The `?` postfix operator is sugar equivalent to the try! macro, but is more amenable to chaining:
`File::open("foo")?.metadata()?.is_dir()`.
`?` is accepted on any *expression* that can return a `Result`, e.g. `x()?`, `y!()?`, `{z}?`,
`(w)?`, etc. And binds more tightly than unary operators, e.g. `!x?` is parsed as `!(x?)`.
cc #31436
Any documentation comments that contain raw-string-looking sequences may pretty-print invalid code when expanding them, as the current logic always uses the `r"literal"` form, without appending any `#`s.
This commit calculates the minimum number of `#`s required to wrap a comment correctly and appends `#`s appropriately.
Fixes#27489.
Any documentation comments that contain raw-string-looking sequences may
pretty-print invalid code when expanding them, as the current logic
always uses the `r"literal"` form, without appending any `#`s.
This commit calculates the minimum number of `#`s required to wrap a
comment correctly and appends `#`s appropriately.
Fixes#27489.
This PR is a rebase of the original PR by @eddyb https://github.com/rust-lang/rust/pull/21836 with some unrebasable parts manually reapplied, feature gate added + type equality restriction added as described below.
This implementation is partial because the type equality restriction is applied to all type ascription expressions and not only those in lvalue contexts. Thus, all difficulties with detection of these contexts and translation of coercions having effect in runtime are avoided.
So, you can't write things with coercions like `let slice = &[1, 2, 3]: &[u8];`. It obviously makes type ascription less useful than it should be, but it's still much more useful than not having type ascription at all.
In particular, things like `let v = something.iter().collect(): Vec<_>;` and `let u = t.into(): U;` work as expected and I'm pretty happy with these improvements alone.
Part of https://github.com/rust-lang/rust/issues/23416
