[es8] More spec compliant syntactic tail calls implementation.

src/parsing/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/parsing/parser.h"
 
 #include "src/api.h"
 #include "src/ast/ast.h"
 #include "src/ast/ast-expression-rewriter.h"
 #include "src/ast/ast-expression-visitor.h"
@@ skipping 747 matching lines @@
     const AstRawString* name, Scanner::Location class_name_location,
     bool name_is_strict_reserved, int pos, bool* ok) {
   return parser_->ParseClassLiteral(name, class_name_location,
                                     name_is_strict_reserved, pos, ok);
 }
 
 void ParserTraits::MarkTailPosition(Expression* expression) {
   expression->MarkTail();
 }
 
+void ParserTraits::MarkCollectedTailCallExpressions() {
+  parser_->MarkCollectedTailCallExpressions();
+}
+
 Parser::Parser(ParseInfo* info)
     : ParserBase<ParserTraits>(info->zone(), &scanner_, info->stack_limit(),
                                info->extension(), info->ast_value_factory(),
                                NULL, this),
       scanner_(info->unicode_cache()),
       reusable_preparser_(NULL),
       original_scope_(NULL),
       target_stack_(NULL),
       compile_options_(info->compile_options()),
       cached_parse_data_(NULL),
@@ skipping 1801 matching lines @@
   //   'return' Expression? ';'
 
   // Consume the return token. It is necessary to do that before
   // reporting any errors on it, because of the way errors are
   // reported (underlining).
   Expect(Token::RETURN, CHECK_OK);
   Scanner::Location loc = scanner()->location();
   function_state_->set_return_location(loc);
 
   Token::Value tok = peek();
-  int tail_call_position = -1;
-  if (FLAG_harmony_explicit_tailcalls && tok == Token::CONTINUE) {
-    Consume(Token::CONTINUE);
-    tail_call_position = position();
-    tok = peek();
-  }
-
   Statement* result;
   Expression* return_value;
   if (scanner()->HasAnyLineTerminatorBeforeNext() ||
       tok == Token::SEMICOLON ||
       tok == Token::RBRACE ||
       tok == Token::EOS) {
     if (IsSubclassConstructor(function_state_->kind())) {
       return_value = ThisExpression(scope_, factory(), loc.beg_pos);
     } else {
       return_value = GetLiteralUndefined(position());
     }
   } else {
     int pos = peek_position();
-    return_value = ParseExpression(true, CHECK_OK);
 
     if (IsSubclassConstructor(function_state_->kind())) {
+      // Because of the return code rewriting that happens in case of a subclass
+      // constructor we don't want to accept tail calls, therefore we don't set
+      // ReturnExprScope to kInsideValidReturnStatement here.
+      return_value = ParseExpression(true, CHECK_OK);
+
       // For subclass constructors we need to return this in case of undefined
       // return a Smi (transformed into an exception in the ConstructStub)
       // for a non object.
       //
       //   return expr;
       //
       // Is rewritten as:
       //
       //   return (temp = expr) === undefined ? this :
       //       %_IsJSReceiver(temp) ? temp : 1;
@@ skipping 18 matching lines @@
 
       // temp === undefined
       Expression* is_undefined = factory()->NewCompareOperation(
           Token::EQ_STRICT, assign,
           factory()->NewUndefinedLiteral(RelocInfo::kNoPosition), pos);
 
       // is_undefined ? this : is_object_conditional
       return_value = factory()->NewConditional(
           is_undefined, ThisExpression(scope_, factory(), pos),
           is_object_conditional, pos);
-    }
+    } else {
+      ReturnExprScope maybe_allow_tail_calls(
+          function_state_, ReturnExprContext::kInsideValidReturnStatement);
+      return_value = ParseExpression(true, CHECK_OK);
 
-    // TODO(ishell): update chapter number.
-    // ES8 XX.YY.ZZ
-    if (tail_call_position >= 0) {
-      ReturnExprContext return_expr_context =
-          function_state_->return_expr_context();
-      if (return_expr_context != ReturnExprContext::kNormal) {
-        ReportIllegalTailCallAt(tail_call_position, return_expr_context);
-        *ok = false;
-        return NULL;
+      if (allow_tailcalls() && !is_sloppy(language_mode())) {
+        // ES6 14.6.1 Static Semantics: IsInTailPosition
+        Scanner::Location loc(pos, pos + 1);
+        function_state_->AddExpressionInTailPosition(return_value, loc);
       }
-      function_state_->AddExpressionInTailPosition(return_value,
-                                                   tail_call_position);
-
-    } else if (allow_tailcalls() && !is_sloppy(language_mode())) {
-      // ES6 14.6.1 Static Semantics: IsInTailPosition
-      function_state_->AddExpressionInTailPosition(return_value, pos);
     }
   }
   ExpectSemicolon(CHECK_OK);
 
   if (is_generator()) {
     return_value = BuildIteratorResult(return_value, true);
   }
 
   result = factory()->NewReturnStatement(return_value, loc.beg_pos);
 
@@ skipping 192 matching lines @@
   Token::Value tok = peek();
   if (tok != Token::CATCH && tok != Token::FINALLY) {
     ReportMessage(MessageTemplate::kNoCatchOrFinally);
     *ok = false;
     return NULL;
   }
 
   Scope* catch_scope = NULL;
   Variable* catch_variable = NULL;
   Block* catch_block = NULL;
-  List<TailCallExpression> expressions_in_tail_position_in_catch_block;
+  TailCallExpressionList tail_call_expressions_in_catch_block(zone());
   if (tok == Token::CATCH) {
     Consume(Token::CATCH);
 
     Expect(Token::LPAREN, CHECK_OK);
     catch_scope = NewScope(scope_, CATCH_SCOPE);
     catch_scope->set_start_position(scanner()->location().beg_pos);
 
     ExpressionClassifier pattern_classifier(this);
     Expression* pattern = ParsePrimaryExpression(&pattern_classifier, CHECK_OK);
     ValidateBindingPattern(&pattern_classifier, CHECK_OK);
 
     const AstRawString* name = ast_value_factory()->dot_catch_string();
     bool is_simple = pattern->IsVariableProxy();
     if (is_simple) {
       auto proxy = pattern->AsVariableProxy();
       scope_->RemoveUnresolved(proxy);
       name = proxy->raw_name();
     }
 
     catch_variable = catch_scope->DeclareLocal(name, VAR, kCreatedInitialized,
                                                Variable::NORMAL);
 
     Expect(Token::RPAREN, CHECK_OK);
 
     {
       CollectExpressionsInTailPositionToListScope
-          collect_expressions_in_tail_position_scope(
-              function_state_, &expressions_in_tail_position_in_catch_block);
+          collect_tail_call_expressions_scope(
+              function_state_, &tail_call_expressions_in_catch_block);
       BlockState block_state(&scope_, catch_scope);
 
       // TODO(adamk): Make a version of ParseBlock that takes a scope and
       // a block.
       catch_block =
           factory()->NewBlock(nullptr, 16, false, RelocInfo::kNoPosition);
       Scope* block_scope = NewScope(scope_, BLOCK_SCOPE);
 
       block_scope->set_start_position(scanner()->location().beg_pos);
       {
@@ skipping 59 matching lines @@
                                         catch_block, RelocInfo::kNoPosition);
     try_block = factory()->NewBlock(NULL, 1, false, RelocInfo::kNoPosition);
     try_block->statements()->Add(statement, zone());
     catch_block = NULL;  // Clear to indicate it's been handled.
   }
 
   TryStatement* result = NULL;
   if (catch_block != NULL) {
     // For a try-catch construct append return expressions from the catch block
     // to the list of return expressions.
-    function_state_->expressions_in_tail_position().AddAll(
-        expressions_in_tail_position_in_catch_block);
+    function_state_->tail_call_expressions().Append(
+        tail_call_expressions_in_catch_block);
 
     DCHECK(finally_block == NULL);
     DCHECK(catch_scope != NULL && catch_variable != NULL);
     result = factory()->NewTryCatchStatement(try_block, catch_scope,
                                              catch_variable, catch_block, pos);
   } else {
     if (FLAG_harmony_explicit_tailcalls &&
-        expressions_in_tail_position_in_catch_block.length() > 0) {
+        !tail_call_expressions_in_catch_block.is_empty()) {
       // TODO(ishell): update chapter number.
       // ES8 XX.YY.ZZ
-      int pos = expressions_in_tail_position_in_catch_block[0].pos;
-      ReportMessageAt(Scanner::Location(pos, pos + 1),
-                      MessageTemplate::kTailCallInCatchBlock);
+      ReportMessageAt(tail_call_expressions_in_catch_block.location(),
+                      MessageTemplate::kUnexpectedTailCallInCatchBlock);
       *ok = false;
       return NULL;
     }
     DCHECK(finally_block != NULL);
     result = factory()->NewTryFinallyStatement(try_block, finally_block, pos);
   }
 
   return result;
 }
 
@@ skipping 1563 matching lines @@
 
     VariableProxy* fproxy = factory()->NewVariableProxy(fvar);
     result->Set(kFunctionNameAssignmentIndex,
                 factory()->NewExpressionStatement(
                     factory()->NewAssignment(Token::INIT, fproxy,
                                              factory()->NewThisFunction(pos),
                                              RelocInfo::kNoPosition),
                     RelocInfo::kNoPosition));
   }
 
-  // ES6 14.6.1 Static Semantics: IsInTailPosition
-  // Mark collected return expressions that are in tail call position.
-  const List<TailCallExpression>& expressions_in_tail_position =
-      function_state_->expressions_in_tail_position();
-  for (int i = 0; i < expressions_in_tail_position.length(); ++i) {
-    MarkTailPosition(expressions_in_tail_position[i].expression);
-  }
+  MarkCollectedTailCallExpressions();
   return result;
 }
 
 
 PreParser::PreParseResult Parser::ParseLazyFunctionBodyWithPreParser(
     SingletonLogger* logger, Scanner::BookmarkScope* bookmark) {
   // This function may be called on a background thread too; record only the
   // main thread preparse times.
   if (pre_parse_timer_ != NULL) {
     pre_parse_timer_->Start();
@@ skipping 53 matching lines @@
     proxy = NewUnresolved(name, CONST);
     Declaration* declaration =
         factory()->NewVariableDeclaration(proxy, CONST, block_scope, pos);
     Declare(declaration, DeclarationDescriptor::NORMAL, true, CHECK_OK);
   }
 
   Expression* extends = NULL;
   if (Check(Token::EXTENDS)) {
     block_scope->set_start_position(scanner()->location().end_pos);
     ExpressionClassifier classifier(this);
-    extends = ParseLeftHandSideExpression(&classifier, CHECK_OK);
+    extends =
+        ParseLeftHandSideExpression(kDontAcceptTCE, &classifier, CHECK_OK);
     RewriteNonPattern(&classifier, CHECK_OK);
   } else {
     block_scope->set_start_position(scanner()->location().end_pos);
   }
 
 
   ClassLiteralChecker checker(this);
   ZoneList<ObjectLiteral::Property*>* properties = NewPropertyList(4, zone());
   FunctionLiteral* constructor = NULL;
   bool has_seen_constructor = false;
@@ skipping 618 matching lines @@
   ++use_counts_[feature];
   scope->SetLanguageMode(mode);
 }
 
 
 void Parser::RaiseLanguageMode(LanguageMode mode) {
   LanguageMode old = scope_->language_mode();
   SetLanguageMode(scope_, old > mode ? old : mode);
 }
 
+void Parser::MarkCollectedTailCallExpressions() {
+  const ZoneList<Expression*>& tail_call_expressions =
+      function_state_->tail_call_expressions().expressions();
+  for (int i = 0; i < tail_call_expressions.length(); ++i) {
+    Expression* expression = tail_call_expressions[i];
+    // If only FLAG_harmony_explicit_tailcalls is enabled then expression
+    // must be a Call expression.
+    DCHECK(FLAG_harmony_tailcalls || !FLAG_harmony_explicit_tailcalls ||
+           expression->IsCall());
+    MarkTailPosition(expression);
+  }
+}
 
 void ParserTraits::RewriteDestructuringAssignments() {
   parser_->RewriteDestructuringAssignments();
 }
 
 Expression* ParserTraits::RewriteExponentiation(Expression* left,
                                                 Expression* right, int pos) {
   return parser_->RewriteExponentiation(left, right, pos);
 }
 
@@ skipping 1493 matching lines @@
                         try_block, target);
     final_loop = target;
   }
 
   return final_loop;
 }
 
 
 }  // namespace internal
 }  // namespace v8