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f870876d92
Fix let_and_return false positive 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. changelog: none |
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