clang-format: distinguish ObjC call subexpressions after r355434

Summary:
The revision r355434 had the unfortunate side-effect that it started to
recognize certain ObjC expressions with a call subexpression followed by a
`a->b` subexpression as C++ lambda expressions.

This patch adds a bit of logic to handle these cases and documents them in
tests.

The commented-out test cases in the new test suite are ones that were
problematic before r355434.

Reviewers: MyDeveloperDay, gribozavr

Reviewed By: MyDeveloperDay, gribozavr

Subscribers: MyDeveloperDay, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59210

llvm-svn: 355831

1 files changed, 19 insertions, 2 deletions

diff --git a/clang/lib/Format/UnwrappedLineParser.cpp b/clang/lib/Format/UnwrappedLineParser.cpp
index de7e646b17c..3abb6f40d74 100644
--- a/clang/lib/Format/UnwrappedLineParser.cpp
+++ b/clang/lib/Format/UnwrappedLineParser.cpp
@@ -1401,6 +1401,8 @@ bool UnwrappedLineParser::tryToParseLambda() {
   if (!tryToParseLambdaIntroducer())
     return false;
 
+  bool SeenArrow = false;
+
   while (FormatTok->isNot(tok::l_brace)) {
     if (FormatTok->isSimpleTypeSpecifier()) {
       nextToken();
@@ -1423,8 +1425,19 @@ bool UnwrappedLineParser::tryToParseLambda() {
     case tok::coloncolon:
     case tok::kw_mutable:
     case tok::kw_noexcept:
+      nextToken();
+      break;
     // Specialization of a template with an integer parameter can contain
     // arithmetic, logical, comparison and ternary operators.
+    //
+    // FIXME: This also accepts sequences of operators that are not in the scope
+    // of a template argument list.
+    //
+    // In a C++ lambda a template type can only occur after an arrow. We use
+    // this as an heuristic to distinguish between Objective-C expressions
+    // followed by an `a->b` expression, such as:
+    // ([obj func:arg] + a->b)
+    // Otherwise the code below would parse as a lambda.
     case tok::plus:
     case tok::minus:
     case tok::exclaim:
@@ -1444,13 +1457,17 @@ bool UnwrappedLineParser::tryToParseLambda() {
     case tok::colon:
     case tok::kw_true:
     case tok::kw_false:
-      nextToken();
-      break;
+      if (SeenArrow) {
+        nextToken();
+        break;
+      }
+      return true;
     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;
+      SeenArrow = true;
       nextToken();
       break;
     default: