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|
//! Helper types and macros for creating custom functions.
/// Defines function types concisely.
#[macro_export]
macro_rules! function {
// Parse a unit struct.
($(#[$outer:meta])* pub struct $type:ident; $($rest:tt)*) => {
$(#[$outer])* pub struct $type;
function!(@meta $type | $($rest)*);
};
// Parse a tuple struct.
($(#[$outer:meta])* pub struct $type:ident($($fields:tt)*); $($rest:tt)*) => {
$(#[$outer])* pub struct $type($($fields)*);
function!(@meta $type | $($rest)*);
};
// Parse a struct with fields.
($(#[$outer:meta])* pub struct $type:ident { $($fields:tt)* } $($rest:tt)*) => {
$(#[$outer])* pub struct $type { $($fields)* }
function!(@meta $type | $($rest)*);
};
// Parse an enum.
($(#[$outer:meta])* pub enum $type:ident { $($fields:tt)* } $($rest:tt)*) => {
$(#[$outer])* pub enum $type { $($fields)* }
function!(@meta $type | $($rest)*);
};
// Parse a metadata type definition.
(@meta $type:ident | type Meta = $meta:ty; $($rest:tt)*) => {
function!(@parse $type $meta | $($rest)*);
};
// Set the metadata to `()` if there is no type definition.
(@meta $type:ident | $($rest:tt)*) => {
function!(@parse $type () | $($rest)*);
};
// Parse a `parse(default)`.
(@parse $type:ident $meta:ty | parse(default) $($rest:tt)*) => {
function!(@parse $type $meta |
parse(_args, _body, _ctx, _meta) { Default::default() }
$($rest)*
);
};
// (0-arg) Parse a parse-definition without arguments.
(@parse $type:ident $meta:ty | parse() $code:block $($rest:tt)*) => {
function!(@parse $type $meta | parse(_args, _body, _ctx, _meta) $code $($rest)*);
};
// (1-arg) Parse a parse-definition with only the first argument.
(@parse $type:ident $meta:ty | parse($args:ident) $code:block $($rest:tt)*) => {
function!(@parse $type $meta | parse($args, _body, _ctx, _meta) $code $($rest)*);
};
// (2-arg) Parse a parse-definition with only the first two arguments.
(@parse $type:ident $meta:ty |
parse($args:ident, $body:pat) $code:block $($rest:tt)*
) => {
function!(@parse $type $meta | parse($args, $body, _ctx, _meta) $code $($rest)*);
};
// (3-arg) Parse a parse-definition with only the first three arguments.
(@parse $type:ident $meta:ty |
parse($args:ident, $body:pat, $ctx:pat) $code:block $($rest:tt)*
) => {
function!(@parse $type $meta | parse($args, $body, $ctx, _meta) $code $($rest)*);
};
// (4-arg) Parse a parse-definition with all four arguments.
(@parse $type:ident $meta:ty |
parse($args:ident, $body:pat, $ctx:pat, $metadata:pat) $code:block
$($rest:tt)*
) => {
impl $crate::func::ParseFunc for $type {
type Meta = $meta;
fn parse(
args: FuncArgs,
$body: Option<Spanned<&str>>,
$ctx: ParseContext,
$metadata: Self::Meta,
) -> ParseResult<Self> where Self: Sized {
#[allow(unused_mut)]
let mut $args = args;
let val = $code;
if !$args.is_empty() {
error!(unexpected_argument);
}
Ok(val)
}
}
function!(@layout $type | $($rest)*);
};
// (0-arg) Parse a layout-definition without arguments.
(@layout $type:ident | layout() $code:block) => {
function!(@layout $type | layout(self, _ctx) $code);
};
// (1-arg) Parse a layout-definition with only the first argument.
(@layout $type:ident | layout($this:ident) $code:block) => {
function!(@layout $type | layout($this, _ctx) $code);
};
// (2-arg) Parse a layout-definition with all arguments.
(@layout $type:ident | layout($this:ident, $ctx:pat) $code:block) => {
impl LayoutFunc for $type {
fn layout<'a, 'life0, 'life1, 'async_trait>(
&'a $this,
$ctx: LayoutContext<'life0, 'life1>
) -> std::pin::Pin<Box<
dyn std::future::Future<Output = LayoutResult<Commands<'a>>> + 'async_trait
>>
where
'a: 'async_trait,
'life0: 'async_trait,
'life1: 'async_trait,
Self: 'async_trait,
{
#[allow(unreachable_code)]
Box::pin(async move { Ok($code) })
}
}
};
}
/// Parse the body of a function.
///
/// - If the function does not expect a body, use `parse!(forbidden: body)`.
/// - If the function can have a body, use `parse!(optional: body, ctx)`.
/// - If the function must have a body, use `parse!(expected: body, ctx)`.
#[macro_export]
macro_rules! parse {
(forbidden: $body:expr) => {
if $body.is_some() {
error!("unexpected body");
}
};
(optional: $body:expr, $ctx:expr) => (
if let Some(body) = $body {
Some($crate::syntax::parse(body.v, $ctx)?)
} else {
None
}
);
(expected: $body:expr, $ctx:expr) => (
if let Some(body) = $body {
$crate::syntax::parse(body.v, $ctx)?
} else {
error!("expected body");
}
)
}
/// Early-return with a formatted typesetting error or construct an error
/// expression.
#[macro_export]
macro_rules! error {
(@unexpected_argument) => (error!(@"unexpected argument"));
(@$($tts:tt)*) => ($crate::TypesetError::with_message(format!($($tts)*)));
($($tts:tt)*) => (return Err(error!(@$($tts)*)););
}
|
