Macro indentation issue with rust-mode

[gsingh93]

I'm using rust-mode in emacs 24.3.

Here is a macro from the Macros guide:

macro_rules! early_return(
    ($inp:expr $sp:ident) => ( // invoke it like `(input_5 SpecialE)`
        match $inp {
            $sp(x) => { return x; }
            _ => {}
        }
    );
)

If I select all and hit tab, this is how it indents it:

macro_rules! try_option_or_fail(
    ($e:expr) => (
        match $e {
            Some(x) => x,
            None => fail!("Expected Some, got None", $e)
        }
        );
    )

[huonw]

cc #8793 and @pnkfelix

[gsingh93]

I was just looking at the code for rust-mode. Can we just use the same rule we use } (unindent one level) when the first non-whitespace character of the line is a )? Or would that cause issues?

[gsingh93]

I just tried this out by changing the code starting at line 113.

((or (looking-at "}") (save-excursion
                        (move-beginning-of-line nil)
                        (looking-at "[ \t]*)")))
 (- baseline rust-indent-offset))

It properly handles the case in the example.

[tomjakubowski]

FWIW you can work around this in the meantime by using {} instead of () for the macro body and transcribers:

macro_rules! early_return {
    ($inp:expr $sp:ident) => { // invoke it like `(input_5 SpecialE)`
        match $inp {
            $sp(x) => { return x; }
            _ => {}
        }
    };
}

Emacs should indent that properly.

[shepmaster]

This may now be fixed indirectly by #18635 via ddb2466. It is now required to have a semicolon at the end of that macro definition.

[steveklabnik]

@gsingh93 , please let me know if @shepmaster is wrong, but yes, this would seem to be fixed.