[PATCH] D69577: [clang-format] [PR35518] C++17 deduction guides are wrongly formatted

[MyDeveloperDay via Phabricator via cfe-commits]

MyDeveloperDay created this revision.
MyDeveloperDay added reviewers: klimek, mitchell-stellar, owenpan, sammccall.
MyDeveloperDay added projects: clang-format, clang-tools-extra.
Herald added a project: clang.

see https://bugs.llvm.org/show_bug.cgi?id=35518

clang-format removes spaces around deduction guides but not trailing return types, make the consistent

  template <typename T> S(T)->S<T>;
  auto f(int, int) -> double;

becomes

  template <typename T> S(T) -> S<T>;
  auto f(int, int) -> double;




Repository:
  rC Clang

https://reviews.llvm.org/D69577

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


Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -4977,6 +4977,15 @@
   verifyFormat("void f() { auto a = b->c(); }");
 }
 
+TEST_F(FormatTest, DeductionGuides) {
+  verifyFormat("template <class T> A(const T &, const T &) -> A<T &>;");
+  verifyFormat("template <class T> explicit A(T &, T &&) -> A<T>;");
+  verifyFormat("template <class... Ts> S(Ts...) -> S<Ts...>;");
+  verifyFormat(
+      "template <class... T>\n"
+      "array(T &&... t) -> array<std::common_type_t<T...>, sizeof...(T)>;");
+}
+
 TEST_F(FormatTest, BreaksFunctionDeclarationsWithTrailingTokens) {
   // Avoid breaking before trailing 'const' or other trailing annotations, if
   // they are not function-like.
Index: clang/lib/Format/TokenAnnotator.cpp
===================================================================
--- clang/lib/Format/TokenAnnotator.cpp
+++ clang/lib/Format/TokenAnnotator.cpp
@@ -2932,6 +2932,16 @@
     return Right.is(TT_TemplateCloser) && Left.is(TT_TemplateCloser) &&
            (Style.Standard < FormatStyle::LS_Cpp11 || Style.SpacesInAngles);
   }
+
+  // Deduction guides add a space around the arrow  "...) -> A<T>".
+  if (Left.is(tok::r_paren) &&
+      Right.startsSequence(tok::arrow, TT_TrailingAnnotation,
+                           TT_TemplateOpener))
+    return true;
+  if (Left.is(tok::arrow) &&
+      Right.startsSequence(TT_TrailingAnnotation, TT_TemplateOpener))
+    return true;
+
   if (Right.isOneOf(tok::arrow, tok::arrowstar, tok::periodstar) ||
       Left.isOneOf(tok::arrow, tok::period, tok::arrowstar, tok::periodstar) ||
       (Right.is(tok::period) && Right.isNot(TT_DesignatedInitializerPeriod)))


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