From 532e3203492ebcac67b2f3aa2a52115f49d51997 Mon Sep 17 00:00:00 2001 From: Alan Donovan Date: Thu, 18 Dec 2025 12:27:11 -0500 Subject: go/types,cmd/compile/internal/types2: better diagnostic for type shadowing This change causes the "x is not a type" diagnostic to describe x's actual kind, helping to reveal when shadowing is at work. (The kind description could improve other errors too.) Fixes #76877 Change-Id: Ia3484998bb384ff570c20b6792cf8461c60aa38c Reviewed-on: https://go-review.googlesource.com/c/go/+/731180 Reviewed-by: Robert Griesemer Auto-Submit: Alan Donovan LUCI-TryBot-Result: Go LUCI Auto-Submit: Robert Griesemer --- src/cmd/compile/internal/types2/object.go | 49 ++++++++++++++++++++++++++++++ src/cmd/compile/internal/types2/typexpr.go | 3 +- 2 files changed, 51 insertions(+), 1 deletion(-) (limited to 'src/cmd/compile') diff --git a/src/cmd/compile/internal/types2/object.go b/src/cmd/compile/internal/types2/object.go index dd2d415790..5d284ee61b 100644 --- a/src/cmd/compile/internal/types2/object.go +++ b/src/cmd/compile/internal/types2/object.go @@ -671,3 +671,52 @@ func writeFuncName(buf *bytes.Buffer, f *Func, qf Qualifier) { } buf.WriteString(f.name) } + +// objectKind returns a description of the object's kind. +func objectKind(obj Object) string { + switch obj := obj.(type) { + case *PkgName: + return "package name" + case *Const: + return "constant" + case *TypeName: + if obj.IsAlias() { + return "type alias" + } else if _, ok := obj.Type().(*TypeParam); ok { + return "type parameter" + } else { + return "defined type" + } + case *Var: + switch obj.Kind() { + case PackageVar: + return "package-level variable" + case LocalVar: + return "local variable" + case RecvVar: + return "receiver" + case ParamVar: + return "parameter" + case ResultVar: + return "result variable" + case FieldVar: + return "struct field" + } + case *Func: + if obj.Signature().Recv() != nil { + return "method" + } else { + return "function" + } + case *Label: + return "label" + case *Builtin: + return "built-in function" + case *Nil: + return "untyped nil" + } + if debug { + panic(fmt.Sprintf("unknown symbol (%T)", obj)) + } + return "unknown symbol" +} diff --git a/src/cmd/compile/internal/types2/typexpr.go b/src/cmd/compile/internal/types2/typexpr.go index a79b54eacc..7d5932eec1 100644 --- a/src/cmd/compile/internal/types2/typexpr.go +++ b/src/cmd/compile/internal/types2/typexpr.go @@ -50,7 +50,8 @@ func (check *Checker) ident(x *operand, e *syntax.Name, wantType bool) { // (see go.dev/issue/65344). _, gotType := obj.(*TypeName) if !gotType && wantType { - check.errorf(e, NotAType, "%s is not a type", obj.Name()) + check.errorf(e, NotAType, "%s (%s) is not a type", obj.Name(), objectKind(obj)) + // avoid "declared but not used" errors // (don't use Checker.use - we don't want to evaluate too much) if v, _ := obj.(*Var); v != nil && v.pkg == check.pkg /* see Checker.use1 */ { -- cgit v1.3