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Implement array patterns #1912

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May 16, 2024
Merged

Implement array patterns #1912

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43 changes: 38 additions & 5 deletions core/src/parser/grammar.lalrpop
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Original file line number Diff line number Diff line change
Expand Up @@ -562,6 +562,7 @@ PatternF<F>: Pattern = {
#[inline]
PatternDataF<F>: PatternData = {
RecordPattern => PatternData::Record(<>),
ArrayPattern => PatternData::Array(<>),
ConstantPattern => PatternData::Constant(<>),
EnumPatternF<F> => PatternData::Enum(<>),
Ident => PatternData::Any(<>),
Expand Down Expand Up @@ -597,15 +598,15 @@ RecordPattern: RecordPattern = {
let tail = match last {
Some(LastPattern::Normal(m)) => {
field_pats.push(*m);
RecordPatternTail::Empty
TailPattern::Empty
},
Some(LastPattern::Ellipsis(Some(captured))) => {
RecordPatternTail::Capture(captured)
TailPattern::Capture(captured)
}
Some(LastPattern::Ellipsis(None)) => {
RecordPatternTail::Open
TailPattern::Open
}
None => RecordPatternTail::Empty,
None => TailPattern::Empty,
};

let pattern = RecordPattern {
Expand All @@ -619,6 +620,32 @@ RecordPattern: RecordPattern = {
},
};

ArrayPattern: ArrayPattern = {
<start: @L> "[" <mut patterns: (<Pattern> ",")*> <last: LastElemPat?> "]" <end: @R> => {
let tail = match last {
Some(LastPattern::Normal(m)) => {
patterns.push(*m);
TailPattern::Empty
},
Some(LastPattern::Ellipsis(Some(captured))) => {
TailPattern::Capture(captured)
}
Some(LastPattern::Ellipsis(None)) => {
TailPattern::Open
}
None => TailPattern::Empty,
};

let pattern = ArrayPattern{
patterns,
tail,
pos: mk_pos(src_id, start, end)
};

pattern
},
};

EnumPatternF<F>: EnumPattern = {
<start: @L> <tag: EnumTag> <end: @R> => EnumPattern {
tag,
Expand Down Expand Up @@ -663,12 +690,18 @@ FieldPattern: FieldPattern = {
},
};

// Last field of a pattern
// Last field pattern of a record pattern
LastFieldPat: LastPattern<FieldPattern> = {
FieldPattern => LastPattern::Normal(Box::new(<>)),
".." <Ident?> => LastPattern::Ellipsis(<>),
};

// Last pattern of an array pattern
LastElemPat: LastPattern<Pattern> = {
Pattern => LastPattern::Normal(Box::new(<>)),
".." <Ident?> => LastPattern::Ellipsis(<>),
}

// A default annotation in a pattern.
DefaultAnnot: RichTerm = "?" <t: Term> => t;

Expand Down
37 changes: 34 additions & 3 deletions core/src/pretty.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -588,6 +588,7 @@ where
PatternData::Wildcard => allocator.text("_"),
PatternData::Any(id) => allocator.as_string(id),
PatternData::Record(rp) => rp.pretty(allocator),
PatternData::Array(ap) => ap.pretty(allocator),
PatternData::Enum(evp) => evp.pretty(allocator),
PatternData::Constant(cp) => cp.pretty(allocator),
}
Expand Down Expand Up @@ -688,9 +689,9 @@ where
allocator.line()
),
match tail {
RecordPatternTail::Empty => allocator.nil(),
RecordPatternTail::Open => docs![allocator, allocator.line(), ".."],
RecordPatternTail::Capture(id) =>
TailPattern::Empty => allocator.nil(),
TailPattern::Open => docs![allocator, allocator.line(), ".."],
TailPattern::Capture(id) =>
docs![allocator, allocator.line(), "..", id.ident().to_string()],
},
]
Expand All @@ -701,6 +702,36 @@ where
}
}

impl<'a, D, A> Pretty<'a, D, A> for &ArrayPattern
where
D: NickelAllocatorExt<'a, A>,
D::Doc: Clone,
A: Clone + 'a,
{
fn pretty(self, allocator: &'a D) -> DocBuilder<'a, D, A> {
docs![
allocator,
allocator.intersperse(
self.patterns.iter(),
docs![allocator, ",", allocator.line()],
),
if !self.patterns.is_empty() && self.is_open() {
docs![allocator, ",", allocator.line()]
} else {
allocator.nil()
},
match self.tail {
TailPattern::Empty => allocator.nil(),
TailPattern::Open => allocator.text(".."),
TailPattern::Capture(id) => docs![allocator, "..", id.ident().to_string()],
},
]
.nest(2)
.brackets()
.group()
}
}

impl<'a, D, A> Pretty<'a, D, A> for &RichTerm
where
D: NickelAllocatorExt<'a, A>,
Expand Down
177 changes: 171 additions & 6 deletions core/src/term/pattern/compile.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,8 @@ use super::*;
use crate::{
mk_app,
term::{
make, record::FieldMetadata, BinaryOp, MatchBranch, MatchData, RecordExtKind, RecordOpKind,
RichTerm, Term, UnaryOp,
make, record::FieldMetadata, BinaryOp, MatchBranch, MatchData, NAryOp, RecordExtKind,
RecordOpKind, RichTerm, Term, UnaryOp,
},
};

Expand Down Expand Up @@ -258,6 +258,7 @@ impl CompilePart for PatternData {
insert_binding(*id, value_id, bindings_id)
}
PatternData::Record(pat) => pat.compile_part(value_id, bindings_id),
PatternData::Array(pat) => pat.compile_part(value_id, bindings_id),
PatternData::Enum(pat) => pat.compile_part(value_id, bindings_id),
PatternData::Constant(pat) => pat.compile_part(value_id, bindings_id),
}
Expand Down Expand Up @@ -312,7 +313,7 @@ impl CompilePart for RecordPattern {
//
// We don't have tuples, and to avoid adding an indirection (by storing the current state
// as `{rest, bindings}` where bindings itself is a record), we store this rest alongside
// the bindings in a special field which is a freshly generated indentifier. This is an
// the bindings in a special field which is a freshly generated identifier. This is an
// implementation detail which isn't very hard to change, should we have to.
//
// if %typeof% value_id == 'Record
Expand Down Expand Up @@ -519,7 +520,7 @@ impl CompilePart for RecordPattern {
// null
// else
// %record_remove% "<REST>" final_bindings_id
RecordPatternTail::Empty => make::if_then_else(
TailPattern::Empty => make::if_then_else(
make::op1(
UnaryOp::BoolNot(),
make::op2(
Expand All @@ -539,7 +540,7 @@ impl CompilePart for RecordPattern {
// final_bindings_id
// (%static_access% <REST_FIELD> final_bindings_id)
// )
RecordPatternTail::Capture(rest) => make::op2(
TailPattern::Capture(rest) => make::op2(
BinaryOp::DynRemove(RecordOpKind::ConsiderAllFields),
Term::Str(rest_field.into()),
mk_app!(
Expand All @@ -555,7 +556,7 @@ impl CompilePart for RecordPattern {
),
),
// %record_remove% "<REST>" final_bindings_id
RecordPatternTail::Open => bindings_without_rest,
TailPattern::Open => bindings_without_rest,
};

// the last `final_bindings_id != null` guard:
Expand All @@ -579,6 +580,170 @@ impl CompilePart for RecordPattern {
}
}

impl CompilePart for ArrayPattern {
// Compilation of an array pattern.
//
// let value_len = %array_length% value_id in
//
// <if self.is_open()>
// if %typeof% value_id == 'Array && value_len >= <self.patterns.len()>
// <else>
// if %typeof% value_id == 'Array && value_len == <self.patterns.len()>
// <end if>
//
// let final_bindings_id =
// <fold (idx, elem_pat) in 0..self.patterns.len()
// - cont is the accumulator
// - initial accumulator is `bindings_id`
// >
//
// let local_bindings_id = cont in
// if local_bindings_id == null then
// null
// else
// let local_value_id = %array_access% <idx> value_id in
// <elem_pat.compile_part(local_value_id, local_bindings_id)>
//
// <end fold>
// in
//
// if final_bindings_id == null then
// null
// else
// <if self.tail is capture(rest)>
// %record_insert%
// <rest>
// final_bindings_id
// (%array_slice% <self.patterns.len()> value_len value_id)
// <else>
// final_bindings_id
// <end if>
// else
// null
fn compile_part(&self, value_id: LocIdent, bindings_id: LocIdent) -> RichTerm {
let value_len_id = LocIdent::fresh();
let pats_len = Term::Num(self.patterns.len().into());

// <fold (idx) in 0..self.patterns.len()
// - cont is the accumulator
// - initial accumulator is `bindings_id`
// >
//
// let local_bindings_id = cont in
// if local_bindings_id == null then
// null
// else
// let local_value_id = %array_access% <idx> value_id in
// <self.patterns[idx].compile_part(local_value_id, local_bindings_id)>
//
// <end fold>
let fold_block: RichTerm = self.patterns.iter().enumerate().fold(
Term::Var(bindings_id).into(),
|cont, (idx, elem_pat)| {
let local_bindings_id = LocIdent::fresh();
let local_value_id = LocIdent::fresh();

// <self.patterns[idx].compile_part(local_value_id, local_bindings_id)>
let updated_bindings_let = elem_pat.compile_part(local_value_id, local_bindings_id);

// %array_access% idx value_id
let extracted_value = make::op2(
BinaryOp::ArrayElemAt(),
Term::Var(value_id),
Term::Num(idx.into()),
);

// let local_value_id = <extracted_value> in <updated_bindings_let>
let inner_else_block =
make::let_in(local_value_id, extracted_value, updated_bindings_let);

// The innermost if:
//
// if local_bindings_id == null then
// null
// else
// <inner_else_block>
let inner_if = make::if_then_else(
make::op2(BinaryOp::Eq(), Term::Var(local_bindings_id), Term::Null),
Term::Null,
inner_else_block,
);

// let local_bindings_id = cont in <inner_if>
make::let_in(local_bindings_id, cont, inner_if)
},
);

// %typeof% value_id == 'Array
let is_array: RichTerm = make::op2(
BinaryOp::Eq(),
make::op1(UnaryOp::Typeof(), Term::Var(value_id)),
Term::Enum("Array".into()),
);

let comp_op = if self.is_open() {
BinaryOp::GreaterOrEq()
} else {
BinaryOp::Eq()
};

// <is_array> && value_len <comp_op> <self.patterns.len()>
let outer_check = mk_app!(
make::op1(UnaryOp::BoolAnd(), is_array),
make::op2(comp_op, Term::Var(value_len_id), pats_len.clone(),)
);

let final_bindings_id = LocIdent::fresh();

// the else block which depends on the tail of the record pattern
let tail_block = match self.tail {
// final_bindings_id
TailPattern::Empty | TailPattern::Open => make::var(final_bindings_id),
// %record_insert%
// <rest>
// final_bindings_id
// (%array_slice% <self.patterns.len()> value_len value_id)
TailPattern::Capture(rest) => mk_app!(
make::op2(
record_insert(),
Term::Str(rest.label().into()),
Term::Var(final_bindings_id),
),
make::opn(
NAryOp::ArraySlice(),
vec![pats_len, Term::Var(value_len_id), Term::Var(value_id)]
)
),
};

// the last `final_bindings_id != null` guard:
//
// if final_bindings_id == null then
// null
// else
// <tail_block>
let guard_tail_block = make::if_then_else(
make::op2(BinaryOp::Eq(), Term::Var(final_bindings_id), Term::Null),
Term::Null,
tail_block,
);

// The let enclosing the fold block and the let binding `final_bindings_id`:
// let final_bindings_id = <fold_block> in <tail_block>
let outer_let = make::let_in(final_bindings_id, fold_block, guard_tail_block);

// if <outer_check> then <outer_let> else null
let outer_if = make::if_then_else(outer_check, outer_let, Term::Null);

// finally, we need to bind `value_len_id` to the length of the array
make::let_in(
value_len_id,
make::op1(UnaryOp::ArrayLength(), Term::Var(value_id)),
outer_if,
)
}
}

impl CompilePart for EnumPattern {
fn compile_part(&self, value_id: LocIdent, bindings_id: LocIdent) -> RichTerm {
// %enum_get_tag% value_id == '<self.tag>
Expand Down
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