cmd/compile: do not set type for OTYPESW

Same as CL 294031, but for OTYPESW.

Updates #43311

Change-Id: I996f5938835baff1d830c17ed75652315106bdfd
Reviewed-on: https://go-review.googlesource.com/c/go/+/298712
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

@@ -876,7 +876,7 @@ func typecheck1(n ir.Node, top int) ir.Node {
 	case ir.OTYPESW:
 		n := n.(*ir.TypeSwitchGuard)
 		base.Errorf("use of .(type) outside type switch")
-		n.SetType(nil)
+		n.SetDiag(true)
 		return n
 
 	case ir.ODCLFUNC:

test/fixedbugs/issue24470.go

@@ -1,4 +1,4 @@
-// errorcheck
+// errorcheck -d=panic
 
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -10,7 +10,7 @@
 package p
 
 func f(i interface{}) {
-	if x, ok := i.(type); ok { // ERROR "outside type switch"
+	if x, ok := i.(type); ok { // ERROR "assignment mismatch|outside type switch"
 		_ = x
 	}
 }