rustc suggest adding an import of `compiler_builtins`

[jendrikw]

Code

fn f() {
    u8::cast_from_lossy(9);
}

Current output

Compiling playground v0.0.1 (/playground)
error[E0599]: no function or associated item named `cast_from_lossy` found for type `u8` in the current scope
 --> src/lib.rs:2:9
  |
2 |     u8::cast_from_lossy(9);
  |         ^^^^^^^^^^^^^^^ function or associated item not found in `u8`
  |
  = help: items from traits can only be used if the trait is in scope
help: trait `CastFrom` which provides `cast_from_lossy` is implemented but not in scope; perhaps you want to import it
  |
1 + use compiler_builtins::math::libm::support::int_traits::CastFrom;
  |

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` (lib) due to 1 previous error

Desired output

Compiling playground v0.0.1 (/playground)
error[E0599]: no function or associated item named `cast_from_lossy` found for type `u8` in the current scope
 --> src/lib.rs:2:9
  |
2 |     u8::cast_from_lossy(9);
  |         ^^^^^^^^^^^^^^^ function or associated item not found in `u8`
  |

For more information about this error, try `rustc --explain E0599`.
error: could not compile `playground` (lib) due to 1 previous error

Rationale and extra context

The suggested import does not work. Additionally, the import will be suggested even if it's already there.

Other cases

A previously reported issue #71090 was supposed to be fixed, but maybe it regressed?

Rust Version

rustc 1.87.0 (17067e9ac 2025-05-09)
binary: rustc
commit-hash: 17067e9ac6d7ecb70e50f92c1944e545188d2359
commit-date: 2025-05-09
host: x86_64-unknown-linux-gnu
release: 1.87.0
LLVM version: 20.1.1

Anything else?

No response