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[clang-format] Improve function pointer CastRParen detection. #126019

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[clang-format] Improve function pointer CastRParen detection. #126019

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7a97263
Improve function pointer cast detection.
rmarker Feb 6, 2025
b5b5ca2
Fix formatting.
rmarker Feb 6, 2025
5216591
Fix test case.
rmarker Feb 7, 2025
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17 changes: 15 additions & 2 deletions clang/lib/Format/TokenAnnotator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2915,14 +2915,27 @@ class AnnotatingParser {
if (Prev->is(tok::r_paren)) {
if (Prev->is(TT_CastRParen))
return false;

// Check for the second pair of parentheses.
Prev = Prev->MatchingParen;
if (!Prev)
return false;

// Now check for the first pair of parentheses.
Prev = Prev->Previous;
if (!Prev || Prev->isNot(tok::r_paren))
return false;
Prev = Prev->MatchingParen;
return Prev && Prev->is(TT_FunctionTypeLParen);
const auto *PrevMatchingParen = Prev->MatchingParen;
if (!PrevMatchingParen)
return false;

// We can quickly tell it is a function pointer type if the paren is the
// right type.
if (PrevMatchingParen->isNot(TT_Unknown))
return PrevMatchingParen->is(TT_FunctionTypeLParen);

// Otherwise check for the trailing * in the parentheses.
return Prev->Previous && Prev->Previous->is(tok::star);
}

// Search for unexpected tokens.
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5 changes: 5 additions & 0 deletions clang/unittests/Format/TokenAnnotatorTest.cpp
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Expand Up @@ -874,6 +874,11 @@ TEST_F(TokenAnnotatorTest, UnderstandsCasts) {
EXPECT_TOKEN(Tokens[14], tok::r_paren, TT_CastRParen);
EXPECT_TOKEN(Tokens[15], tok::amp, TT_UnaryOperator);

Tokens = annotate("func((foo(bar::*)(void))&a);");
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What's foo here? Can you show an example in Compiler Explorer?

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Here foo is a type.

It looks like I accidentally trimmed too much when making the test case. Whoops.
Good catch.
It should be func((foo(bar::*)(void))&bar::a);
I've pushed a commit to adjust that.

Here is a Compiler Explorer link with what I was going for.
https://godbolt.org/z/Yhn65zx8P

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So foo is a return type. Then the ( that follows should be annotated as a FunctionLParen, and there should be a space between them like in int (*)().

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Ah, I was so focused on the behaviour from 19, that I didn't realise about the space after the return type.
Yeah, it seems like even with missing the annotation of the left paren clang-format 19, managed to get lucky with the right cast paren. With the extra fix in 20 revealing the underlying issue.
Nice work.

ASSERT_EQ(Tokens.size(), 18u) << Tokens;
EXPECT_TOKEN(Tokens[12], tok::r_paren, TT_CastRParen);
EXPECT_TOKEN(Tokens[13], tok::amp, TT_UnaryOperator);

auto Style = getLLVMStyle();
Style.TypeNames.push_back("Foo");
Tokens = annotate("#define FOO(bar) foo((Foo)&bar)", Style);
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