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use crate::collections::HashMap;
use crate::shared::Custom;
use crate::Spanned;
use thiserror::Error;
pub(crate) struct Scopes<T> {
scopes: Vec<Scope<T>>,
}
impl<T> Scopes<T> {
pub(crate) fn clear_current<S>(&mut self, spanned: S) -> Result<(), Custom>
where
S: Spanned,
{
let last = self
.scopes
.last_mut()
.ok_or_else(|| Custom::new(spanned, "expected at least one scope"))?;
last.locals.clear();
Ok(())
}
pub(crate) fn decl<S>(&mut self, name: &str, value: T, spanned: S) -> Result<(), Custom>
where
S: Spanned,
{
let last = self
.last_mut()
.ok_or_else(|| Custom::new(spanned, "expected at least one scope"))?;
last.locals.insert(name.to_owned(), value);
Ok(())
}
pub(crate) fn try_get<'a>(&'a self, name: &str) -> Option<&'a T> {
for scope in self.scopes.iter().rev() {
if let Some(current) = scope.locals.get(name) {
return Some(current);
}
if let ScopeKind::Isolate = scope.kind {
break;
}
}
None
}
pub(crate) fn get_name<'a, S>(&'a self, name: &str, spanned: S) -> Result<&'a T, ScopeError>
where
S: Spanned,
{
for scope in self.scopes.iter().rev() {
if let Some(current) = scope.locals.get(name) {
return Ok(current);
}
if let ScopeKind::Isolate = scope.kind {
break;
}
}
Err(ScopeError::new(
spanned,
ScopeErrorKind::MissingLocal { name: name.into() },
))
}
pub(crate) fn get_name_mut<'a, S>(
&'a mut self,
name: &str,
spanned: S,
) -> Result<&'a mut T, ScopeError>
where
S: Spanned,
{
for scope in self.scopes.iter_mut().rev() {
if let Some(current) = scope.locals.get_mut(name) {
return Ok(current);
}
if let ScopeKind::Isolate = scope.kind {
break;
}
}
Err(ScopeError::new(
spanned,
ScopeErrorKind::MissingLocal { name: name.into() },
))
}
pub(crate) fn push(&mut self) -> ScopeGuard {
let length = self.scopes.len();
self.scopes.push(Scope::default());
ScopeGuard { length }
}
pub(crate) fn isolate(&mut self) -> ScopeGuard {
let length = self.scopes.len();
let mut scope = Scope::default();
scope.kind = ScopeKind::Isolate;
self.scopes.push(scope);
ScopeGuard { length }
}
pub(crate) fn pop<S>(&mut self, spanned: S, guard: ScopeGuard) -> Result<(), Custom>
where
S: Spanned,
{
if self.scopes.pop().is_none() {
return Err(Custom::new(spanned, "expected at least one scope to pop"));
}
if self.scopes.len() != guard.length {
return Err(Custom::new(spanned, "scope length mismatch"));
}
Ok(())
}
pub(crate) fn last_mut(&mut self) -> Option<&mut Scope<T>> {
self.scopes.last_mut()
}
}
impl<T> Default for Scopes<T> {
fn default() -> Self {
Self {
scopes: vec![Scope::default()],
}
}
}
#[repr(transparent)]
pub(crate) struct ScopeGuard {
length: usize,
}
#[derive(Debug, Clone, Copy)]
enum ScopeKind {
None,
Isolate,
}
pub(crate) struct Scope<T> {
kind: ScopeKind,
locals: HashMap<String, T>,
}
impl<T> Default for Scope<T> {
fn default() -> Self {
Self {
kind: ScopeKind::None,
locals: Default::default(),
}
}
}
error! {
#[derive(Debug)]
pub struct ScopeError {
kind: ScopeErrorKind,
}
}
#[allow(missing_docs)]
#[derive(Debug, Error)]
pub enum ScopeErrorKind {
#[error("{message}")]
Custom { message: &'static str },
#[error("missing local {name}")]
MissingLocal { name: Box<str> },
}