From 25c99300b9316e5a983af421d4d1a180b7aabf3a Mon Sep 17 00:00:00 2001
From: Robert Griesemer <gri@golang.org>
Date: Wed, 27 Feb 2013 15:22:14 -0800
Subject: [PATCH] go/types: don't crash if there are no hints

R=r
CC=golang-dev
https://golang.org/cl/7375060
---
 src/pkg/go/types/expr.go | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/src/pkg/go/types/expr.go b/src/pkg/go/types/expr.go
index 5aacb02f862..8b645e4e20f 100644
--- a/src/pkg/go/types/expr.go
+++ b/src/pkg/go/types/expr.go
@@ -293,6 +293,11 @@ func (check *checker) convertUntyped(x *operand, target Type) {
 
 	// typed target
 	switch t := underlying(target).(type) {
+	case nil:
+		// We may reach here due to previous type errors.
+		// Be conservative and don't crash.
+		x.mode = invalid
+		return
 	case *Basic:
 		check.isRepresentable(x, t)
 	case *Interface:
@@ -304,6 +309,7 @@ func (check *checker) convertUntyped(x *operand, target Type) {
 			goto Error
 		}
 	default:
+		check.dump("x = %v, target = %v", x, target) // leave for debugging
 		unreachable()
 	}