Block scoped const variables.

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index ba5ee8731ed0929ae009fee70872d171468c7947..d235676f933cd91a93f777415753a6b34a5b36f8 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -46,24 +46,43 @@ enum ContextLookupFlags {
 
 // ES5 10.2 defines lexical environments with mutable and immutable bindings.
 // Immutable bindings have two states, initialized and uninitialized, and
-// their state is changed by the InitializeImmutableBinding method.
+// their state is changed by the InitializeImmutableBinding method. The
+// BindingFlags enum represents information if a binding has definitely been
+// initialized. A mutable binding does not need to be checked and thus has
+// the BindingFlag MUTABLE_IS_INITIALIZED.
+//
+// There are two possibilities for immutable bindings
+//  * 'const' declared variables. They are initialized when evaluating the
+//    corresponding declaration statement. They need to be checked for being
+//    initialized and thus get the flag IMMUTABLE_CHECK_INITIALIZED.
+//  * The function name of a named function literal. The binding is immediately
+//    initialized when entering the function and thus does not need to be
+//    checked. it gets the BindingFlag IMMUTABLE_IS_INITIALIZED.
+// Accessing an uninitialized binding produces the undefined value.
 //
 // The harmony proposal for block scoped bindings also introduces the
-// uninitialized state for mutable bindings. A 'let' declared variable
-// is a mutable binding that is created uninitalized upon activation of its
-// lexical environment and it is initialized when evaluating its declaration
-// statement. Var declared variables are mutable bindings that are
-// immediately initialized upon creation. The BindingFlags enum represents
-// information if a binding has definitely been initialized. 'const' declared
-// variables are created as uninitialized immutable bindings.
-
-// In harmony mode accessing an uninitialized binding produces a reference
-// error.
+// uninitialized state for mutable bindings.
+//  * A 'let' declared variable. They are initialized when evaluating the
+//    corresponding declaration statement. They need to be checked for being
+//    initialized and thus get the flag MUTABLE_CHECK_INITIALIZED.
+//  * A 'var' declared variable. It is initialized immediately upon creation
+//    and thus doesn't need to be checked. It gets the flag
+//    MUTABLE_IS_INITIALIZED.
+//  * Catch bound variables, function parameters and variables introduced by
+//    function declarations are initialized immediately and do not need to be
+//    checked. Thus they get the flag MUTABLE_IS_INITIALIZED.
+// Immutable bindings in harmony mode get the _HARMONY flag variants. Accessing
+// an uninitialized binding produces a reference error.
+//
+// In V8 uninitialized bindings are set to the hole value upon creation and set
+// to a different value upon initialization.
 enum BindingFlags {
   MUTABLE_IS_INITIALIZED,
   MUTABLE_CHECK_INITIALIZED,
   IMMUTABLE_IS_INITIALIZED,
   IMMUTABLE_CHECK_INITIALIZED,
+  IMMUTABLE_IS_INITIALIZED_HARMONY,
+  IMMUTABLE_CHECK_INITIALIZED_HARMONY,
   MISSING_BINDING
 };