From 90f01468b4c82e895f43432ea6b1504d47d0a294 Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Mon, 24 Sep 2012 22:21:49 +0000
Subject: [PATCH] compiler: Better warning for switch on non-comparable type.

From-SVN: r191683
---
 gcc/go/gofrontend/statements.cc | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gcc/go/gofrontend/statements.cc b/gcc/go/gofrontend/statements.cc
index fa7f208..a96e6bd 100644
--- a/gcc/go/gofrontend/statements.cc
+++ b/gcc/go/gofrontend/statements.cc
@@ -3846,6 +3846,16 @@ Switch_statement::do_lower(Gogo*, Named_object*, Block* enclosing,
     return new Constant_switch_statement(this->val_, this->clauses_,
 					 this->break_label_, loc);
 
+  if (this->val_ != NULL
+      && !this->val_->type()->is_comparable()
+      && !Type::are_compatible_for_comparison(true, this->val_->type(),
+					      Type::make_nil_type(), NULL))
+    {
+      error_at(this->val_->location(),
+	       "cannot switch on value whose type that may not be compared");
+      return Statement::make_error_statement(loc);
+    }
+
   Block* b = new Block(enclosing, loc);
 
   if (this->clauses_->empty())
-- 
2.7.4