[clang-format/ObjC] Do not detect "[]" as ObjC method expression

[benhamilton]

Summary

The following C++ code was being detected by
guessLanguage() as Objective-C:

#define FOO(...) auto bar = [] __VA_ARGS__;

This was because [] __VA_ARGS__ is not currently detected as a C++
lambda expression (it has no parens or braces), so
TokenAnnotator::parseSquare() incorrectly treats the opening square
as an ObjC method expression.

We have two options to fix this:

1. Parse [] __VA_ARGS__ explicitly as a C++ lambda
2. Make it so [] is never parsed as an Objective-C method expression

This diff implements option 2, which causes the [ to be parsed
as TT_ArraySubscriptLSquare instead of TT_ObjCMethodExpr.

Note that when I fixed this, it caused one change in formatting
behavior, where the following was implicitly relying on the [
being parsed as TT_ObjCMethodExpr:

A<int * []> a;

becomes:

A<int *[]> a;

with Style.PointerAlignment = Middle.

I don't really know what the desired format is for this syntax; the
test was added by Janusz Sobczak and integrated by @djasper in
https://github.com/llvm-mirror/clang/commit/b511fe9818829d7ece0cc0b2ce1fbe04a1f0739a
.

I went ahead and changed the test for now.

Test Plan: New tests added. Ran tests with:

% make -j12 FormatTests && ./tools/clang/unittests/Format/FormatTests

Fixes: https://bugs.llvm.org/show_bug.cgi?id=36248

[djasper]

Looks good. I like option 2 :).

cfe/trunk/lib/Format/TokenAnnotator.cpp

bool CppArrayTemplates =
          Contexts.back().InTemplateArgument);
 
     bool IsCpp11AttributeSpecifier = isCpp11AttributeSpecifier(*Left) ||
                                      Contexts.back().InCpp11AttributeSpecifier;
 
     bool StartsObjCMethodExpr =
         !CppArrayTemplates && Style.isCpp() && !IsCpp11AttributeSpecifier &&
         Contexts.back().CanBeExpression && Left->isNot(TT_LambdaLSquare) &&
-        CurrentToken->isNot(tok::l_brace) &&
+        !CurrentToken->isOneOf(tok::l_brace, tok::r_square) &&
         (!Parent ||
          Parent->isOneOf(tok::colon, tok::l_square, tok::l_paren,
                          tok::kw_return, tok::kw_throw) ||
          Parent->isUnaryOperator() ||
          Parent->isOneOf(TT_ObjCForIn, TT_CastRParen) ||
          getBinOpPrecedence(Parent->Tok.getKind(), true, true) > prec::Unknown);
     bool ColonFound = false;
 

cfe/trunk/unittests/Format/FormatTest.cpp

TEST_F(FormatTest, UnderstandsUsesOfStarAndAmp) {
   // FIXME: We cannot handle this case yet; we might be able to figure out that
   // foo<x> d > v; doesn't make sense.
   verifyFormat("foo<a<b && c> d> v;");
 
   FormatStyle PointerMiddle = getLLVMStyle();
   PointerMiddle.PointerAlignment = FormatStyle::PAS_Middle;
   verifyFormat("delete *x;", PointerMiddle);
   verifyFormat("int * x;", PointerMiddle);
+  verifyFormat("int *[] x;", PointerMiddle);
   verifyFormat("template <int * y> f() {}", PointerMiddle);
   verifyFormat("int * f(int * a) {}", PointerMiddle);
   verifyFormat("int main(int argc, char ** argv) {}", PointerMiddle);
   verifyFormat("Test::Test(int b) : a(b * b) {}", PointerMiddle);
   verifyFormat("A<int *> a;", PointerMiddle);
   verifyFormat("A<int **> a;", PointerMiddle);
   verifyFormat("A<int *, int *> a;", PointerMiddle);
-  verifyFormat("A<int * []> a;", PointerMiddle);
+  verifyFormat("A<int *[]> a;", PointerMiddle);
   verifyFormat("A = new SomeType *[Length]();", PointerMiddle);
   verifyFormat("A = new SomeType *[Length];", PointerMiddle);
   verifyFormat("T ** t = new T *;", PointerMiddle);
 
   // Member function reference qualifiers aren't binary operators.
   verifyFormat("string // break\n"
                "operator()() & {}");
   verifyFormat("string // break\n"
TEST_F(FormatTest, FileAndCode) {
   EXPECT_EQ(FormatStyle::LK_Cpp, guessLanguage("foo", ""));
   EXPECT_EQ(FormatStyle::LK_ObjC, guessLanguage("foo", "@interface Foo\n@end\n"));
   EXPECT_EQ(FormatStyle::LK_ObjC,
             guessLanguage("foo.h", "int DoStuff(CGRect rect);\n"));
   EXPECT_EQ(
       FormatStyle::LK_ObjC,
       guessLanguage("foo.h",
                     "#define MY_POINT_MAKE(x, y) CGPointMake((x), (y));\n"));
+  EXPECT_EQ(
+      FormatStyle::LK_Cpp,
+      guessLanguage("foo.h", "#define FOO(...) auto bar = [] __VA_ARGS__;"));
 }
 
 TEST_F(FormatTest, GuessLanguageWithCpp11AttributeSpecifiers) {
   EXPECT_EQ(FormatStyle::LK_Cpp, guessLanguage("foo.h", "[[noreturn]];"));
   EXPECT_EQ(FormatStyle::LK_ObjC,
             guessLanguage("foo.h", "array[[calculator getIndex]];"));
   EXPECT_EQ(FormatStyle::LK_Cpp,
             guessLanguage("foo.h", "[[noreturn, deprecated(\"so sorry\")]];"));