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smarter unary minus parsing

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This commit is contained in:
Folkert 2021-03-12 16:44:33 +01:00
parent 214112d751
commit f01424ac11
1 changed files with 34 additions and 1 deletions
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35
compiler/parse/src/expr.rs
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@ -469,11 +469,44 @@ fn unary_negate<'a>() -> impl Parser<'a, (), EExpr<'a>> {
}
}
fn unary_negate_better<'a>() -> impl Parser<'a, (), EExpr<'a>> {
move |_arena: &'a Bump, state: State<'a>| {
// a minus is unary iff
//
// - it is preceded by whitespace (spaces, newlines, comments)
// - it is not followed by whitespace
let followed_by_whitespace = state
.bytes
.get(1)
.map(
|c| c.is_ascii_whitespace() || *c == b'#', /*|| c.is_ascii_digit()*/
)
.unwrap_or(false);
if state.bytes.starts_with(b"-") && !followed_by_whitespace {
// the negate is only unary if it is not followed by whitespace
Ok((
MadeProgress,
(),
State {
bytes: &state.bytes[1..],
column: state.column + 1,
..state
},
))
} else {
// this is not a negated expression
Err((NoProgress, EExpr::UnaryNot(state.line, state.column), state))
}
}
}
/// Unary (!) or (-)
///
/// e.g. `!x` or `-x`
fn unary_op_help<'a>(min_indent: u16) -> impl Parser<'a, Expr<'a>, EExpr<'a>> {
one_of!(
specialize(EExpr::Number, number_literal_help()),
map_with_arena!(
// must backtrack to distinguish `!x` from `!= y`
and!(loc!(unary_not()), move |arena, state| parse_expr_help(
@ -486,7 +519,7 @@ fn unary_op_help<'a>(min_indent: u16) -> impl Parser<'a, Expr<'a>, EExpr<'a>> {
map_with_arena!(
and!(
// must backtrack to distinguish `x - 1` from `-1`
loc!(unary_negate()),
loc!(unary_negate_better()),
move |arena, state| parse_expr_help(min_indent, arena, state)
),
|arena: &'a Bump, (loc_op, loc_expr): (Located<()>, Located<Expr<'a>>)| {