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use std::rc::Rc;
use super::{Scope, Scopes, Value};
use crate::syntax::ast::{ClosureParam, Expr, Imports};
use crate::syntax::RedRef;
/// A visitor that captures variable slots.
pub struct CapturesVisitor<'a> {
external: &'a Scopes<'a>,
internal: Scopes<'a>,
captures: Scope,
}
impl<'a> CapturesVisitor<'a> {
/// Create a new visitor for the given external scopes.
pub fn new(external: &'a Scopes) -> Self {
Self {
external,
internal: Scopes::new(None),
captures: Scope::new(),
}
}
pub fn visit(&mut self, node: RedRef) {
let expr: Option<Expr> = node.cast();
match expr.as_ref() {
Some(Expr::Let(expr)) => {
self.visit(expr.init_ref());
let ident = expr.binding();
self.internal.def_mut(ident.as_str(), Value::None);
}
Some(Expr::Closure(closure)) => {
for arg in closure.params() {
match arg {
ClosureParam::Pos(ident) | ClosureParam::Sink(ident) => {
self.internal.def_mut(ident.as_str(), Value::None);
}
ClosureParam::Named(name) => {
self.internal.def_mut(name.name().as_str(), Value::None);
}
}
}
self.visit(closure.body_ref());
}
Some(Expr::For(forloop)) => {
let pattern = forloop.pattern();
self.internal.def_mut(pattern.value().as_str(), Value::None);
if let Some(key) = pattern.key() {
self.internal.def_mut(key.as_str(), Value::None);
}
self.visit(forloop.body_ref());
}
Some(Expr::Import(import)) => {
if let Imports::Idents(idents) = import.imports() {
for ident in idents {
self.internal.def_mut(ident.as_str(), Value::None);
}
}
}
Some(Expr::Ident(ident)) => {
if self.internal.get(ident.as_str()).is_none() {
if let Some(slot) = self.external.get(ident.as_str()) {
self.captures.def_slot(ident.as_str(), Rc::clone(slot));
}
}
}
_ => {}
}
match expr.as_ref() {
Some(Expr::Let(_)) | Some(Expr::For(_)) | Some(Expr::Closure(_)) => {}
Some(Expr::Block(_)) => {
self.internal.enter();
for child in node.children() {
self.visit(child);
}
self.internal.exit();
}
Some(Expr::Template(_)) => {
self.internal.enter();
for child in node.children() {
self.visit(child);
}
self.internal.exit();
}
_ => {
for child in node.children() {
self.visit(child);
}
}
}
}
/// Return the scope of captured variables.
pub fn finish(self) -> Scope {
self.captures
}
}
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