j/Doughlang
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

ast: Give for loops a dedicated node and remove eager desugar

Browse Source
This commit is contained in:
John
2025-12-01 23:16:47 -05:00
parent 7ea483fe26
commit e566ea62e5
3 changed files with 19 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

81
src/parser/expr.rs
View File

@@ -398,19 +398,12 @@ fn parse_match(p: &mut Parser<'_>) -> PResult<Expr> {
Ok(expr)
}
/// Parses and desugars a `for` loop expression
///
/// Assumes the existence of the following items:
///
/// 1. `enum<T> Option { None, Some(T) }`
/// 2. `fn T::into_iter(&mut self) -> U`
/// 3. `U::next() -> Option<V>`
/// Parses a `for` loop expression
fn parse_for(p: &mut Parser<'_>, _level: ()) -> PResult<Expr> {
// for Pat
let pat = p.consume().parse(PPrec::Tuple)?;
// in Expr
let iter: Anno<Expr> = p.expect(TKind::In)?.parse(Prec::Logical.next())?;
let cspan = iter.1;
// Expr
let pass: Anno<Expr> = p.parse(Prec::Body.next())?;
let pspan = pass.1;
@@ -419,8 +412,8 @@ fn parse_for(p: &mut Parser<'_>, _level: ()) -> PResult<Expr> {
Some(Ok(_)) => p.parse(Prec::Body.next())?,
_ => Expr::Op(Op::Tuple, vec![]).anno(pspan),
};
let fspan = fail.1;
/*
TODO: desugar for into loop-match:
for `pat in `iter `pass else `fail
==>
match (`iter).into_iter() {
@@ -431,70 +424,12 @@ fn parse_for(p: &mut Parser<'_>, _level: ()) -> PResult<Expr> {
}
*/
// TODO: A better way to do this kind of substitution desugaring
// without losing span information!
Ok(Expr::Op(
Op::Match,
vec![
Expr::Op(
Op::Dot,
vec![
iter,
Expr::Op(Op::Call, vec![Expr::Id("into_iter".into()).anno(cspan)]).anno(cspan),
],
)
.anno(cspan),
Expr::Bind(Box::new(Bind(
BindOp::Match,
vec![],
Pat::Name("#iter".into()),
vec![
Expr::Op(
Op::Loop,
vec![
Expr::Op(
Op::Match,
vec![
Expr::Op(
Op::Dot,
vec![
Expr::Id("#iter".into()).anno(cspan),
Expr::Op(
Op::Call,
vec![Expr::Id("next".into()).anno(cspan)],
)
.anno(cspan),
],
)
.anno(cspan),
Expr::Bind(Box::new(Bind(
BindOp::Match,
vec![],
Pat::Name("None".into()),
vec![Expr::Op(Op::Break, vec![fail]).anno(fspan)],
)))
.anno(fspan),
Expr::Bind(Box::new(Bind(
BindOp::Match,
vec![],
Pat::NamedTuple(
"Some".into(),
Box::new(Pat::Op(PatOp::Tuple, vec![pat])),
),
vec![pass],
)))
.anno(pspan),
],
)
.anno(pspan),
],
)
.anno(pspan),
],
)))
.anno(pspan),
],
))
Ok(Expr::Bind(Box::new(Bind(
BindOp::For,
vec![],
pat,
vec![iter, pass, fail],
))))
}
/// Returns the [BindOp], [pattern precedence](PPrec), [arrow TKind](TKind), [body precedence](Prec),