Updates for go.mod

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

vendor/golang.org/x/tools/internal/aliases/aliases.go

@@ -0,0 +1,28 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package aliases
+
+import (
+	"go/token"
+	"go/types"
+)
+
+// Package aliases defines backward compatible shims
+// for the types.Alias type representation added in 1.22.
+// This defines placeholders for x/tools until 1.26.
+
+// NewAlias creates a new TypeName in Package pkg that
+// is an alias for the type rhs.
+//
+// When GoVersion>=1.22 and GODEBUG=gotypesalias=1,
+// the Type() of the return value is a *types.Alias.
+func NewAlias(pos token.Pos, pkg *types.Package, name string, rhs types.Type) *types.TypeName {
+	if enabled() {
+		tname := types.NewTypeName(pos, pkg, name, nil)
+		newAlias(tname, rhs)
+		return tname
+	}
+	return types.NewTypeName(pos, pkg, name, rhs)
+}

vendor/golang.org/x/tools/internal/aliases/aliases_go121.go

@@ -0,0 +1,30 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !go1.22
+// +build !go1.22
+
+package aliases
+
+import (
+	"go/types"
+)
+
+// Alias is a placeholder for a go/types.Alias for <=1.21.
+// It will never be created by go/types.
+type Alias struct{}
+
+func (*Alias) String() string { panic("unreachable") }
+
+func (*Alias) Underlying() types.Type { panic("unreachable") }
+
+func (*Alias) Obj() *types.TypeName { panic("unreachable") }
+
+// Unalias returns the type t for go <=1.21.
+func Unalias(t types.Type) types.Type { return t }
+
+// Always false for go <=1.21. Ignores GODEBUG.
+func enabled() bool { return false }
+
+func newAlias(name *types.TypeName, rhs types.Type) *Alias { panic("unreachable") }

vendor/golang.org/x/tools/internal/aliases/aliases_go122.go

@@ -0,0 +1,72 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.22
+// +build go1.22
+
+package aliases
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"go/types"
+	"os"
+	"strings"
+	"sync"
+)
+
+// Alias is an alias of types.Alias.
+type Alias = types.Alias
+
+// Unalias is a wrapper of types.Unalias.
+func Unalias(t types.Type) types.Type { return types.Unalias(t) }
+
+// newAlias is an internal alias around types.NewAlias.
+// Direct usage is discouraged as the moment.
+// Try to use NewAlias instead.
+func newAlias(tname *types.TypeName, rhs types.Type) *Alias {
+	a := types.NewAlias(tname, rhs)
+	// TODO(go.dev/issue/65455): Remove kludgy workaround to set a.actual as a side-effect.
+	Unalias(a)
+	return a
+}
+
+// enabled returns true when types.Aliases are enabled.
+func enabled() bool {
+	// Use the gotypesalias value in GODEBUG if set.
+	godebug := os.Getenv("GODEBUG")
+	value := -1 // last set value.
+	for _, f := range strings.Split(godebug, ",") {
+		switch f {
+		case "gotypesalias=1":
+			value = 1
+		case "gotypesalias=0":
+			value = 0
+		}
+	}
+	switch value {
+	case 0:
+		return false
+	case 1:
+		return true
+	default:
+		return aliasesDefault()
+	}
+}
+
+// aliasesDefault reports if aliases are enabled by default.
+func aliasesDefault() bool {
+	// Dynamically check if Aliases will be produced from go/types.
+	aliasesDefaultOnce.Do(func() {
+		fset := token.NewFileSet()
+		f, _ := parser.ParseFile(fset, "a.go", "package p; type A = int", 0)
+		pkg, _ := new(types.Config).Check("p", fset, []*ast.File{f}, nil)
+		_, gotypesaliasDefault = pkg.Scope().Lookup("A").Type().(*types.Alias)
+	})
+	return gotypesaliasDefault
+}
+
+var gotypesaliasDefault bool
+var aliasesDefaultOnce sync.Once

vendor/golang.org/x/tools/internal/gcimporter/gcimporter.go

@@ -259,13 +259,6 @@ func Import(packages map[string]*types.Package, path, srcDir string, lookup func
 	return
 }
 
-func deref(typ types.Type) types.Type {
-	if p, _ := typ.(*types.Pointer); p != nil {
-		return p.Elem()
-	}
-	return typ
-}
-
 type byPath []*types.Package
 
 func (a byPath) Len() int           { return len(a) }

vendor/golang.org/x/tools/internal/gcimporter/iexport.go

@@ -23,6 +23,7 @@ import (
 	"strings"
 
 	"golang.org/x/tools/go/types/objectpath"
+	"golang.org/x/tools/internal/aliases"
 	"golang.org/x/tools/internal/tokeninternal"
 )
 
@@ -506,13 +507,13 @@ func (p *iexporter) doDecl(obj types.Object) {
 	case *types.TypeName:
 		t := obj.Type()
 
-		if tparam, ok := t.(*types.TypeParam); ok {
+		if tparam, ok := aliases.Unalias(t).(*types.TypeParam); ok {
 			w.tag('P')
 			w.pos(obj.Pos())
 			constraint := tparam.Constraint()
 			if p.version >= iexportVersionGo1_18 {
 				implicit := false
-				if iface, _ := constraint.(*types.Interface); iface != nil {
+				if iface, _ := aliases.Unalias(constraint).(*types.Interface); iface != nil {
 					implicit = iface.IsImplicit()
 				}
 				w.bool(implicit)
@@ -738,6 +739,8 @@ func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
 		}()
 	}
 	switch t := t.(type) {
+	// TODO(adonovan): support types.Alias.
+
 	case *types.Named:
 		if targs := t.TypeArgs(); targs.Len() > 0 {
 			w.startType(instanceType)
@@ -843,7 +846,7 @@ func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
 		for i := 0; i < n; i++ {
 			ft := t.EmbeddedType(i)
 			tPkg := pkg
-			if named, _ := ft.(*types.Named); named != nil {
+			if named, _ := aliases.Unalias(ft).(*types.Named); named != nil {
 				w.pos(named.Obj().Pos())
 			} else {
 				w.pos(token.NoPos)

vendor/golang.org/x/tools/internal/gcimporter/iimport.go

@@ -22,6 +22,8 @@ import (
 	"strings"
 
 	"golang.org/x/tools/go/types/objectpath"
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 type intReader struct {
@@ -224,6 +226,7 @@ func iimportCommon(fset *token.FileSet, getPackages GetPackagesFunc, data []byte
 
 	// Gather the relevant packages from the manifest.
 	items := make([]GetPackagesItem, r.uint64())
+	uniquePkgPaths := make(map[string]bool)
 	for i := range items {
 		pkgPathOff := r.uint64()
 		pkgPath := p.stringAt(pkgPathOff)
@@ -248,6 +251,12 @@ func iimportCommon(fset *token.FileSet, getPackages GetPackagesFunc, data []byte
 		}
 
 		items[i].nameIndex = nameIndex
+
+		uniquePkgPaths[pkgPath] = true
+	}
+	// Debugging #63822; hypothesis: there are duplicate PkgPaths.
+	if len(uniquePkgPaths) != len(items) {
+		reportf("found duplicate PkgPaths while reading export data manifest: %v", items)
 	}
 
 	// Request packages all at once from the client,
@@ -515,7 +524,7 @@ func canReuse(def *types.Named, rhs types.Type) bool {
 	if def == nil {
 		return true
 	}
-	iface, _ := rhs.(*types.Interface)
+	iface, _ := aliases.Unalias(rhs).(*types.Interface)
 	if iface == nil {
 		return true
 	}
@@ -580,14 +589,13 @@ func (r *importReader) obj(name string) {
 				// If the receiver has any targs, set those as the
 				// rparams of the method (since those are the
 				// typeparams being used in the method sig/body).
-				base := baseType(recv.Type())
-				assert(base != nil)
-				targs := base.TypeArgs()
+				_, recvNamed := typesinternal.ReceiverNamed(recv)
+				targs := recvNamed.TypeArgs()
 				var rparams []*types.TypeParam
 				if targs.Len() > 0 {
 					rparams = make([]*types.TypeParam, targs.Len())
 					for i := range rparams {
-						rparams[i] = targs.At(i).(*types.TypeParam)
+						rparams[i] = aliases.Unalias(targs.At(i)).(*types.TypeParam)
 					}
 				}
 				msig := r.signature(recv, rparams, nil)
@@ -617,7 +625,7 @@ func (r *importReader) obj(name string) {
 		}
 		constraint := r.typ()
 		if implicit {
-			iface, _ := constraint.(*types.Interface)
+			iface, _ := aliases.Unalias(constraint).(*types.Interface)
 			if iface == nil {
 				errorf("non-interface constraint marked implicit")
 			}
@@ -824,7 +832,7 @@ func (r *importReader) typ() types.Type {
 }
 
 func isInterface(t types.Type) bool {
-	_, ok := t.(*types.Interface)
+	_, ok := aliases.Unalias(t).(*types.Interface)
 	return ok
 }
 
@@ -1023,7 +1031,7 @@ func (r *importReader) tparamList() []*types.TypeParam {
 	for i := range xs {
 		// Note: the standard library importer is tolerant of nil types here,
 		// though would panic in SetTypeParams.
-		xs[i] = r.typ().(*types.TypeParam)
+		xs[i] = aliases.Unalias(r.typ()).(*types.TypeParam)
 	}
 	return xs
 }
@@ -1070,13 +1078,3 @@ func (r *importReader) byte() byte {
 	}
 	return x
 }
-
-func baseType(typ types.Type) *types.Named {
-	// pointer receivers are never types.Named types
-	if p, _ := typ.(*types.Pointer); p != nil {
-		typ = p.Elem()
-	}
-	// receiver base types are always (possibly generic) types.Named types
-	n, _ := typ.(*types.Named)
-	return n
-}

vendor/golang.org/x/tools/internal/gcimporter/support_go117.go

@@ -1,16 +0,0 @@
-// Copyright 2021 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.18
-// +build !go1.18
-
-package gcimporter
-
-import "go/types"
-
-const iexportVersion = iexportVersionGo1_11
-
-func additionalPredeclared() []types.Type {
-	return nil
-}

vendor/golang.org/x/tools/internal/gcimporter/support_go118.go

@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.18
-// +build go1.18
-
 package gcimporter
 
 import "go/types"

vendor/golang.org/x/tools/internal/gcimporter/unified_no.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !(go1.18 && goexperiment.unified)
-// +build !go1.18 !goexperiment.unified
+//go:build !goexperiment.unified
+// +build !goexperiment.unified
 
 package gcimporter
 

vendor/golang.org/x/tools/internal/gcimporter/unified_yes.go

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.18 && goexperiment.unified
-// +build go1.18,goexperiment.unified
+//go:build goexperiment.unified
+// +build goexperiment.unified
 
 package gcimporter
 

vendor/golang.org/x/tools/internal/gcimporter/ureader_no.go

@@ -1,19 +0,0 @@
-// Copyright 2022 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.18
-// +build !go1.18
-
-package gcimporter
-
-import (
-	"fmt"
-	"go/token"
-	"go/types"
-)
-
-func UImportData(fset *token.FileSet, imports map[string]*types.Package, data []byte, path string) (_ int, pkg *types.Package, err error) {
-	err = fmt.Errorf("go/tools compiled with a Go version earlier than 1.18 cannot read unified IR export data")
-	return
-}

vendor/golang.org/x/tools/internal/gcimporter/ureader_yes.go

@@ -4,9 +4,6 @@
 
 // Derived from go/internal/gcimporter/ureader.go
 
-//go:build go1.18
-// +build go1.18
-
 package gcimporter
 
 import (
@@ -16,6 +13,7 @@ import (
 	"sort"
 	"strings"
 
+	"golang.org/x/tools/internal/aliases"
 	"golang.org/x/tools/internal/pkgbits"
 )
 
@@ -553,7 +551,7 @@ func (pr *pkgReader) objIdx(idx pkgbits.Index) (*types.Package, string) {
 				// If the underlying type is an interface, we need to
 				// duplicate its methods so we can replace the receiver
 				// parameter's type (#49906).
-				if iface, ok := underlying.(*types.Interface); ok && iface.NumExplicitMethods() != 0 {
+				if iface, ok := aliases.Unalias(underlying).(*types.Interface); ok && iface.NumExplicitMethods() != 0 {
 					methods := make([]*types.Func, iface.NumExplicitMethods())
 					for i := range methods {
 						fn := iface.ExplicitMethod(i)

vendor/golang.org/x/tools/internal/tokeninternal/tokeninternal.go

@@ -34,30 +34,16 @@ func GetLines(file *token.File) []int {
 		lines []int
 		_     []struct{}
 	}
-	type tokenFile118 struct {
-		_ *token.FileSet // deleted in go1.19
-		tokenFile119
-	}
 
-	type uP = unsafe.Pointer
-	switch unsafe.Sizeof(*file) {
-	case unsafe.Sizeof(tokenFile118{}):
-		var ptr *tokenFile118
-		*(*uP)(uP(&ptr)) = uP(file)
-		ptr.mu.Lock()
-		defer ptr.mu.Unlock()
-		return ptr.lines
-
-	case unsafe.Sizeof(tokenFile119{}):
-		var ptr *tokenFile119
-		*(*uP)(uP(&ptr)) = uP(file)
-		ptr.mu.Lock()
-		defer ptr.mu.Unlock()
-		return ptr.lines
-
-	default:
+	if unsafe.Sizeof(*file) != unsafe.Sizeof(tokenFile119{}) {
 		panic("unexpected token.File size")
 	}
+	var ptr *tokenFile119
+	type uP = unsafe.Pointer
+	*(*uP)(uP(&ptr)) = uP(file)
+	ptr.mu.Lock()
+	defer ptr.mu.Unlock()
+	return ptr.lines
 }
 
 // AddExistingFiles adds the specified files to the FileSet if they

vendor/golang.org/x/tools/internal/typeparams/common.go

@@ -2,20 +2,10 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package typeparams contains common utilities for writing tools that interact
-// with generic Go code, as introduced with Go 1.18.
-//
-// Many of the types and functions in this package are proxies for the new APIs
-// introduced in the standard library with Go 1.18. For example, the
-// typeparams.Union type is an alias for go/types.Union, and the ForTypeSpec
-// function returns the value of the go/ast.TypeSpec.TypeParams field. At Go
-// versions older than 1.18 these helpers are implemented as stubs, allowing
-// users of this package to write code that handles generic constructs inline,
-// even if the Go version being used to compile does not support generics.
-//
-// Additionally, this package contains common utilities for working with the
-// new generic constructs, to supplement the standard library APIs. Notably,
-// the StructuralTerms API computes a minimal representation of the structural
+// Package typeparams contains common utilities for writing tools that
+// interact with generic Go code, as introduced with Go 1.18. It
+// supplements the standard library APIs. Notably, the StructuralTerms
+// API computes a minimal representation of the structural
 // restrictions on a type parameter.
 //
 // An external version of these APIs is available in the
@@ -27,6 +17,9 @@ import (
 	"go/ast"
 	"go/token"
 	"go/types"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 // UnpackIndexExpr extracts data from AST nodes that represent index
@@ -72,9 +65,9 @@ func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack toke
 	}
 }
 
-// IsTypeParam reports whether t is a type parameter.
+// IsTypeParam reports whether t is a type parameter (or an alias of one).
 func IsTypeParam(t types.Type) bool {
-	_, ok := t.(*types.TypeParam)
+	_, ok := aliases.Unalias(t).(*types.TypeParam)
 	return ok
 }
 
@@ -90,13 +83,8 @@ func OriginMethod(fn *types.Func) *types.Func {
 	if recv == nil {
 		return fn
 	}
-	base := recv.Type()
-	p, isPtr := base.(*types.Pointer)
-	if isPtr {
-		base = p.Elem()
-	}
-	named, isNamed := base.(*types.Named)
-	if !isNamed {
+	_, named := typesinternal.ReceiverNamed(recv)
+	if named == nil {
 		// Receiver is a *types.Interface.
 		return fn
 	}
@@ -158,6 +146,9 @@ func OriginMethod(fn *types.Func) *types.Func {
 // In this case, GenericAssignableTo reports that instantiations of Container
 // are assignable to the corresponding instantiation of Interface.
 func GenericAssignableTo(ctxt *types.Context, V, T types.Type) bool {
+	V = aliases.Unalias(V)
+	T = aliases.Unalias(T)
+
 	// If V and T are not both named, or do not have matching non-empty type
 	// parameter lists, fall back on types.AssignableTo.
 

vendor/golang.org/x/tools/internal/typeparams/coretype.go

@@ -5,7 +5,10 @@
 package typeparams
 
 import (
+	"fmt"
 	"go/types"
+
+	"golang.org/x/tools/internal/aliases"
 )
 
 // CoreType returns the core type of T or nil if T does not have a core type.
@@ -109,7 +112,7 @@ func CoreType(T types.Type) types.Type {
 // _NormalTerms makes no guarantees about the order of terms, except that it
 // is deterministic.
 func _NormalTerms(typ types.Type) ([]*types.Term, error) {
-	switch typ := typ.(type) {
+	switch typ := aliases.Unalias(typ).(type) {
 	case *types.TypeParam:
 		return StructuralTerms(typ)
 	case *types.Union:
@@ -120,3 +123,15 @@ func _NormalTerms(typ types.Type) ([]*types.Term, error) {
 		return []*types.Term{types.NewTerm(false, typ)}, nil
 	}
 }
+
+// MustDeref returns the type of the variable pointed to by t.
+// It panics if t's core type is not a pointer.
+//
+// TODO(adonovan): ideally this would live in typesinternal, but that
+// creates an import cycle. Move there when we melt this package down.
+func MustDeref(t types.Type) types.Type {
+	if ptr, ok := CoreType(t).(*types.Pointer); ok {
+		return ptr.Elem()
+	}
+	panic(fmt.Sprintf("%v is not a pointer", t))
+}

vendor/golang.org/x/tools/internal/typesinternal/recv.go

@@ -0,0 +1,43 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package typesinternal
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/internal/aliases"
+)
+
+// ReceiverNamed returns the named type (if any) associated with the
+// type of recv, which may be of the form N or *N, or aliases thereof.
+// It also reports whether a Pointer was present.
+func ReceiverNamed(recv *types.Var) (isPtr bool, named *types.Named) {
+	t := recv.Type()
+	if ptr, ok := aliases.Unalias(t).(*types.Pointer); ok {
+		isPtr = true
+		t = ptr.Elem()
+	}
+	named, _ = aliases.Unalias(t).(*types.Named)
+	return
+}
+
+// Unpointer returns T given *T or an alias thereof.
+// For all other types it is the identity function.
+// It does not look at underlying types.
+// The result may be an alias.
+//
+// Use this function to strip off the optional pointer on a receiver
+// in a field or method selection, without losing the named type
+// (which is needed to compute the method set).
+//
+// See also [typeparams.MustDeref], which removes one level of
+// indirection from the type, regardless of named types (analogous to
+// a LOAD instruction).
+func Unpointer(t types.Type) types.Type {
+	if ptr, ok := aliases.Unalias(t).(*types.Pointer); ok {
+		return ptr.Elem()
+	}
+	return t
+}

vendor/golang.org/x/tools/internal/typesinternal/types_118.go

@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.18
-// +build go1.18
-
 package typesinternal
 
 import (

vendor/golang.org/x/tools/internal/versions/features.go

@@ -0,0 +1,43 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package versions
+
+// This file contains predicates for working with file versions to
+// decide when a tool should consider a language feature enabled.
+
+// GoVersions that features in x/tools can be gated to.
+const (
+	Go1_18 = "go1.18"
+	Go1_19 = "go1.19"
+	Go1_20 = "go1.20"
+	Go1_21 = "go1.21"
+	Go1_22 = "go1.22"
+)
+
+// Future is an invalid unknown Go version sometime in the future.
+// Do not use directly with Compare.
+const Future = ""
+
+// AtLeast reports whether the file version v comes after a Go release.
+//
+// Use this predicate to enable a behavior once a certain Go release
+// has happened (and stays enabled in the future).
+func AtLeast(v, release string) bool {
+	if v == Future {
+		return true // an unknown future version is always after y.
+	}
+	return Compare(Lang(v), Lang(release)) >= 0
+}
+
+// Before reports whether the file version v is strictly before a Go release.
+//
+// Use this predicate to disable a behavior once a certain Go release
+// has happened (and stays enabled in the future).
+func Before(v, release string) bool {
+	if v == Future {
+		return false // an unknown future version happens after y.
+	}
+	return Compare(Lang(v), Lang(release)) < 0
+}

vendor/golang.org/x/tools/internal/versions/toolchain.go

@@ -0,0 +1,14 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package versions
+
+// toolchain is maximum version (<1.22) that the go toolchain used
+// to build the current tool is known to support.
+//
+// When a tool is built with >=1.22, the value of toolchain is unused.
+//
+// x/tools does not support building with go <1.18. So we take this
+// as the minimum possible maximum.
+var toolchain string = Go1_18

vendor/golang.org/x/tools/internal/versions/toolchain_go119.go

@@ -0,0 +1,14 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.19
+// +build go1.19
+
+package versions
+
+func init() {
+	if Compare(toolchain, Go1_19) < 0 {
+		toolchain = Go1_19
+	}
+}

vendor/golang.org/x/tools/internal/versions/toolchain_go120.go

@@ -0,0 +1,14 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.20
+// +build go1.20
+
+package versions
+
+func init() {
+	if Compare(toolchain, Go1_20) < 0 {
+		toolchain = Go1_20
+	}
+}

vendor/golang.org/x/tools/internal/versions/toolchain_go121.go

@@ -0,0 +1,14 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build go1.21
+// +build go1.21
+
+package versions
+
+func init() {
+	if Compare(toolchain, Go1_21) < 0 {
+		toolchain = Go1_21
+	}
+}

vendor/golang.org/x/tools/internal/versions/types_go121.go

@@ -12,9 +12,19 @@ import (
 	"go/types"
 )
 
-// FileVersions always reports the a file's Go version as the
-// zero version at this Go version.
-func FileVersions(info *types.Info, file *ast.File) string { return "" }
+// FileVersion returns a language version (<=1.21) derived from runtime.Version()
+// or an unknown future version.
+func FileVersion(info *types.Info, file *ast.File) string {
+	// In x/tools built with Go <= 1.21, we do not have Info.FileVersions
+	// available. We use a go version derived from the toolchain used to
+	// compile the tool by default.
+	// This will be <= go1.21. We take this as the maximum version that
+	// this tool can support.
+	//
+	// There are no features currently in x/tools that need to tell fine grained
+	// differences for versions <1.22.
+	return toolchain
+}
 
-// InitFileVersions is a noop at this Go version.
+// InitFileVersions is a noop when compiled with this Go version.
 func InitFileVersions(*types.Info) {}

vendor/golang.org/x/tools/internal/versions/types_go122.go

@@ -12,10 +12,27 @@ import (
 	"go/types"
 )
 
-// FileVersions maps a file to the file's semantic Go version.
-// The reported version is the zero version if a version cannot be determined.
-func FileVersions(info *types.Info, file *ast.File) string {
-	return info.FileVersions[file]
+// FileVersions returns a file's Go version.
+// The reported version is an unknown Future version if a
+// version cannot be determined.
+func FileVersion(info *types.Info, file *ast.File) string {
+	// In tools built with Go >= 1.22, the Go version of a file
+	// follow a cascades of sources:
+	// 1) types.Info.FileVersion, which follows the cascade:
+	//   1.a) file version (ast.File.GoVersion),
+	//   1.b) the package version (types.Config.GoVersion), or
+	// 2) is some unknown Future version.
+	//
+	// File versions require a valid package version to be provided to types
+	// in Config.GoVersion. Config.GoVersion is either from the package's module
+	// or the toolchain (go run). This value should be provided by go/packages
+	// or unitchecker.Config.GoVersion.
+	if v := info.FileVersions[file]; IsValid(v) {
+		return v
+	}
+	// Note: we could instead return runtime.Version() [if valid].
+	// This would act as a max version on what a tool can support.
+	return Future
 }
 
 // InitFileVersions initializes info to record Go versions for Go files.

vendor/golang.org/x/tools/internal/versions/versions.go

@@ -4,6 +4,10 @@
 
 package versions
 
+import (
+	"strings"
+)
+
 // Note: If we use build tags to use go/versions when go >=1.22,
 // we run into go.dev/issue/53737. Under some operations users would see an
 // import of "go/versions" even if they would not compile the file.
@@ -45,6 +49,7 @@ func IsValid(x string) bool { return isValid(stripGo(x)) }
 // stripGo converts from a "go1.21" version to a "1.21" version.
 // If v does not start with "go", stripGo returns the empty string (a known invalid version).
 func stripGo(v string) string {
+	v, _, _ = strings.Cut(v, "-") // strip -bigcorp suffix.
 	if len(v) < 2 || v[:2] != "go" {
 		return ""
 	}