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Merge pull request #964 from rtfeldman/def-backtracking

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backtracking fix
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Richard Feldman 2021-02-08 00:10:43 -05:00 • committed by GitHub
commit 49446fa552
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2 changed files with 178 additions and 85 deletions
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165
compiler/parse/src/expr.rs
View file

@ -487,10 +487,25 @@ pub fn assigned_pattern_field_to_pattern<'a>(
/// The '=' used in a def can't be followed by another '=' (or else it's actually
/// an "==") and also it can't be followed by '>' (or else it's actually an "=>")
fn equals_for_def<'a>() -> impl Parser<'a, ()> {
not_followed_by(
ascii_char(b'='),
one_of!(ascii_char(b'='), ascii_char(b'>')),
)
|arena, state: State<'a>| match state.bytes.get(0) {
Some(b'=') => match state.bytes.get(1) {
Some(b'=') | Some(b'>') => Err((
NoProgress,
Bag::from_state(arena, &state, FailReason::ConditionFailed),
state,
)),
_ => {
let state = state.advance_without_indenting(arena, 1)?;
Ok((MadeProgress, (), state))
}
},
_ => Err((
NoProgress,
Bag::from_state(arena, &state, FailReason::ConditionFailed),
state,
)),
}
}
/// A definition, consisting of one of these:
@ -500,38 +515,81 @@ fn equals_for_def<'a>() -> impl Parser<'a, ()> {
/// * A type annotation
/// * A type annotation followed on the next line by a pattern, an `=`, and an expression
pub fn def<'a>(min_indent: u16) -> impl Parser<'a, Def<'a>> {
// we should fix this backtracking!
attempt(
Attempting::Def,
map_with_arena!(
either!(backtrackable(annotated_body(min_indent)), body(min_indent)),
to_def
),
)
let indented_more = min_indent + 1;
enum DefKind {
DefColon,
DefEqual,
}
fn to_def<'a>(
arena: &'a Bump,
ann_body_or_body: Either<AnnotationOrAnnotatedBody<'a>, Body<'a>>,
) -> Def<'a> {
match ann_body_or_body {
Either::First(((ann_pattern, ann_type), None)) => {
annotation_or_alias(arena, &ann_pattern.value, ann_pattern.region, ann_type)
}
Either::First((
(ann_pattern, ann_type),
Some((opt_comment, (body_pattern, body_expr))),
)) => Def::AnnotatedBody {
ann_pattern: arena.alloc(ann_pattern),
let def_colon_or_equals = one_of![
map!(equals_for_def(), |_| DefKind::DefEqual),
map!(ascii_char(b':'), |_| DefKind::DefColon)
];
attempt(
Attempting::Def,
then(
// backtrackable because
//
// i = 0
// i
//
// on the last line, we parse a pattern `i`, but it's not actually a def, so need to
// backtrack
and!(backtrackable(pattern(min_indent)), def_colon_or_equals),
move |arena, state, _progress, (loc_pattern, def_kind)| match def_kind {
DefKind::DefColon => {
// Spaces after the ':' (at a normal indentation level) and then the type.
// The type itself must be indented more than the pattern and ':'
let (_, ann_type, state) =
space0_before(type_annotation::located(indented_more), min_indent)
.parse(arena, state)?;
// see if there is a definition (assuming the preceding characters were a type
// annotation
let (_, opt_rest, state) = optional(and!(
spaces_then_comment_or_newline(),
body_at_indent(min_indent)
))
.parse(arena, state)?;
let def = match opt_rest {
None => annotation_or_alias(
arena,
&loc_pattern.value,
loc_pattern.region,
ann_type,
),
Some((opt_comment, (body_pattern, body_expr))) => Def::AnnotatedBody {
ann_pattern: arena.alloc(loc_pattern),
ann_type: arena.alloc(ann_type),
comment: opt_comment,
body_pattern: arena.alloc(body_pattern),
body_expr: arena.alloc(body_expr),
},
Either::Second((body_pattern, body_expr)) => {
Def::Body(arena.alloc(body_pattern), arena.alloc(body_expr))
};
Ok((MadeProgress, def, state))
}
DefKind::DefEqual => {
// Spaces after the '=' (at a normal indentation level) and then the expr.
// The expr itself must be indented more than the pattern and '='
let (_, body_expr, state) = space0_before(
loc!(move |arena, state| { parse_expr(indented_more, arena, state) }),
min_indent,
)
.parse(arena, state)?;
Ok((
MadeProgress,
Def::Body(arena.alloc(loc_pattern), arena.alloc(body_expr)),
state,
))
}
},
),
)
}
// PARSER HELPERS
@ -540,21 +598,6 @@ fn pattern<'a>(min_indent: u16) -> impl Parser<'a, Located<Pattern<'a>>> {
space0_after(loc_closure_param(min_indent), min_indent)
}
fn annotation<'a>(
min_indent: u16,
) -> impl Parser<'a, (Located<Pattern<'a>>, Located<TypeAnnotation<'a>>)> {
let indented_more = min_indent + 1;
and!(
pattern(min_indent),
skip_first!(
ascii_char(b':'),
// Spaces after the ':' (at a normal indentation level) and then the type.
// The type itself must be indented more than the pattern and ':'
space0_before(type_annotation::located(indented_more), min_indent)
)
)
}
fn spaces_then_comment_or_newline<'a>() -> impl Parser<'a, Option<&'a str>> {
skip_first!(
zero_or_more!(ascii_char(b' ')),
@ -570,29 +613,6 @@ fn spaces_then_comment_or_newline<'a>() -> impl Parser<'a, Option<&'a str>> {
type Body<'a> = (Located<Pattern<'a>>, Located<Expr<'a>>);
fn body<'a>(min_indent: u16) -> impl Parser<'a, Body<'a>> {
let indented_more = min_indent + 1;
and!(
// this backtrackable is required for the case
//
// i = 64
//
// i
//
// so the final i is not considered the start of a def
backtrackable(pattern(min_indent)),
skip_first!(
equals_for_def(),
// Spaces after the '=' (at a normal indentation level) and then the expr.
// The expr itself must be indented more than the pattern and '='
space0_before(
loc!(move |arena, state| { parse_expr(indented_more, arena, state) }),
min_indent,
)
)
)
}
fn body_at_indent<'a>(indent_level: u16) -> impl Parser<'a, Body<'a>> {
let indented_more = indent_level + 1;
and!(
@ -609,21 +629,6 @@ fn body_at_indent<'a>(indent_level: u16) -> impl Parser<'a, Body<'a>> {
)
}
type AnnotationOrAnnotatedBody<'a> = (
(Located<Pattern<'a>>, Located<TypeAnnotation<'a>>),
Option<(Option<&'a str>, Body<'a>)>,
);
fn annotated_body<'a>(min_indent: u16) -> impl Parser<'a, AnnotationOrAnnotatedBody<'a>> {
and!(
annotation(min_indent),
optional(and!(
spaces_then_comment_or_newline(),
body_at_indent(min_indent)
))
)
}
fn annotation_or_alias<'a>(
arena: &'a Bump,
pattern: &Pattern<'a>,

88
compiler/reporting/tests/test_reporting.rs
View file

@ -181,6 +181,15 @@ mod test_reporting {
list_reports(&arena, src, &mut buf, callback);
// convenient to copy-paste the generated message
if true {
if buf != expected_rendering {
for line in buf.split("\n") {
println!(" {}", line);
}
}
}
assert_eq!(buf, expected_rendering);
}
@ -3995,4 +4004,83 @@ mod test_reporting {
),
)
}
#[test]
fn type_annotation_dubble_colon() {
report_problem_as(
indoc!(
r#"
f :: I64
f = 42
f
"#
),
indoc!(
r#"
── PARSE PROBLEM ───────────────────────────────────────────────────────────────
Unexpected token while parsing a definition:
1│ f :: I64
^
"#
),
)
}
#[test]
fn double_equals_in_def() {
// NOTE: VERY BAD ERROR MESSAGE
//
// looks like `x y` are considered argument to the add, even though they are
// on a lower indentation level
report_problem_as(
indoc!(
r#"
x = 3
y =
x == 5
Num.add 1 2
x y
"#
),
indoc!(
r#"
── TOO MANY ARGS ───────────────────────────────────────────────────────────────
The `add` function expects 2 arguments, but it got 4 instead:
4│ Num.add 1 2
^^^^^^^
Are there any missing commas? Or missing parentheses?
"#
),
)
}
#[test]
fn invalid_operator() {
// NOTE: VERY BAD ERROR MESSAGE
report_problem_as(
indoc!(
r#"
main =
5 ** 3
"#
),
indoc!(
r#"
── PARSE PROBLEM ───────────────────────────────────────────────────────────────
Unexpected token here:
2│ 5 ** 3
^
"#
),
)
}
}