Unneeded casts in a comparison

What it does

Some comparisons are too obvious and just get in the way of understanding the code, and could be simplified.

Overall logic should check if the value grows in size (e.g. u8 -> i32), in which case if both values start as u8, or if one of the value type will be auto-detected (e.g. an integer without the type 0_i32), then the comparison should be simplified.

P.S. This was seen in the auto-converted Brotli C code, which generated tons of boilerplate code that Clippy should be able to catch. More lint suggestions forthcoming. See example for this lint.

Advantage

• Cleaner, more readable, simpler code

Drawbacks

No response

Example

fn compare(u8_value: u8, u8_value2: u8) -> bool {
    (u8_value as i32) < b'a' as i32
    &&
    (u8_value as i32) == (u8_value2 as (i32))
    &&
    ((u8_value as i32) == 0_i32)    // note that we don't need specific integer type either
}

Could be written as:

fn compare(u8_value: u8, u8_value2: u8) -> bool {
    u8_value < b'a'
    &&
    u8_value == u8_value2
    &&
    u8_value == 0
}

Start by reading the Brotli comparison example in src/enc/static_dict.rs around line 570 and compare the casts with the intended simplified expressions in the issue. Identify the existing Clippy lint entry points for comparison analysis, then verify that the proposed lint handles widening casts and inferred integer literals without changing comparison behavior.