[Format/ObjC] Fix [foo bar]->baz formatting as lambda arrow

Summary:
Currently, `UnwrappedLineParser` thinks an arrow token after
an ObjC method expression is a C++ lambda arrow, so it formats:

```
[foo bar]->baz
```

as:

```
[foo bar] -> baz
```

Because `UnwrappedLineParser` runs before `TokenAnnotator`, it can't
know if the arrow token is after an ObjC method expression or not.

This diff makes `TokenAnnotator` remove the TT_LambdaArrow on
the arrow token if it follows an ObjC method expression.

Test Plan: New test added. Ran test with:
  % ninja FormatTests && ./tools/clang/unittests/Format/FormatTests
  Confirmed test failed before diff and passed after diff.

Reviewers: krasimir, djasper, sammccall

Reviewed By: sammccall

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D57923

llvm-svn: 353531

1 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index f6727fcfa97..80bfca644c9 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1426,6 +1426,9 @@ bool UnwrappedLineParser::tryToParseLambda() {
       nextToken();
       break;
     case tok::arrow:
+      // This might or might not actually be a lambda arrow (this could be an
+      // ObjC method invocation followed by a dereferencing arrow). We might
+      // reset this back to TT_Unknown in TokenAnnotator.
       FormatTok->Type = TT_LambdaArrow;
       nextToken();
       break;