[PATCH] D130299: [clang-format] FIX: Misformatting lambdas with trailing return type 'auto' in braced lists

[Denis Fatkulin via Phabricator via cfe-commits]

denis-fatkulin created this revision.
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denis-fatkulin added a project: clang-format.
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Lambdas with trailing return type 'auto' are formatted incorrectly in braced lists. The simpliest reproduction code is:

  cpp
  auto list = {[]() -> auto { return 0; }};

Was reported at https://github.com/llvm/llvm-project/issues/54798


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D130299

Files:
  clang/lib/Format/TokenAnnotator.cpp
  clang/lib/Format/UnwrappedLineParser.cpp
  clang/unittests/Format/FormatTest.cpp


Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -23546,6 +23546,13 @@
   verifyFormat("auto lambda = [&a = a]() { a = 2; };", AlignStyle);
 }
 
+TEST_F(FormatTest, LambdaWithTrailingAutoInBracedList) {
+  FormatStyle Style = getLLVMStyle();
+  verifyFormat("auto list = {[]() -> auto { return Val; }};", Style);
+  verifyFormat("auto list = {[]() -> auto * { return Ptr; }};", Style);
+  verifyFormat("auto list = {[]() -> auto & { return Ref; }};", Style);
+}
+
 TEST_F(FormatTest, SpacesInConditionalStatement) {
   FormatStyle Spaces = getLLVMStyle();
   Spaces.IfMacros.clear();
Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -2108,6 +2108,7 @@
     case tok::l_square:
       parseSquare();
       break;
+    case tok::kw_auto:
     case tok::kw_class:
     case tok::kw_template:
     case tok::kw_typename:
Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -3310,6 +3310,10 @@
     }
   }
 
+  // Lambda with trailing return type 'auto': []() -> auto { return T; }
+  if (Left.is(tok::kw_auto) && Right.getType() == TT_LambdaLBrace)
+    return true;
+
   // auto{x} auto(x)
   if (Left.is(tok::kw_auto) && Right.isOneOf(tok::l_paren, tok::l_brace))
     return false;


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