[es6] Check declaration conflicts between non-simple parameters and the function body

src/scopes.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/bootstrapper.h"
 #include "src/messages.h"
 #include "src/parser.h"
@@ skipping 557 matching lines @@
 void Scope::VisitIllegalRedeclaration(AstVisitor* visitor) {
   DCHECK(HasIllegalRedeclaration());
   illegal_redecl_->Accept(visitor);
 }
 
 
 Declaration* Scope::CheckConflictingVarDeclarations() {
   int length = decls_.length();
   for (int i = 0; i < length; i++) {
     Declaration* decl = decls_[i];
-    if (decl->mode() != VAR) continue;
+    if (decl->mode() != VAR && !is_block_scope()) continue;
     const AstRawString* name = decl->proxy()->raw_name();
 
     // Iterate through all scopes until and including the declaration scope.
+    // If the declaration scope is a (declaration) block scope, also continue
+    // (that is to handle the special inner scope of functions with
+    // destructuring parameters, which may not shadow any variables from
+    // the surrounding function scope).
     Scope* previous = NULL;
     Scope* current = decl->scope();
+    // Lexical vs lexical conflicts within the same scope have already been
+    // 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_;
     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) {
         return decl;
       }
       previous = current;
       current = current->outer_scope_;
-    } while (!previous->is_declaration_scope());
+    } while (!previous->is_declaration_scope() || previous->is_block_scope());
   }
   return NULL;
 }
 
 
 class VarAndOrder {
  public:
   VarAndOrder(Variable* var, int order) : var_(var), order_(order) { }
   Variable* var() const { return var_; }
   int order() const { return order_; }
@@ skipping 1013 matching lines @@
   bool is_function_var_in_context =
       function_ != NULL && function_->proxy()->var()->IsContextSlot();
   return num_heap_slots() - Context::MIN_CONTEXT_SLOTS -
          2 * num_global_slots() - (is_function_var_in_context ? 1 : 0);
 }
 
 
 int Scope::ContextGlobalCount() const { return num_global_slots(); }
 }  // namespace internal
 }  // namespace v8