[clang-format] Correctly recognize arrays in template parameter list.

[curdeius]

Summary

Fixes https://github.com/llvm/llvm-project/issues/54245.

[krasimir]

It appears that this regressed some ObjC patterns:

% cat test.m  # before: good
void f() {
  //
  BOOL a = [b.c count] > 1;
  int b = a;
}
% clang-format -style=google test.m  # after: bad, statements joined on the same line
void f() {
  //
  BOOL a = [b.c count] > 1; int b = a;
}
%

@curdeius could you please take a look?

[curdeius]

In D121584#3395937, @krasimir wrote:

It appears that this regressed some ObjC patterns:

% cat test.m  # before: good
void f() {
  //
  BOOL a = [b.c count] > 1;
  int b = a;
}
% clang-format -style=google test.m  # after: bad, statements joined on the same line
void f() {
  //
  BOOL a = [b.c count] > 1; int b = a;
}
%

@curdeius could you please take a look?

Yes, will do.

[krasimir]

It appears that this regressed some ObjC patterns:

@curdeius any progress on this? If not, could we revert this for now? Internally we've got enough of these regressing ObjC patterns that we can't release clang-format with this.

[curdeius]

Yes, let's revert this. I should have a fix soon though.

[carlosgalvezp]

In D121584#3404704, @curdeius wrote:

Yes, let's revert this. I should have a fix soon though.

@curdeius Did you manage to find a fix suitable for both use cases?

[HazardyKnusperkeks]

In D121584#4233165, @carlosgalvezp wrote:

In D121584#3404704, @curdeius wrote:

Yes, let's revert this. I should have a fix soon though.

@curdeius Did you manage to find a fix suitable for both use cases?

We haven't heard from @curdeius in a very long time. I think he is (currently) not available for clang-format anymore.

[owenpan]

See https://reviews.llvm.org/D147295.

clang/lib/Format/UnwrappedLineParser.cpp

if (!Style.isCpp()) {
     nextToken();
     return false;
   }
   assert(FormatTok->is(tok::l_square));
   FormatToken &LSquare = *FormatTok;
   if (!tryToParseLambdaIntroducer())
     return false;
 
+  // `[something] >` is not a lambda, but an array type in a template parameter
+  // list.
+  if (FormatTok->is(tok::greater))
+    return false;
+
   bool SeenArrow = false;
   bool InTemplateParameterList = false;
 
   while (FormatTok->isNot(tok::l_brace)) {
     if (FormatTok->isSimpleTypeSpecifier()) {
       nextToken();
       continue;
     }
do {
       }
       if (FormatTok->is(tok::l_square)) {
         FormatToken *Previous = FormatTok->Previous;
         if (!Previous ||
             !(Previous->is(tok::r_paren) || Previous->isTypeOrIdentifier())) {
           // Don't try parsing a lambda if we had a closing parenthesis before,
           // it was probably a pointer to an array: int (*)[].
           if (!tryToParseLambda())
-            break;
+            continue;
         } else {
           parseSquare();
           continue;
         }
       }
       if (FormatTok->is(tok::semi))
         return;
       if (Style.isCSharp() && FormatTok->is(Keywords.kw_where)) {

clang/unittests/Format/TokenAnnotatorTest.cpp

TEST_F(TokenAnnotatorTest, UnderstandsClasses) {
   EXPECT_EQ(Tokens.size(), 7u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::l_brace, TT_ClassLBrace);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsStructs) {
   auto Tokens = annotate("struct S {};");
   EXPECT_EQ(Tokens.size(), 6u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::l_brace, TT_StructLBrace);
+
+  Tokens = annotate("template <typename T> struct S<const T[N]> {};");
+  EXPECT_EQ(Tokens.size(), 18u) << Tokens;
+  EXPECT_TOKEN(Tokens[7], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[10], tok::l_square, TT_ArraySubscriptLSquare);
+  EXPECT_TOKEN(Tokens[13], tok::greater, TT_TemplateCloser);
+  EXPECT_TOKEN(Tokens[14], tok::l_brace, TT_StructLBrace);
+
+  Tokens = annotate("template <typename T> struct S<T const[N]> {};");
+  EXPECT_EQ(Tokens.size(), 18u) << Tokens;
+  EXPECT_TOKEN(Tokens[7], tok::less, TT_TemplateOpener);
+  EXPECT_TOKEN(Tokens[10], tok::l_square, TT_ArraySubscriptLSquare);
+  EXPECT_TOKEN(Tokens[13], tok::greater, TT_TemplateCloser);
+  EXPECT_TOKEN(Tokens[14], tok::l_brace, TT_StructLBrace);
 }
 
 TEST_F(TokenAnnotatorTest, UnderstandsUnions) {
   auto Tokens = annotate("union U {};");
   EXPECT_EQ(Tokens.size(), 6u) << Tokens;
   EXPECT_TOKEN(Tokens[2], tok::l_brace, TT_UnionLBrace);
 
   Tokens = annotate("union U { void f() { return; } };");