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//! This module implements the runtime representation of functions.
use std::{collections::BTreeMap, hash::Hash, rc::Rc};
use codemap::Span;
use smol_str::SmolStr;
use crate::{chunk::Chunk, upvalues::Upvalues};
use super::NixString;
#[derive(Clone, Debug, PartialEq)]
pub(crate) struct Formals {
/// Map from argument name, to whether that argument is required
pub(crate) arguments: BTreeMap<NixString, bool>,
/// Do the formals of this function accept extra arguments
pub(crate) ellipsis: bool,
/// The span of the formals themselves, to use to emit errors
pub(crate) span: Span,
}
impl Formals {
/// Returns true if the given arg is a valid argument to these formals.
///
/// This is true if it is either listed in the list of arguments, or the formals have an
/// ellipsis
pub(crate) fn contains<Q>(&self, arg: &Q) -> bool
where
Q: ?Sized + Hash + Ord + Eq,
NixString: std::borrow::Borrow<Q>,
{
self.ellipsis || self.arguments.contains_key(arg)
}
}
/// The opcodes for a thunk or closure, plus the number of
/// non-executable opcodes which are allowed after an OpThunkClosure or
/// OpThunkSuspended referencing it. At runtime `Lambda` is usually wrapped
/// in `Rc` to avoid copying the `Chunk` it holds (which can be
/// quite large).
///
/// In order to correctly reproduce cppnix's "pointer equality"
/// semantics it is important that we never clone a Lambda --
/// use `Rc<Lambda>::clone()` instead. This struct deliberately
/// does not `derive(Clone)` in order to prevent this from being
/// done accidentally.
///
#[derive(/* do not add Clone here */ Debug, Default)]
pub struct Lambda {
pub(crate) chunk: Chunk,
/// Name of the function (equivalent to the name of the
/// identifier (e.g. a value in a let-expression or an attribute
/// set entry) it is located in).
pub(crate) name: Option<SmolStr>,
/// Number of upvalues which the code in this Lambda closes
/// over, and which need to be initialised at
/// runtime. Information about the variables is emitted using
/// data-carrying opcodes (see [`crate::opcode::OpCode::DataStackIdx`]).
pub(crate) upvalue_count: usize,
pub(crate) formals: Option<Formals>,
}
impl Lambda {
pub fn chunk(&mut self) -> &mut Chunk {
&mut self.chunk
}
}
///
/// In order to correctly reproduce cppnix's "pointer equality"
/// semantics it is important that we never clone a Lambda --
/// use `Rc<Lambda>::clone()` instead. This struct deliberately
/// does not `derive(Clone)` in order to prevent this from being
/// done accidentally.
///
#[derive(/* do not add Clone here */ Debug)]
pub struct Closure {
pub lambda: Rc<Lambda>,
pub upvalues: Rc<Upvalues>,
}
impl Closure {
pub fn new(lambda: Rc<Lambda>) -> Self {
Self::new_with_upvalues(
Rc::new(Upvalues::with_capacity(lambda.upvalue_count)),
lambda,
)
}
pub fn new_with_upvalues(upvalues: Rc<Upvalues>, lambda: Rc<Lambda>) -> Self {
Closure { upvalues, lambda }
}
pub fn chunk(&self) -> &Chunk {
&self.lambda.chunk
}
pub fn lambda(&self) -> Rc<Lambda> {
self.lambda.clone()
}
pub fn upvalues(&self) -> Rc<Upvalues> {
self.upvalues.clone()
}
}
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