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Go patch committed: Permit label on fallthrough statement

Message ID CAOyqgcUk1iYWEbWoSYf0_gedFepbUZdmxwD-QV92T0BnjaB3Jw@mail.gmail.com
State New
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Commit Message

Ian Lance Taylor March 13, 2015, 8:48 p.m. UTC 
The gccgo parser had a bug: it rejected labels on fallthrough
statements, because those statements can only appear in specific
contexts (at the end of a switch block just before the next case
statement).  This patch fixes the problem.  I will add a test to the
master testsuite for this, which will be brought into the gccgo
testsuite in due course (https://go-review.googlesource.com/7523).
Bootstrapped and ran Go testsuite on x86_64-unknown-linux-gnu.
Committed to mainline.

Ian
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Patch

diff -r 52642b1b9500 go/parse.cc
--- a/go/parse.cc	Fri Mar 13 11:52:24 2015 -0700
+++ b/go/parse.cc	Fri Mar 13 13:43:52 2015 -0700
@@ -3735,6 +3735,17 @@ 
 
   if (!this->statement_may_start_here())
     {
+      if (this->peek_token()->is_keyword(KEYWORD_FALLTHROUGH))
+	{
+	  // We don't treat the fallthrough keyword as a statement,
+	  // because it can't appear most places where a statement is
+	  // permitted, but it may have a label.  We introduce a
+	  // semicolon because the caller expects to see a statement.
+	  this->unget_token(Token::make_operator_token(OPERATOR_SEMICOLON,
+						       location));
+	  return;
+	}
+
       // Mark the label as used to avoid a useless error about an
       // unused label.
       if (label != NULL)