suggest Option::as_deref(_mut) on type mismatch in option combinator if it passes typeck
#111659
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| //~^ ERROR expected a `FnOnce<(String,)>` closure, found `for<'a> unsafe fn(&'a str) -> Option<()> {takes_str_but_unsafe}` | ||
| let _ = produces_string().and_then(no_args); | ||
| //~^ ERROR function is expected to take 1 argument, but it takes 0 arguments | ||
| let _ = produces_string().and_then(generic_ref); |
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Should this case suggest as_ref?
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I initially had it suggest as_ref() where applicable too, but there's already a help message for calling and_then with an fn(&T) on some Option<T>, though it suggests removing the borrow on the function parameter and I'm not sure how it would work out when there are two suggestions made by the compiler (is that fine?)
help: do not borrow the argument
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14 - fn generic<T>(_: &T) {}
14 + fn generic<T>(_: T) {}
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help: call `Option::as_ref()` first
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18 | let x = produces_string().as_ref().and_then(generic);
| +++++++++
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compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
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@bors r+ rollup |
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suggest `Option::as_deref(_mut)` on type mismatch in option combinator if it passes typeck Fixes rust-lang#106342. This adds a suggestion to call `.as_deref()` (or `.as_deref_mut()` resp.) if typeck fails due to a type mismatch in the function passed to an `Option` combinator such as `.map()` or `.and_then()`. For example: ```rs fn foo(_: &str) {} Some(String::new()).map(foo); ``` The `.map()` method requires its argument to satisfy `F: FnOnce(String)`, but it received `fn(&str)`, which won't pass. However, placing a `.as_deref()` before the `.map()` call fixes this since `&str == &<String as Deref>::Target`
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…iaskrgr Rollup of 7 pull requests Successful merges: - rust-lang#111659 (suggest `Option::as_deref(_mut)` on type mismatch in option combinator if it passes typeck) - rust-lang#111702 (Option::map_or_else: Show an example of integrating with Result) - rust-lang#111878 (Fix codegen test suite for bare-metal-like targets) - rust-lang#111969 (bootstrap: Make `clean` respect `dry-run`) - rust-lang#111998 (Add other workspaces to `linkedProjects` in rust_analyzer_settings) - rust-lang#112215 (only suppress coercion error if type is definitely unsized) - rust-lang#112231 (Make sure the build.rustc version is either the same or 1 apart (revised)) r? `@ghost` `@rustbot` modify labels: rollup
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Fixes #106342.
This adds a suggestion to call
.as_deref()(or.as_deref_mut()resp.) if typeck fails due to a type mismatch in the function passed to anOptioncombinator such as.map()or.and_then().For example:
The
.map()method requires its argument to satisfyF: FnOnce(String), but it receivedfn(&str), which won't pass. However, placing a.as_deref()before the.map()call fixes this since&str == &<String as Deref>::Target