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use std::cell::RefCell;
use std::collections::BTreeSet;
use std::rc::Rc;
/// Stack of local variables in nested scopes
///
/// Each scope represents a Ruby scope:
///
/// ```test
/// # 1
/// class A
/// # 1, 2
/// def m
/// # 1, 2, 3
/// end
/// # 1, 2
/// end
/// # 1
/// ```
///
/// In the example above comments show what's in the stack.
/// Basically, it's pushed when you enter a new scope
/// and it's popped when exit it.
#[derive(Debug, Clone, Default)]
pub struct StaticEnvironment {
variables: Rc<RefCell<BTreeSet<String>>>,
stack: Rc<RefCell<Vec<BTreeSet<String>>>>,
}
const FORWARD_ARGS: &str = "FORWARD_ARGS";
impl StaticEnvironment {
/// Constructor
pub fn new() -> Self {
Self {
variables: Rc::new(RefCell::new(BTreeSet::new())),
stack: Rc::new(RefCell::new(vec![])),
}
}
pub(crate) fn is_empty(&self) -> bool {
self.stack.borrow().is_empty()
}
#[allow(dead_code)]
pub(crate) fn reset(&self) {
self.variables.borrow_mut().clear();
self.stack.borrow_mut().clear();
}
/// Performs a push, doesn't inherit previously declared variables in the new scope
///
/// Handles class/module scopes
pub fn extend_static(&self) {
let variables = std::mem::take(&mut *self.variables.borrow_mut());
self.stack.borrow_mut().push(variables);
}
/// Performs a puch, inherits previously declared variables in the new scope
///
/// Handles block/lambda scopes
pub fn extend_dynamic(&self) {
self.stack
.borrow_mut()
.push(self.variables.borrow().clone());
}
/// Performs pop
pub fn unextend(&self) {
*self.variables.borrow_mut() = self
.stack
.borrow_mut()
.pop()
.expect("expected static_env to have at least one frame");
}
/// Declares a new variable in the current scope
pub fn declare(&self, name: &str) {
self.variables.borrow_mut().insert(name.to_string());
}
/// Returns `true` if variable with a given `name` is declared in the current scope
pub fn is_declared(&self, name: &str) -> bool {
self.variables.borrow().get(name).is_some()
}
pub(crate) fn declare_forward_args(&self) {
self.declare(FORWARD_ARGS);
}
pub(crate) fn is_forward_args_declared(&self) -> bool {
self.is_declared(FORWARD_ARGS)
}
}