Reland shipping of --harmony-destructuring-bind

Also fix CheckConflictingVarDeclarations() to properly handle
legacy const bindings. Without that change enabling the flag
causes code like:

  function f() { const x; var x; }

to throw an early error, rather than wait to throw the error
until f is invoked.

The previous patch ran into problems with the fuzzer; that crash was fixed
(with test coverage added) in https://crrev.com/ceb92ebfdfb561d71038793c02b42aa973f55ec4

BUG=v8:811
LOG=y
TBR=rossberg@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1473243006

Cr-Commit-Position: refs/heads/master@{#32306}

src/flag-definitions.h

@@ -211,7 +211,6 @@ DEFINE_IMPLICATION(es_staging, harmony_destructuring_bind)
 
 // Features that are complete (but still behind --harmony/es-staging flag).
 #define HARMONY_STAGED(V)                                     \
-  V(harmony_destructuring_bind, "harmony destructuring")      \
   V(harmony_regexps, "harmony regular expression extensions") \
   V(harmony_sloppy, "harmony features in sloppy mode")        \
   V(harmony_sloppy_let, "harmony let in sloppy mode")
@@ -220,6 +219,7 @@ DEFINE_IMPLICATION(es_staging, harmony_destructuring_bind)
 #define HARMONY_SHIPPING(V)                                     \
   V(harmony_array_includes, "harmony Array.prototype.includes") \
   V(harmony_default_parameters, "harmony default parameters")   \
+  V(harmony_destructuring_bind, "harmony destructuring bind")   \
   V(harmony_object_observe, "harmony Object.observe")           \
   V(harmony_rest_parameters, "harmony rest parameters")         \
   V(harmony_concat_spreadable, "harmony isConcatSpreadable")    \

src/scopes.cc

@@ -610,7 +610,11 @@ Declaration* Scope::CheckConflictingVarDeclarations() {
   int length = decls_.length();
   for (int i = 0; i < length; i++) {
     Declaration* decl = decls_[i];
-    if (decl->mode() != VAR && !is_block_scope()) continue;
+    // We don't create a separate scope to hold the function name of a function
+    // expression, so we have to make sure not to consider it when checking for
+    // conflicts (since it's conceptually "outside" the declaration scope).
+    if (is_function_scope() && decl == function()) continue;
+    if (IsLexicalVariableMode(decl->mode()) && !is_block_scope()) continue;
     const AstRawString* name = decl->proxy()->raw_name();
 
     // Iterate through all scopes until and including the declaration scope.
@@ -620,11 +624,11 @@ Declaration* Scope::CheckConflictingVarDeclarations() {
     // captured in Parser::Declare. The only conflicts we still need to check
     // are lexical vs VAR, or any declarations within a declaration block scope
     // vs lexical declarations in its surrounding (function) scope.
-    if (decl->mode() != VAR) current = current->outer_scope_;
+    if (IsLexicalVariableMode(decl->mode())) current = current->outer_scope_;
     do {
       // There is a conflict if there exists a non-VAR binding.
       Variable* other_var = current->variables_.Lookup(name);
-      if (other_var != NULL && other_var->mode() != VAR) {
+      if (other_var != NULL && IsLexicalVariableMode(other_var->mode())) {
         return decl;
       }
       previous = current;

test/mozilla/mozilla.status

@@ -624,11 +624,6 @@
   'js1_5/Regress/regress-417893': [FAIL_OK],
 
 
-  # Unsupported use of "[]" as function parameter. We match JSC.
-  'js1_5/Regress/regress-416737-01': [FAIL_OK],
-  'js1_5/Regress/regress-416737-02': [FAIL_OK],
-
-
   # Illegal escape-sequences in string literals. Has already been fixed
   # by most engines (i.e. V8, JSC, Opera and FF).
   'ecma/Array/15.4.5.1-1': [FAIL_OK],