Implement the dead temporal zone

With const and let it is possible to access the declared member before
initialization. This is expected to throw a type reference error at
run-time.

We initialize such variables with the empty value when entering their
scope and check upon access for that. For locals we place the lexically
scoped variables at the end. For register allocated lexical variables we
group them into one batch and remember the index/size.

Change-Id: Icb493ee0de0525bb682e1bc58981a4dfd33f750e
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/qml/compiler/qv4codegen_p.h b/src/qml/compiler/qv4codegen_p.h
index 516f506396..b7992bd8f2 100644
--- a/src/qml/compiler/qv4codegen_p.h
+++ b/src/qml/compiler/qv4codegen_p.h
@@ -219,7 +219,7 @@ public:
             case Subscript:
                 return true;
             default:
-                return false;
+                return requiresTDZCheck;
             }
         }
         bool isConstant() const { return type == Const; }
@@ -394,6 +394,7 @@ public:
         mutable bool isArgOrEval = false;
         bool isReadonly = false;
         bool isReferenceToConst = false;
+        bool requiresTDZCheck = false;
         bool stackSlotIsLocalOrArgument = false;
         bool isVolatile = false;
         bool global = false;