[rustc.git] / src / tools / clippy / src / docs / fn_to_numeric_cast_any.txt

### What it does
Checks for casts of a function pointer to any integer type.

### Why is this bad?
Casting a function pointer to an integer can have surprising results and can occur
accidentally if parentheses are omitted from a function call. If you aren't doing anything
low-level with function pointers then you can opt-out of casting functions to integers in
order to avoid mistakes. Alternatively, you can use this lint to audit all uses of function
pointer casts in your code.

### Example
```
// fn1 is cast as `usize`
fn fn1() -> u16 {
    1
};
let _ = fn1 as usize;
```

Use instead:
```
// maybe you intended to call the function?
fn fn2() -> u16 {
    1
};
let _ = fn2() as usize;

// or

// maybe you intended to cast it to a function type?
fn fn3() -> u16 {
    1
}
let _ = fn3 as fn() -> u16;
```
Commit	Line	Data
f2b60f7d FG	1	### What it does
	2	Checks for casts of a function pointer to any integer type.
	3
	4	### Why is this bad?
	5	Casting a function pointer to an integer can have surprising results and can occur
	6	accidentally if parentheses are omitted from a function call. If you aren't doing anything
	7	low-level with function pointers then you can opt-out of casting functions to integers in
	8	order to avoid mistakes. Alternatively, you can use this lint to audit all uses of function
	9	pointer casts in your code.
	10
	11	### Example
	12	```
	13	// fn1 is cast as `usize`
	14	fn fn1() -> u16 {
	15	1
	16	};
	17	let _ = fn1 as usize;
	18	```
	19
	20	Use instead:
	21	```
	22	// maybe you intended to call the function?
	23	fn fn2() -> u16 {
	24	1
	25	};
	26	let _ = fn2() as usize;
	27
	28	// or
	29
	30	// maybe you intended to cast it to a function type?
	31	fn fn3() -> u16 {
	32	1
	33	}
	34	let _ = fn3 as fn() -> u16;
	35	```