[es8] Remove syntactic tail calls support.

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 <memory>
 
 #include "src/api.h"
 #include "src/ast/ast-expression-rewriter.h"
@@ skipping 3609 matching lines @@
         factory()->NewVariableDeclaration(proxy, block_state.scope(), pos);
     Declare(declaration, DeclarationDescriptor::NORMAL, CONST,
             Variable::DefaultInitializationFlag(CONST), CHECK_OK);
   }
 
   Expression* extends = nullptr;
   if (Check(Token::EXTENDS)) {
     block_state.set_start_position(scanner()->location().end_pos);
     ExpressionClassifier extends_classifier(this);
     extends = ParseLeftHandSideExpression(CHECK_OK);
-    CheckNoTailCallExpressions(CHECK_OK);
     RewriteNonPattern(CHECK_OK);
     impl()->AccumulateFormalParameterContainmentErrors();
   } else {
     block_state.set_start_position(scanner()->location().end_pos);
   }
 
 
   ClassLiteralChecker checker(this);
   ZoneList<ClassLiteral::Property*>* properties = NewClassPropertyList(4);
   ZoneList<Expression*>* instance_field_initializers =
@@ skipping 650 matching lines @@
   // incremented after parsing is done.
   ++use_counts_[v8::Isolate::kUseAsm];
   DCHECK(scope()->is_declaration_scope());
   scope()->AsDeclarationScope()->set_asm_module();
 }
 
 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);
+    MarkTailPosition(tail_call_expressions[i]);
   }
 }
 
 Expression* Parser::ExpressionListToExpression(ZoneList<Expression*>* args) {
   Expression* expr = args->at(0);
   for (int i = 1; i < args->length(); ++i) {
     expr = factory()->NewBinaryOperation(Token::COMMA, expr, args->at(i),
                                          expr->position());
   }
   return expr;
@@ skipping 1259 matching lines @@
 
   return final_loop;
 }
 
 #undef CHECK_OK
 #undef CHECK_OK_VOID
 #undef CHECK_FAILED
 
 }  // namespace internal
 }  // namespace v8