diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmd/compile/internal/types2/decl.go | 9 | ||||
| -rw-r--r-- | src/go/types/decl.go | 9 | ||||
| -rw-r--r-- | src/internal/types/testdata/fixedbugs/issue75885.go | 15 |
3 files changed, 29 insertions, 4 deletions
diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go index 60371651ab..5cb52fdbe4 100644 --- a/src/cmd/compile/internal/types2/decl.go +++ b/src/cmd/compile/internal/types2/decl.go @@ -497,9 +497,14 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *TypeN rhs = check.declaredType(tdecl.Type, obj) assert(rhs != nil) - alias.fromRHS = rhs - unalias(alias) // populate alias.actual + + // spec: In an alias declaration the given type cannot be a type parameter declared in the same declaration." + // (see also go.dev/issue/75884, go.dev/issue/#75885) + if tpar, ok := rhs.(*TypeParam); ok && alias.tparams != nil && slices.Index(alias.tparams.list(), tpar) >= 0 { + check.error(tdecl.Type, MisplacedTypeParam, "cannot use type parameter declared in alias declaration as RHS") + alias.fromRHS = Typ[Invalid] + } } else { if !versionErr && tparam0 != nil { check.error(tdecl, UnsupportedFeature, "generic type alias requires GODEBUG=gotypesalias=1 or unset") diff --git a/src/go/types/decl.go b/src/go/types/decl.go index 4b374fb66d..fffcb590e6 100644 --- a/src/go/types/decl.go +++ b/src/go/types/decl.go @@ -572,9 +572,14 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *TypeName rhs = check.declaredType(tdecl.Type, obj) assert(rhs != nil) - alias.fromRHS = rhs - unalias(alias) // populate alias.actual + + // spec: In an alias declaration the given type cannot be a type parameter declared in the same declaration." + // (see also go.dev/issue/75884, go.dev/issue/#75885) + if tpar, ok := rhs.(*TypeParam); ok && alias.tparams != nil && slices.Index(alias.tparams.list(), tpar) >= 0 { + check.error(tdecl.Type, MisplacedTypeParam, "cannot use type parameter declared in alias declaration as RHS") + alias.fromRHS = Typ[Invalid] + } } else { // With Go1.23, the default behavior is to use Alias nodes, // reflected by check.enableAlias. Signal non-default behavior. diff --git a/src/internal/types/testdata/fixedbugs/issue75885.go b/src/internal/types/testdata/fixedbugs/issue75885.go new file mode 100644 index 0000000000..f0cf4a65ed --- /dev/null +++ b/src/internal/types/testdata/fixedbugs/issue75885.go @@ -0,0 +1,15 @@ +// -gotypesalias=1 + +// Copyright 2025 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 p + +type A[P any] = P // ERROR "cannot use type parameter declared in alias declaration as RHS" + +func _[P any]() { + type A[P any] = P // ERROR "cannot use type parameter declared in alias declaration as RHS" + type B = P + type C[Q any] = P +} |