Code may not be accepted by the compiler in the future

[J0HN50N133]

greptimedb/src/datatypes/src/macros.rs

Line 43 in 2ae2a66

( $_ $T:ident ) => {

What does $_ exactly means here? It's missing fragment specifier, and may not be accepted by the compiler in the future.

@killme2008

[evenyag]

It is the captured $ so $S should become $Int8Type, $Int16Type after the outer macro expanded.

greptimedb/src/common/function/src/scalars/aggregate/argmax.rs

Lines 119 to 132 in 547730a

	with_match_primitive_type_id!(
	input_type.logical_type_id(),
	|$S| {
	Ok(Box::new(Argmax::<<$S as LogicalPrimitiveType>::Wrapper>::default()))
	},
	{
	let err_msg = format!(
	"\"ARGMAX\" aggregate function not support data type {:?}",
	input_type.logical_type_id(),
	);
	CreateAccumulatorSnafu { err_msg }.fail()?
	}
	)
	});

If I understood correctly......