Go patch committed: Implement append([]byte, string...)

Go patch committed: Implement append([]byte, string...)

[Ian Lance Taylor]

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The Go language was extended to permit calling the builtin function
append with the first argument having type []byte and the second
argument having type string, followed by an ellipsis.  This appends the
string to the slice.  This patch implements this new functionality.
Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.

Ian


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diff -r 118281731edd go/expressions.cc
--- a/go/expressions.cc	Sun Oct 23 21:56:14 2011 -0700
+++ b/go/expressions.cc	Sun Oct 23 21:58:35 2011 -0700
@@ -8228,6 +8228,17 @@
 	    this->report_error(_("too many arguments"));
 	    break;
 	  }
+
+	// The language permits appending a string to a []byte, as a
+	// special case.
+	if (args->back()->type()->is_string_type())
+	  {
+	    const Array_type* at = args->front()->type()->array_type();
+	    const Type* e = at->element_type()->forwarded();
+	    if (e == Type::lookup_integer_type("uint8"))
+	      break;
+	  }
+
 	std::string reason;
 	if (!Type::are_assignable(args->front()->type(), args->back()->type(),
 				  &reason))
@@ -8766,30 +8777,50 @@
 	  return error_mark_node;
 
 	Array_type* at = arg1->type()->array_type();
-	Type* element_type = at->element_type();
-
-	arg2_tree = Expression::convert_for_assignment(context, at,
-						       arg2->type(),
-						       arg2_tree,
-						       location);
-	if (arg2_tree == error_mark_node)
-	  return error_mark_node;
-
-	arg2_tree = save_expr(arg2_tree);
-	tree arg2_val = at->value_pointer_tree(gogo, arg2_tree);
-	tree arg2_len = at->length_tree(gogo, arg2_tree);
-	if (arg2_val == error_mark_node || arg2_len == error_mark_node)
-	  return error_mark_node;
+	Type* element_type = at->element_type()->forwarded();
+
+	tree arg2_val;
+	tree arg2_len;
+	tree element_size;
+	if (arg2->type()->is_string_type()
+	    && element_type == Type::lookup_integer_type("uint8"))
+	  {
+	    arg2_tree = save_expr(arg2_tree);
+	    arg2_val = String_type::bytes_tree(gogo, arg2_tree);
+	    arg2_len = String_type::length_tree(gogo, arg2_tree);
+	    element_size = size_int(1);
+	  }
+	else
+	  {
+	    arg2_tree = Expression::convert_for_assignment(context, at,
+							   arg2->type(),
+							   arg2_tree,
+							   location);
+	    if (arg2_tree == error_mark_node)
+	      return error_mark_node;
+
+	    arg2_tree = save_expr(arg2_tree);
+
+	     arg2_val = at->value_pointer_tree(gogo, arg2_tree);
+	     arg2_len = at->length_tree(gogo, arg2_tree);
+
+	     Btype* element_btype = element_type->get_backend(gogo);
+	     tree element_type_tree = type_to_tree(element_btype);
+	     if (element_type_tree == error_mark_node)
+	       return error_mark_node;
+	     element_size = TYPE_SIZE_UNIT(element_type_tree);
+	  }
+
 	arg2_val = fold_convert_loc(location, ptr_type_node, arg2_val);
 	arg2_len = fold_convert_loc(location, size_type_node, arg2_len);
-
-	tree element_type_tree = type_to_tree(element_type->get_backend(gogo));
-	if (element_type_tree == error_mark_node)
-	  return error_mark_node;
-	tree element_size = TYPE_SIZE_UNIT(element_type_tree);
 	element_size = fold_convert_loc(location, size_type_node,
 					element_size);
 
+	if (arg2_val == error_mark_node
+	    || arg2_len == error_mark_node
+	    || element_size == error_mark_node)
+	  return error_mark_node;
+
 	// We rebuild the decl each time since the slice types may
 	// change.
 	tree append_fndecl = NULL_TREE;