[clang-format] Improve identification of C# nullables

[jbcoe]

Summary

Consider ? identifier = and ? identifier; to be nullable within function bodies.

[krasimir]

Looks good with 1 suggestion.

clang/lib/Format/TokenAnnotator.cpp

1018

The check for tok::semi here is redundant: in an example like Type? name;, Line.MustBeDeclaration is true and this is not reached.

[jbcoe]

Remove duplicate check following review comment.

clang/lib/Format/TokenAnnotator.cpp

case tok::question:
         break;
       }
       // Declarations cannot be conditional expressions, this can only be part
       // of a type declaration.
       if (Line.MustBeDeclaration && !Contexts.back().IsExpression &&
           Style.Language == FormatStyle::LK_JavaScript)
         break;
       if (Style.isCSharp()) {
-        if (Line.MustBeDeclaration && !Contexts.back().IsExpression) {
+        // `Type? name;` and `Type? name =` can only be nullable types.
+        // Line.MustBeDeclaration will be true for `Type? name;`.
+        if (!Contexts.back().IsExpression &&
+            (Line.MustBeDeclaration ||
+             (Tok->Next && Tok->Next->is(tok::identifier) && Tok->Next->Next &&
+              Tok->Next->Next->is(tok::equal)))) {
           Tok->Type = TT_CSharpNullable;
           break;
         }
       }
       parseConditional();
       break;
     case tok::kw_template:
       parseTemplateDeclaration();

clang/unittests/Format/FormatTestCSharp.cpp

TEST_F(FormatTestCSharp, CSharpSpaces) {
   verifyFormat(R"(private float[ , ] Values;)", Style);
   verifyFormat(R"(string dirPath = args?[ 0 ];)", Style);
 }
 
 TEST_F(FormatTestCSharp, CSharpNullableTypes) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
   Style.SpacesInSquareBrackets = false;
 
+  verifyFormat(R"(//
+public class A {
+  void foo() { int? value = some.bar(); }
+})",
+               Style); // int? is nullable not a conditional expression.
+
+  verifyFormat(R"(void foo(int? x, int? y, int? z) {})",
+               Style); // Nullables in function definitions.
+
   verifyFormat(R"(public float? Value;)", Style); // no space before `?`.
+
   verifyFormat(R"(int?[] arr = new int?[10];)",
                Style); // An array of a nullable type.
 }
 
 TEST_F(FormatTestCSharp, CSharpArraySubscripts) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
 
   // Do not format array subscript operators as attributes.
   verifyFormat(R"(if (someThings[index].Contains(myThing)) {)", Style);
   verifyFormat(R"(if (someThings[i][j][k].Contains(myThing)) {)", Style);
 }
 
 } // namespace format
 } // end namespace clang