1580  	} {
  1581  		var info Info
  1582  		if _, err := new(Config).Check("main", fset, test.files, &info); err != nil {
  1583  			t.Fatal(err)
  1584  		}
  1585  		if got := fmt.Sprint(info.InitOrder); got != test.want {
  1586  			t.Fatalf("got %s; want %s", got, test.want)
  1587  		}
  1588  	}
  1589  }
  1590  
  1591  func TestFiles(t *testing.T) {
  1592  	var sources = []string{
  1593  		"package p; type T struct{}; func (T) m1() {}",
  1594  		"package p; func (T) m2() {}; var x interface{ m1(); m2() } = T{}",
  1595  		"package p; func (T) m3() {}; var y interface{ m1(); m2(); m3() } = T{}",
  1596  		"package p",
  1597  	}
  1598  
  1599  	var conf Config
  1600  	fset := token.NewFileSet()
  1601  	pkg := NewPackage("p", "p")
  1602  	var info Info
  1603  	check := NewChecker(&conf, fset, pkg, &info)
  1604  
  1605  	for _, src := range sources {
  1606  		if err := check.Files([]*ast.File{mustParse(fset, src)}); err != nil {
  1607  			t.Error(err)
  1608  		}
  1609  	}
  1610  
  1611  	// check InitOrder is [x y]
  1612  	var vars []string
  1613  	for _, init := range info.InitOrder {
  1614  		for _, v := range init.Lhs {
  1615  			vars = append(vars, v.Name())
  1616  		}
  1617  	}
  1618  	if got, want := fmt.Sprint(vars), "[x y]"; got != want {
  1619  		t.Errorf("InitOrder == %s, want %s", got, want)
  1620  	}
  1621  }
  1622  
  1623  type testImporter map[string]*Package
  1624  
  1625  func (m testImporter) Import(path string) (*Package, error) {
  1626  	if pkg := m[path]; pkg != nil {
  1627  		return pkg, nil
  1628  	}
  1629  	return nil, fmt.Errorf("package %q not found", path)
  1630  }
  1631  
  1632  func TestSelection(t *testing.T) {
  1633  	selections := make(map[*ast.SelectorExpr]*Selection)
  1634  
  1635  	// We need a specific fileset in this test below for positions.
  1636  	// Cannot use typecheck helper.
  1637  	fset := token.NewFileSet()
  1638  	imports := make(testImporter)
  1639  	conf := Config{Importer: imports}
  1640  	makePkg := func(path, src string) {
  1641  		pkg, err := conf.Check(path, fset, []*ast.File{mustParse(fset, src)}, &Info{Selections: selections})
  1642  		if err != nil {
  1643  			t.Fatal(err)
  1644  		}
  1645  		imports[path] = pkg
  1646  	}
  1647  
  1648  	const libSrc = `
  1649  package lib
  1650  type T float64
  1651  const C T = 3
  1652  var V T
  1653  func F() {}
  1654  func (T) M() {}
  1655  `
  1656  	const mainSrc = `
  1657  package main
  1658  import "lib"
  1659  
  1660  type A struct {
  1661  	*B
  1662  	C
  1663  }
  1664  
  1665  type B struct {
  1666  	b int
  1667  }
  1668  
  1669  func (B) f(int)
  1670  
  1671  type C struct {
  1672  	c int
  1673  }
  1674  
  1675  type G[P any] struct {
  1676  	p P
  1677  }
  1678  
  1679  func (G[P]) m(P) {}
  1680  
  1681  var Inst G[int]
  1682  
  1683  func (C) g()
  1684  func (*C) h()
  1685  
  1686  func main() {
  1687  	// qualified identifiers
  1688  	var _ lib.T
  1689  	_ = lib.C
  1690  	_ = lib.F
  1691  	_ = lib.V
  1692  	_ = lib.T.M
  1693  
  1694  	// fields
  1695  	_ = A{}.B
  1696  	_ = new(A).B
  1697  
  1698  	_ = A{}.C
  1699  	_ = new(A).C
  1700  
  1701  	_ = A{}.b
  1702  	_ = new(A).b
  1703  
  1704  	_ = A{}.c
  1705  	_ = new(A).c
  1706  
  1707  	_ = Inst.p
  1708  	_ = G[string]{}.p
  1709  
  1710  	// methods
  1711  	_ = A{}.f
  1712  	_ = new(A).f
  1713  	_ = A{}.g
  1714  	_ = new(A).g
  1715  	_ = new(A).h
  1716  
  1717  	_ = B{}.f
  1718  	_ = new(B).f
  1719  
  1720  	_ = C{}.g
  1721  	_ = new(C).g
  1722  	_ = new(C).h
  1723  	_ = Inst.m
  1724  
  1725  	// method expressions
  1726  	_ = A.f
  1727  	_ = (*A).f
  1728  	_ = B.f
  1729  	_ = (*B).f
  1730  	_ = G[string].m
  1731  }`
  1732  
  1733  	wantOut := map[string][2]string{
  1734  		"lib.T.M": {"method expr (lib.T) M(lib.T)", ".[0]"},
  1735  
  1736  		"A{}.B":    {"field (main.A) B *main.B", ".[0]"},
  1737  		"new(A).B": {"field (*main.A) B *main.B", "->[0]"},
  1738  		"A{}.C":    {"field (main.A) C main.C", ".[1]"},
  1739  		"new(A).C": {"field (*main.A) C main.C", "->[1]"},
  1740  		"A{}.b":    {"field (main.A) b int", "->[0 0]"},
  1741  		"new(A).b": {"field (*main.A) b int", "->[0 0]"},
  1742  		"A{}.c":    {"field (main.A) c int", ".[1 0]"},
  1743  		"new(A).c": {"field (*main.A) c int", "->[1 0]"},
  1744  		"Inst.p":   {"field (main.G[int]) p int", ".[0]"},
  1745  
  1746  		"A{}.f":    {"method (main.A) f(int)", "->[0 0]"},
  1747  		"new(A).f": {"method (*main.A) f(int)", "->[0 0]"},
  1748  		"A{}.g":    {"method (main.A) g()", ".[1 0]"},
  1749  		"new(A).g": {"method (*main.A) g()", "->[1 0]"},
  1750  		"new(A).h": {"method (*main.A) h()", "->[1 1]"}, // TODO(gri) should this report .[1 1] ?
  1751  		"B{}.f":    {"method (main.B) f(int)", ".[0]"},
  1752  		"new(B).f": {"method (*main.B) f(int)", "->[0]"},
  1753  		"C{}.g":    {"method (main.C) g()", ".[0]"},
  1754  		"new(C).g": {"method (*main.C) g()", "->[0]"},
  1755  		"new(C).h": {"method (*main.C) h()", "->[1]"}, // TODO(gri) should this report .[1] ?
  1756  		"Inst.m":   {"method (main.G[int]) m(int)", ".[0]"},
  1757  
  1758  		"A.f":           {"method expr (main.A) f(main.A, int)", "->[0 0]"},
  1759  		"(*A).f":        {"method expr (*main.A) f(*main.A, int)", "->[0 0]"},
  1760  		"B.f":           {"method expr (main.B) f(main.B, int)", ".[0]"},
  1761  		"(*B).f":        {"method expr (*main.B) f(*main.B, int)", "->[0]"},
  1762  		"G[string].m":   {"method expr (main.G[string]) m(main.G[string], string)", ".[0]"},
  1763  		"G[string]{}.p": {"field (main.G[string]) p string", ".[0]"},
  1764  	}
  1765  
  1766  	makePkg("lib", libSrc)
  1767  	makePkg("main", mainSrc)
  1768  
  1769  	for e, sel := range selections {
  1770  		_ = sel.String() // assertion: must not panic
  1771  
  1772  		start := fset.Position(e.Pos()).Offset
  1773  		end := fset.Position(e.End()).Offset
  1774  		syntax := mainSrc[start:end] // (all SelectorExprs are in main, not lib)
  1775  
  1776  		direct := "."
  1777  		if sel.Indirect() {
  1778  			direct = "->"
  1779  		}
  1780  		got := [2]string{
  1781  			sel.String(),
  1782  			fmt.Sprintf("%s%v", direct, sel.Index()),
  1783  		}
  1784  		want := wantOut[syntax]
  1785  		if want != got {
  1786  			t.Errorf("%s: got %q; want %q", syntax, got, want)
  1787  		}
  1788  		delete(wantOut, syntax)
  1789  
  1790  		// We must explicitly assert properties of the
  1791  		// Signature's receiver since it doesn't participate
  1792  		// in Identical() or String().
  1793  		sig, _ := sel.Type().(*Signature)
  1794  		if sel.Kind() == MethodVal {
  1795  			got := sig.Recv().Type()
  1796  			want := sel.Recv()
  1797  			if !Identical(got, want) {
  1798  				t.Errorf("%s: Recv() = %s, want %s", syntax, got, want)
  1799  			}
  1800  		} else if sig != nil && sig.Recv() != nil {
  1801  			t.Errorf("%s: signature has receiver %s", sig, sig.Recv().Type())
  1802  		}
  1803  	}
  1804  	// Assert that all wantOut entries were used exactly once.
  1805  	for syntax := range wantOut {
  1806  		t.Errorf("no ast.Selection found with syntax %q", syntax)
  1807  	}
  1808  }
  1809  
  1810  func TestIssue8518(t *testing.T) {
  1811  	fset := token.NewFileSet()
  1812  	imports := make(testImporter)
  1813  	conf := Config{
  1814  		Error:    func(err error) { t.Log(err) }, // don't exit after first error
  1815  		Importer: imports,
  1816  	}
  1817  	makePkg := func(path, src string) {
  1818  		imports[path], _ = conf.Check(path, fset, []*ast.File{mustParse(fset, src)}, nil) // errors logged via conf.Error
  1819  	}
  1820  
  1821  	const libSrc = `
  1822  package a
  1823  import "missing"
  1824  const C1 = foo
  1825  const C2 = missing.C
  1826  `
  1827  
  1828  	const mainSrc = `
  1829  package main
  1830  import "a"
  1831  var _ = a.C1
  1832  var _ = a.C2
  1833  `
  1834  
  1835  	makePkg("a", libSrc)
  1836  	makePkg("main", mainSrc) // don't crash when type-checking this package
  1837  }
  1838  
  1839  func TestIssue59603(t *testing.T) {
  1840  	fset := token.NewFileSet()
  1841  	imports := make(testImporter)
  1842  	conf := Config{
  1843  		Error:    func(err error) { t.Log(err) }, // don't exit after first error
  1844  		Importer: imports,
  1845  	}
  1846  	makePkg := func(path, src string) {
  1847  		imports[path], _ = conf.Check(path, fset, []*ast.File{mustParse(fset, src)}, nil) // errors logged via conf.Error
  1848  	}
  1849  
  1850  	const libSrc = `
  1851  package a
  1852  const C = foo
  1853  `
  1854  
  1855  	const mainSrc = `
  1856  package main
  1857  import "a"
  1858  const _ = a.C
  1859  `
  1860  
  1861  	makePkg("a", libSrc)
  1862  	makePkg("main", mainSrc) // don't crash when type-checking this package
  1863  }
  1864  
  1865  func TestLookupFieldOrMethodOnNil(t *testing.T) {
  1866  	// LookupFieldOrMethod on a nil type is expected to produce a run-time panic.
  1867  	defer func() {
  1868  		const want = "LookupFieldOrMethod on nil type"
  1869  		p := recover()
  1870  		if s, ok := p.(string); !ok || s != want {
  1871  			t.Fatalf("got %v, want %s", p, want)
  1872  		}
  1873  	}()
  1874  	LookupFieldOrMethod(nil, false, nil, "")
  1875  }
  1876  
  1877  func TestLookupFieldOrMethod(t *testing.T) {
  1878  	// Test cases assume a lookup of the form a.f or x.f, where a stands for an
  1879  	// addressable value, and x for a non-addressable value (even though a variable
  1880  	// for ease of test case writing).
  1881  	//
  1882  	// Should be kept in sync with TestMethodSet.
  1883  	var tests = []struct {
  1884  		src      string
  1885  		found    bool
  1886  		index    []int
  1887  		indirect bool
  1888  	}{
  1889  		// field lookups
  1890  		{"var x T; type T struct{}", false, nil, false},
  1891  		{"var x T; type T struct{ f int }", true, []int{0}, false},
  1892  		{"var x T; type T struct{ a, b, f, c int }", true, []int{2}, false},
  1893  
  1894  		// field lookups on a generic type
  1895  		{"var x T[int]; type T[P any] struct{}", false, nil, false},
  1896  		{"var x T[int]; type T[P any] struct{ f P }", true, []int{0}, false},
  1897  		{"var x T[int]; type T[P any] struct{ a, b, f, c P }", true, []int{2}, false},
  1898  
  1899  		// method lookups
  1900  		{"var a T; type T struct{}; func (T) f() {}", true, []int{0}, false},
  1901  		{"var a *T; type T struct{}; func (T) f() {}", true, []int{0}, true},
  1902  		{"var a T; type T struct{}; func (*T) f() {}", true, []int{0}, false},
  1903  		{"var a *T; type T struct{}; func (*T) f() {}", true, []int{0}, true}, // TODO(gri) should this report indirect = false?
  1904  
  1905  		// method lookups on a generic type
  1906  		{"var a T[int]; type T[P any] struct{}; func (T[P]) f() {}", true, []int{0}, false},
  1907  		{"var a *T[int]; type T[P any] struct{}; func (T[P]) f() {}", true, []int{0}, true},
  1908  		{"var a T[int]; type T[P any] struct{}; func (*T[P]) f() {}", true, []int{0}, false},
  1909  		{"var a *T[int]; type T[P any] struct{}; func (*T[P]) f() {}", true, []int{0}, true}, // TODO(gri) should this report indirect = false?
  1910  
  1911  		// collisions
  1912  		{"type ( E1 struct{ f int }; E2 struct{ f int }; x struct{ E1; *E2 })", false, []int{1, 0}, false},
  1913  		{"type ( E1 struct{ f int }; E2 struct{}; x struct{ E1; *E2 }); func (E2) f() {}", false, []int{1, 0}, false},
  1914  
  1915  		// collisions on a generic type
  1916  		{"type ( E1[P any] struct{ f P }; E2[P any] struct{ f P }; x struct{ E1[int]; *E2[int] })", false, []int{1, 0}, false},
  1917  		{"type ( E1[P any] struct{ f P }; E2[P any] struct{}; x struct{ E1[int]; *E2[int] }); func (E2[P]) f() {}", false, []int{1, 0}, false},
  1918  
  1919  		// outside methodset
  1920  		// (*T).f method exists, but value of type T is not addressable
  1921  		{"var x T; type T struct{}; func (*T) f() {}", false, nil, true},
  1922  
  1923  		// outside method set of a generic type
  1924  		{"var x T[int]; type T[P any] struct{}; func (*T[P]) f() {}", false, nil, true},
  1925  
  1926  		// recursive generic types; see go.dev/issue/52715
  1927  		{"var a T[int]; type ( T[P any] struct { *N[P] }; N[P any] struct { *T[P] } ); func (N[P]) f() {}", true, []int{0, 0}, true},
  1928  		{"var a T[int]; type ( T[P any] struct { *N[P] }; N[P any] struct { *T[P] } ); func (T[P]) f() {}", true, []int{0}, false},
  1929  	}
  1930  
  1931  	for _, test := range tests {
  1932  		pkg := mustTypecheck("package p;"+test.src, nil, nil)
  1933  
  1934  		obj := pkg.Scope().Lookup("a")
  1935  		if obj == nil {
  1936  			if obj = pkg.Scope().Lookup("x"); obj == nil {
  1937  				t.Errorf("%s: incorrect test case - no object a or x", test.src)
  1938  				continue
  1939  			}
  1940  		}
  1941  
  1942  		f, index, indirect := LookupFieldOrMethod(obj.Type(), obj.Name() == "a", pkg, "f")
  1943  		if (f != nil) != test.found {
  1944  			if f == nil {
  1945  				t.Errorf("%s: got no object; want one", test.src)
  1946  			} else {
  1947  				t.Errorf("%s: got object = %v; want none", test.src, f)
  1948  			}
  1949  		}
  1950  		if !slices.Equal(index, test.index) {
  1951  			t.Errorf("%s: got index = %v; want %v", test.src, index, test.index)
  1952  		}
  1953  		if indirect != test.indirect {
  1954  			t.Errorf("%s: got indirect = %v; want %v", test.src, indirect, test.indirect)
  1955  		}
  1956  	}
  1957  }
  1958  
  1959  // Test for go.dev/issue/52715
  1960  func TestLookupFieldOrMethod_RecursiveGeneric(t *testing.T) {
  1961  	const src = `
  1962  package pkg
  1963  
  1964  type Tree[T any] struct {
  1965  	*Node[T]
  1966  }
  1967  
  1968  func (*Tree[R]) N(r R) R { return r }
  1969  
  1970  type Node[T any] struct {
  1971  	*Tree[T]
  1972  }
  1973  
  1974  type Instance = *Tree[int]
  1975  `
  1976  
  1977  	fset := token.NewFileSet()
  1978  	f := mustParse(fset, src)
  1979  	pkg := NewPackage("pkg", f.Name.Name)
  1980  	if err := NewChecker(nil, fset, pkg, nil).Files([]*ast.File{f}); err != nil {
  1981  		panic(err)
  1982  	}
  1983  
  1984  	T := pkg.Scope().Lookup("Instance").Type()
  1985  	_, _, _ = LookupFieldOrMethod(T, false, pkg, "M") // verify that LookupFieldOrMethod terminates
  1986  }
  1987  
  1988  // newDefined creates a new defined type named T with the given underlying type.
  1989  // Helper function for use with TestIncompleteInterfaces only.
  1990  func newDefined(underlying Type) *Named {
  1991  	tname := NewTypeName(nopos, nil, "T", nil)
  1992  	return NewNamed(tname, underlying, nil)
  1993  }
  1994  
  1995  func TestConvertibleTo(t *testing.T) {
  1996  	for _, test := range []struct {
  1997  		v, t Type
  1998  		want bool
  1999  	}{
  2000  		{Typ[Int], Typ[Int], true},
  2001  		{Typ[Int], Typ[Float32], true},
  2002  		{Typ[Int], Typ[String], true},
  2003  		{newDefined(Typ[Int]), Typ[Int], true},
  2004  		{newDefined(new(Struct)), new(Struct), true},
  2005  		{newDefined(Typ[Int]), new(Struct), false},
  2006  		{Typ[UntypedInt], Typ[Int], true},
  2007  		{NewSlice(Typ[Int]), NewArray(Typ[Int], 10), true},
  2008  		{NewSlice(Typ[Int]), NewArray(Typ[Uint], 10), false},
  2009  		{NewSlice(Typ[Int]), NewPointer(NewArray(Typ[Int], 10)), true},
  2010  		{NewSlice(Typ[Int]), NewPointer(NewArray(Typ[Uint], 10)), false},
  2011  		// Untyped string values are not permitted by the spec, so the behavior below is undefined.
  2012  		{Typ[UntypedString], Typ[String], true},
  2013  	} {
  2014  		if got := ConvertibleTo(test.v, test.t); got != test.want {
  2015  			t.Errorf("ConvertibleTo(%v, %v) = %t, want %t", test.v, test.t, got, test.want)
  2016  		}
  2017  	}
  2018  }
  2019  
  2020  func TestAssignableTo(t *testing.T) {
  2021  	for _, test := range []struct {
  2022  		v, t Type
  2023  		want bool
  2024  	}{
  2025  		{Typ[Int], Typ[Int], true},
  2026  		{Typ[Int], Typ[Float32], false},
  2027  		{newDefined(Typ[Int]), Typ[Int], false},
  2028  		{newDefined(new(Struct)), new(Struct), true},
  2029  		{Typ[UntypedBool], Typ[Bool], true},
  2030  		{Typ[UntypedString], Typ[Bool], false},
  2031  		// Neither untyped string nor untyped numeric assignments arise during
  2032  		// normal type checking, so the below behavior is technically undefined by
  2033  		// the spec.
  2034  		{Typ[UntypedString], Typ[String], true},
  2035  		{Typ[UntypedInt], Typ[Int], true},
  2036  	} {
  2037  		if got := AssignableTo(test.v, test.t); got != test.want {
  2038  			t.Errorf("AssignableTo(%v, %v) = %t, want %t", test.v, test.t, got, test.want)
  2039  		}
  2040  	}
  2041  }
  2042  
  2043  func TestIdentical(t *testing.T) {
  2044  	// For each test, we compare the types of objects X and Y in the source.
  2045  	tests := []struct {
  2046  		src  string
  2047  		want bool
  2048  	}{
  2049  		// Basic types.
  2050  		{"var X int; var Y int", true},
  2051  		{"var X int; var Y string", false},
  2052  
  2053  		// TODO: add more tests for complex types.
  2054  
  2055  		// Named types.
  2056  		{"type X int; type Y int", false},
  2057  
  2058  		// Aliases.
  2059  		{"type X = int; type Y = int", true},
  2060  
  2061  		// Functions.
  2062  		{`func X(int) string { return "" }; func Y(int) string { return "" }`, true},
  2063  		{`func X() string { return "" }; func Y(int) string { return "" }`, false},
  2064  		{`func X(int) string { return "" }; func Y(int) {}`, false},
  2065  
  2066  		// Generic functions. Type parameters should be considered identical modulo
  2067  		// renaming. See also go.dev/issue/49722.
  2068  		{`func X[P ~int](){}; func Y[Q ~int]() {}`, true},
  2069  		{`func X[P1 any, P2 ~*P1](){}; func Y[Q1 any, Q2 ~*Q1]() {}`, true},
  2070  		{`func X[P1 any, P2 ~[]P1](){}; func Y[Q1 any, Q2 ~*Q1]() {}`, false},
  2071  		{`func X[P ~int](P){}; func Y[Q ~int](Q) {}`, true},
  2072  		{`func X[P ~string](P){}; func Y[Q ~int](Q) {}`, false},
  2073  		{`func X[P ~int]([]P){}; func Y[Q ~int]([]Q) {}`, true},
  2074  	}
  2075  
  2076  	for _, test := range tests {
  2077  		pkg := mustTypecheck("package p;"+test.src, nil, nil)
  2078  		X := pkg.Scope().Lookup("X")
  2079  		Y := pkg.Scope().Lookup("Y")
  2080  		if X == nil || Y == nil {
  2081  			t.Fatal("test must declare both X and Y")
  2082  		}
  2083  		if got := Identical(X.Type(), Y.Type()); got != test.want {
  2084  			t.Errorf("Identical(%s, %s) = %t, want %t", X.Type(), Y.Type(), got, test.want)
  2085  		}
  2086  	}
  2087  }
  2088  
  2089  func TestIdentical_issue15173(t *testing.T) {
  2090  	// Identical should allow nil arguments and be symmetric.
  2091  	for _, test := range []struct {
  2092  		x, y Type
  2093  		want bool
  2094  	}{
  2095  		{Typ[Int], Typ[Int], true},
  2096  		{Typ[Int], nil, false},
  2097  		{nil, Typ[Int], false},
  2098  		{nil, nil, true},
  2099  	} {
  2100  		if got := Identical(test.x, test.y); got != test.want {
  2101  			t.Errorf("Identical(%v, %v) = %t", test.x, test.y, got)
  2102  		}
  2103  	}
  2104  }
  2105  
  2106  func TestIdenticalUnions(t *testing.T) {
  2107  	tname := NewTypeName(nopos, nil, "myInt", nil)
  2108  	myInt := NewNamed(tname, Typ[Int], nil)
  2109  	tmap := map[string]*Term{
  2110  		"int":     NewTerm(false, Typ[Int]),
  2111  		"~int":    NewTerm(true, Typ[Int]),
  2112  		"string":  NewTerm(false, Typ[String]),
  2113  		"~string": NewTerm(true, Typ[String]),
  2114  		"myInt":   NewTerm(false, myInt),
  2115  	}
  2116  	makeUnion := func(s string) *Union {
  2117  		parts := strings.Split(s, "|")
  2118  		var terms []*Term
  2119  		for _, p := range parts {
  2120  			term := tmap[p]
  2121  			if term == nil {
  2122  				t.Fatalf("missing term %q", p)
  2123  			}
  2124  			terms = append(terms, term)
  2125  		}
  2126  		return NewUnion(terms)
  2127  	}
  2128  	for _, test := range []struct {
  2129  		x, y string
  2130  		want bool
  2131  	}{
  2132  		// These tests are just sanity checks. The tests for type sets and
  2133  		// interfaces provide much more test coverage.
  2134  		{"int|~int", "~int", true},
  2135  		{"myInt|~int", "~int", true},
  2136  		{"int|string", "string|int", true},
  2137  		{"int|int|string", "string|int", true},
  2138  		{"myInt|string", "int|string", false},
  2139  	} {
  2140  		x := makeUnion(test.x)
  2141  		y := makeUnion(test.y)
  2142  		if got := Identical(x, y); got != test.want {
  2143  			t.Errorf("Identical(%v, %v) = %t", test.x, test.y, got)
  2144  		}
  2145  	}
  2146  }
  2147  
  2148  func TestIssue61737(t *testing.T) {
  2149  	// This test verifies that it is possible to construct invalid interfaces
  2150  	// containing duplicate methods using the go/types API.
  2151  	//
  2152  	// It must be possible for importers to construct such invalid interfaces.
  2153  	// Previously, this panicked.
  2154  
  2155  	sig1 := NewSignatureType(nil, nil, nil, NewTuple(NewParam(nopos, nil, "", Typ[Int])), nil, false)
  2156  	sig2 := NewSignatureType(nil, nil, nil, NewTuple(NewParam(nopos, nil, "", Typ[String])), nil, false)
  2157  
  2158  	methods := []*Func{
  2159  		NewFunc(nopos, nil, "M", sig1),
  2160  		NewFunc(nopos, nil, "M", sig2),
  2161  	}
  2162  
  2163  	embeddedMethods := []*Func{
  2164  		NewFunc(nopos, nil, "M", sig2),
  2165  	}
  2166  	embedded := NewInterfaceType(embeddedMethods, nil)
  2167  	iface := NewInterfaceType(methods, []Type{embedded})
  2168  	iface.Complete()
  2169  }
  2170  
  2171  func TestNewAlias_Issue65455(t *testing.T) {
  2172  	obj := NewTypeName(nopos, nil, "A", nil)
  2173  	alias := NewAlias(obj, Typ[Int])
  2174  	alias.Underlying() // must not panic
  2175  }
  2176  
  2177  func TestIssue15305(t *testing.T) {
  2178  	const src = "package p; func f() int16; var _ = f(undef)"
  2179  	fset := token.NewFileSet()
  2180  	f := mustParse(fset, src)
  2181  	conf := Config{
  2182  		Error: func(err error) {}, // allow errors
  2183  	}
  2184  	info := &Info{
  2185  		Types: make(map[ast.Expr]TypeAndValue),
  2186  	}
  2187  	conf.Check("p", fset, []*ast.File{f}, info) // ignore result
  2188  	for e, tv := range info.Types {
  2189  		if _, ok := e.(*ast.CallExpr); ok {
  2190  			if tv.Type != Typ[Int16] {
  2191  				t.Errorf("CallExpr has type %v, want int16", tv.Type)
  2192  			}
  2193  			return
  2194  		}
  2195  	}
  2196  	t.Errorf("CallExpr has no type")
  2197  }
  2198  
  2199  // TestCompositeLitTypes verifies that Info.Types registers the correct
  2200  // types for composite literal expressions and composite literal type
  2201  // expressions.
  2202  func TestCompositeLitTypes(t *testing.T) {
  2203  	for i, test := range []struct {
  2204  		lit, typ string
  2205  	}{
  2206  		{`[16]byte{}`, `[16]byte`},
  2207  		{`[...]byte{}`, `[0]byte`},                // test for go.dev/issue/14092
  2208  		{`[...]int{1, 2, 3}`, `[3]int`},           // test for go.dev/issue/14092
  2209  		{`[...]int{90: 0, 98: 1, 2}`, `[100]int`}, // test for go.dev/issue/14092
  2210  		{`[]int{}`, `[]int`},
  2211  		{`map[string]bool{"foo": true}`, `map[string]bool`},
  2212  		{`struct{}{}`, `struct{}`},
  2213  		{`struct{x, y int; z complex128}{}`, `struct{x int; y int; z complex128}`},
  2214  	} {
  2215  		fset := token.NewFileSet()
  2216  		f := mustParse(fset, fmt.Sprintf("package p%d; var _ = %s", i, test.lit))
  2217  		types := make(map[ast.Expr]TypeAndValue)
  2218  		if _, err := new(Config).Check("p", fset, []*ast.File{f}, &Info{Types: types}); err != nil {
  2219  			t.Fatalf("%s: %v", test.lit, err)
  2220  		}
  2221  
  2222  		cmptype := func(x ast.Expr, want string) {
  2223  			tv, ok := types[x]
  2224  			if !ok {
  2225  				t.Errorf("%s: no Types entry found", test.lit)
  2226  				return
  2227  			}
  2228  			if tv.Type == nil {
  2229  				t.Errorf("%s: type is nil", test.lit)
  2230  				return
  2231  			}
  2232  			if got := tv.Type.String(); got != want {
  2233  				t.Errorf("%s: got %v, want %s", test.lit, got, want)
  2234  			}
  2235  		}
  2236  
  2237  		// test type of composite literal expression
  2238  		rhs := f.Decls[0].(*ast.GenDecl).Specs[0].(*ast.ValueSpec).Values[0]
  2239  		cmptype(rhs, test.typ)
  2240  
  2241  		// test type of composite literal type expression
  2242  		cmptype(rhs.(*ast.CompositeLit).Type, test.typ)
  2243  	}
  2244  }
  2245  
  2246  // TestObjectParents verifies that objects have parent scopes or not
  2247  // as specified by the Object interface.
  2248  func TestObjectParents(t *testing.T) {
  2249  	const src = `
  2250  package p
  2251  
  2252  const C = 0
  2253  
  2254  type T1 struct {
  2255  	a, b int
  2256  	T2
  2257  }
  2258  
  2259  type T2 interface {
  2260  	im1()
  2261  	im2()
  2262  }
  2263  
  2264  func (T1) m1() {}
  2265  func (*T1) m2() {}
  2266  
  2267  func f(x int) { y := x; print(y) }
  2268  `
  2269  
  2270  	fset := token.NewFileSet()
  2271  	f := mustParse(fset, src)
  2272  
  2273  	info := &Info{
  2274  		Defs: make(map[*ast.Ident]Object),
  2275  	}
  2276  	if _, err := new(Config).Check("p", fset, []*ast.File{f}, info); err != nil {
  2277  		t.Fatal(err)
  2278  	}
  2279  
  2280  	for ident, obj := range info.Defs {
  2281  		if obj == nil {
  2282  			// only package names and implicit vars have a nil object
  2283  			// (in this test we only need to handle the package name)
  2284  			if ident.Name != "p" {
  2285  				t.Errorf("%v has nil object", ident)
  2286  			}
  2287  			continue
  2288  		}
  2289  
  2290  		// struct fields, type-associated and interface methods
  2291  		// have no parent scope
  2292  		wantParent := true
  2293  		switch obj := obj.(type) {
  2294  		case *Var:
  2295  			if obj.IsField() {
  2296  				wantParent = false
  2297  			}
  2298  		case *Func:
  2299  			if obj.Signature().Recv() != nil { // method
  2300  				wantParent = false
  2301  			}
  2302  		}
  2303  
  2304  		gotParent := obj.Parent() != nil
  2305  		switch {
  2306  		case gotParent && !wantParent:
  2307  			t.Errorf("%v: want no parent, got %s", ident, obj.Parent())
  2308  		case !gotParent && wantParent:
  2309  			t.Errorf("%v: no parent found", ident)
  2310  		}
  2311  	}
  2312  }
  2313  
  2314  // TestFailedImport tests that we don't get follow-on errors
  2315  // elsewhere in a package due to failing to import a package.
  2316  func TestFailedImport(t *testing.T) {
  2317  	testenv.MustHaveGoBuild(t)
  2318  
  2319  	const src = `
  2320  package p
  2321  
  2322  import foo "go/types/thisdirectorymustnotexistotherwisethistestmayfail/foo" // should only see an error here
  2323  
  2324  const c = foo.C
  2325  type T = foo.T
  2326  var v T = c
  2327  func f(x T) T { return foo.F(x) }
  2328  `
  2329  	fset := token.NewFileSet()
  2330  	f := mustParse(fset, src)
  2331  	files := []*ast.File{f}
  2332  
  2333  	// type-check using all possible importers
  2334  	for _, compiler := range []string{"gc", "gccgo", "source"} {
  2335  		errcount := 0
  2336  		conf := Config{
  2337  			Error: func(err error) {
  2338  				// we should only see the import error
  2339  				if errcount > 0 || !strings.Contains(err.Error(), "could not import") {
  2340  					t.Errorf("for %s importer, got unexpected error: %v", compiler, err)
  2341  				}
  2342  				errcount++
  2343  			},
  2344  			Importer: importer.For(compiler, nil),
  2345  		}
  2346  
  2347  		info := &Info{
  2348  			Uses: make(map[*ast.Ident]Object),
  2349  		}
  2350  		pkg, _ := conf.Check("p", fset, files, info)
  2351  		if pkg == nil {
  2352  			t.Errorf("for %s importer, type-checking failed to return a package", compiler)
  2353  			continue
  2354  		}
  2355  
  2356  		imports := pkg.Imports()
  2357  		if len(imports) != 1 {
  2358  			t.Errorf("for %s importer, got %d imports, want 1", compiler, len(imports))
  2359  			continue
  2360  		}
  2361  		imp := imports[0]
  2362  		if imp.Name() != "foo" {
  2363  			t.Errorf(`for %s importer, got %q, want "foo"`, compiler, imp.Name())
  2364  			continue
  2365  		}
  2366  
  2367  		// verify that all uses of foo refer to the imported package foo (imp)
  2368  		for ident, obj := range info.Uses {
  2369  			if ident.Name == "foo" {
  2370  				if obj, ok := obj.(*PkgName); ok {
  2371  					if obj.Imported() != imp {
  2372  						t.Errorf("%s resolved to %v; want %v", ident, obj.Imported(), imp)
  2373  					}
  2374  				} else {
  2375  					t.Errorf("%s resolved to %v; want package name", ident, obj)
  2376  				}
  2377  			}
  2378  		}
  2379  	}
  2380  }
  2381  
  2382  func TestInstantiate(t *testing.T) {
  2383  	// eventually we like more tests but this is a start
  2384  	const src = "package p; type T[P any] *T[P]"
  2385  	pkg := mustTypecheck(src, nil, nil)
  2386  
  2387  	// type T should have one type parameter
  2388  	T := pkg.Scope().Lookup("T").Type().(*Named)
  2389  	if n := T.TypeParams().Len(); n != 1 {
  2390  		t.Fatalf("expected 1 type parameter; found %d", n)
  2391  	}
  2392  
  2393  	// instantiation should succeed (no endless recursion)
  2394  	// even with a nil *Checker
  2395  	res, err := Instantiate(nil, T, []Type{Typ[Int]}, false)
  2396  	if err != nil {
  2397  		t.Fatal(err)
  2398  	}
  2399  
  2400  	// instantiated type should point to itself
  2401  	if p := res.Underlying().(*Pointer).Elem(); p != res {
  2402  		t.Fatalf("unexpected result type: %s points to %s", res, p)
  2403  	}
  2404  }
  2405  
  2406  func TestInstantiateConcurrent(t *testing.T) {
  2407  	const src = `package p
  2408  
  2409  type I[P any] interface {
  2410  	m(P)
  2411  	n() P
  2412  }
  2413  
  2414  type J = I[int]
  2415  
  2416  type Nested[P any] *interface{b(P)}
  2417  
  2418  type K = Nested[string]
  2419  `
  2420  	pkg := mustTypecheck(src, nil, nil)
  2421  
  2422  	insts := []*Interface{
  2423  		pkg.Scope().Lookup("J").Type().Underlying().(*Interface),
  2424  		pkg.Scope().Lookup("K").Type().Underlying().(*Pointer).Elem().(*Interface),
  2425  	}
  2426  
  2427  	// Use the interface instances concurrently.
  2428  	for _, inst := range insts {
  2429  		var (
  2430  			counts  [2]int      // method counts
  2431  			methods [2][]string // method strings
  2432  		)
  2433  		var wg sync.WaitGroup
  2434  		for i := 0; i < 2; i++ {
  2435  			i := i
  2436  			wg.Add(1)
  2437  			go func() {
  2438  				defer wg.Done()
  2439  
  2440  				counts[i] = inst.NumMethods()
  2441  				for mi := 0; mi < counts[i]; mi++ {
  2442  					methods[i] = append(methods[i], inst.Method(mi).String())
  2443  				}
  2444  			}()
  2445  		}
  2446  		wg.Wait()
  2447  
  2448  		if counts[0] != counts[1] {
  2449  			t.Errorf("mismatching method counts for %s: %d vs %d", inst, counts[0], counts[1])
  2450  			continue
  2451  		}
  2452  		for i := 0; i < counts[0]; i++ {
  2453  			if m0, m1 := methods[0][i], methods[1][i]; m0 != m1 {
  2454  				t.Errorf("mismatching methods for %s: %s vs %s", inst, m0, m1)
  2455  			}
  2456  		}
  2457  	}
  2458  }
  2459  
  2460  func TestInstantiateErrors(t *testing.T) {
  2461  	tests := []struct {
  2462  		src    string // by convention, T must be the type being instantiated
  2463  		targs  []Type
  2464  		wantAt int // -1 indicates no error
  2465  	}{
  2466  		{"type T[P interface{~string}] int", []Type{Typ[Int]}, 0},
  2467  		{"type T[P1 interface{int}, P2 interface{~string}] int", []Type{Typ[Int], Typ[Int]}, 1},
  2468  		{"type T[P1 any, P2 interface{~[]P1}] int", []Type{Typ[Int], NewSlice(Typ[String])}, 1},
  2469  		{"type T[P1 interface{~[]P2}, P2 any] int", []Type{NewSlice(Typ[String]), Typ[Int]}, 0},
  2470  	}
  2471  
  2472  	for _, test := range tests {
  2473  		src := "package p; " + test.src
  2474  		pkg := mustTypecheck(src, nil, nil)
  2475  
  2476  		T := pkg.Scope().Lookup("T").Type().(*Named)
  2477  
  2478  		_, err := Instantiate(nil, T, test.targs, true)
  2479  		if err == nil {
  2480  			t.Fatalf("Instantiate(%v, %v) returned nil error, want non-nil", T, test.targs)
  2481  		}
  2482  
  2483  		var argErr *ArgumentError
  2484  		if !errors.As(err, &argErr) {
  2485  			t.Fatalf("Instantiate(%v, %v): error is not an *ArgumentError", T, test.targs)
  2486  		}
  2487  
  2488  		if argErr.Index != test.wantAt {
  2489  			t.Errorf("Instantiate(%v, %v): error at index %d, want index %d", T, test.targs, argErr.Index, test.wantAt)
  2490  		}
  2491  	}
  2492  }
  2493  
  2494  func TestArgumentErrorUnwrapping(t *testing.T) {
  2495  	var err error = &ArgumentError{
  2496  		Index: 1,
  2497  		Err:   Error{Msg: "test"},
  2498  	}
  2499  	var e Error
  2500  	if !errors.As(err, &e) {
  2501  		t.Fatalf("error %v does not wrap types.Error", err)
  2502  	}
  2503  	if e.Msg != "test" {
  2504  		t.Errorf("e.Msg = %q, want %q", e.Msg, "test")
  2505  	}
  2506  }
  2507  
  2508  func TestInstanceIdentity(t *testing.T) {
  2509  	imports := make(testImporter)
  2510  	conf := Config{Importer: imports}
  2511  	makePkg := func(src string) {
  2512  		fset := token.NewFileSet()
  2513  		f := mustParse(fset, src)
  2514  		name := f.Name.Name
  2515  		pkg, err := conf.Check(name, fset, []*ast.File{f}, nil)
  2516  		if err != nil {
  2517  			t.Fatal(err)
  2518  		}
  2519  		imports[name] = pkg
  2520  	}
  2521  	makePkg(`package lib; type T[P any] struct{}`)
  2522  	makePkg(`package a; import "lib"; var A lib.T[int]`)
  2523  	makePkg(`package b; import "lib"; var B lib.T[int]`)
  2524  	a := imports["a"].Scope().Lookup("A")
  2525  	b := imports["b"].Scope().Lookup("B")
  2526  	if !Identical(a.Type(), b.Type()) {
  2527  		t.Errorf("mismatching types: a.A: %s, b.B: %s", a.Type(), b.Type())
  2528  	}
  2529  }
  2530  
  2531  // TestInstantiatedObjects verifies properties of instantiated objects.
  2532  func TestInstantiatedObjects(t *testing.T) {
  2533  	const src = `
  2534  package p
  2535  
  2536  type T[P any] struct {
  2537  	field P
  2538  }
  2539  
  2540  func (recv *T[Q]) concreteMethod(mParam Q) (mResult Q) { return }
  2541  
  2542  type FT[P any] func(ftParam P) (ftResult P)
  2543  
  2544  func F[P any](fParam P) (fResult P){ return }
  2545  
  2546  type I[P any] interface {
  2547  	interfaceMethod(P)
  2548  }
  2549  
  2550  type R[P any] T[P]
  2551  
  2552  func (R[P]) m() {} // having a method triggers expansion of R
  2553  
  2554  var (
  2555  	t T[int]
  2556  	ft FT[int]
  2557  	f = F[int]
  2558  	i I[int]
  2559  )
  2560  
  2561  func fn() {
  2562  	var r R[int]
  2563  	_ = r
  2564  }
  2565  `
  2566  	info := &Info{
  2567  		Defs: make(map[*ast.Ident]Object),
  2568  	}
  2569  	fset := token.NewFileSet()
  2570  	f := mustParse(fset, src)
  2571  	conf := Config{}
  2572  	pkg, err := conf.Check(f.Name.Name, fset, []*ast.File{f}, info)
  2573  	if err != nil {
  2574  		t.Fatal(err)
  2575  	}
  2576  
  2577  	lookup := func(name string) Type { return pkg.Scope().Lookup(name).Type() }
  2578  	fnScope := pkg.Scope().Lookup("fn").(*Func).Scope()
  2579  
  2580  	tests := []struct {
  2581  		name string
  2582  		obj  Object
  2583  	}{
  2584  		// Struct fields
  2585  		{"field", lookup("t").Underlying().(*Struct).Field(0)},
  2586  		{"field", fnScope.Lookup("r").Type().Underlying().(*Struct).Field(0)},
  2587  
  2588  		// Methods and method fields
  2589  		{"concreteMethod", lookup("t").(*Named).Method(0)},
  2590  		{"recv", lookup("t").(*Named).Method(0).Signature().Recv()},
  2591  		{"mParam", lookup("t").(*Named).Method(0).Signature().Params().At(0)},
  2592  		{"mResult", lookup("t").(*Named).Method(0).Signature().Results().At(0)},
  2593  
  2594  		// Interface methods
  2595  		{"interfaceMethod", lookup("i").Underlying().(*Interface).Method(0)},
  2596  
  2597  		// Function type fields
  2598  		{"ftParam", lookup("ft").Underlying().(*Signature).Params().At(0)},
  2599  		{"ftResult", lookup("ft").Underlying().(*Signature).Results().At(0)},
  2600  
  2601  		// Function fields
  2602  		{"fParam", lookup("f").(*Signature).Params().At(0)},
  2603  		{"fResult", lookup("f").(*Signature).Results().At(0)},
  2604  	}
  2605  
  2606  	// Collect all identifiers by name.
  2607  	idents := make(map[string][]*ast.Ident)
  2608  	ast.Inspect(f, func(n ast.Node) bool {
  2609  		if id, ok := n.(*ast.Ident); ok {
  2610  			idents[id.Name] = append(idents[id.Name], id)
  2611  		}
  2612  		return true
  2613  	})
  2614  
  2615  	for _, test := range tests {
  2616  		test := test
  2617  		t.Run(test.name, func(t *testing.T) {
  2618  			if got := len(idents[test.name]); got != 1 {
  2619  				t.Fatalf("found %d identifiers named %s, want 1", got, test.name)
  2620  			}
  2621  			ident := idents[test.name][0]
  2622  			def := info.Defs[ident]
  2623  			if def == test.obj {
  2624  				t.Fatalf("info.Defs[%s] contains the test object", test.name)
  2625  			}
  2626  			if orig := originObject(test.obj); def != orig {
  2627  				t.Errorf("info.Defs[%s] does not match obj.Origin()", test.name)
  2628  			}
  2629  			if def.Pkg() != test.obj.Pkg() {
  2630  				t.Errorf("Pkg() = %v, want %v", def.Pkg(), test.obj.Pkg())
  2631  			}
  2632  			if def.Name() != test.obj.Name() {
  2633  				t.Errorf("Name() = %v, want %v", def.Name(), test.obj.Name())
  2634  			}
  2635  			if def.Pos() != test.obj.Pos() {
  2636  				t.Errorf("Pos() = %v, want %v", def.Pos(), test.obj.Pos())
  2637  			}
  2638  			if def.Parent() != test.obj.Parent() {
  2639  				t.Fatalf("Parent() = %v, want %v", def.Parent(), test.obj.Parent())
  2640  			}
  2641  			if def.Exported() != test.obj.Exported() {
  2642  				t.Fatalf("Exported() = %v, want %v", def.Exported(), test.obj.Exported())
  2643  			}
  2644  			if def.Id() != test.obj.Id() {
  2645  				t.Fatalf("Id() = %v, want %v", def.Id(), test.obj.Id())
  2646  			}
  2647  			// String and Type are expected to differ.
  2648  		})
  2649  	}
  2650  }
  2651  
  2652  func originObject(obj Object) Object {
  2653  	switch obj := obj.(type) {
  2654  	case *Var:
  2655  		return obj.Origin()
  2656  	case *Func:
  2657  		return obj.Origin()
  2658  	}
  2659  	return obj
  2660  }
  2661  
  2662  func TestImplements(t *testing.T) {
  2663  	const src = `
  2664  package p
  2665  
  2666  type EmptyIface interface{}
  2667  
  2668  type I interface {
  2669  	m()
  2670  }
  2671  
  2672  type C interface {
  2673  	m()
  2674  	~int
  2675  }
  2676  
  2677  type Integer interface{
  2678  	int8 | int16 | int32 | int64
  2679  }
  2680  
  2681  type EmptyTypeSet interface{
  2682  	Integer
  2683  	~string
  2684  }
  2685  
  2686  type N1 int
  2687  func (N1) m() {}
  2688  
  2689  type N2 int
  2690  func (*N2) m() {}
  2691  
  2692  type N3 int
  2693  func (N3) m(int) {}
  2694  
  2695  type N4 string
  2696  func (N4) m()
  2697  
  2698  type Bad Bad // invalid type
  2699  `
  2700  
  2701  	fset := token.NewFileSet()
  2702  	f := mustParse(fset, src)
  2703  	conf := Config{Error: func(error) {}}
  2704  	pkg, _ := conf.Check(f.Name.Name, fset, []*ast.File{f}, nil)
  2705  
  2706  	lookup := func(tname string) Type { return pkg.Scope().Lookup(tname).Type() }
  2707  	var (
  2708  		EmptyIface   = lookup("EmptyIface").Underlying().(*Interface)
  2709  		I            = lookup("I").(*Named)
  2710  		II           = I.Underlying().(*Interface)
  2711  		C            = lookup("C").(*Named)
  2712  		CI           = C.Underlying().(*Interface)
  2713  		Integer      = lookup("Integer").Underlying().(*Interface)
  2714  		EmptyTypeSet = lookup("EmptyTypeSet").Underlying().(*Interface)
  2715  		N1           = lookup("N1")
  2716  		N1p          = NewPointer(N1)
  2717  		N2           = lookup("N2")
  2718  		N2p          = NewPointer(N2)
  2719  		N3           = lookup("N3")
  2720  		N4           = lookup("N4")
  2721  		Bad          = lookup("Bad")
  2722  	)
  2723  
  2724  	tests := []struct {
  2725  		V    Type
  2726  		T    *Interface
  2727  		want bool
  2728  	}{
  2729  		{I, II, true},
  2730  		{I, CI, false},
  2731  		{C, II, true},
  2732  		{C, CI, true},
  2733  		{Typ[Int8], Integer, true},
  2734  		{Typ[Int64], Integer, true},
  2735  		{Typ[String], Integer, false},
  2736  		{EmptyTypeSet, II, true},
  2737  		{EmptyTypeSet, EmptyTypeSet, true},
  2738  		{Typ[Int], EmptyTypeSet, false},
  2739  		{N1, II, true},
  2740  		{N1, CI, true},
  2741  		{N1p, II, true},
  2742  		{N1p, CI, false},
  2743  		{N2, II, false},
  2744  		{N2, CI, false},
  2745  		{N2p, II, true},
  2746  		{N2p, CI, false},
  2747  		{N3, II, false},
  2748  		{N3, CI, false},
  2749  		{N4, II, true},
  2750  		{N4, CI, false},
  2751  		{Bad, II, false},
  2752  		{Bad, CI, false},
  2753  		{Bad, EmptyIface, true},
  2754  	}
  2755  
  2756  	for _, test := range tests {
  2757  		if got := Implements(test.V, test.T); got != test.want {
  2758  			t.Errorf("Implements(%s, %s) = %t, want %t", test.V, test.T, got, test.want)
  2759  		}
  2760  
  2761  		// The type assertion x.(T) is valid if T is an interface or if T implements the type of x.
  2762  		// The assertion is never valid if T is a bad type.
  2763  		V := test.T
  2764  		T := test.V
  2765  		want := false
  2766  		if _, ok := T.Underlying().(*Interface); (ok || Implements(T, V)) && T != Bad {
  2767  			want = true
  2768  		}
  2769  		if got := AssertableTo(V, T); got != want {
  2770  			t.Errorf("AssertableTo(%s, %s) = %t, want %t", V, T, got, want)
  2771  		}
  2772  	}
  2773  }
  2774  
  2775  func TestMissingMethodAlternative(t *testing.T) {
  2776  	const src = `
  2777  package p
  2778  type T interface {
  2779  	m()
  2780  }
  2781  
  2782  type V0 struct{}
  2783  func (V0) m() {}
  2784  
  2785  type V1 struct{}
  2786  
  2787  type V2 struct{}
  2788  func (V2) m() int
  2789  
  2790  type V3 struct{}
  2791  func (*V3) m()
  2792  
  2793  type V4 struct{}
  2794  func (V4) M()
  2795  `
  2796  
  2797  	pkg := mustTypecheck(src, nil, nil)
  2798  
  2799  	T := pkg.Scope().Lookup("T").Type().Underlying().(*Interface)
  2800  	lookup := func(name string) (*Func, bool) {
  2801  		return MissingMethod(pkg.Scope().Lookup(name).Type(), T, true)
  2802  	}
  2803  
  2804  	// V0 has method m with correct signature. Should not report wrongType.
  2805  	method, wrongType := lookup("V0")
  2806  	if method != nil || wrongType {
  2807  		t.Fatalf("V0: got method = %v, wrongType = %v", method, wrongType)
  2808  	}
  2809  
  2810  	checkMissingMethod := func(tname string, reportWrongType bool) {
  2811  		method, wrongType := lookup(tname)
  2812  		if method == nil || method.Name() != "m" || wrongType != reportWrongType {
  2813  			t.Fatalf("%s: got method = %v, wrongType = %v", tname, method, wrongType)
  2814  		}
  2815  	}
  2816  
  2817  	// V1 has no method m. Should not report wrongType.
  2818  	checkMissingMethod("V1", false)
  2819  
  2820  	// V2 has method m with wrong signature type (ignoring receiver). Should report wrongType.
  2821  	checkMissingMethod("V2", true)
  2822  
  2823  	// V3 has no method m but it exists on *V3. Should report wrongType.
  2824  	checkMissingMethod("V3", true)
  2825  
  2826  	// V4 has no method m but has M. Should not report wrongType.
  2827  	checkMissingMethod("V4", false)
  2828  }
  2829  
  2830  func TestErrorURL(t *testing.T) {
  2831  	var conf Config
  2832  	*stringFieldAddr(&conf, "_ErrorURL") = " [go.dev/e/%s]"
  2833  
  2834  	// test case for a one-line error
  2835  	const src1 = `
  2836  package p
  2837  var _ T
  2838  `
  2839  	_, err := typecheck(src1, &conf, nil)
  2840  	if err == nil || !strings.HasSuffix(err.Error(), " [go.dev/e/UndeclaredName]") {
  2841  		t.Errorf("src1: unexpected error: got %v", err)
  2842  	}
  2843  
  2844  	// test case for a multi-line error
  2845  	const src2 = `
  2846  package p
  2847  func f() int { return 0 }
  2848  var _ = f(1, 2)
  2849  `
  2850  	_, err = typecheck(src2, &conf, nil)
  2851  	if err == nil || !strings.Contains(err.Error(), " [go.dev/e/WrongArgCount]\n") {
  2852  		t.Errorf("src1: unexpected error: got %v", err)
  2853  	}
  2854  }
  2855  
  2856  func TestModuleVersion(t *testing.T) {
  2857  	// version go1.dd must be able to typecheck go1.dd.0, go1.dd.1, etc.
  2858  	goversion := fmt.Sprintf("go1.%d", goversion.Version)
  2859  	for _, v := range []string{
  2860  		goversion,
  2861  		goversion + ".0",
  2862  		goversion + ".1",
  2863  		goversion + ".rc",
  2864  	} {
  2865  		conf := Config{GoVersion: v}
  2866  		pkg := mustTypecheck("package p", &conf, nil)
  2867  		if pkg.GoVersion() != conf.GoVersion {
  2868  			t.Errorf("got %s; want %s", pkg.GoVersion(), conf.GoVersion)
  2869  		}
  2870  	}
  2871  }
  2872  
  2873  func TestFileVersions(t *testing.T) {
  2874  	for _, test := range []struct {
  2875  		goVersion   string
  2876  		fileVersion string
  2877  		wantVersion string
  2878  	}{
  2879  		{"", "", ""},                    // no versions specified
  2880  		{"go1.19", "", "go1.19"},        // module version specified
  2881  		{"", "go1.20", "go1.21"},        // file version specified below minimum of 1.21
  2882  		{"go1", "", "go1"},              // no file version specified
  2883  		{"go1", "goo1.22", "go1"},       // invalid file version specified
  2884  		{"go1", "go1.19", "go1.21"},     // file version specified below minimum of 1.21
  2885  		{"go1", "go1.20", "go1.21"},     // file version specified below minimum of 1.21
  2886  		{"go1", "go1.21", "go1.21"},     // file version specified at 1.21
  2887  		{"go1", "go1.22", "go1.22"},     // file version specified above 1.21
  2888  		{"go1.19", "", "go1.19"},        // no file version specified
  2889  		{"go1.19", "goo1.22", "go1.19"}, // invalid file version specified
  2890  		{"go1.19", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2891  		{"go1.19", "go1.21", "go1.21"},  // file version specified at 1.21
  2892  		{"go1.19", "go1.22", "go1.22"},  // file version specified above 1.21
  2893  		{"go1.20", "", "go1.20"},        // no file version specified
  2894  		{"go1.20", "goo1.22", "go1.20"}, // invalid file version specified
  2895  		{"go1.20", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
  2896  		{"go1.20", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2897  		{"go1.20", "go1.21", "go1.21"},  // file version specified at 1.21
  2898  		{"go1.20", "go1.22", "go1.22"},  // file version specified above 1.21
  2899  		{"go1.21", "", "go1.21"},        // no file version specified
  2900  		{"go1.21", "goo1.22", "go1.21"}, // invalid file version specified
  2901  		{"go1.21", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
  2902  		{"go1.21", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2903  		{"go1.21", "go1.21", "go1.21"},  // file version specified at 1.21
  2904  		{"go1.21", "go1.22", "go1.22"},  // file version specified above 1.21
  2905  		{"go1.22", "", "go1.22"},        // no file version specified
  2906  		{"go1.22", "goo1.22", "go1.22"}, // invalid file version specified
  2907  		{"go1.22", "go1.19", "go1.21"},  // file version specified below minimum of 1.21
  2908  		{"go1.22", "go1.20", "go1.21"},  // file version specified below minimum of 1.21
  2909  		{"go1.22", "go1.21", "go1.21"},  // file version specified at 1.21
  2910  		{"go1.22", "go1.22", "go1.22"},  // file version specified above 1.21
  2911  
  2912  		// versions containing release numbers
  2913  		// (file versions containing release numbers are considered invalid)
  2914  		{"go1.19.0", "", "go1.19.0"},         // no file version specified
  2915  		{"go1.20.1", "go1.19.1", "go1.20.1"}, // invalid file version
  2916  		{"go1.20.1", "go1.21.1", "go1.20.1"}, // invalid file version
  2917  		{"go1.21.1", "go1.19.1", "go1.21.1"}, // invalid file version
  2918  		{"go1.21.1", "go1.21.1", "go1.21.1"}, // invalid file version
  2919  		{"go1.22.1", "go1.19.1", "go1.22.1"}, // invalid file version
  2920  		{"go1.22.1", "go1.21.1", "go1.22.1"}, // invalid file version
  2921  	} {
  2922  		var src string
  2923  		if test.fileVersion != "" {
  2924  			src = "//go:build " + test.fileVersion + "\n"
  2925  		}
  2926  		src += "package p"
  2927  
  2928  		conf := Config{GoVersion: test.goVersion}
  2929  		versions := make(map[*ast.File]string)
  2930  		var info Info
  2931  		info.FileVersions = versions
  2932  		mustTypecheck(src, &conf, &info)
  2933  
  2934  		n := 0
  2935  		for _, v := range versions {
  2936  			want := test.wantVersion
  2937  			if v != want {
  2938  				t.Errorf("%q: unexpected file version: got %q, want %q", src, v, want)
  2939  			}
  2940  			n++
  2941  		}
  2942  		if n != 1 {
  2943  			t.Errorf("%q: incorrect number of map entries: got %d", src, n)
  2944  		}
  2945  	}
  2946  }
  2947  
  2948  // TestTooNew ensures that "too new" errors are emitted when the file
  2949  // or module is tagged with a newer version of Go than this go/types.
  2950  func TestTooNew(t *testing.T) {
  2951  	for _, test := range []struct {
  2952  		goVersion   string // package's Go version (as if derived from go.mod file)
  2953  		fileVersion string // file's Go version (becomes a build tag)
  2954  		wantErr     string // expected substring of concatenation of all errors
  2955  	}{
  2956  		{"go1.98", "", "package requires newer Go version go1.98"},
  2957  		{"", "go1.99", "p:2:9: file requires newer Go version go1.99"},
  2958  		{"go1.98", "go1.99", "package requires newer Go version go1.98"}, // (two
  2959  		{"go1.98", "go1.99", "file requires newer Go version go1.99"},    // errors)
  2960  	} {
  2961  		var src string
  2962  		if test.fileVersion != "" {
  2963  			src = "//go:build " + test.fileVersion + "\n"
  2964  		}
  2965  		src += "package p; func f()"
  2966  
  2967  		var errs []error
  2968  		conf := Config{
  2969  			GoVersion: test.goVersion,
  2970  			Error:     func(err error) { errs = append(errs, err) },
  2971  		}
  2972  		info := &Info{Defs: make(map[*ast.Ident]Object)}
  2973  		typecheck(src, &conf, info)
  2974  		got := fmt.Sprint(errs)
  2975  		if !strings.Contains(got, test.wantErr) {
  2976  			t.Errorf("%q: unexpected error: got %q, want substring %q",
  2977  				src, got, test.wantErr)
  2978  		}
  2979  
  2980  		// Assert that declarations were type checked nonetheless.
  2981  		var gotObjs []string
  2982  		for id, obj := range info.Defs {
  2983  			if obj != nil {
  2984  				objStr := strings.ReplaceAll(fmt.Sprintf("%s:%T", id.Name, obj), "types2", "types")
  2985  				gotObjs = append(gotObjs, objStr)
  2986  			}
  2987  		}
  2988  		wantObjs := "f:*types.Func"
  2989  		if !strings.Contains(fmt.Sprint(gotObjs), wantObjs) {
  2990  			t.Errorf("%q: got %s, want substring %q",
  2991  				src, gotObjs, wantObjs)
  2992  		}
  2993  	}
  2994  }
  2995  
  2996  // This is a regression test for #66704.
  2997  func TestUnaliasTooSoonInCycle(t *testing.T) {
  2998  	setGotypesalias(t, true)
  2999  	const src = `package a
  3000  
  3001  var x T[B] // this appears to cause Unalias to be called on B while still Invalid
  3002  
  3003  type T[_ any] struct{}
  3004  type A T[B]
  3005  type B = T[A]
  3006  `
  3007  	pkg := mustTypecheck(src, nil, nil)
  3008  	B := pkg.Scope().Lookup("B")
  3009  
  3010  	got, want := Unalias(B.Type()).String(), "a.T[a.A]"
  3011  	if got != want {
  3012  		t.Errorf("Unalias(type B = T[A]) = %q, want %q", got, want)
  3013  	}
  3014  }
  3015  
  3016  func TestAlias_Rhs(t *testing.T) {
  3017  	setGotypesalias(t, true)
  3018  	const src = `package p
  3019  
  3020  type A = B
  3021  type B = C
  3022  type C = int
  3023  `
  3024  
  3025  	pkg := mustTypecheck(src, nil, nil)
  3026  	A := pkg.Scope().Lookup("A")
  3027  
  3028  	got, want := A.Type().(*Alias).Rhs().String(), "p.B"
  3029  	if got != want {
  3030  		t.Errorf("A.Rhs = %s, want %s", got, want)
  3031  	}
  3032  }
  3033  
  3034  // Test the hijacking described of "any" described in golang/go#66921, for type
  3035  // checking.
  3036  func TestAnyHijacking_Check(t *testing.T) {
  3037  	for _, enableAlias := range []bool{false, true} {
  3038  		t.Run(fmt.Sprintf("EnableAlias=%t", enableAlias), func(t *testing.T) {
  3039  			setGotypesalias(t, enableAlias)
  3040  			var wg sync.WaitGroup
  3041  			for i := 0; i < 10; i++ {
  3042  				wg.Add(1)
  3043  				go func() {
  3044  					defer wg.Done()
  3045  					pkg := mustTypecheck("package p; var x any", nil, nil)
  3046  					x := pkg.Scope().Lookup("x")
  3047  					if _, gotAlias := x.Type().(*Alias); gotAlias != enableAlias {
  3048  						t.Errorf(`Lookup("x").Type() is %T: got Alias: %t, want %t`, x.Type(), gotAlias, enableAlias)
  3049  					}
  3050  				}()
  3051  			}
  3052  			wg.Wait()
  3053  		})
  3054  	}
  3055  }
  3056  
  3057  // Test the hijacking described of "any" described in golang/go#66921, for
  3058  // Scope.Lookup outside of type checking.
  3059  func TestAnyHijacking_Lookup(t *testing.T) {
  3060  	for _, enableAlias := range []bool{false, true} {
  3061  		t.Run(fmt.Sprintf("EnableAlias=%t", enableAlias), func(t *testing.T) {
  3062  			setGotypesalias(t, enableAlias)
  3063  			a := Universe.Lookup("any")
  3064  			if _, gotAlias := a.Type().(*Alias); gotAlias != enableAlias {
  3065  				t.Errorf(`Lookup("x").Type() is %T: got Alias: %t, want %t`, a.Type(), gotAlias, enableAlias)
  3066  			}
  3067  		})
  3068  	}
  3069  }
  3070  
  3071  func setGotypesalias(t *testing.T, enable bool) {
  3072  	if enable {
  3073  		t.Setenv("GODEBUG", "gotypesalias=1")
  3074  	} else {
  3075  		t.Setenv("GODEBUG", "gotypesalias=0")
  3076  	}
  3077  }
  3078  
  3079  // TestVersionIssue69477 is a regression test for issue #69477,
  3080  // in which the type checker would panic while attempting
  3081  // to compute which file it is "in" based on syntax position.
  3082  func TestVersionIssue69477(t *testing.T) {
  3083  	fset := token.NewFileSet()
  3084  	f, _ := parser.ParseFile(fset, "a.go", "package p; const k = 123", 0)
  3085  
  3086  	// Set an invalid Pos on the BasicLit.
  3087  	ast.Inspect(f, func(n ast.Node) bool {
  3088  		if lit, ok := n.(*ast.BasicLit); ok {
  3089  			lit.ValuePos = 99999
  3090  		}
  3091  		return true
  3092  	})
  3093  
  3094  	// Type check. The checker will consult the effective
  3095  	// version for the BasicLit 123. This used to panic.
  3096  	pkg := NewPackage("p", "p")
  3097  	check := NewChecker(&Config{}, fset, pkg, nil)
  3098  	if err := check.Files([]*ast.File{f}); err != nil {
  3099  		t.Fatal(err)
  3100  	}
  3101  }
  3102  
  3103  // TestVersionWithoutPos is a regression test for issue #69477,
  3104  // in which the type checker would use position information
  3105  // to compute which file it is "in" based on syntax position.
  3106  //
  3107  // As a rule the type checker should not depend on position
  3108  // information for correctness, only for error messages and
  3109  // Object.Pos. (Scope.LookupParent was a mistake.)
  3110  //
  3111  // The Checker now holds the effective version in a state variable.
  3112  func TestVersionWithoutPos(t *testing.T) {
  3113  	fset := token.NewFileSet()
  3114  	f, _ := parser.ParseFile(fset, "a.go", "//go:build go1.22\n\npackage p; var _ int", 0)
  3115  
  3116  	// Splice in a decl from another file. Its pos will be wrong.
  3117  	f2, _ := parser.ParseFile(fset, "a.go", "package q; func _(s func(func() bool)) { for range s {} }", 0)
  3118  	f.Decls[0] = f2.Decls[0]
  3119  
  3120  	// Type check. The checker will consult the effective
  3121  	// version (1.22) for the for-range stmt to know whether
  3122  	// range-over-func are permitted: they are not.
  3123  	// (Previously, no error was reported.)
  3124  	pkg := NewPackage("p", "p")
  3125  	check := NewChecker(&Config{}, fset, pkg, nil)
  3126  	err := check.Files([]*ast.File{f})
  3127  	got := fmt.Sprint(err)
  3128  	want := "range over s (variable of type func(func() bool)): requires go1.23"
  3129  	if !strings.Contains(got, want) {
  3130  		t.Errorf("check error was %q, want substring %q", got, want)
  3131  	}
  3132  }
  3133  
  3134  func TestVarKind(t *testing.T) {
  3135  	fset := token.NewFileSet()
  3136  	f, _ := parser.ParseFile(fset, "a.go", `package p
  3137  
  3138  var global int
  3139  
  3140  type T struct { field int }
  3141  
  3142  func (recv T) f(param int) (result int) {
  3143  	var local int
  3144  	local2 := 0
  3145  	switch local3 := any(local).(type) {
  3146  	default:
  3147  		_ = local3
  3148  	}
  3149  	return local2
  3150  }
  3151  `, 0)
  3152  
  3153  	pkg := NewPackage("p", "p")
  3154  	info := &Info{Defs: make(map[*ast.Ident]Object)}
  3155  	check := NewChecker(&Config{}, fset, pkg, info)
  3156  	if err := check.Files([]*ast.File{f}); err != nil {
  3157  		t.Fatal(err)
  3158  	}
  3159  	var got []string
  3160  	for _, obj := range info.Defs {
  3161  		if v, ok := obj.(*Var); ok {
  3162  			got = append(got, fmt.Sprintf("%s: %v", v.Name(), v.Kind()))
  3163  		}
  3164  	}
  3165  	sort.Strings(got)
  3166  	want := []string{
  3167  		"field: FieldVar",
  3168  		"global: PackageVar",
  3169  		"local2: LocalVar",
  3170  		"local: LocalVar",
  3171  		"param: ParamVar",
  3172  		"recv: RecvVar",
  3173  		"result: ResultVar",
  3174  	}
  3175  	if !slices.Equal(got, want) {
  3176  		t.Errorf("got:\n%s\nwant:\n%s", got, want)
  3177  	}
  3178  }
  3179  

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