cmd/compile: do not set type for OTYPE

That's an invalid operation and depend on gc.hidePanic to report error.

Updates #43311

Change-Id: Ib0761dcf4d9d2a23c41de7eff0376677a90b942e
Reviewed-on: https://go-review.googlesource.com/c/go/+/294033
Trust: Cuong Manh Le <[email protected]>
Run-TryBot: Cuong Manh Le <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>

Author: cuonglm

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

@@ -433,8 +433,8 @@ func typecheck(n ir.Node, top int) (res ir.Node) {
 	case top&ctxType == 0 && n.Op() == ir.OTYPE && t != nil:
 		if !n.Type().Broke() {
 			base.Errorf("type %v is not an expression", n.Type())
+			n.SetDiag(true)
 		}
-		n.SetType(nil)
 
 	case top&(ctxStmt|ctxExpr) == ctxStmt && !isStmt && t != nil:
 		if !n.Diag() {