[parser] Inline ParseStatemantAsUnlabelled into its only useful caller

Tracking labels for most of these statements made no difference: only
try-statements require the special treatment of being wrapped in a
block. The previous code existed to support strong mode, which is
long gone.

This also results in a tiny regression of the error message for
a labelled `continue` statement targeting itself, but I'm not
convinced that anyone would ever intend to label a continue
statement (and Chakra and SpiderMonkey give similarly inaccurate
error messages for this case).

This is effectively a revert of d8bccfe974.

Bug: v8:6092
Change-Id: I25b62e10f6a20597e9686f08df76ba9724249618
Reviewed-on: https://chromium-review.googlesource.com/653380
Reviewed-by: Marja Hölttä <marja@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47904}

src/parsing/parser-base.h

@@ -1181,8 +1181,6 @@ class ParserBase {
   StatementT ParseStatement(ZoneList<const AstRawString*>* labels,
                             AllowLabelledFunctionStatement allow_function,
                             bool* ok);
-  StatementT ParseStatementAsUnlabelled(ZoneList<const AstRawString*>* labels,
-                                        bool* ok);
   BlockT ParseBlock(ZoneList<const AstRawString*>* labels, bool* ok);
 
   // Parse a SubStatement in strict mode, or with an extra block scope in
@@ -4867,23 +4865,25 @@ typename ParserBase<Impl>::StatementT ParserBase<Impl>::ParseStatement(
       }
       return ParseForStatement(labels, ok);
     case Token::CONTINUE:
+      return ParseContinueStatement(ok);
     case Token::BREAK:
+      return ParseBreakStatement(labels, ok);
     case Token::RETURN:
+      return ParseReturnStatement(ok);
     case Token::THROW:
+      return ParseThrowStatement(ok);
     case Token::TRY: {
-      // These statements must have their labels preserved in an enclosing
-      // block, as the corresponding AST nodes do not currently store their
-      // labels.
-      // TODO(nikolaos, marja): Consider adding the labels to the AST nodes.
-      if (labels == nullptr) {
-        return ParseStatementAsUnlabelled(labels, ok);
-      } else {
-        BlockT result = factory()->NewBlock(1, false, labels);
-        typename Types::Target target(this, result);
-        StatementT statement = ParseStatementAsUnlabelled(labels, CHECK_OK);
-        result->statements()->Add(statement, zone());
-        return result;
-      }
+      // It is somewhat complicated to have labels on try-statements.
+      // When breaking out of a try-finally statement, one must take
+      // great care not to treat it as a fall-through. It is much easier
+      // just to wrap the entire try-statement in a statement block and
+      // put the labels there.
+      if (labels == nullptr) return ParseTryStatement(ok);
+      BlockT result = factory()->NewBlock(1, false, labels);
+      typename Types::Target target(this, result);
+      StatementT statement = ParseTryStatement(CHECK_OK);
+      result->statements()->Add(statement, zone());
+      return result;
     }
     case Token::WITH:
       return ParseWithStatement(labels, ok);
@@ -4920,29 +4920,6 @@ typename ParserBase<Impl>::StatementT ParserBase<Impl>::ParseStatement(
   }
 }
 
-// This method parses a subset of statements (break, continue, return, throw,
-// try) which are to be grouped because they all require their labeles to be
-// preserved in an enclosing block.
-template <typename Impl>
-typename ParserBase<Impl>::StatementT
-ParserBase<Impl>::ParseStatementAsUnlabelled(
-    ZoneList<const AstRawString*>* labels, bool* ok) {
-  switch (peek()) {
-    case Token::CONTINUE:
-      return ParseContinueStatement(ok);
-    case Token::BREAK:
-      return ParseBreakStatement(labels, ok);
-    case Token::RETURN:
-      return ParseReturnStatement(ok);
-    case Token::THROW:
-      return ParseThrowStatement(ok);
-    case Token::TRY:
-      return ParseTryStatement(ok);
-    default:
-      UNREACHABLE();
-  }
-}
-
 template <typename Impl>
 typename ParserBase<Impl>::BlockT ParserBase<Impl>::ParseBlock(
     ZoneList<const AstRawString*>* labels, bool* ok) {

test/webkit/js-continue-break-restrictions-expected.txt

@@ -42,17 +42,17 @@ PASS if (0) { L:A:{ continue; } } threw exception SyntaxError: Illegal continue
 PASS if(0){ L:for(;;) continue L; } is undefined.
 PASS if(0){ L:A:for(;;) continue L; } is undefined.
 PASS if(0){ A:L:for(;;) continue L; } is undefined.
-PASS if(0){ A:for(;;) L:continue L; } threw exception SyntaxError: Illegal continue statement: 'L' does not denote an iteration statement.
+PASS if(0){ A:for(;;) L:continue L; } threw exception SyntaxError: Undefined label 'L'.
 PASS if(0){ L:for(;;) A:continue L; } is undefined.
 PASS if(0){ L:do continue L; while(0); } is undefined.
 PASS if(0){ L:A:do continue L; while(0); } is undefined.
 PASS if(0){ A:L:do continue L; while(0);} is undefined.
-PASS if(0){ A:do L:continue L; while(0); } threw exception SyntaxError: Illegal continue statement: 'L' does not denote an iteration statement.
+PASS if(0){ A:do L:continue L; while(0); } threw exception SyntaxError: Undefined label 'L'.
 PASS if(0){ L:do A:continue L; while(0); } is undefined.
 PASS if(0){ L:while(0) continue L; } is undefined.
 PASS if(0){ L:A:while(0) continue L; } is undefined.
 PASS if(0){ A:L:while(0) continue L; } is undefined.
-PASS if(0){ A:while(0) L:continue L; } threw exception SyntaxError: Illegal continue statement: 'L' does not denote an iteration statement.
+PASS if(0){ A:while(0) L:continue L; } threw exception SyntaxError: Undefined label 'L'.
 PASS if(0){ L:while(0) A:continue L; } is undefined.
 PASS successfullyParsed is true