`rustc_middle` is a huge crate and it's always good to move stuff out of
it. There are lots of similar methods already on `Span`, so these two
functions, `in_external_macro` and `is_from_async_await`, fit right in.
The diff is big because `in_external_macro` is used a lot by clippy
lints.
- Rename them both `as_str`, which is the typical name for a function
that returns a `&str`. (`to_string` is appropriate for functions
returning `String` or maybe `Cow<'a, str>`.)
- Change `UnOp::as_str` from an associated function (weird!) to a
method.
- Avoid needless `self` dereferences.
Most notably, this commit changes the `pub use crate::*;` in that file
to `use crate::*;`. This requires a lot of `use` items in other crates
to be adjusted, because everything defined within `rustc_span::*` was
also available via `rustc_span::source_map::*`, which is bizarre.
The commit also removes `SourceMap::span_to_relative_line_string`, which
is unused.
`must_use_unit` lints unit-returning functions with a `#[must_use]`
attribute, suggesting to remove it.
`double_must_use` lints functions with a plain `#[must_use]`
attribute, but which return a type which is already `#[must_use]`,
so the attribute has no benefit.
`must_use_candidate` is a pedantic lint that lints functions and
methods that return some non-unit type that is not already
`#[must_use]` and suggests to add the annotation.
Lints when, on the RHS of a BinOp, there is a UnOp without a space
before the operator but with a space after (e.g. foo >- 1).
Signed-off-by: Nikos Filippakis <nikolaos.filippakis@cern.ch>
