cmd/compile: make backingArrayPtrLen to return typecheck-ed nodes

Fixes #61908

Change-Id: Ief8e3a6c42c0644c9f71ebef5f28a294cd7c153f
Reviewed-on: https://go-review.googlesource.com/c/go/+/517936
Run-TryBot: Cuong Manh Le <[email protected]>
Auto-Submit: Cuong Manh Le <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: cuonglm

src/cmd/compile/internal/walk/walk.go

@@ -275,8 +275,10 @@ func backingArrayPtrLen(n ir.Node) (ptr, length ir.Node) {
 	} else {
 		ptr.SetType(n.Type().Elem().PtrTo())
 	}
+	ptr.SetTypecheck(1)
 	length = ir.NewUnaryExpr(base.Pos, ir.OLEN, n)
 	length.SetType(types.Types[types.TINT])
+	length.SetTypecheck(1)
 	return ptr, length
 }
 

test/fixedbugs/issue61908.go

@@ -0,0 +1,16 @@
+// compile
+
+// 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 p
+
+func f(p []byte) int {
+	switch "" < string(p) {
+	case true:
+		return 0
+	default:
+		return 1
+	}
+}