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use std::collections::HashMap;
use crate::error::{Error, ImportError};
use crate::semantics::{AlphaVar, Cache, ImportLocation, VarEnv};
use crate::syntax::{Hash, Label, V};
use crate::Typed;
/// Environment for resolving names.
#[derive(Debug, Clone, Default)]
pub struct NameEnv {
names: Vec<Label>,
}
pub type MemCache = HashMap<ImportLocation, Typed>;
pub type CyclesStack = Vec<ImportLocation>;
/// Environment for resolving imports
#[derive(Debug)]
pub struct ImportEnv {
disk_cache: Option<Cache>, // Missing if it failed to initialize
mem_cache: MemCache,
stack: CyclesStack,
}
impl NameEnv {
pub fn new() -> Self {
NameEnv::default()
}
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 {
disk_cache: Cache::new().ok(),
mem_cache: Default::default(),
stack: Default::default(),
}
}
pub fn get_from_mem_cache(
&mut self,
location: &ImportLocation,
) -> Option<Typed> {
Some(self.mem_cache.get(location)?.clone())
}
pub fn get_from_disk_cache(
&mut self,
hash: &Option<Hash>,
) -> Option<Typed> {
let hash = hash.as_ref()?;
let expr = self.disk_cache.as_ref()?.get(hash).ok()?;
Some(expr)
}
pub fn write_to_mem_cache(
&mut self,
location: ImportLocation,
expr: Typed,
) {
self.mem_cache.insert(location, expr);
}
pub fn write_to_disk_cache(&mut self, hash: &Option<Hash>, expr: &Typed) {
if let Some(disk_cache) = self.disk_cache.as_ref() {
if let Some(hash) = hash {
let _ = disk_cache.insert(hash, &expr);
}
}
}
pub fn with_cycle_detection(
&mut self,
location: ImportLocation,
do_resolve: impl FnOnce(&mut Self) -> Result<Typed, Error>,
) -> Result<Typed, Error> {
if self.stack.contains(&location) {
return Err(
ImportError::ImportCycle(self.stack.clone(), location).into()
);
}
// Push the current location on the stack
self.stack.push(location);
// Resolve the import recursively
// WARNING: do not propagate errors here or the stack will get messed up.
let result = do_resolve(self);
// Remove location from the stack.
self.stack.pop().unwrap();
result
}
}
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