[clang-format] Incorrectly identifies empty function as bracedList

[mydeveloperday]

Because clang-format cannot determine {} as an empty function is leaves out a space between the ) and the { as it doesn't identify the { as a TT_FunctionLBrace

Add an issue for tracking a potential change to fix that.

void function(){};
void function() { int a; };

[llvmbot]

@llvm/issue-subscribers-bug

[llvmbot]

@llvm/issue-subscribers-clang-format

[mydeveloperday]

While working on a fix for #58217 (namely https://reviews.llvm.org/D135466) we identified that foo(){} was not being identified the same as foo() { return; }

[rymiel]

Also see #57305 (comment). Not exactly a duplicate but the same underlying bug, i'm assuming

[mydeveloperday]

The more I look at this the more I think this is harder than we first think, simply assuming ) { to be a function would change, would then identify the { as a FunctionLBrace, which in turn RemoveSemicolons would remove the trailing ; which is needed i.e.

this

auto i = decltype(x) {};

to this

auto i = decltype(x) {}

which would be a compile error

So we'd really need yet more semantic (or derived semantic) information about what makes {}; a function body.

The unwrappered parser when we are determining the block type is before the annotator which identified the ')' as a TypeDeclarationParen, but this would be useful information to have.

I wonder if there is something we can do after the function name has been identified as FunctionDeclarationName

At present we get this..

Expected & Input

void a() {}
void a() {};
void a() { return a;}
void a() { return a;};

Clang-Format current output

void a() {}
void a(){};
void a() { return a; }
void a() { return a; };

[rymiel]

The more I look at this the more I think this is harder than we first think

I definitely couldn't fix it. I concluded that determining if a function declaration is being dealt with (i.e. Line.MightBeFunctionDecl) happens way later and I couldn't find a non-invasive heuristic that didn't involve lots of duplicated work

[mydeveloperday]

feel free to have a go.