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Add minimal support for improper lists in macro expansion (#226)
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@mattwparas
mattwparas authored Jun 23, 2024
1 parent 03cb6a1 commit a818390
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Showing 5 changed files with 91 additions and 19 deletions.
4 changes: 4 additions & 0 deletions crates/steel-core/src/parser/expand_visitor.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -190,6 +190,10 @@ impl<'a> VisitorMutRef for Expander<'a> {
if let ExprKind::LambdaFunction(mut lambda) =
parse_lambda(ident.clone(), std::mem::take(&mut l.args))?
{
if l.improper {
lambda.rest = true;
}

self.visit_lambda_function(&mut lambda)?;

*expr = ExprKind::LambdaFunction(lambda);
Expand Down
49 changes: 40 additions & 9 deletions crates/steel-core/src/parser/expander.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -352,6 +352,7 @@ impl MacroCase {
&expr[1..],
&mut bindings,
&mut binding_kind,
expr.improper,
)?;

let mut body = self.body.clone();
Expand Down Expand Up @@ -884,6 +885,7 @@ pub fn collect_bindings(
list: &[ExprKind],
bindings: &mut FxHashMap<InternedString, ExprKind>,
binding_kind: &mut FxHashMap<InternedString, BindingKind>,
improper: bool,
) -> Result<()> {
let mut token_iter = list.iter();

Expand Down Expand Up @@ -919,7 +921,7 @@ pub fn collect_bindings(
// bind the ellipses to the rest of the statement
MacroPattern::Many(ident) => {
let rest: Vec<_> = token_iter.cloned().collect();
bindings.insert(*ident, List::new(rest).into());
bindings.insert(*ident, List::new_maybe_improper(rest, improper).into());
binding_kind.insert(*ident, BindingKind::Many);
break;
}
Expand All @@ -929,7 +931,7 @@ pub fn collect_bindings(
.ok_or_else(throw!(ArityMismatch => "Macro expected a pattern"))?;

if let ExprKind::List(l) = child {
collect_bindings(children, l, bindings, binding_kind)?;
collect_bindings(children, l, bindings, binding_kind, l.improper)?;
} else if let ExprKind::Quote(q) = child {
if let &[MacroPattern::Quote(x)] = children.as_slice() {
bindings.insert(x, q.expr.clone());
Expand All @@ -941,8 +943,6 @@ pub fn collect_bindings(
}
}
MacroPattern::ManyNested(children) => {
// dbg!(children);

let exprs_to_destruct = token_iter.collect::<smallvec::SmallVec<[_; 8]>>();

for i in 0..children.len() {
Expand All @@ -956,7 +956,9 @@ pub fn collect_bindings(

if is_ellipses_pattern {
// Bind the "rest" of the values into this
values_to_bind.push(List::new(l[i..].to_vec()).into());
values_to_bind.push(
List::new_maybe_improper(l[i..].to_vec(), l.improper).into(),
);
} else {
values_to_bind.push(l[i].clone());
}
Expand Down Expand Up @@ -995,6 +997,7 @@ pub fn collect_bindings(
list_expr,
&mut new_bindings,
binding_kind,
list_expr.improper,
)?;

for (key, value) in new_bindings {
Expand Down Expand Up @@ -1238,7 +1241,14 @@ mod collect_bindings_tests {
])),
]);

collect_bindings(&pattern_args, &list_expr, &mut bindings, &mut binding_kind).unwrap();
collect_bindings(
&pattern_args,
&list_expr,
&mut bindings,
&mut binding_kind,
false,
)
.unwrap();

let mut post_bindings = FxHashMap::default();
post_bindings.insert(
Expand Down Expand Up @@ -1285,7 +1295,14 @@ mod collect_bindings_tests {
])),
]);

collect_bindings(&pattern_args, &list_expr, &mut bindings, &mut binding_kind).unwrap();
collect_bindings(
&pattern_args,
&list_expr,
&mut bindings,
&mut binding_kind,
false,
)
.unwrap();

let mut post_bindings = FxHashMap::default();
post_bindings.insert(
Expand Down Expand Up @@ -1329,7 +1346,14 @@ mod collect_bindings_tests {
atom_identifier("y"),
]);

collect_bindings(&pattern_args, &list_expr, &mut bindings, &mut binding_kind).unwrap();
collect_bindings(
&pattern_args,
&list_expr,
&mut bindings,
&mut binding_kind,
false,
)
.unwrap();
let mut post_bindings = FxHashMap::default();

post_bindings.insert(
Expand Down Expand Up @@ -1379,7 +1403,14 @@ mod collect_bindings_tests {

let mut post_bindings = FxHashMap::default();

collect_bindings(&pattern_args, &list_expr, &mut bindings, &mut binding_kind).unwrap();
collect_bindings(
&pattern_args,
&list_expr,
&mut bindings,
&mut binding_kind,
false,
)
.unwrap();
post_bindings.insert("a".into(), atom_int(1));
post_bindings.insert("b".into(), atom_identifier("apple"));
post_bindings.insert(
Expand Down
37 changes: 27 additions & 10 deletions crates/steel-core/src/parser/replace_idents.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -144,10 +144,11 @@ impl<'a> ReplaceExpressions<'a> {
// ExprKind::Atom(expr)
// }

fn expand_ellipses(&mut self, vec_exprs: &mut Vec<ExprKind>) -> Result<()> {
// Note: Returns a bool indicating if this should be made improper/rest or not
fn expand_ellipses(&mut self, vec_exprs: &mut Vec<ExprKind>) -> Result<bool> {
if let Some(ellipses_pos) = vec_exprs.iter().position(check_ellipses) {
if ellipses_pos == 0 {
return Ok(());
return Ok(false);
}

let variable_to_lookup = vec_exprs.get(ellipses_pos - 1).ok_or_else(
Expand All @@ -162,24 +163,30 @@ impl<'a> ReplaceExpressions<'a> {
..
},
}) => {
let improper;

// let rest = self.bindings.get(var).ok_or_else(throw!(BadSyntax => format!("macro expansion failed at finding the variable when expanding ellipses: {var}")))?;

let rest = if let Some(rest) = self.bindings.get(var) {
rest
} else {
return Ok(());
return Ok(false);
};

let list_of_exprs = if let ExprKind::List(list_of_exprs) = rest {
improper = list_of_exprs.improper;

list_of_exprs
} else {
let res = if let Some(res) = self.fallback_bindings.get(var) {
res.list_or_else(
throw!(BadSyntax => "macro expansion failed, expected list of expressions, found: {}, within {}", rest, super::ast::List::new(vec_exprs.clone())))?
} else {
return Ok(());
return Ok(false);
};

improper = res.improper;

// let res = self.fallback_bindings.get(var).ok_or_else(throw!(BadSyntax => format!("macro expansion failed at finding the variable when expanding ellipses: {var}")))?.list_or_else(
// throw!(BadSyntax => "macro expansion failed, expected list of expressions, found: {}, within {}", rest, super::ast::List::new(vec_exprs.clone()))
// )?;
Expand All @@ -206,10 +213,12 @@ impl<'a> ReplaceExpressions<'a> {

// *vec_exprs = first_chunk;

Ok(())
Ok(improper)
}

ExprKind::List(_) => {
ExprKind::List(bound_list) => {
let improper = bound_list.improper;

let visitor = EllipsesExpanderVisitor::find_expansion_width_and_collect_ellipses_expanders(self.bindings, self.binding_kind, variable_to_lookup);

if let Some(error) = visitor.error {
Expand Down Expand Up @@ -273,7 +282,7 @@ impl<'a> ReplaceExpressions<'a> {

// *vec_exprs = first_chunk;

Ok(())
Ok(improper)

// Ok(())

Expand All @@ -285,7 +294,7 @@ impl<'a> ReplaceExpressions<'a> {
}
}
} else {
Ok(())
Ok(false)
}
}

Expand Down Expand Up @@ -481,12 +490,16 @@ impl<'a> VisitorMutRef for ReplaceExpressions<'a> {
// return self.visit(expanded);
}

self.expand_ellipses(&mut l.args)?;
let improper = self.expand_ellipses(&mut l.args)?;

for expr in l.args.iter_mut() {
self.visit(expr)?;
}

if improper {
l.set_improper();
}

if let Some(expanded) = self.vec_syntax_span_object(&l.args)? {
*expr = expanded;
return Ok(());
Expand Down Expand Up @@ -523,14 +536,18 @@ impl<'a> VisitorMutRef for ReplaceExpressions<'a> {
&mut self,
lambda_function: &mut super::ast::LambdaFunction,
) -> Self::Output {
self.expand_ellipses(&mut lambda_function.args)?;
let improper = self.expand_ellipses(&mut lambda_function.args)?;

for arg in lambda_function.args.iter_mut() {
self.visit(arg)?;
}

self.visit(&mut lambda_function.body)?;

if improper {
lambda_function.rest = true;
}

// TODO: @Matt - 2/28/12 -> clean up this
// This mangles the values
// lambda_function.args.iter_mut().for_each(|x| {
Expand Down
7 changes: 7 additions & 0 deletions crates/steel-core/src/tests/success/docs.scm
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Original file line number Diff line number Diff line change
Expand Up @@ -4,3 +4,10 @@
(list 10 20 30 40 x))

(assert! (equal? "This is a function that does something\n" foo__doc__))

;;@doc
;; This is a function that takes multiple arguments
(define (bar . args)
(list 10 20 30 40 args))

(assert! (equal? (list 10 20 30 40 (list 50 60)) (bar 50 60)))
13 changes: 13 additions & 0 deletions crates/steel-parser/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -992,6 +992,15 @@ impl List {
}
}

pub fn new_maybe_improper(args: Vec<ExprKind>, improper: bool) -> Self {
List {
args,
syntax_object_id: SyntaxObjectId::fresh().0,
improper,
location: None,
}
}

pub fn with_spans(args: Vec<ExprKind>, open: Span, close: Span) -> Self {
List {
args,
Expand All @@ -1006,6 +1015,10 @@ impl List {
self
}

pub fn set_improper(&mut self) {
self.improper = true;
}

pub fn is_empty(&self) -> bool {
self.args.is_empty()
}
Expand Down

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