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correctly parse trailing commas in record

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Sébastien Besnier 2020-11-13 18:43:32 +01:00
parent 7ec161c415
commit 58acc59b01
8 changed files with 135 additions and 57 deletions
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90
compiler/parse/src/parser.rs
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@ -604,6 +604,46 @@ where
}
}
/// Parse zero or more values separated by a delimiter (e.g. a comma)
/// with an optional trailing delimiter whose values are discarded
pub fn trailing_sep_by0<'a, P, D, Val>(delimiter: D, parser: P) -> impl Parser<'a, Vec<'a, Val>>
where
D: Parser<'a, ()>,
P: Parser<'a, Val>,
{
move |arena, state: State<'a>| {
match parser.parse(arena, state) {
Ok((first_output, next_state)) => {
let mut state = next_state;
let mut buf = Vec::with_capacity_in(1, arena);
buf.push(first_output);
loop {
match delimiter.parse(arena, state) {
Ok(((), next_state)) => {
// If the delimiter passed, check the element parser.
match parser.parse(arena, next_state) {
Ok((next_output, next_state)) => {
state = next_state;
buf.push(next_output);
}
Err((_, old_state)) => {
// If the delimiter parsed, but the following
// element did not, that means we saw a trailing comma
return Ok((buf, old_state));
}
}
}
Err((_, old_state)) => return Ok((buf, old_state)),
}
}
}
Err((_, new_state)) => Ok((Vec::new_in(arena), new_state)),
}
}
}
/// Parse one or more values separated by a delimiter (e.g. a comma) whose
/// values are discarded
pub fn sep_by1<'a, P, D, Val>(delimiter: D, parser: P) -> impl Parser<'a, Vec<'a, Val>>
@ -827,6 +867,42 @@ macro_rules! collection {
};
}
/// Parse zero or more elements between two braces (e.g. square braces).
/// Elements can be optionally surrounded by spaces, and are separated by a
/// delimiter (e.g comma-separated) with optionally a trailing delimiter.
/// Braces and delimiters get discarded.
#[macro_export]
macro_rules! collection_trailing_sep {
($opening_brace:expr, $elem:expr, $delimiter:expr, $closing_brace:expr, $min_indent:expr) => {
skip_first!(
$opening_brace,
skip_first!(
// We specifically allow space characters inside here, so that
// `[ ]` can be successfully parsed as an empty list, and then
// changed by the formatter back into `[]`.
//
// We don't allow newlines or comments in the middle of empty
// roc_collections because those are normally stored in an Expr,
// and there's no Expr in which to store them in an empty collection!
//
// We could change the AST to add extra storage specifically to
// support empty literals containing newlines or comments, but this
// does not seem worth even the tiniest regression in compiler performance.
zero_or_more!($crate::parser::ascii_char(b' ')),
skip_second!(
and!(
$crate::parser::trailing_sep_by0(
$delimiter,
$crate::blankspace::space0_around($elem, $min_indent)
), $crate::blankspace::spaces0($min_indent)
),
$closing_brace
)
)
)
};
}
#[macro_export]
macro_rules! and {
($p1:expr, $p2:expr) => {
@ -1126,12 +1202,14 @@ macro_rules! record {
// does not seem worth even the tiniest regression in compiler performance.
zero_or_more!($crate::parser::ascii_char(b' ')),
skip_second!(
$crate::parser::sep_by0(
$crate::parser::ascii_char(b','),
$crate::blankspace::space0_around(
loc!(record_field!($val_parser, $min_indent)),
$min_indent
)
and!(
$crate::parser::trailing_sep_by0(
$crate::parser::ascii_char(b','),
$crate::blankspace::space0_around(
loc!(record_field!($val_parser, $min_indent)),
$min_indent
),
), $crate::blankspace::space0($min_indent)
),
$crate::parser::ascii_char(b'}')
)