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use elsa::vec::FrozenVec;
use once_cell::sync::OnceCell;
use std::marker::PhantomData;
use std::ops::{Deref, Index};
use crate::semantics::{Import, ImportLocation};
use crate::syntax::Span;
use crate::Typed;
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct ImportId<'cx>(usize, PhantomData<&'cx ()>);
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub struct ImportResultId<'cx>(usize, PhantomData<&'cx ()>);
/// What's stored for each `ImportId`. Allows getting and setting a result for this import.
pub struct StoredImport<'cx> {
cx: Ctxt<'cx>,
pub base_location: ImportLocation,
pub import: Import,
pub span: Span,
result: OnceCell<ImportResultId<'cx>>,
}
/// Implementation detail. Made public for the `Index` instances.
#[derive(Default)]
pub struct CtxtS<'cx> {
imports: FrozenVec<Box<StoredImport<'cx>>>,
import_results: FrozenVec<Box<Typed<'cx>>>,
}
/// Context for the dhall compiler. Stores various global maps.
/// Access the relevant value using `cx[id]`.
#[derive(Copy, Clone)]
pub struct Ctxt<'cx>(&'cx CtxtS<'cx>);
impl Ctxt<'_> {
pub fn with_new<T>(f: impl for<'cx> FnOnce(Ctxt<'cx>) -> T) -> T {
let cx = CtxtS::default();
let cx = Ctxt(&cx);
f(cx)
}
}
impl<'cx> Ctxt<'cx> {
/// Store an import and the location relative to which it must be resolved.
pub fn push_import(
self,
base_location: ImportLocation,
import: Import,
span: Span,
) -> ImportId<'cx> {
let stored = StoredImport {
cx: self,
base_location,
import,
span,
result: OnceCell::new(),
};
let id = self.0.imports.len();
self.0.imports.push(Box::new(stored));
ImportId(id, PhantomData)
}
/// Store the result of fetching an import.
pub fn push_import_result(self, res: Typed<'cx>) -> ImportResultId<'cx> {
let id = self.0.import_results.len();
self.0.import_results.push(Box::new(res));
ImportResultId(id, PhantomData)
}
}
impl<'cx> StoredImport<'cx> {
/// Get the id of the result of fetching this import. Returns `None` if the result has not yet
/// been fetched.
pub fn get_resultid(&self) -> Option<ImportResultId<'cx>> {
self.result.get().copied()
}
/// Store the result of fetching this import.
pub fn set_resultid(&self, res: ImportResultId<'cx>) {
let _ = self.result.set(res);
}
/// Get the result of fetching this import. Returns `None` if the result has not yet been
/// fetched.
pub fn get_result(&self) -> Option<&'cx Typed<'cx>> {
let res = self.get_resultid()?;
Some(&self.cx[res])
}
/// Get the result of fetching this import. Panicx if the result has not yet been
/// fetched.
pub fn unwrap_result(&self) -> &'cx Typed<'cx> {
self.get_result()
.expect("imports should all have been resolved at this stage")
}
/// Store the result of fetching this import.
pub fn set_result(&self, res: Typed<'cx>) -> ImportResultId<'cx> {
let res = self.cx.push_import_result(res);
self.set_resultid(res);
res
}
}
impl<'cx> Deref for Ctxt<'cx> {
type Target = &'cx CtxtS<'cx>;
fn deref(&self) -> &&'cx CtxtS<'cx> {
&self.0
}
}
impl<'cx> Index<ImportId<'cx>> for CtxtS<'cx> {
type Output = StoredImport<'cx>;
fn index(&self, id: ImportId<'cx>) -> &StoredImport<'cx> {
&self.imports[id.0]
}
}
impl<'cx> Index<ImportResultId<'cx>> for CtxtS<'cx> {
type Output = Typed<'cx>;
fn index(&self, id: ImportResultId<'cx>) -> &Typed<'cx> {
&self.import_results[id.0]
}
}
impl<'a, 'cx, T> Index<&'a T> for CtxtS<'cx>
where
Self: Index<T>,
T: Copy,
{
type Output = <Self as Index<T>>::Output;
fn index(&self, id: &'a T) -> &Self::Output {
&self[*id]
}
}
/// Empty impl, because `FrozenVec` does not implement `Debug` and I can't be bothered to do it
/// myself.
impl<'cx> std::fmt::Debug for Ctxt<'cx> {
fn fmt(&self, _: &mut std::fmt::Formatter) -> std::fmt::Result {
Ok(())
}
}
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