Suggest adding a => after match guard
#94932
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Does the following still parse after your change? fn main() {
let x = Some(It { a: 1 });
match x {
Some(x) if x == It { a: 0 } => {}
_ => {}
}
}
#[derive(PartialEq, Eq)]
struct It { a: i32 } |
TaKO8Ki
changed the title
=> after match guard=> after match guard
TaKO8Ki
changed the title
=> after match guard=> after match guard
| @@ -2617,6 +2626,26 @@ impl<'a> Parser<'a> { | |||
| } | |||
| } | |||
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| fn parse_match_guard_cond(&mut self) -> PResult<'a, P<Expr>> { | |||
| let snapshot = self.clone(); | |||
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The only issue I'm seeing here is that this pessimises the parsing of every match arm. In this case I think it is reasonable to instead catch the problem in line 2499 and only in the error arm try to conditionally parse the match arm body. Probably also do that for the substitution cases handled right below.
| let (is_lhs_struct, is_rhs_struct) = match cond.kind { | ||
| ExprKind::Binary(_, ref lhs, ref rhs) => { | ||
| (matches!(lhs.kind, ExprKind::Struct(..)), matches!(rhs.kind, ExprKind::Struct(..))) | ||
| } | ||
| _ => (false, false), | ||
| }; |
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As you recognize here, we might want to also detect when a struct literal was parsed that instead was supposed to be an ident and the match arm body, but that is not as critical, I think.
davidtwco
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☔ The latest upstream changes (presumably #98545) made this pull request unmergeable. Please resolve the merge conflicts. |
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@TaKO8Ki any updates on this? |
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Closing this as inactive |
Dylan-DPC
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closes #78585