[clang-format/ObjC] Correctly annotate single-component ObjC method invocations

[benhamilton]

Summary

Previously, clang-format's parser would fail to annotate the
selector in a single-component Objective-C method invocation with
TT_SelectorName. For example, the following:

[foo bar];

would parse bar as TT_Unknown:

M=0 C=1 T=Unknown S=0 B=0 BK=0 P=140 Name=identifier L=34 PPK=2
FakeLParens= FakeRParens=0 II=0x559d5db51770 Text='bar'

This caused us to fail to insert a space after a closing cast rparen,
so the following:

[((Foo *)foo) bar];

would format as:

[((Foo *)foo)bar];

This diff fixes the issue by ensuring we annotate the selector
in a single-component Objective-C method invocation as
TT_SelectorName.

Test Plan: New tests added. Ran tests with:

% make -j16 FormatTests && ./tools/clang/unittests/Format/FormatTests

[jolesiak]

lib/Format/TokenAnnotator.cpp

510

I'd remove braces for consistency.

[benhamilton]

Style

lib/Format/TokenAnnotator.cpp

510

Thanks, done.

lib/Format/TokenAnnotator.cpp

while (CurrentToken) {
                  Left->is(TT_ObjCMethodExpr)) {
           // An ObjC method call is rarely followed by an open parenthesis.
           // FIXME: Do we incorrectly label ":" with this?
           StartsObjCMethodExpr = false;
           Left->Type = TT_Unknown;
         }
         if (StartsObjCMethodExpr && CurrentToken->Previous != Left) {
           CurrentToken->Type = TT_ObjCMethodExpr;
+          // If we haven't seen a colon yet, make sure the last identifier
+          // before the r_square is tagged as a selector name component.
+          if (!ColonFound && CurrentToken->Previous &&
+              CurrentToken->Previous->is(TT_Unknown) &&
+              canBeObjCSelectorComponent(*CurrentToken->Previous))
+            CurrentToken->Previous->Type = TT_SelectorName;
           // determineStarAmpUsage() thinks that '*' '[' is allocating an
           // array of pointers, but if '[' starts a selector then '*' is a
           // binary operator.
           if (Parent && Parent->is(TT_PointerOrReference))
             Parent->Type = TT_BinaryOperator;
         }
         Left->MatchingParen = CurrentToken;
         CurrentToken->MatchingParen = Left;
         if (Contexts.back().FirstObjCSelectorName) {

unittests/Format/FormatTestObjC.cpp

verifyFormat("[object\n"
                "    firstBlock:^{\n"
                "      a = 42;\n"
                "    }\n"
                "    notBlock:42\n"
                "    secondBlock:^{\n"
                "      a = 42;\n"
                "    }];");
 
+  // Space between cast rparen and selector name component.
+  verifyFormat("[((Foo *)foo) bar];");
+  verifyFormat("[((Foo *)foo) bar:1 blech:2];");
+
   // Message receiver taking multiple lines.
   Style.ColumnLimit = 20;
   // Non-corner case.
   verifyFormat("[[object block:^{\n"
                "  return 42;\n"
                "}] a:42 b:42];");
   // Arguments just fit into one line.
   verifyFormat("[[object block:^{\n"