The issue:
See this Rust playground link: https://play.rust-lang.org/?edition=2018&gist=12cb5d1e7527f8c37743b87fc4a53748
Run the above with clippy to see the following warning:
```
warning: returning the result of a `let` binding from a block
--> src/main.rs:24:5
|
23 | let value = Foo::new(&x).value();
| --------------------------------- unnecessary `let` binding
24 | value
| ^^^^^
|
= note: `#[warn(clippy::let_and_return)]` on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return
help: return the expression directly
|
23 |
24 | Foo::new(&x).value()
|
```
Implementing the suggested fix, removing the temporary let binding,
yields a compiler error:
```
error[E0597]: `x` does not live long enough
--> src/main.rs:23:14
|
23 | Foo::new(&x).value()
| ---------^^-
| | |
| | borrowed value does not live long enough
| a temporary with access to the borrow is created here ...
24 | }
| -
| |
| `x` dropped here while still borrowed
| ... and the borrow might be used here, when that temporary is dropped and runs the `Drop` code for type `Foo`
|
= note: the temporary is part of an expression at the end of a block;
consider forcing this temporary to be dropped sooner, before the block's local variables are dropped
help: for example, you could save the expression's value in a new local variable `x` and then make `x` be the expression at the end of the block
|
23 | let x = Foo::new(&x).value(); x
| ^^^^^^^ ^^^
```
The fix:
Of course, clippy looks like it should already handle this edge case;
however, it appears `utils::fn_def_id` is not returning a `DefId` for
`Foo::new`. Changing the `qpath_res` lookup to use the child Path
`hir_id` instead of the parent Call `hir_id` fixes the issue.
add "cargo dev crater" to run clippy on a fixed set of crates and diff the lint warnings
`cargo dev crater` now does the following:
build clippy in debug mode
for a fixed set of crates:
download and extract the crate
run compiled clippy on the crate
dump the warnings into a file that is inside the repo
We can then do a "git diff" and see what effects our clippy changes had on a tiny fraction of the rust ecosystem and can see when an change unexpectedly added or silenced a lot of warnings.
Checking all the crates took less than 5 minutes on my system.
Should help with https://github.com/rust-lang/rust-clippy/issues/6429
---
*Please write a short comment explaining your change (or "none" for internal only changes)*
changelog: extend cargo dev to run clippy against a fixed set of crates and compare warnings
Similar names ignore underscore prefixed names
changelog: Ignore underscore-prefixed names for similar_names
IMO, this lint is not very helpful for underscore-prefixed variables. Usually they are unused or are just there to ignore part of a destructuring.
`manual_filter_map` and `manual_find_map`
changelog: Add `manual_filter_map` and replace `find_map` with `manual_find_map`
Replaces #6453Fixes#3188Fixes#4193
~Depends on #6567 (to fix an internal lint false positive)~
This replaces `filter_map` and `find_map` with `manual_filter_map` and `manual_find_map` respectively. However, `filter_map` is left in place since it is used for a variety of other cases. See discussion in #6453.
