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// 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/stdlib"
"golang.org/x/tools/internal/versions"
)
// TooNewStdSymbols computes the set of package-level symbols
// exported by pkg that are not available at the specified version.
// The result maps each symbol to its minimum version.
//
// The pkg is allowed to contain type errors.
func TooNewStdSymbols(pkg *types.Package, version string) map[types.Object]string {
disallowed := make(map[types.Object]string)
// Pass 1: package-level symbols.
symbols := stdlib.PackageSymbols[pkg.Path()]
for _, sym := range symbols {
symver := sym.Version.String()
if versions.Before(version, symver) {
switch sym.Kind {
case stdlib.Func, stdlib.Var, stdlib.Const, stdlib.Type:
disallowed[pkg.Scope().Lookup(sym.Name)] = symver
}
}
}
// Pass 2: fields and methods.
//
// We allow fields and methods if their associated type is
// disallowed, as otherwise we would report false positives
// for compatibility shims. Consider:
//
// //go:build go1.22
// type T struct { F std.Real } // correct new API
//
// //go:build !go1.22
// type T struct { F fake } // shim
// type fake struct { ... }
// func (fake) M () {}
//
// These alternative declarations of T use either the std.Real
// type, introduced in go1.22, or a fake type, for the field
// F. (The fakery could be arbitrarily deep, involving more
// nested fields and methods than are shown here.) Clients
// that use the compatibility shim T will compile with any
// version of go, whether older or newer than go1.22, but only
// the newer version will use the std.Real implementation.
//
// Now consider a reference to method M in new(T).F.M() in a
// module that requires a minimum of go1.21. The analysis may
// occur using a version of Go higher than 1.21, selecting the
// first version of T, so the method M is Real.M. This would
// spuriously cause the analyzer to report a reference to a
// too-new symbol even though this expression compiles just
// fine (with the fake implementation) using go1.21.
for _, sym := range symbols {
symVersion := sym.Version.String()
if !versions.Before(version, symVersion) {
continue // allowed
}
var obj types.Object
switch sym.Kind {
case stdlib.Field:
typename, name := sym.SplitField()
if t := pkg.Scope().Lookup(typename); t != nil && disallowed[t] == "" {
obj, _, _ = types.LookupFieldOrMethod(t.Type(), false, pkg, name)
}
case stdlib.Method:
ptr, recvname, name := sym.SplitMethod()
if t := pkg.Scope().Lookup(recvname); t != nil && disallowed[t] == "" {
obj, _, _ = types.LookupFieldOrMethod(t.Type(), ptr, pkg, name)
}
}
if obj != nil {
disallowed[obj] = symVersion
}
}
return disallowed
}
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