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use std::collections::HashMap;
use crate::error::{Error, ImportError};
use crate::semantics::{AlphaVar, Hir, Import, VarEnv};
use crate::syntax::{Label, V};
/// Environment for resolving names.
#[derive(Debug, Clone)]
pub(crate) struct NameEnv {
names: Vec<Label>,
}
pub(crate) type ImportCache = HashMap<Import, Hir>;
pub(crate) type ImportStack = Vec<Import>;
/// Environment for resolving imports
#[derive(Debug, Clone)]
pub(crate) struct ImportEnv {
cache: ImportCache,
stack: ImportStack,
}
impl NameEnv {
pub fn new() -> Self {
NameEnv { names: Vec::new() }
}
pub fn as_varenv(&self) -> VarEnv {
VarEnv::from_size(self.names.len())
}
pub fn insert(&self, x: &Label) -> Self {
let mut env = self.clone();
env.insert_mut(x);
env
}
pub fn insert_mut(&mut self, x: &Label) {
self.names.push(x.clone())
}
pub fn remove_mut(&mut self) {
self.names.pop();
}
pub fn unlabel_var(&self, var: &V) -> Option<AlphaVar> {
let V(name, idx) = var;
let (idx, _) = self
.names
.iter()
.rev()
.enumerate()
.filter(|(_, n)| *n == name)
.nth(*idx)?;
Some(AlphaVar::new(idx))
}
pub fn label_var(&self, var: &AlphaVar) -> V {
let name = &self.names[self.names.len() - 1 - var.idx()];
let idx = self
.names
.iter()
.rev()
.take(var.idx())
.filter(|n| *n == name)
.count();
V(name.clone(), idx)
}
}
impl ImportEnv {
pub fn new() -> Self {
ImportEnv {
cache: HashMap::new(),
stack: Vec::new(),
}
}
pub fn handle_import(
&mut self,
import: Import,
mut do_resolve: impl FnMut(&mut Self, &Import) -> Result<Hir, Error>,
) -> Result<Hir, Error> {
if self.stack.contains(&import) {
return Err(
ImportError::ImportCycle(self.stack.clone(), import).into()
);
}
Ok(match self.cache.get(&import) {
Some(expr) => expr.clone(),
None => {
// Push the current import on the stack
self.stack.push(import.clone());
// Resolve the import recursively
let expr = do_resolve(self, &import)?;
// Remove import from the stack.
self.stack.pop();
// Add the import to the cache
self.cache.insert(import, expr.clone());
expr
}
})
}
}
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