From 0b7495e18087b0676af7e25a18f1434dc40b963b Mon Sep 17 00:00:00 2001
From: Jan Korous <jkorous@apple.com>
Date: Mon, 6 Nov 2017 17:42:17 +0000
Subject: [Parser] Fix TryParseLambdaIntroducer() error handling

rdar://35066196

Differential Revision: https://reviews.llvm.org/D39419

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@317493 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Parse/ParseExprCXX.cpp              | 35 ++++++++++++++++++++-------------
 test/Parser/objcxx11-invalid-lambda.cpp | 10 ++++++++++
 2 files changed, 31 insertions(+), 14 deletions(-)
 create mode 100644 test/Parser/objcxx11-invalid-lambda.cpp

diff --git a/lib/Parse/ParseExprCXX.cpp b/lib/Parse/ParseExprCXX.cpp
index ce6aa64de6..ad4801971a 100644
--- a/lib/Parse/ParseExprCXX.cpp
+++ b/lib/Parse/ParseExprCXX.cpp
@@ -991,27 +991,34 @@ Optional<unsigned> Parser::ParseLambdaIntroducer(LambdaIntroducer &Intro,
 ///
 /// Returns true if it hit something unexpected.
 bool Parser::TryParseLambdaIntroducer(LambdaIntroducer &Intro) {
-  TentativeParsingAction PA(*this);
+  {
+    bool SkippedInits = false;
+    TentativeParsingAction PA1(*this);
 
-  bool SkippedInits = false;
-  Optional<unsigned> DiagID(ParseLambdaIntroducer(Intro, &SkippedInits));
+    if (ParseLambdaIntroducer(Intro, &SkippedInits)) {
+      PA1.Revert();
+      return true;
+    }
 
-  if (DiagID) {
-    PA.Revert();
-    return true;
+    if (!SkippedInits) {
+      PA1.Commit();
+      return false;
+    }
+
+    PA1.Revert();
   }
 
-  if (SkippedInits) {
-    // Parse it again, but this time parse the init-captures too.
-    PA.Revert();
-    Intro = LambdaIntroducer();
-    DiagID = ParseLambdaIntroducer(Intro);
-    assert(!DiagID && "parsing lambda-introducer failed on reparse");
+  // Try to parse it again, but this time parse the init-captures too.
+  Intro = LambdaIntroducer();
+  TentativeParsingAction PA2(*this);
+
+  if (!ParseLambdaIntroducer(Intro)) {
+    PA2.Commit();
     return false;
   }
 
-  PA.Commit();
-  return false;
+  PA2.Revert();
+  return true;
 }
 
 static void
diff --git a/test/Parser/objcxx11-invalid-lambda.cpp b/test/Parser/objcxx11-invalid-lambda.cpp
new file mode 100644
index 0000000000..74c5636b6a
--- /dev/null
+++ b/test/Parser/objcxx11-invalid-lambda.cpp
@@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -x objective-c++ -std=c++11 %s
+
+void foo() {  // expected-note {{to match this '{'}}
+  int bar;
+  auto baz = [
+      bar(  // expected-note {{to match this '('}} expected-note {{to match this '('}}
+        foo_undeclared() // expected-error{{use of undeclared identifier 'foo_undeclared'}} expected-error{{use of undeclared identifier 'foo_undeclared'}}
+      /* ) */
+    ] () { };   // expected-error{{expected ')'}}
+}               // expected-error{{expected ')'}} expected-error{{expected ';' at end of declaration}} expected-error{{expected '}'}}
-- 
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