add Result to question_mark #7135
Description
What it does
The lint should hint to flatten the error propagation from using match/if let to a more readable declarative propagation with the ? operator.
Categories
- Kind:
clippy::style, maybeclippy::pedantic
The control structures distract in the flow of reading and therefore the ? operator was created. A comprehensive list of arguments can be found in the documentation of Rust
Drawbacks
As long as only the Err will always return an Err, there should be no false-positives.
Example
fn propagate_match_input(input: Result<String, u64>) -> Result<String, u64> {
let inner = match input {
Ok(inner) => inner,
Err(code) => return Err(code),
};
Ok(inner)
}
fn match_input(input: Result<String, u64>) -> Result<String, bool> {
let inner = match input {
Ok(inner) => inner,
Err(code) => return Err(code != 0),
};
Ok(inner)
}
fn if_let_input(input: Result<String, u64>) -> Result<(), bool> {
if let Err(code) = input {
return Err(code != 0);
}
Ok(())
}Could be written as:
fn propagate_match_input(input: Result<String, u64>) -> Result<String, u64> {
let inner = input?;
Ok(inner)
}
fn match_input(input: Result<String, u64>) -> Result<String, bool> {
let inner = input.map_err(|code| code != 0)?;
Ok(inner)
}
fn if_let_input(input: Result<String, u64>) -> Result<(), bool> {
input.map_err(|code| code != 0)?;
Ok(())
}