false positive of lossy_float_literal for bigger powers of 2

Powers of 2 which exceed the size of the mantissa seem to yield a lossy_float_literal warning even though those are perfectly representable.

I tried this code:

fn main() {
    let x64 = 4_294_967_296_f64;
    let x32 = 4_294_967_296_f32;
    println!("x64 {:016x}", x64.to_bits());
    println!("x32 {:08x}", x32.to_bits());
    println!("x32 as x64 {:016x}", (x32 as f64).to_bits());
}

I expected to see this happen:

No clippy warnings.

Instead, this happened:

4_294_967_296_f32 get reported as not being covered by f32. The output shows that this value could successfully be converted into the expected bit-pattern.

x64 41f0000000000000
x32 4f800000
x32 as x64 41f0000000000000

Meta

• cargo clippy -V: clippy 0.1.54 (e82b650 2021-06-20)
• rustc -Vv:

  rustc 1.55.0-nightly (e82b65026 2021-06-20)
  binary: rustc
  commit-hash: e82b65026dcadf0998e3abf9dabc677f63160de7
  commit-date: 2021-06-20
  host: x86_64-unknown-linux-gnu
  release: 1.55.0-nightly
  LLVM version: 12.0.1
  

Start by reproducing the reported Rust example and locating the lossy_float_literal lint. Check how the lint evaluates the larger powers-of-two literals, then verify that the shown f32 value no longer produces a warning while the existing warning behavior remains covered.