Parser: Fix crash on stack overflow when lazy-parsing arrow functions

src/parser.cc

Index: src/parser.cc
diff --git a/src/parser.cc b/src/parser.cc
index 4bcdfdbda7e2233fd25a710caea8f23d9d6d0510..96ee2bd033537d85169f342668757b9a0544c69f 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -1145,8 +1145,24 @@ FunctionLiteral* Parser::ParseLazy(Isolate* isolate, ParseInfo* info,
       // from creating unresolved variables in already-resolved scopes.
       parsing_lazy_arrow_parameters_ = true;
       Expression* expression = ParseExpression(false, &ok);
-      DCHECK(expression->IsFunctionLiteral());
-      result = expression->AsFunctionLiteral();
+      if (ok) {
+        // Scanning must end at the same position that was recorded
+        // previously. If not, parsing has been interrupted due to a
+        // stack overflow, at which point the partially parsed arrow
+        // function concise body happens to be a valid expression. This
+        // is a problem only for arrow functions with single statement
+        // bodies, since there is no end token suck as "}" for normal

[marja, 2015/03/23 10:56:31]

... unintentional swearing? :)

+        // functions.
+        if (scanner()->location().end_pos == shared_info->end_position()) {
+          // The pre-parser saw an arrow function here, so the full parser
+          // must produce a FunctionLiteral.
+          DCHECK(expression->IsFunctionLiteral());
+          result = expression->AsFunctionLiteral();
+        } else {
+          result = NULL;
+          ok = false;
+        }
+      }
     } else if (shared_info->is_default_constructor()) {
       result = DefaultConstructor(IsSubclassConstructor(shared_info->kind()),
                                   scope, shared_info->start_position(),