cmd/compile: fix wrong condition in tcShift

CL 279442 refactored typecheck arithmetic operators, but using wrong
condition for checking invalid rhs.

Updates #43311

Change-Id: I7a03a5535b82ac4ea4806725776b0a4f7af1b79a
Reviewed-on: https://go-review.googlesource.com/c/go/+/298714
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/expr.go

@@ -48,7 +48,7 @@ func tcAddr(n *ir.AddrExpr) ir.Node {
 }
 
 func tcShift(n, l, r ir.Node) (ir.Node, ir.Node, *types.Type) {
-	if l.Type() == nil || l.Type() == nil {
+	if l.Type() == nil || r.Type() == nil {
 		return l, r, nil
 	}
 

test/fixedbugs/bug297.go

@@ -1,4 +1,4 @@
-// errorcheck
+// errorcheck -d=panic
 
 // Copyright 2010 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
@@ -9,7 +9,8 @@
 package main
 
 type ByteSize float64
+
 const (
-	_ = iota;   // ignore first value by assigning to blank identifier
-	KB ByteSize = 1<<(10*X) // ERROR "undefined"
+	_           = iota          // ignore first value by assigning to blank identifier
+	KB ByteSize = 1 << (10 * X) // ERROR "undefined"
 )