Initial commit: Go 1.23 release state

test/alias2.go

@@ -0,0 +1,104 @@
+// errorcheck
+
+// Copyright 2016 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.
+
+// Test basic restrictions on type aliases.
+
+package p
+
+import (
+	"reflect"
+	. "reflect"
+)
+
+type T0 struct{}
+
+// Valid type alias declarations.
+
+type _ = T0
+type _ = int
+type _ = struct{}
+type _ = reflect.Value
+type _ = Value
+
+type (
+	A0 = T0
+	A1 = int
+	A2 = struct{}
+	A3 = reflect.Value
+	A4 = Value
+	A5 = Value
+
+	N0 A0
+)
+
+// Methods can be declared on the original named type and the alias.
+func (T0) m1()  {} // GCCGO_ERROR "previous"
+func (*T0) m1() {} // ERROR "method redeclared: T0\.m1|T0\.m1 already declared|redefinition of .m1."
+func (A0) m1()  {} // ERROR "T0\.m1 already declared|redefinition of .m1."
+func (A0) m1()  {} // ERROR "T0\.m1 already declared|redefinition of .m1."
+func (A0) m2()  {}
+
+// Type aliases and the original type name can be used interchangeably.
+var _ A0 = T0{}
+var _ T0 = A0{}
+
+// But aliases and original types cannot be used with new types based on them.
+var _ N0 = T0{} // ERROR "cannot use T0{} \(value of type T0\) as N0 value in variable declaration"
+var _ N0 = A0{} // ERROR "cannot use A0{} \(value of type A0\) as N0 value in variable declaration"
+
+var _ A5 = Value{}
+
+var _ interface {
+	m1()
+	m2()
+} = T0{}
+
+var _ interface {
+	m1()
+	m2()
+} = A0{}
+
+func _() {
+	type _ = T0
+	type _ = int
+	type _ = struct{}
+	type _ = reflect.Value
+	type _ = Value
+
+	type (
+		A0 = T0
+		A1 = int
+		A2 = struct{}
+		A3 = reflect.Value
+		A4 = Value
+		A5 Value
+
+		N0 A0
+	)
+
+	var _ A0 = T0{}
+	var _ T0 = A0{}
+
+	var _ N0 = T0{} // ERROR "cannot use T0{} \(value of type T0\) as N0 value in variable declaration"
+	var _ N0 = A0{} // ERROR "cannot use A0{} \(value of type A0\) as N0 value in variable declaration"
+
+	var _ A5 = Value{} // ERROR "cannot use Value{} \(value of type reflect\.Value\) as A5 value in variable declaration"
+}
+
+// Invalid type alias declarations.
+
+type _ = reflect.ValueOf // ERROR "reflect.ValueOf .*is not a type|expected type"
+
+func (A1) m() {} // ERROR "cannot define new methods on non-local type|may not define methods on non-local type"
+func (A2) m() {} // ERROR "invalid receiver type"
+func (A3) m() {} // ERROR "cannot define new methods on non-local type|may not define methods on non-local type"
+func (A4) m() {} // ERROR "cannot define new methods on non-local type|may not define methods on non-local type"
+
+type B1 = struct{}
+
+func (B1) m() {} // ERROR "invalid receiver type"
+
+// TODO(gri) expand