[es6] implement destructuring assignment

src/parser.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/parser.h"
 
 #include "src/api.h"
 #include "src/ast.h"
 #include "src/ast-literal-reindexer.h"
 #include "src/bailout-reason.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
 #include "src/char-predicates-inl.h"
 #include "src/codegen.h"
 #include "src/compiler.h"
 #include "src/messages.h"
 #include "src/parameter-initializer-rewriter.h"
 #include "src/preparser.h"
 #include "src/rewriter.h"
 #include "src/runtime/runtime.h"
 #include "src/scanner-character-streams.h"
 #include "src/scopeinfo.h"
 #include "src/string-stream.h"
+#include "src/ast-expression-visitor.h"
 
 namespace v8 {
 namespace internal {
 
 ScriptData::ScriptData(const byte* data, int length)
     : owns_data_(false), rejected_(false), data_(data), length_(length) {
   if (!IsAligned(reinterpret_cast<intptr_t>(data), kPointerAlignment)) {
     byte* copy = NewArray<byte>(length);
     DCHECK(IsAligned(reinterpret_cast<intptr_t>(copy), kPointerAlignment));
     CopyBytes(copy, data, length);
@@ skipping 879 matching lines @@
   // ParseInfo during background parsing.
   DCHECK(!info->script().is_null() || info->source_stream() != NULL);
   set_allow_lazy(info->allow_lazy_parsing());
   set_allow_natives(FLAG_allow_natives_syntax || info->is_native());
   set_allow_harmony_sloppy(FLAG_harmony_sloppy);
   set_allow_harmony_sloppy_function(FLAG_harmony_sloppy_function);
   set_allow_harmony_sloppy_let(FLAG_harmony_sloppy_let);
   set_allow_harmony_rest_parameters(FLAG_harmony_rest_parameters);
   set_allow_harmony_default_parameters(FLAG_harmony_default_parameters);
   set_allow_harmony_destructuring(FLAG_harmony_destructuring);
+  set_allow_harmony_destructuring_assignment(
+      FLAG_harmony_destructuring_assignment);
   set_allow_strong_mode(FLAG_strong_mode);
   set_allow_legacy_const(FLAG_legacy_const);
   set_allow_harmony_do_expressions(FLAG_harmony_do_expressions);
   for (int feature = 0; feature < v8::Isolate::kUseCounterFeatureCount;
        ++feature) {
     use_counts_[feature] = 0;
   }
   if (info->ast_value_factory() == NULL) {
     // info takes ownership of AstValueFactory.
     info->set_ast_value_factory(new AstValueFactory(zone(), info->hash_seed()));
@@ skipping 150 matching lines @@
       if (body->length() != 1 ||
           !body->at(0)->IsExpressionStatement() ||
           !body->at(0)->AsExpressionStatement()->
               expression()->IsFunctionLiteral()) {
         ReportMessage(MessageTemplate::kSingleFunctionLiteral);
         ok = false;
       }
     }
 
     if (ok) {
+      ParserTraits::RewriteDestructuringAssignments();
       result = factory()->NewFunctionLiteral(
           ast_value_factory()->empty_string(), ast_value_factory(), scope_,
           body, function_state.materialized_literal_count(),
           function_state.expected_property_count(), 0,
           FunctionLiteral::kNoDuplicateParameters,
           FunctionLiteral::ANONYMOUS_EXPRESSION, FunctionLiteral::kGlobalOrEval,
           FunctionLiteral::kShouldLazyCompile, FunctionKind::kNormalFunction,
           0);
     }
   }
@@ skipping 2288 matching lines @@
                        assign_iterator,
                        next_result,
                        result_done,
                        assign_each);
   } else {
     stmt->Initialize(each, subject, body);
   }
 }
 
 
+Expression* Parser::RewriteDestructuringAssignmentExpression(
+    Expression* expression) {
+  return expression;
+}
+
+
 Statement* Parser::DesugarLexicalBindingsInForStatement(
     Scope* inner_scope, bool is_const, ZoneList<const AstRawString*>* names,
     ForStatement* loop, Statement* init, Expression* cond, Statement* next,
     Statement* body, bool* ok) {
   // ES6 13.7.4.8 specifies that on each loop iteration the let variables are
   // copied into a new environment.  Moreover, the "next" statement must be
   // evaluated not in the environment of the just completed iteration but in
   // that of the upcoming one.  We achieve this with the following desugaring.
   // Extra care is needed to preserve the completion value of the original loop.
   //
@@ skipping 994 matching lines @@
       CheckStrictOctalLiteral(scope->start_position(), scope->end_position(),
                               CHECK_OK);
     }
     if (is_sloppy(language_mode) && allow_harmony_sloppy_function()) {
       InsertSloppyBlockFunctionVarBindings(scope, CHECK_OK);
     }
     if (is_strict(language_mode) || allow_harmony_sloppy() ||
         allow_harmony_destructuring()) {
       CheckConflictingVarDeclarations(scope, CHECK_OK);
     }
+
+    ParserTraits::RewriteDestructuringAssignments();
   }
 
   bool has_duplicate_parameters =
       !formals_classifier.is_valid_formal_parameter_list_without_duplicates();
   FunctionLiteral::ParameterFlag duplicate_parameters =
       has_duplicate_parameters ? FunctionLiteral::kHasDuplicateParameters
                                : FunctionLiteral::kNoDuplicateParameters;
 
   FunctionLiteral* function_literal = factory()->NewFunctionLiteral(
       function_name, ast_value_factory(), scope, body,
@@ skipping 108 matching lines @@
       RelocInfo::kNoPosition);
   IfStatement* if_statement = factory()->NewIfStatement(
       condition, factory()->NewExpressionStatement(throw_type_error,
                                                    RelocInfo::kNoPosition),
       factory()->NewEmptyStatement(RelocInfo::kNoPosition),
       RelocInfo::kNoPosition);
   return if_statement;
 }
 
 
+class InitializerRewriter : public AstExpressionVisitor {
+ public:
+  InitializerRewriter(uintptr_t stack_limit, Expression* root, Parser* parser,
+                      Scope* scope)
+      : AstExpressionVisitor(stack_limit, root),
+        parser_(parser),
+        scope_(scope) {}
+
+ private:
+  void VisitExpression(Expression* expr) {
+    if (expr->IsAssignment()) {
+      Assignment* node = expr->AsAssignment();
+      Expression* target = node->target();
+      if (node->op() == Token::ASSIGN && target->IsAssignmentPattern() &&
+          !target->AsAssignmentPattern()->is_rewritten()) {
+        bool ok = true;
+        Parser::PatternRewriter::RewriteDestructuringAssignment(parser_, node,
+                                                                scope_, &ok);
+        DCHECK(ok);
+      }
+    }
+  }
+  /*
+  #define NOT_INITIALIZER(T) void Visit##T(T* node) {}
+    NOT_INITIALIZER(FunctionLiteral)
+    NOT_INITIALIZER(ClassLiteral)
+    NOT_INITIALIZER(NativeFunctionLiteral)
+    NOT_INITIALIZER(Conditional)
+    NOT_INITIALIZER(VariableProxy)
+    NOT_INITIALIZER(Literal)
+    NOT_INITIALIZER(RegExpLiteral)
+    NOT_INITIALIZER(ObjectLiteral)
+    NOT_INITIALIZER(ArrayLiteral)
+    NOT_INITIALIZER(AssignmentPattern)
+    NOT_INITIALIZER(Yield)
+    NOT_INITIALIZER(Throw)
+    NOT_INITIALIZER(Property)
+    NOT_INITIALIZER(Call)
+    NOT_INITIALIZER(CallNew)
+    NOT_INITIALIZER(CallRuntime)
+    NOT_INITIALIZER(UnaryOperation)
+    NOT_INITIALIZER(CountOperation)
+    NOT_INITIALIZER(BinaryOperation)
+    NOT_INITIALIZER(CompareOperation)
+    NOT_INITIALIZER(Spread)
+    NOT_INITIALIZER(ThisFunction)
+    NOT_INITIALIZER(SuperPropertyReference)
+    NOT_INITIALIZER(SuperCallReference)
+    NOT_INITIALIZER(CaseClause)
+    NOT_INITIALIZER(EmptyParentheses)
+    NOT_INITIALIZER(DoExpression)
+  #undef NOT_INITIALIZER*/
+ private:
+  Parser* parser_;
+  Scope* scope_;
+};
+
+
+void Parser::RewriteParameterInitializer(Expression* expr, Scope* scope) {
+  InitializerRewriter rewriter(stack_limit_, expr, this, scope);
+  rewriter.Run();
+}
+
+
 Block* Parser::BuildParameterInitializationBlock(
     const ParserFormalParameters& parameters, bool* ok) {
   DCHECK(!parameters.is_simple);
   DCHECK(scope_->is_function_scope());
   Block* init_block =
       factory()->NewBlock(NULL, 1, true, RelocInfo::kNoPosition);
   for (int i = 0; i < parameters.params.length(); ++i) {
     auto parameter = parameters.params[i];
     DeclarationDescriptor descriptor;
     descriptor.declaration_kind = DeclarationDescriptor::PARAMETER;
     descriptor.parser = this;
     descriptor.declaration_scope = scope_;
     descriptor.scope = scope_;
     descriptor.hoist_scope = nullptr;
     descriptor.mode = LET;
     descriptor.is_const = false;
     descriptor.needs_init = true;
     descriptor.declaration_pos = parameter.pattern->position();
     descriptor.initialization_pos = parameter.pattern->position();
     descriptor.init_op = Token::INIT_LET;
     Expression* initial_value =
         factory()->NewVariableProxy(parameters.scope->parameter(i));
     if (parameter.initializer != nullptr) {
       // IS_UNDEFINED($param) ? initializer : $param
       DCHECK(!parameter.is_rest);
+
+      // Ensure initializer is rewritten
+      RewriteParameterInitializer(parameter.initializer, scope_);
+
       auto condition = factory()->NewCompareOperation(
           Token::EQ_STRICT,
           factory()->NewVariableProxy(parameters.scope->parameter(i)),
           factory()->NewUndefinedLiteral(RelocInfo::kNoPosition),
           RelocInfo::kNoPosition);
       initial_value = factory()->NewConditional(
           condition, parameter.initializer, initial_value,
           RelocInfo::kNoPosition);
       descriptor.initialization_pos = parameter.initializer->position();
     } else if (parameter.is_rest) {
@@ skipping 1848 matching lines @@
 }
 
 
 void Parser::RaiseLanguageMode(LanguageMode mode) {
   SetLanguageMode(scope_,
                   static_cast<LanguageMode>(scope_->language_mode() | mode));
 }
 
 }  // namespace internal
 }  // namespace v8