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

[MyDeveloperDay via Phabricator via cfe-commits]

MyDeveloperDay updated this revision to Diff 227166.
MyDeveloperDay added a comment.

move detection of deduction guides into a function, add additional negative tests


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69577/new/

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 +4977,21 @@
   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)>;");
+
+  // Ensure not deduction guides.
+  verifyFormat("c()->f<int>();");
+  verifyFormat("x()->foo<1>;");
+  verifyFormat("x = p->foo<3>();");
+  verifyFormat("A()->A<decltype(p->foo<3>())>;");
+}
+
 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
@@ -1350,6 +1350,38 @@
     }
   }
 
+  static bool isDeductionGuide(FormatToken &Current) {
+    // Look for a deduction guide A()...) -> A<...>;
+    if (Current.Previous && Current.Previous->is(tok::r_paren) &&
+        Current.startsSequence(tok::arrow, tok::identifier, tok::less)) {
+      // Find the TemplateCloser.
+      FormatToken *TemplateCloser = Current.Next->Next;
+      int NestingLevel = 1;
+      while (TemplateCloser && NestingLevel > 0) {
+        TemplateCloser = TemplateCloser->Next;
+        if (TemplateCloser->is(tok::less))
+          NestingLevel++;
+        if (TemplateCloser->is(tok::greater))
+          NestingLevel--;
+        if (TemplateCloser->is(tok::kw_decltype))
+          return false;
+      }
+      // Assuming we have found the end of the template ensure its followed
+      // with a ;
+      if (TemplateCloser && TemplateCloser->Next &&
+          TemplateCloser->Next->is(tok::semi) &&
+          Current.Previous->MatchingParen) {
+        // Determine if the identifier `A` prior to the A<..>; is the same as
+        // prior to the A(..)
+        FormatToken *LeadingIdentifier =
+            Current.Previous->MatchingParen->Previous;
+        return (LeadingIdentifier &&
+                LeadingIdentifier->TokenText == Current.Next->TokenText);
+      }
+    }
+    return false;
+  }
+
   void determineTokenType(FormatToken &Current) {
     if (!Current.is(TT_Unknown))
       // The token type is already known.
@@ -1397,6 +1429,10 @@
                !Current.Previous->is(tok::kw_operator)) {
       // not auto operator->() -> xxx;
       Current.Type = TT_TrailingReturnArrow;
+
+    } else if (isDeductionGuide(Current)) {
+      // Deduction guides trailing arrow "...) -> A<T>;".
+      Current.Type = TT_TrailingReturnArrow;
     } else if (Current.isOneOf(tok::star, tok::amp, tok::ampamp)) {
       Current.Type = determineStarAmpUsage(Current,
                                            Contexts.back().CanBeExpression &&


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