dmutil 0.1.0

///
/// Declares an [eager!](macro.eager.html)-enabled macro.
///
/// # Usage
///
/// Works exactly as `macro_rules!`, except the following difference:
///
/// * The name of the macro to be declared is given in the body as the first token.
/// * Two identifiers must be given after the name of the macro. Each must be preceded by
/// a '$' sign, and must not collide with any macro variable name used in any rule.
///
/// # `eager!`-enabling
///
/// To [eager!](macro.eager.html)-enable the following macro:
/// ```ignore
/// macro_rules! some_macro{
/// 	...
/// }
/// ```
/// The whole above declaration must be changed to:
/// ```ignore
/// eager_macro_rules! {
/// 	some_macro $eager_1 $eager2
/// 	...
/// }
/// ```
/// where `...` is the list of rules that comprise the macro, and no macro variable is called
/// `$eager_1` or `$eager_2`. Additionally, no rule should accept `@eager`, as this could conflict
/// with the implementation of `eager!`.
///
#[macro_export]
macro_rules! eager_macro_rules{

// Start by decoding the initial values
	(
		$(#[$($metas:tt)*])*
		$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
		$($rules:tt => $expansions:tt);* $(;)*
	)=>{
		eager_macro_rules_internal!{
			@first[
				$(#[$($metas)*])*
				$macro_name $dollar1 $id_1 $dollar2 $id_2
			]
			$($rules => $expansions)*
		}
	};
}

#[macro_export]
#[doc(hidden)]
macro_rules! eager_macro_rules_internal{
// If there are no more rules, finish
	(
		@first[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$($prev_grammar:tt => $prev_expansion:tt)*
		]
	) => {
		eager_macro_rules_internal!{
			@final[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$($prev_grammar => $prev_expansion)*
			]
		}
	};

//Handle the 3 different block type before the '=>'
	(
		@first[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$($prev_grammar:tt => $prev_expansion:tt)*
		]
		{$($next_grammar:tt)*} $($rest:tt)+
	) => {
		eager_macro_rules_internal!{
			@expansion[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$($prev_grammar => $prev_expansion)*
				[$($next_grammar)*]
			]
			$($rest)+
		}
	};
	(
		@first[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$($prev_grammar:tt => $prev_expansion:tt)*
		]
		($($next_grammar:tt)*) $($rest:tt)+
	) => {
		eager_macro_rules_internal!{
			@expansion[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$($prev_grammar => $prev_expansion)*
				[$($next_grammar)*]
			]
			$($rest)+
		}
	};
	(
		@first[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$($prev_grammar:tt => $prev_expansion:tt)*
		]
		[$($next_grammar:tt)*] $($rest:tt)+
	) => {
		eager_macro_rules_internal!{
			@expansion[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$($prev_grammar => $prev_expansion)*
				[$($next_grammar)*]
			]
			$($rest)+
		}
	};
	
// Handle the 3 different block types after the '=>'
	(
		@expansion[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$({$($prev_grammar:tt)*} => $prev_expansion:tt)*
			[$($next_grammar:tt)*]
		]
		 => {$($next_expansion:tt)*} $($rest:tt)*
	) => {
		eager_macro_rules_internal!{
			@first[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$({$($prev_grammar)*}  => $prev_expansion)*
				{$($next_grammar)*} => {$($next_expansion)*}
			]
			$($rest)*
		}
	};
	(
		@expansion[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$({$($prev_grammar:tt)*} => $prev_expansion:tt)*
			[$($next_grammar:tt)*]
		]
		 => ($($next_expansion:tt)*) $($rest:tt)*
	) => {
		eager_macro_rules_internal!{
			@first[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$({$($prev_grammar)*}  => $prev_expansion)*
				{$($next_grammar)*} => {$($next_expansion)*}
			]
			$($rest)*
		}
	};
	(
		@expansion[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$({$($prev_grammar:tt)*} => $prev_expansion:tt)*
			[$($next_grammar:tt)*]
		]
		 => [$($next_expansion:tt)*] $($rest:tt)*
	) => {
		eager_macro_rules_internal!{
			@first[
				$(#[$($metas)*])*
				$macro_name$dollar1 $id_1 $dollar2 $id_2
				$({$($prev_grammar)*}  => $prev_expansion)*
				{$($next_grammar)*} => {$($next_expansion)*}
			]
			$($rest)*
		}
	};

// Output
	(	@final[
			$(#[$($metas:tt)*])*
			$macro_name:ident $dollar1:tt $id_1:ident $dollar2:tt $id_2:ident
			$({$($rules_grammar:tt)*} => {$($rules_expansion:tt)*})+
		]
	)=>{
		$(#[$($metas)*])*
		macro_rules! $macro_name{
			$(
				// First the eager supporting version
				{
					@eager[[$dollar1($dollar1 $id_1:tt)*] $dollar2($dollar2 $id_2:tt)*]
					$($rules_grammar)*
				} => {
					eager_internal!{
						@from_macro[$dollar2($dollar2$id_2)*]
						$($rules_expansion)*
						$dollar1($dollar1$id_1)*
					}
				};
			)+
			
			$(
				// Then the pure version. We put the pure versions
				// last such that if it contains a '$($all:tt)*' rule,
				// the pure version will not catch an eager call.
				{$($rules_grammar)*} => {$($rules_expansion)*};
			)+
		}
	};
}