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use super::{ast::Variable, error::VariableError, typed::Type};
#[derive(Debug, Default)]
pub struct Context {
vars: Vec<Type>,
unguard_points: Vec<usize>,
}
impl Context {
pub fn new() -> Self {
Self::default()
}
pub fn depth(&self) -> usize {
self.vars.len()
}
pub fn is_unguarded(&self, var: &Variable) -> Option<bool> {
if self.vars.len() <= var.index() {
None
} else if self.unguard_points.is_empty() {
Some(false)
} else {
Some(
self.unguard_points[self.unguard_points.len() - 1] + var.index() >= self.vars.len(),
)
}
}
pub fn with_unguard<F: FnOnce(&mut Self) -> R, R>(&mut self, f: F) -> R {
self.unguard_points.push(self.vars.len());
let res = f(self);
self.unguard_points.pop();
res
}
pub fn get_variable_type(&self, var: &Variable) -> Result<&Type, VariableError> {
match self.is_unguarded(var) {
None => Err(VariableError::FreeVariable(var.clone())),
Some(false) => Err(VariableError::GuardedVariable(var.clone())),
Some(true) => Ok(&self.vars[self.vars.len() - var.index() - 1]),
}
}
pub fn with_variable_type<F: FnOnce(&mut Self) -> R, R>(&mut self, ty: Type, f: F) -> R {
self.vars.push(ty);
let res = f(self);
self.vars.pop();
res
}
}
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