rust/tests/ui/suggestions/chain-method-call-mutation-in-place.rs

fn main() {
    let x: Vec<i32> = vec![1, 2, 3].into_iter().collect::<Vec<i32>>().sort_by_key(|i| i); //~ ERROR mismatched types
    vec![1, 2, 3].into_iter().collect::<Vec<i32>>().sort_by_key(|i| i).sort(); //~ ERROR no method named `sort` found for unit type `()` in the current scope
}

fn foo(mut s: String) -> String {
    s.push_str("asdf") //~ ERROR mismatched types
}
Emit "modifies receiver" diagnostic when no method is found If no method is found when checking method call, we check if we called a method with signature (&mut T, ...) -> (). If this is the case then we emit a diagnostic message 2023-03-14 13:12:47 +00:00			`fn main() {`
			`let x: Vec<i32> = vec![1, 2, 3].into_iter().collect::<Vec<i32>>().sort_by_key(\|i\| i); //~ ERROR mismatched types`
			vec![1, 2, 3].into_iter().collect::<Vec<i32>>().sort_by_key(\|i\| i).sort(); //~ ERROR no method named `sort` found for unit type `()` in the current scope
			`}`

Add explanation for `&mut self` method call when expecting `-> Self` When a user tries to use a method as if it returned a new value of the same type as its receiver, we will emit a type error. Try to detect this and provide extra explanation that the method modifies the receiver in-place. This has confused people in the wild, like in https://users.rust-lang.org/t/newbie-why-the-commented-line-stops-the-snippet-from-compiling/47322 2020-08-17 01:33:30 +00:00			`fn foo(mut s: String) -> String {`
			`s.push_str("asdf") //~ ERROR mismatched types`
			`}`