test: add another regression test for issue 73309

Fixed #73309

Change-Id: Id715b9c71c95c92143a7fdb5a66b24305346dd3b
Reviewed-on: https://go-review.googlesource.com/c/go/+/678415
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/cmd/compile/internal/types2/stdlib_test.go

@@ -333,6 +333,7 @@ func TestStdFixed(t *testing.T) {
 		"issue56103.go",  // anonymous interface cycles; will be a type checker error in 1.22
 		"issue52697.go",  // types2 does not have constraints on stack size
 		"issue73309.go",  // this test requires GODEBUG=gotypesalias=1
+		"issue73309b.go", // this test requires GODEBUG=gotypesalias=1
 
 		// These tests requires runtime/cgo.Incomplete, which is only available on some platforms.
 		// However, types2 does not know about build constraints.

src/go/types/stdlib_test.go

@@ -335,6 +335,7 @@ func TestStdFixed(t *testing.T) {
 		"issue56103.go",  // anonymous interface cycles; will be a type checker error in 1.22
 		"issue52697.go",  // go/types does not have constraints on stack size
 		"issue73309.go",  // this test requires GODEBUG=gotypesalias=1
+		"issue73309b.go", // this test requires GODEBUG=gotypesalias=1
 
 		// These tests requires runtime/cgo.Incomplete, which is only available on some platforms.
 		// However, go/types does not know about build constraints.

test/fixedbugs/issue73309b.go

@@ -0,0 +1,88 @@
+// compile
+
+// 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 main
+
+type Unsigned interface {
+	~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr
+}
+
+// a Validator instance
+type Validator []Validable
+
+type Numeric interface {
+	~int | ~int8 | ~int16 | ~int32 | ~int64 | ~float32 | ~float64
+}
+
+func (v Validator) Valid() bool {
+	for _, field := range v {
+		if !field.Validate() {
+			return false
+		}
+	}
+	return true
+}
+
+type Validable interface {
+	Validate() bool
+}
+
+type FieldDef[T any] struct {
+	value T
+	rules []Rule[T]
+}
+
+func (f FieldDef[T]) Validate() bool {
+	for _, rule := range f.rules {
+		if !rule(f) {
+			return false
+		}
+	}
+	return true
+}
+
+type Rule[T any] = func(FieldDef[T]) bool
+
+func Field[T any](value T, rules ...Rule[T]) *FieldDef[T] {
+	return &FieldDef[T]{value: value, rules: rules}
+}
+
+type StringRule = Rule[string]
+
+type NumericRule[T Numeric] = Rule[T]
+
+type UnsignedRule[T Unsigned] = Rule[T]
+
+func MinS(n int) StringRule {
+	return func(fd FieldDef[string]) bool {
+		return len(fd.value) < n
+	}
+}
+
+func MinD[T Numeric](n T) NumericRule[T] {
+	return func(fd FieldDef[T]) bool {
+		return fd.value < n
+	}
+}
+
+func MinU[T Unsigned](n T) UnsignedRule[T] {
+	return func(fd FieldDef[T]) bool {
+		return fd.value < n
+	}
+}
+
+func main() {
+	v := Validator{
+		Field("test", MinS(5)),
+	}
+
+	if !v.Valid() {
+		println("invalid")
+		return
+	}
+
+	println("valid")
+}