From e7d9342c7b51b4a66d3341d53d55bc9add186c0b Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <ian@gcc.gnu.org>
Date: Thu, 10 Oct 2013 00:04:23 +0000
Subject: compiler: A type conversion of a constant is not always a constant.

From-SVN: r203332
---
 gcc/go/gofrontend/expressions.cc | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

(limited to 'gcc/go/gofrontend')

diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc
index 9d59349..e96ab76 100644
--- a/gcc/go/gofrontend/expressions.cc
+++ b/gcc/go/gofrontend/expressions.cc
@@ -3055,8 +3055,7 @@ class Type_conversion_expression : public Expression
   do_lower(Gogo*, Named_object*, Statement_inserter*, int);
 
   bool
-  do_is_constant() const
-  { return this->expr_->is_constant(); }
+  do_is_constant() const;
 
   bool
   do_numeric_constant_value(Numeric_constant*) const;
@@ -3198,6 +3197,27 @@ Type_conversion_expression::do_lower(Gogo*, Named_object*,
   return this;
 }
 
+// Return whether a type conversion is a constant.
+
+bool
+Type_conversion_expression::do_is_constant() const
+{
+  if (!this->expr_->is_constant())
+    return false;
+
+  // A conversion to a type that may not be used as a constant is not
+  // a constant.  For example, []byte(nil).
+  Type* type = this->type_;
+  if (type->integer_type() == NULL
+      && type->float_type() == NULL
+      && type->complex_type() == NULL
+      && !type->is_boolean_type()
+      && !type->is_string_type())
+    return false;
+
+  return true;
+}
+
 // Return the constant numeric value if there is one.
 
 bool
-- 
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