[clang-format] Do not format C# array subscript operators as attributes

[jbcoe]

Summary

Fix misidentification of C# array subscript operators.

[krasimir]

clang/lib/Format/TokenAnnotator.cpp

376

nit: // Chains of [] in ...

clang/unittests/Format/FormatTestCSharp.cpp

626

please add a } at the end of this examples so that the braces are balanced, otherwise the examples read as incomplete.

[krasimir]

sorry could you please take another look at the comments I left

clang/lib/Format/TokenAnnotator.cpp

bool parseParens(bool LookForDecls = false) {
     }
     return false;
   }
 
   bool isCSharpAttributeSpecifier(const FormatToken &Tok) {
     if (!Style.isCSharp())
       return false;
 
+    // `identifier[i]` is not an attribute.
+    if (Tok.Previous && Tok.Previous->is(tok::identifier))
+      return false;
+
+    // Chains [] in of `identifier[i][j][k]` are not attributes.
+    if (Tok.Previous && Tok.Previous->is(tok::r_square)) {
+      auto *MatchingParen = Tok.Previous->MatchingParen;
+      if (!MatchingParen || MatchingParen->is(TT_ArraySubscriptLSquare))
+        return false;
+    }
+
     const FormatToken *AttrTok = Tok.Next;
     if (!AttrTok)
       return false;
 
     // Just an empty declaration e.g. string [].
     if (AttrTok->is(tok::r_square))
       return false;
 

clang/unittests/Format/FormatTestCSharp.cpp

TEST_F(FormatTestCSharp, CSharpNullableTypes) {
   FormatStyle Style = getGoogleStyle(FormatStyle::LK_CSharp);
   Style.SpacesInSquareBrackets = false;
 
   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