std.builtin.TypeInfo.Declaration.data.FnDecl.arg_names is populated inconsistently for struct declarations

[vsergeev]

Zig Version

0.9.1

Steps to Reproduce

Case 1:

fn reflect(comptime entity: anytype) void {
    @compileLog(@typeInfo(entity).Struct.decls[0].name);
    @compileLog(@typeInfo(entity).Struct.decls[0].data.Fn.arg_names);
    @compileLog(@typeInfo(entity).Struct.decls[1].name);
    @compileLog(@typeInfo(entity).Struct.decls[1].data.Fn.arg_names);
}

pub const Foo = struct {
    pub fn init(a: u32, b: u64) Foo {
        _ = a;
        _ = b;
        return Foo{};
    }

    pub fn foo(self: *Foo, c: u32) void {
        _ = self;
        _ = c;
    }
};

pub fn main() !void {
    reflect(Foo);
}

Case 2:

fn reflect(comptime entity: anytype) void {
    @compileLog(@typeInfo(entity).Struct.decls[0].name);
    @compileLog(@typeInfo(entity).Struct.decls[0].data.Fn.arg_names);
    @compileLog(@typeInfo(entity).Struct.decls[1].name);
    @compileLog(@typeInfo(entity).Struct.decls[1].data.Fn.arg_names);
}

pub const Foo = struct {
    pub fn init(a: u32, b: u64) Foo {
        reflect(@This());
        _ = a;
        _ = b;
        return Foo{};
    }

    pub fn foo(self: *Foo, c: u32) void {
        _ = self;
        _ = c;
    }
};

pub fn main() !void {
    var foo = Foo.init(1, 2);
    _ = foo;
}

Expected Behavior

Both cases:

| "init"
| []const []const u8{"a","b"}
| "foo"
| []const []const u8{"self","c"}

Actual Behavior

Case 1:

| "init"
| []const []const u8{}
| "foo"
| []const []const u8{}

Case 2:

| "init"
| []const []const u8{"a","b"}
| "foo"
| []const []const u8{}

This issue appears to be similar to the later comments in #8259, but that issue was closed in March. Unsure how the closing comment applies here.

[vsergeev]

Testing with 0.10.0-dev.4330+fb366f3cd, it seems Struct member of type info has been reorganized and that arg_names have been removed. I guess that's what the closing comment of #8259 referred to. If anybody knows of an alternate way to get the argument names, feel free to let me know 😉. Closing for now.