clang-format: Allow optimizer to break template declaration.

Summary:
Introduce `PenaltyBreakTemplateDeclaration` to control the penalty,
and change `AlwaysBreakTemplateDeclarations` to an enum with 3 modes:
* `No` for regular, penalty based, wrapping of template declaration
* `MultiLine` for always wrapping before multi-line declarations (e.g.
  same as legacy behavior when `AlwaysBreakTemplateDeclarations=false`)
* `Yes` for always wrapping (e.g. same as legacy behavior when
  `AlwaysBreakTemplateDeclarations=true`)

Reviewers: krasimir, djasper, klimek

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D42684

llvm-svn: 332436

1 files changed, 7 insertions, 1 deletions

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index 20eb5c03b8b..9a07c5ed591 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -402,6 +402,12 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
         Style.Language == FormatStyle::LK_JavaScript))
     return true;
 
+  // If the template declaration spans multiple lines, force wrap before the
+  // function/class declaration
+  if (Previous.ClosesTemplateDeclaration &&
+      State.Stack.back().BreakBeforeParameter)
+    return true;
+
   if (State.Column <= NewLineColumn)
     return false;
 
@@ -453,7 +459,7 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
     // for cases where the entire line does not fit on a single line as a
     // different LineFormatter would be used otherwise.
     if (Previous.ClosesTemplateDeclaration)
-      return true;
+      return Style.AlwaysBreakTemplateDeclarations != FormatStyle::BTDS_No;
     if (Previous.is(TT_FunctionAnnotationRParen))
       return true;
     if (Previous.is(TT_LeadingJavaAnnotation) && Current.isNot(tok::l_paren) &&