they are used without a feature-gate. This is both kinder to existing
code and should make it easier to land this PR, since we don't
have to catch EVERY SINGLE SUFFIX.
This can be considered partial work on #8256.
The main observable change: macro expansion sometimes results in spans
where `lo > hi`; so for now, when we have such a span, do not attempt
to return a snippet result.
(Longer term, we might think about whether we could still present a
snippet for the cases where this arises, e.g. perhaps by showing the
whole macro as the snippet, assuming that is the sole cause of such
spans; or by somehow looking up the closest AST node that holds both
`lo` and `hi`, and showing that.)
As a drive-by, revised the API to return a `Result` rather than an
`Option`, with better information-packed error value that should help
us (and maybe also our users) identify the causes of such problems in
the future. Ideally the call-sites that really want an actual snippet
would be updated to catch the newly added `Err` case and print
something meaningful about it, but that is not part of this PR.
Now that associated types are fully implemented the iterator adaptors only need
type parameters which are associated with actual storage. All other type
parameters can either be derived from these (e.g. they are an associated type)
or can be bare on the `impl` block itself.
This is a breaking change due to the removal of type parameters on these
iterator adaptors, but code can fairly easily migrate by just deleting the
relevant type parameters for each adaptor. Other behavior should not be
affected.
Closes#21839
[breaking-change]
Now that associated types are fully implemented the iterator adaptors only need
type parameters which are associated with actual storage. All other type
parameters can either be derived from these (e.g. they are an associated type)
or can be bare on the `impl` block itself.
This is a breaking change due to the removal of type parameters on these
iterator adaptors, but code can fairly easily migrate by just deleting the
relevant type parameters for each adaptor. Other behavior should not be
affected.
Closes#21839
[breaking-change]
This commits adds an associated type to the `FromStr` trait representing an
error payload for parses which do not succeed. The previous return value,
`Option<Self>` did not allow for this form of payload. After the associated type
was added, the following attributes were applied:
* `FromStr` is now stable
* `FromStr::Err` is now stable
* `FromStr::from_str` is now stable
* `StrExt::parse` is now stable
* `FromStr for bool` is now stable
* `FromStr for $float` is now stable
* `FromStr for $integral` is now stable
* Errors returned from stable `FromStr` implementations are stable
* Errors implement `Display` and `Error` (both impl blocks being `#[stable]`)
Closes#15138
Note: Do not merge until we get a newer snapshot that includes #21374
There was some type inference fallout (see 4th commit) because type inference with `a..b` is not as good as with `range(a, b)` (see #21672).
r? @alexcrichton
fmt::Show is for debugging, and can and should be implemented for
all public types. This trait is used with `{:?}` syntax. There still
exists #[derive(Show)].
fmt::String is for types that faithfully be represented as a String.
Because of this, there is no way to derive fmt::String, all
implementations must be purposeful. It is used by the default format
syntax, `{}`.
This will break most instances of `{}`, since that now requires the type
to impl fmt::String. In most cases, replacing `{}` with `{:?}` is the
correct fix. Types that were being printed specifically for users should
receive a fmt::String implementation to fix this.
Part of #20013
[breaking-change]
