macro_rules! parse {
(
$callback:path { $($callback_args:tt)* } < $($token:tt)*
) => { ... };
(
$callback:path { $($callback_args:tt)* } $($token:tt)*
) => { ... };
}
Expand description
Parses (optional) generics and (optional) subsequent where clause.
This macro accepts an input in the following form:
ⓘ
$callback_macro { $($callback_macro_args)* }
$(
< $generics >
$( $tokens_between_generics_and_where_clause )*
$(
where $where_clause
)?
)?
$(
$( ; | { $($body)* } )
$($remaining_tokens)*
)?
and expands into
ⓘ
$callback_macro! {
$( $callback_macro_args )*
[ $( < $generics > )? ]
[ $( < $generics_without_constraints > )? ]
[ $( where $where_clause )? ]
$($( $tokens_between_generics_and_where_clause )*)?
$(
$( ; | { $($body)* } )
$($remaining_tokens)*
)?
}
Examples
pub trait TheTrait { }
#[doc(hidden)]
pub use generics::parse as generics_parse;
#[doc(hidden)]
pub use std::compile_error as std_compile_error;
#[macro_export]
macro_rules! impl_the_trait {
(
$name:ident $($token:tt)*
) => {
$crate::generics_parse! {
$crate::impl_the_trait {
@impl $name
}
$($token)*
}
};
(
@impl $name:ident [$($g:tt)*] [$($r:tt)*] [$($w:tt)*]
) => {
impl $($g)* $crate::TheTrait for $name $($r)* $($w)* { }
};
(
@impl $name:ident [$($g:tt)*] [$($r:tt)*] [$($w:tt)*] $($token:tt)+
) => {
$crate::std_compile_error!(
"invalid input, allowed input is '$name $( < $generics > $(where $where_clause)? )?'"
);
};
}