Support trailing commas in lint_array

[theotherphil]

rust-lang/rust-clippy#2350 (comment)

[kennytm]

Basically just change this macro to recognize and discard the trailing comma.

rust/src/librustc/lint/mod.rs

Lines 98 to 105 in adc9d86

	/// Declare a static `LintArray` and return it as an expression.
	#[macro_export]
	macro_rules! lint_array { ($( $lint:expr ),*) => (
	{
	static ARRAY: LintArray = &[ $( &$lint ),* ];
	ARRAY
	}
	) }

[durka]

That macro declaration is formatted in a weird way. But anyway it should be enough to add $(,)* to the rule (unless accepting multiple trailing commas is undesired). I could mentor.

[mark-i-m]

How about this:

macro_rules! lint_array { 
    ($( $lint:expr ),*,) => { lint_array!( $( &$lint ),* ) };
    ($( $lint:expr ),*) => {{ 
         static ARRAY: LintArray = &[ $( &$lint ),* ]; 
         ARRAY 
    }} 
} 

[mark-i-m]

Out of curiosity, why doesn't rust allow trailing commas after $(pat),* automatically? Does it make it hard to write some macros? Alternately, why isn't there a ? (optional) repetition specification (e.g. $(pat)? would be 0 or 1 times)?

[durka]

The extra rule is fine too. It's just more annoying (extra repetition). And there's no technical reason not to support one-or-none patterns as far as I'm aware.

…

On Sun, Jan 14, 2018 at 10:47 PM, Who? Me?! ***@***.***> wrote: Out of curiosity, why doesn't rust allow trailing commas after $(pat),* automatically? Does it make it hard to write some macros? Alternately, why isn't there a ? (optional) repetition specification (e.g. $(pat)? would be 0 or 1 times)? — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#47428 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAC3n34JOkRf6pQsXcniOmsnEFCSZw7eks5tKspjgaJpZM4RdrQH> .

[mark-i-m]

Made a PR :)