[clang-format] Handle C# where clause in SeparateDefinitionBlocks (#139034)

Fix #61956

Author: owenca

clang/lib/Format/DefinitionBlockSeparator.cpp

@@ -137,6 +137,10 @@ void DefinitionBlockSeparator::separateBlocks(
     const auto MayPrecedeDefinition = [&](const int Direction = -1) {
       assert(Direction >= -1);
       assert(Direction <= 1);
+
+      if (Lines[OpeningLineIndex]->First->is(TT_CSharpGenericTypeConstraint))
+        return true;
+
       const size_t OperateIndex = OpeningLineIndex + Direction;
       assert(OperateIndex < Lines.size());
       const auto &OperateLine = Lines[OperateIndex];

clang/unittests/Format/DefinitionBlockSeparatorTest.cpp

@@ -574,6 +574,11 @@ TEST_F(DefinitionBlockSeparatorTest, CSharp) {
                "\r\n"
                "public class FoobarClass {\r\n"
                "  int foobar;\r\n"
+               "}\r\n"
+               "\r\n"
+               "public class LogFactory<TLogger>\r\n"
+               "    where TLogger : class, new() {\r\n"
+               "  int i;\r\n"
                "}",
                Style);
 }