Fix cacthing exception object: a null exception is always caught.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
===================================================================
--- runtime/vm/parser.cc	(revision 4404)
+++ runtime/vm/parser.cc	(working copy)
@@ -4920,10 +4920,17 @@
       }
       AstNode* exception_type = new TypeNode(catch_pos, *exception_param.type);
       AstNode* exception_var = new LoadLocalNode(catch_pos, *catch_excp_var);
-      AstNode* cond_expr = new ComparisonNode(
+      // Null is also allowed.
+      AstNode* null_literal =
+          new LiteralNode(catch_pos, Instance::ZoneHandle(Instance::null()));
+      AstNode* null_cond_expr = new ComparisonNode(
+          catch_pos, Token::kEQ_STRICT, exception_var, null_literal);
+      AstNode* type_cond_expr = new ComparisonNode(
           catch_pos, Token::kIS, exception_var, exception_type);
+      AstNode* or_node = new BinaryOpNode(
+          catch_pos, Token::kOR, null_cond_expr, type_cond_expr);

[hausner, 2012/02/21 21:46:41]

As discussed offline, this compare has to be done only once in the first catch
clause.

[srdjan, 2012/02/21 21:53:52]

Done.

       current_block_->statements->Add(
-          new IfNode(catch_pos, cond_expr, catch_handler, NULL));
+          new IfNode(catch_pos, or_node, catch_handler, NULL));
     } else {
       // No exception type exists in the catch specifier so execute the
       // catch handler code unconditionally.