[clang-format] Improve C# handling of spaces in square brackets

clang/lib/Format/TokenAnnotator.cpp

if (Style.isCpp()) {
     // Spaces around '=>'.
     if (Left.is(TT_JsFatArrow) || Right.is(TT_JsFatArrow))
       return true;
 
     // space between type and variable e.g. Dictionary<string,string> foo;
     if (Left.is(TT_TemplateCloser) && Right.is(TT_StartOfName))
       return true;
 
-    // space after comma in '[,]'.
-    if (Left.is(tok::comma) && Right.is(tok::r_square))
+    // spaces inside square brackets.
+    if (Left.is(tok::l_square) || Right.is(tok::r_square))
       return Style.SpacesInSquareBrackets;
 
     // No space before ? in nullable types.
     if (Right.is(TT_CSharpNullableTypeQuestionMark))
       return false;
 
     // space between keywords and paren e.g. "using ("
     if (Right.is(tok::l_paren))

clang/unittests/Format/FormatTestCSharp.cpp

verifyFormat(R"(new Dictionary<string, string> { ["Key"] = "Value" };)",
                Style);
   verifyFormat(R"(Apply(x => x.Name, x => () => x.ID);)", Style);
   verifyFormat(R"(bool[] xs = { true, true };)", Style);
   verifyFormat(R"(taskContext.Factory.Run(async () => doThing(args);)", Style);
   verifyFormat(R"(catch (TestException) when (innerFinallyExecuted))", Style);
   verifyFormat(R"(private float[,] Values;)", Style);
 
   Style.SpacesInSquareBrackets = true;
-  verifyFormat(R"(private float[, ] Values;)", Style);
+  verifyFormat(R"(private float[ , ] Values;)", Style);
 }
 
 TEST_F(FormatTestCSharp, CSharpNullableTypes) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
   Style.SpacesInSquareBrackets = false;
 
   verifyFormat(R"(public float? Value;)", Style); // no space before `?`.
-
-  // Erroneous spaces in square brackets here will be tackled in a follow-up
-  // patch and are not addressed by setting
-  // `Style.SpacesInSquareBrackets = false;`
-  verifyFormat(R"(int?[] arr = new int?[ 10 ];)",
+  verifyFormat(R"(int?[] arr = new int?[10];)",
                Style); // An array of a nullable type.
 }
 
 } // namespace format
 } // end namespace clang