[clang-format] Correct line breaks in C# generic type constraints

Reviewers: krasimir

Reviewed By: krasimir

Subscribers: cfe-commits

Tags: #clang-format, #clang

Differential Revision: https://reviews.llvm.org/D77064

Author: Jonathan Coe

clang/lib/Format/ContinuationIndenter.cpp

@@ -346,6 +346,11 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
       Current.startsSequence(TT_SelectorName, tok::colon, tok::caret)) {
     return true;
   }
+  // Avoid producing inconsistent states by requiring breaks where they are not
+  // permitted for C# generic type constraints.
+  if (State.Stack.back().IsCSharpGenericTypeConstraint &&
+      Previous.isNot(TT_CSharpGenericTypeConstraintComma))
+    return false;
   if ((startsNextParameter(Current, Style) || Previous.is(tok::semi) ||
        (Previous.is(TT_TemplateCloser) && Current.is(TT_StartOfName) &&
         Style.isCpp() &&

clang/lib/Format/TokenAnnotator.cpp

@@ -1060,15 +1060,20 @@ class AnnotatingParser {
   }
 
   void parseCSharpGenericTypeConstraint() {
+    int OpenAngleBracketsCount = 0;
     while (CurrentToken) {
       if (CurrentToken->is(tok::less)) {
         // parseAngle is too greedy and will consume the whole line.
         CurrentToken->Type = TT_TemplateOpener;
+        ++OpenAngleBracketsCount;
         next();
       } else if (CurrentToken->is(tok::greater)) {
         CurrentToken->Type = TT_TemplateCloser;
+        --OpenAngleBracketsCount;
         next();
-      } else if (CurrentToken->is(tok::comma)) {
+      } else if (CurrentToken->is(tok::comma) && OpenAngleBracketsCount == 0) {
+        // We allow line breaks after GenericTypeConstraintComma's
+        // so do not flag commas in Generics as GenericTypeConstraintComma's.
         CurrentToken->Type = TT_CSharpGenericTypeConstraintComma;
         next();
       } else if (CurrentToken->is(Keywords.kw_where)) {

clang/lib/Format/UnwrappedLineParser.cpp

@@ -2340,6 +2340,12 @@ void UnwrappedLineParser::parseRecord(bool ParseAsExpr) {
       }
       if (FormatTok->Tok.is(tok::semi))
         return;
+      if (Style.isCSharp() && FormatTok->is(Keywords.kw_where)) {
+        addUnwrappedLine();
+        nextToken();
+        parseCSharpGenericTypeConstraint();
+        break;
+      }
       nextToken();
     }
   }

clang/unittests/Format/FormatTestCSharp.cpp

@@ -564,7 +564,7 @@ var myDict = new Dictionary<string, string> {
 
 TEST_F(FormatTestCSharp, CSharpArrayInitializers) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
-  
+
   verifyFormat(R"(//
 private MySet<Node>[] setPoints = {
   new Point<Node>(),
@@ -710,6 +710,15 @@ class ItemFactory<T>
               IAnotherInterfaceStill<T> {})",
                Style);
 
+  Style.ColumnLimit = 50; // Force lines to be wrapped.
+  verifyFormat(R"(//
+class ItemFactory<T, U>
+    where T : new(),
+              IAnInterface<T>,
+              IAnotherInterface<T, U>,
+              IAnotherInterfaceStill<T, U> {})",
+               Style);
+
   // In other languages `where` can be used as a normal identifier.
   // This example is in C++!
   verifyFormat(R"(//