cmd/compile: ensure size is computed for shape types

Fixes #50993

Change-Id: I5f1bf5a8375c3da3203083b11de26962523ccb36
Reviewed-on: https://go-review.googlesource.com/c/go/+/382874
Trust: Keith Randall <khr@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Trust: Dan Scales <danscales@google.com>

src/cmd/compile/internal/typecheck/subr.go

@@ -1480,6 +1480,7 @@ func Shapify(t *types.Type, index int, tparam *types.Type) *types.Type {
 	s.SetUnderlying(u)
 	s.SetIsShape(true)
 	s.SetHasShape(true)
+	types.CalcSize(s)
 	name.SetType(s)
 	name.SetTypecheck(1)
 	submap[u] = s

test/typeparam/issue50993.go

@@ -0,0 +1,35 @@
+// compile -d=checkptr
+
+// 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 main
+
+import (
+	"sync/atomic"
+	"unsafe"
+)
+
+type Node[T any] struct {
+	Next *Node[T]
+	// Prev  *Node[T]
+}
+
+func LoadPointer[T any](addr **T) (val *T) {
+	return (*T)(
+		atomic.LoadPointer(
+			(*unsafe.Pointer)(unsafe.Pointer(addr)),
+		))
+}
+
+func (q *Node[T]) Pop() {
+	var tail, head *Node[T]
+	if head == LoadPointer(&tail) {
+	}
+}
+
+func main() {
+	ch := Node[uint64]{}
+	ch.Pop()
+}