[es8] Initial set of changes to support syntactic tail calls.

src/parsing/preparser.cc

Index: src/parsing/preparser.cc
diff --git a/src/parsing/preparser.cc b/src/parsing/preparser.cc
index b5d5c287282a993c8c50ebb295dd22567abd2cd2..abe3479ce3f15d3d1c3eefb0c8f59695eea22667 100644
--- a/src/parsing/preparser.cc
+++ b/src/parsing/preparser.cc
@@ -12,8 +12,8 @@
 #include "src/hashmap.h"
 #include "src/list.h"
 #include "src/parsing/parser-base.h"
-#include "src/parsing/preparse-data.h"
 #include "src/parsing/preparse-data-format.h"
+#include "src/parsing/preparse-data.h"
 #include "src/parsing/preparser.h"
 #include "src/unicode.h"
 #include "src/utils.h"
@@ -681,11 +681,27 @@ PreParser::Statement PreParser::ParseReturnStatement(bool* ok) {
   // This is not handled during preparsing.
 
   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();
+  }
   if (!scanner()->HasAnyLineTerminatorBeforeNext() &&
       tok != Token::SEMICOLON &&
       tok != Token::RBRACE &&
       tok != Token::EOS) {
     ParseExpression(true, CHECK_OK);
+    if (tail_call_position >= 0) {
+      if (!function_state_->collect_expressions_in_tail_position()) {
+        Scanner::Location loc(tail_call_position, tail_call_position + 1);
+        ReportMessageAt(loc, MessageTemplate::kTailCallInTryBlock);
+        *ok = false;
+        return Statement::Default();
+      }
+      function_state_->AddExpressionInTailPosition(
+          PreParserExpression::Default(), tail_call_position);
+    }
   }
   ExpectSemicolon(CHECK_OK);
   return Statement::Jump();
@@ -936,7 +952,10 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
 
   Expect(Token::TRY, CHECK_OK);
 
-  ParseBlock(CHECK_OK);
+  {
+    DontCollectExpressionsInTailPositionScope no_tail_calls(function_state_);
+    ParseBlock(CHECK_OK);
+  }
 
   Token::Value tok = peek();
   if (tok != Token::CATCH && tok != Token::FINALLY) {
@@ -944,6 +963,8 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
     *ok = false;
     return Statement::Default();
   }
+  List<TailCallExpression> expressions_in_tail_position_in_catch_block;
+  bool catch_block_exists = false;
   if (tok == Token::CATCH) {
     Consume(Token::CATCH);
     Expect(Token::LPAREN, CHECK_OK);
@@ -953,6 +974,9 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
     ValidateBindingPattern(&pattern_classifier, CHECK_OK);
     Expect(Token::RPAREN, CHECK_OK);
     {
+      CollectExpressionsInTailPositionToListScope
+          collect_expressions_in_tail_position_scope(
+              function_state_, &expressions_in_tail_position_in_catch_block);
       BlockState block_state(&scope_, catch_scope);
       Scope* block_scope = NewScope(scope_, BLOCK_SCOPE);
       {
@@ -960,11 +984,22 @@ PreParser::Statement PreParser::ParseTryStatement(bool* ok) {
         ParseBlock(CHECK_OK);
       }
     }
+    catch_block_exists = true;
     tok = peek();
   }
   if (tok == Token::FINALLY) {
     Consume(Token::FINALLY);
     ParseBlock(CHECK_OK);
+    if (FLAG_harmony_explicit_tailcalls && catch_block_exists &&

[rossberg, 2016/04/26 14:56:57]

Same question here, where is the corresponding logic for implicit tail calls?

[Igor Sheludko, 2016/04/26 16:48:17]

Implicit tail calls does not produce any errors, therefore there was no code in
the preparser at all. However in case of STC we have to report syntax errors for
tail call expression in wrong places.

+        expressions_in_tail_position_in_catch_block.length() > 0) {
+      // TODO(ishell): update chapter number.
+      // ES7 XX.YY.ZZ
+      int pos = expressions_in_tail_position_in_catch_block[0].pos;
+      ReportMessageAt(Scanner::Location(pos, pos + 1),
+                      MessageTemplate::kTailCallInCatchBlock);
+      *ok = false;
+      return Statement::Default();
+    }
   }
   return Statement::Default();
 }