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parser: Move parse_for below impl Parse<'t> for Expr, and allow a single semi at EOF

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This commit is contained in:
John
2025-10-21 07:44:13 -04:00
parent 6c57263492
commit 3fd089ad11
1 changed files with 97 additions and 88 deletions
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185
src/parser.rs
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@@ -731,93 +731,6 @@ impl<'t> Parse<'t> for MakeArm {
} }
} }
fn parse_for<'t>(p: &mut Parser<'t>, _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;
// else Expr?
let fail = match p.next_if(TKind::Else).allow_eof()? {
Some(Ok(_)) => p.parse(Prec::Body.next())?,
_ => Expr::Op(Op::Tuple, vec![]).anno(pspan),
};
let fspan = fail.1;
/*
for `pat in `iter `pass else `fail
==>
match (`iter).into_iter() {
#iter => loop match #iter.next() {
None => break `fail,
Some(`pat) => `pass,
},
}
*/
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(
BindKind::Match,
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(
BindKind::Match,
Pat::Name("None".into()),
vec![Expr::Op(Op::Break, vec![fail]).anno(fspan)],
)))
.anno(fspan),
Expr::Bind(Box::new(Bind(
BindKind::Match,
Pat::NamedTuple(
"Some".into(),
Box::new(Pat::Op(PatOp::Tuple, vec![pat])),
),
vec![pass],
)))
.anno(pspan),
],
)
.anno(pspan),
],
)
.anno(pspan),
],
)))
.anno(pspan),
],
))
}
impl<'t> Parse<'t> for Expr { impl<'t> Parse<'t> for Expr {
type Prec = usize; type Prec = usize;
@@ -939,7 +852,14 @@ impl<'t> Parse<'t> for Expr {
// As is ImplicitDo (semicolon elision) // As is ImplicitDo (semicolon elision)
Ps::ImplicitDo if p.elide_do => head.and_do(span, p.parse(prec.next())?), Ps::ImplicitDo if p.elide_do => head.and_do(span, p.parse(prec.next())?),
Ps::ImplicitDo => break, Ps::ImplicitDo => break,
Ps::Op(Op::Do) => head.and_do(span, p.consume().parse(prec.next())?), // Allow `;` at end of file
Ps::Op(Op::Do) => head.and_do(
span,
match p.consume().peek().allow_eof()? {
Some(_) => p.parse(prec.next())?,
None => Anno(Default::default(), span),
},
),
Ps::Op(Op::Index) => Expr::Op( Ps::Op(Op::Index) => Expr::Op(
Op::Index, Op::Index,
p.consume() p.consume()
@@ -1008,6 +928,95 @@ fn parse_match<'t>(p: &mut Parser<'t>) -> PResult<Expr> {
Ok(expr) Ok(expr)
} }
fn parse_for<'t>(p: &mut Parser<'t>, _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;
// else Expr?
let fail = match p.next_if(TKind::Else).allow_eof()? {
Some(Ok(_)) => p.parse(Prec::Body.next())?,
_ => Expr::Op(Op::Tuple, vec![]).anno(pspan),
};
let fspan = fail.1;
/*
for `pat in `iter `pass else `fail
==>
match (`iter).into_iter() {
#iter => loop match #iter.next() {
None => break `fail,
Some(`pat) => `pass,
},
}
*/
// 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(
BindKind::Match,
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(
BindKind::Match,
Pat::Name("None".into()),
vec![Expr::Op(Op::Break, vec![fail]).anno(fspan)],
)))
.anno(fspan),
Expr::Bind(Box::new(Bind(
BindKind::Match,
Pat::NamedTuple(
"Some".into(),
Box::new(Pat::Op(PatOp::Tuple, vec![pat])),
),
vec![pass],
)))
.anno(pspan),
],
)
.anno(pspan),
],
)
.anno(pspan),
],
)))
.anno(pspan),
],
))
}
impl<'t, P: Parse<'t> + Annotation> Parse<'t> for Anno<P> { impl<'t, P: Parse<'t> + Annotation> Parse<'t> for Anno<P> {
type Prec = P::Prec; type Prec = P::Prec;
fn parse(p: &mut Parser<'t>, level: P::Prec) -> PResult<Self> fn parse(p: &mut Parser<'t>, level: P::Prec) -> PResult<Self>