initial clippy::ref_pattern implementation
This implements a new lint that discourages the use of the `ref` keyword as outlined in #9010. I think there are still some things to improve about this lint, but I need some feedback before I can implement those.
- [x] ~~Maybe it's desirable that a quick fix is listed too, instead of a generic `avoid using the ref keyword` lint.~~
- [x] `let ref x = y` already has a lint (`clippy::toplevel_ref_arg`). This implementation will report this too, so you get two lints for the same issue, which is not great. I don't really know a way around this though.
- [X] The dogfood test is currently failing locally, though I ran `cargo clippy -- -D clippy::all -D clippy::pedantic` and got no output, so I'm not sure why this is.
Any help with these would be greatly appreciated.
fixes#9010
changelog: [`ref_pattern`]: newly added lint
Inherit stdout/stderr for `cargo dev dogfood`
changelog: none
Prints progress as it happens and in colour, and will also show anything printed to stderr
Fixes#10609: Adds lint to detect construction of unit struct using `default`
Using `default` to construct a unit struct increases code complexity and adds a function call. This can be avoided by simply removing the call to `default` and simply construct by name.
changelog: [`default_constructed_unit_structs`]: detects construction of unit structs using `default`
fixes#10609
Currently a `{D,Subd}iagnosticMessage` can be created from any type that
impls `Into<String>`. That includes `&str`, `String`, and `Cow<'static,
str>`, which are reasonable. It also includes `&String`, which is pretty
weird, and results in many places making unnecessary allocations for
patterns like this:
```
self.fatal(&format!(...))
```
This creates a string with `format!`, takes a reference, passes the
reference to `fatal`, which does an `into()`, which clones the
reference, doing a second allocation. Two allocations for a single
string, bleh.
This commit changes the `From` impls so that you can only create a
`{D,Subd}iagnosticMessage` from `&str`, `String`, or `Cow<'static,
str>`. This requires changing all the places that currently create one
from a `&String`. Most of these are of the `&format!(...)` form
described above; each one removes an unnecessary static `&`, plus an
allocation when executed. There are also a few places where the existing
use of `&String` was more reasonable; these now just use `clone()` at
the call site.
As well as making the code nicer and more efficient, this is a step
towards possibly using `Cow<'static, str>` in
`{D,Subd}iagnosticMessage::{Str,Eager}`. That would require changing
the `From<&'a str>` impls to `From<&'static str>`, which is doable, but
I'm not yet sure if it's worthwhile.
