[dev.typeparams] go/types: fix generic type indirection

This is a port of CL 333890 to go/types.

Change-Id: I8ee20f405dad98083bb5e91636044d132a95d909
Reviewed-on: https://go-review.googlesource.com/c/go/+/335081
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/go/types/expr.go b/src/go/types/expr.go
index 751a3608900ea6e952b87a1216d439a3ce39d80d..b55f51185fd5114da3e2df3e149c99149e5fef3b 100644 (file)
--- a/src/go/types/expr.go
+++ b/src/go/types/expr.go
@@ -1400,13 +1400,24 @@ func (check *Checker) exprInternal(x *operand, e ast.Expr, hint Type) exprKind {
                case typexpr:
                        x.typ = &Pointer{base: x.typ}
                default:
-                       if typ := asPointer(x.typ); typ != nil {
-                               x.mode = variable
-                               x.typ = typ.base
-                       } else {
-                               check.invalidOp(x, _InvalidIndirection, "cannot indirect %s", x)
+                       var base Type
+                       if !underIs(x.typ, func(u Type) bool {
+                               p, _ := u.(*Pointer)
+                               if p == nil {
+                                       check.invalidOp(x, _InvalidIndirection, "cannot indirect %s", x)
+                                       return false
+                               }
+                               if base != nil && !Identical(p.base, base) {
+                                       check.invalidOp(x, _Todo, "pointers of %s must have identical base types", x)
+                                       return false
+                               }
+                               base = p.base
+                               return true
+                       }) {
                                goto Error
                        }
+                       x.mode = variable
+                       x.typ = base
                }
 
        case *ast.UnaryExpr:

diff --git a/src/go/types/testdata/examples/operations.go2 b/src/go/types/testdata/examples/operations.go2
new file mode 100644 (file)
index 0000000..18e4d60
--- /dev/null
+++ b/src/go/types/testdata/examples/operations.go2
@@ -0,0 +1,29 @@
+// Copyright 2021 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
+
+// indirection
+
+func _[P any](p P) {
+        _ = *p // ERROR cannot indirect p
+}
+
+func _[P interface{ int }](p P) {
+        _ = *p // ERROR cannot indirect p
+}
+
+func _[P interface{ *int }](p P) {
+        _ = *p
+}
+
+func _[P interface{ *int | *string }](p P) {
+        _ = *p // ERROR must have identical base types
+}
+
+type intPtr *int
+
+func _[P interface{ *int | intPtr } ](p P) {
+        var _ int = *p
+}