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use crate::{AstNode, SyntaxNode};
use std::marker::PhantomData;
pub fn visitor<'a, T>() -> impl Visitor<'a, Output = T> {
EmptyVisitor { ph: PhantomData }
}
pub fn visitor_ctx<'a, T, C>(ctx: C) -> impl VisitorCtx<'a, Output = T, Ctx = C> {
EmptyVisitorCtx { ph: PhantomData, ctx }
}
pub trait Visitor<'a>: Sized {
type Output;
fn accept(self, node: &'a SyntaxNode) -> Option<Self::Output>;
fn visit<N, F>(self, f: F) -> Vis<Self, N, F>
where
N: AstNode + 'a,
F: FnOnce(N) -> Self::Output,
{
Vis { inner: self, f, ph: PhantomData }
}
}
pub trait VisitorCtx<'a>: Sized {
type Output;
type Ctx;
fn accept(self, node: &'a SyntaxNode) -> Result<Self::Output, Self::Ctx>;
fn visit<N, F>(self, f: F) -> VisCtx<Self, N, F>
where
N: AstNode + 'a,
F: FnOnce(N, Self::Ctx) -> Self::Output,
{
VisCtx { inner: self, f, ph: PhantomData }
}
}
#[derive(Debug)]
struct EmptyVisitor<T> {
ph: PhantomData<fn() -> T>,
}
impl<'a, T> Visitor<'a> for EmptyVisitor<T> {
type Output = T;
fn accept(self, _node: &'a SyntaxNode) -> Option<T> {
None
}
}
#[derive(Debug)]
struct EmptyVisitorCtx<T, C> {
ctx: C,
ph: PhantomData<fn() -> T>,
}
impl<'a, T, C> VisitorCtx<'a> for EmptyVisitorCtx<T, C> {
type Output = T;
type Ctx = C;
fn accept(self, _node: &'a SyntaxNode) -> Result<T, C> {
Err(self.ctx)
}
}
#[derive(Debug)]
pub struct Vis<V, N, F> {
inner: V,
f: F,
ph: PhantomData<fn(N)>,
}
impl<'a, V, N, F> Visitor<'a> for Vis<V, N, F>
where
V: Visitor<'a>,
N: AstNode + 'a,
F: FnOnce(N) -> <V as Visitor<'a>>::Output,
{
type Output = <V as Visitor<'a>>::Output;
fn accept(self, node: &'a SyntaxNode) -> Option<Self::Output> {
let Vis { inner, f, .. } = self;
inner.accept(node).or_else(|| N::cast(node.clone()).map(f))
}
}
#[derive(Debug)]
pub struct VisCtx<V, N, F> {
inner: V,
f: F,
ph: PhantomData<fn(N)>,
}
impl<'a, V, N, F> VisitorCtx<'a> for VisCtx<V, N, F>
where
V: VisitorCtx<'a>,
N: AstNode + 'a,
F: FnOnce(N, <V as VisitorCtx<'a>>::Ctx) -> <V as VisitorCtx<'a>>::Output,
{
type Output = <V as VisitorCtx<'a>>::Output;
type Ctx = <V as VisitorCtx<'a>>::Ctx;
fn accept(self, node: &'a SyntaxNode) -> Result<Self::Output, Self::Ctx> {
let VisCtx { inner, f, .. } = self;
inner.accept(node).or_else(|ctx| match N::cast(node.clone()) {
None => Err(ctx),
Some(node) => Ok(f(node, ctx)),
})
}
}
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