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

### What it does
Checks for comparisons where one side of the relation is
either the minimum or maximum value for its type and warns if it involves a
case that is always true or always false. Only integer and boolean types are
checked.

### Why is this bad?
An expression like `min <= x` may misleadingly imply
that it is possible for `x` to be less than the minimum. Expressions like
`max < x` are probably mistakes.

### Known problems
For `usize` the size of the current compile target will
be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
a comparison to detect target pointer width will trigger this lint. One can
use `mem::sizeof` and compare its value or conditional compilation
attributes
like `#[cfg(target_pointer_width = "64")] ..` instead.

### Example
```
let vec: Vec<isize> = Vec::new();
if vec.len() <= 0 {}
if 100 > i32::MAX {}
```
Commit	Line	Data
f2b60f7d FG	1	### What it does
	2	Checks for comparisons where one side of the relation is
	3	either the minimum or maximum value for its type and warns if it involves a
	4	case that is always true or always false. Only integer and boolean types are
	5	checked.
	6
	7	### Why is this bad?
	8	An expression like `min <= x` may misleadingly imply
	9	that it is possible for `x` to be less than the minimum. Expressions like
	10	`max < x` are probably mistakes.
	11
	12	### Known problems
	13	For `usize` the size of the current compile target will
	14	be assumed (e.g., 64 bits on 64 bit systems). This means code that uses such
	15	a comparison to detect target pointer width will trigger this lint. One can
	16	use `mem::sizeof` and compare its value or conditional compilation
	17	attributes
	18	like `#[cfg(target_pointer_width = "64")] ..` instead.
	19
	20	### Example
	21	```
	22	let vec: Vec<isize> = Vec::new();
	23	if vec.len() <= 0 {}
	24	if 100 > i32::MAX {}
	25	```