clang-format: Prefer breaking before trailing return arrows.

Before:
  auto SomeFunction(
      A aaaaaaaaaaaaaaaaaaaaa) const -> decltype(f(aaaaaaaaaaaaaaaaaaaaa)) {}

After:
  auto SomeFunction(A aaaaaaaaaaaaaaaaaaaaa) const
      -> decltype(f(aaaaaaaaaaaaaaaaaaaaa)) {}

llvm-svn: 220043

3 files changed, 5 insertions, 2 deletions

diff --git a/clang/lib/Format/FormatToken.h b/clang/lib/Format/FormatToken.h
index 38f157776f3..dc2c8a466ef 100644
--- a/clang/lib/Format/FormatToken.h
+++ b/clang/lib/Format/FormatToken.h
@@ -325,7 +325,8 @@ struct FormatToken {
   /// \brief Returns \c true if this is a "." or "->" accessing a member.
   bool isMemberAccess() const {
     return isOneOf(tok::arrow, tok::period, tok::arrowstar) &&
-           Type != TT_DesignatedInitializerPeriod;
+           Type != TT_DesignatedInitializerPeriod &&
+           Type != TT_TrailingReturnArrow;
   }
 
   bool isUnaryOperator() const {
diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 14382021b52..7e589c7a649 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -1902,7 +1902,7 @@ bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
     return true;
   return Left.isOneOf(tok::comma, tok::coloncolon, tok::semi, tok::l_brace,
                       tok::kw_class, tok::kw_struct) ||
-         Right.isMemberAccess() ||
+         Right.isMemberAccess() || Right.Type == TT_TrailingReturnArrow ||
          Right.isOneOf(tok::lessless, tok::colon, tok::l_square, tok::at) ||
          (Left.is(tok::r_paren) &&
           Right.isOneOf(tok::identifier, tok::kw_const)) ||
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index aebfef6fbea..b669795534d 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -3514,6 +3514,8 @@ TEST_F(FormatTest, TrailingReturnType) {
   verifyFormat("template <size_t Order, typename T>\n"
                "auto load_img(const std::string &filename)\n"
                "    -> alias::tensor<Order, T, mem::tag::cpu> {}");
+  verifyFormat("auto SomeFunction(A aaaaaaaaaaaaaaaaaaaaa) const\n"
+               "    -> decltype(f(aaaaaaaaaaaaaaaaaaaaa)) {}");
 
   // Not trailing return types.
   verifyFormat("void f() { auto a = b->c(); }");