cmd/compile: don't crash in size computation for invalid type

An invalid program may produce invalid types. If the program
calls unsafe.Sizeof on such a type, which is a compile-time
computation, the size-computation must be able to handle it.
Add the invalid type to the list of permissible basic types
and give it a size of 1 (word).

Fixes #52748.

Change-Id: I6c409628f9b77044758caf71cdcb199f9e77adea
Reviewed-on: https://go-review.googlesource.com/c/go/+/404894
Run-TryBot: Robert Griesemer <[email protected]>
Reviewed-by: Cuong Manh Le <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Auto-Submit: Robert Griesemer <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: griesemer

src/cmd/compile/internal/noder/sizes.go

@@ -134,6 +134,7 @@ func (s *gcSizes) Sizeof(T types2.Type) int64 {
 }
 
 var basicSizes = [...]byte{
+	types2.Invalid:    1,
 	types2.Bool:       1,
 	types2.Int8:       1,
 	types2.Int16:      2,

test/fixedbugs/issue52748.go

@@ -0,0 +1,13 @@
+// errorcheck
+
+// Copyright 2022 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
+
+import "unsafe"
+
+type S[T any] struct{}
+
+const c = unsafe.Sizeof(S[[c]byte]{}) // ERROR "initialization loop"