`std_instead_of_core` does not detect uses of non-fully qualified items

Summary

std_instead_of_core does not detect the use of, for example, the std::fmt::Display trait when it appears as fmt::Display accompanied by use std::fmt

Lint Name

clippy::std_instead_of_core

Reproducer

I tried this code:

#![deny(clippy::std_instead_of_core)]
use std::fmt;
struct S;
impl fmt::Display for S {
    fn fmt(&self, _: &mut fmt::Formatter<'_>) -> fmt::Result {
        todo!()
    }
}

I expected to see this happen: 3 warnings on fmt::Display, fmt::Formatter and fmt::Result

Instead, this happened: no warnings were produced

The lint is able to detect imported items and items qualified by absolute path:

#![deny(clippy::std_instead_of_core)]
use std::fmt::{self, Display};
struct S;
impl Display for S {
    fn fmt(&self, _: &mut std::fmt::Formatter<'_>) -> fmt::Result {
        todo!()
    }
}

in this second version, both Display and Formatter are detected but fmt::Result is not.

Version

rustc 1.73.0-nightly (7bd81ee19 2023-07-13)
binary: rustc
commit-hash: 7bd81ee1902c049691d0a1f03be5558bee51d100
commit-date: 2023-07-13
host: x86_64-unknown-linux-gnu
release: 1.73.0-nightly
LLVM version: 16.0.5

Start by locating the implementation and tests for the clippy::std_instead_of_core lint, then reproduce the issue with the Rust examples in this report. The work is done when qualified uses such as fmt::Display, fmt::Formatter, and fmt::Result are detected consistently alongside imported and absolute-path uses.