Build quine-mc_cluskey with `opt-level=3` in dev builds
While doing some profiling I noticed that debug clippy running on the `clippy_lints` crate spends 35s out of 160s in one specific code path of `nonminimal_bool`, which seemed a bit excessive.
I've found that just enabling optimizations for quine-mc_cluskey (used by nonminimal_bool) cuts down the part that took 35s to 3s
While this doesn't really change anything for users, this helps dogfood a bit as it cuts off about half a minute of runtime (in some of my tests, at least).
Something similar was attempted in #10576, however that involved compiling everything in release mode including clippy itself, whereas this only affects a single dependency that's compiled in parallel with something that takes longer so this should hopefully not have a negative impact in any case (and changing clippy doesn't require recompiling that dependency)
changelog: none
Unused trait imports (formerly anonymous trait import)
For #11969
I'm looking for help and feedback on implementing a new lint for suggesting `use ... as _` for traits where possible.
I have had a go at implementing this but I don't know if this is the best way to do it as I am new to clippy.
There are some edge cases I can think of where this doesn't work but have aired on the side of false negatives instead of false positives.
An example of a false negative. I couldn't figure out the best way to resolve an import from within clippy. The sub module imports MyAny so that cannot be anonymized but `use std::any::Any` could be. In this case it is not caught because `Any` and `MyAny` have the same DefId.
```rust
mod nested_mod_used_bad1 {
use std::any::Any;
use std::any::Any as MyAny;
mod foo {
use crate::nested_mod_used_bad1::MyAny;
fn foo() {
println!("{:?}", MyAny::type_id("foo"));
}
}
}
```
Any feedback is much appreciated.
-------
changelog: new lint: `unused_trait_names`
Fix `if_then_some_else_none` sugg missing closure intro
Fixes#13407#13407 works in current stable. The suggestion-generating code got trampled over in 0532104247 :-)
changelog: [`if_then_some_else_none`]: Fix missing closure in suggestion
Initial impl of `unnecessary_first_then_check`
Fixes#11212
Checks for `{slice/vec/Box<[]>}.first().is_some()` and suggests replacing the unnecessary `Option`-construct with a direct `{slice/...}.is_empty()`. Other lints guide constructs like `if let Some(_) = v.get(0)` into this, which end up as `!v.is_empty()`.
changelog: [`unnecessary_first_then_check`]: Initial implementation
