`imprecise_flops` not raised in some situations

[oppiliappan]

Summary

The lint imprecise_flops is not raised when a literal is used in combination with powf (and maybe other functions as well). Discovered in #9201.

Reproducer

I tried this code:

#![warn(clippy::imprecise_flops)]

fn main() {
    let _ = 1.5_f64.powf(1.0 / 3.0);
}

I expected to see this happen:

The lint imprecise_flops is raised on the line with a message such as "cube-root of a number can be computed more accurately".

Instead, this happened:

No lint is raised.

However, it does work as expected with the following code:

#![warn(clippy::imprecise_flops)]

fn main() {
    let x = 1.5_f64;
    let _ = x.powf(1.0 / 3.0);
}

// λ cargo clippy
//     Checking testuff v0.1.0 (/home/np/code/rust/testuff)
// warning: cube-root of a number can be computed more accurately
//  --> src/main.rs:5:13
//   |
// 5 |     let _ = x.powf(1.0 / 3.0);
//   |             ^^^^^^^^^^^^^^^^^ help: consider using: `x.cbrt()`
//   |
// note: the lint level is defined here
//  --> src/main.rs:1:9
//   |
// 1 | #![warn(clippy::imprecise_flops)]
//   |         ^^^^^^^^^^^^^^^^^^^^^^^
//   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#imprecise_flops

Version

rustc 1.65.0-nightly (addacb587 2022-08-24)
binary: rustc
commit-hash: addacb5878b9970ebc1665768a05cb601e7aea15
commit-date: 2022-08-24
host: x86_64-unknown-linux-gnu
release: 1.65.0-nightly
LLVM version: 15.0.0

Additional Labels

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