clang-format: Handle "if constexpr".

c++1z adds the following constructions to the language:

  if constexpr (cond)
    statement1;
  else if constexpr (cond)
    statement2;
  else if constexpr (cond)
    statement3;
  else
    statement4;

A first version of this was proposed in reviews.llvm.org/D26953 by
Francis Visoiu Mistrih, but never commited. This patch additionally
fixes the behavior when allowing short if statements on a single line
and was authored by Jacob Bandes-Storch. Thank you to both authors.

llvm-svn: 305666

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index 27436dda67a..f7678bb6b2a 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1516,6 +1516,8 @@ void UnwrappedLineParser::parseSquare() {
 void UnwrappedLineParser::parseIfThenElse() {
   assert(FormatTok->Tok.is(tok::kw_if) && "'if' expected");
   nextToken();
+  if (FormatTok->Tok.is(tok::kw_constexpr))
+    nextToken();
   if (FormatTok->Tok.is(tok::l_paren))
     parseParens();
   bool NeedsUnwrappedLine = false;