types2, go/types: fix type checking of ~[]E passing to unsafe builtins

Fixes #64406

Change-Id: I58002ad722a229fe6db0be08d745fbad86048c6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/545395
Reviewed-by: Robert Griesemer <[email protected]>
Run-TryBot: Robert Griesemer <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
Auto-Submit: Robert Griesemer <[email protected]>

Author: cuonglm

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

@@ -799,7 +799,7 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 		// unsafe.Slice(ptr *T, len IntegerType) []T
 		check.verifyVersionf(call.Fun, go1_17, "unsafe.Slice")
 
-		ptr, _ := under(x.typ).(*Pointer) // TODO(gri) should this be coreType rather than under?
+		ptr, _ := coreType(x.typ).(*Pointer)
 		if ptr == nil {
 			check.errorf(x, InvalidUnsafeSlice, invalidArg+"%s is not a pointer", x)
 			return
@@ -820,7 +820,7 @@ func (check *Checker) builtin(x *operand, call *syntax.CallExpr, id builtinId) (
 		// unsafe.SliceData(slice []T) *T
 		check.verifyVersionf(call.Fun, go1_20, "unsafe.SliceData")
 
-		slice, _ := under(x.typ).(*Slice) // TODO(gri) should this be coreType rather than under?
+		slice, _ := coreType(x.typ).(*Slice)
 		if slice == nil {
 			check.errorf(x, InvalidUnsafeSliceData, invalidArg+"%s is not a slice", x)
 			return

src/go/types/builtins.go

@@ -798,7 +798,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// unsafe.Slice(ptr *T, len IntegerType) []T
 		check.verifyVersionf(call.Fun, go1_17, "unsafe.Slice")
 
-		ptr, _ := under(x.typ).(*Pointer) // TODO(gri) should this be coreType rather than under?
+		ptr, _ := coreType(x.typ).(*Pointer)
 		if ptr == nil {
 			check.errorf(x, InvalidUnsafeSlice, invalidArg+"%s is not a pointer", x)
 			return
@@ -819,7 +819,7 @@ func (check *Checker) builtin(x *operand, call *ast.CallExpr, id builtinId) (_ b
 		// unsafe.SliceData(slice []T) *T
 		check.verifyVersionf(call.Fun, go1_20, "unsafe.SliceData")
 
-		slice, _ := under(x.typ).(*Slice) // TODO(gri) should this be coreType rather than under?
+		slice, _ := coreType(x.typ).(*Slice)
 		if slice == nil {
 			check.errorf(x, InvalidUnsafeSliceData, invalidArg+"%s is not a slice", x)
 			return

src/internal/types/testdata/fixedbugs/issue64406.go

@@ -0,0 +1,23 @@
+// Copyright 2023 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 issue64406
+
+import (
+	"unsafe"
+)
+
+func sliceData[E any, S ~[]E](s S) *E {
+	return unsafe.SliceData(s)
+}
+
+func slice[E any, S ~*E](s S) []E {
+	return unsafe.Slice(s, 0)
+}
+
+func f() {
+	s := []uint32{0}
+	_ = sliceData(s)
+	_ = slice(&s)
+}