What causes "not implemented" in rust-lang/rust-analyzer?

Replace .display() with the Display trait, e.g. format!("{}", path) or write!(out, "{}", path)

not implemented

Error message

not implemented

What it means

AbsPath::display() in the paths crate is a deliberate trap: it always panics with 'not implemented' and never returns. It exists only so that code accidentally calling the old Path::display()-style API fails loudly at runtime, pushing users toward the Display trait implementation instead. The function is also marked #[deprecated] to catch uses at compile time.

Source

Thrown at crates/paths/src/lib.rs:300

    pub fn file_name(&self) -> Option<&str> {
        self.0.file_name()
    }
    pub fn extension(&self) -> Option<&str> {
        self.0.extension()
    }
    pub fn file_stem(&self) -> Option<&str> {
        self.0.file_stem()
    }
    pub fn as_os_str(&self) -> &OsStr {
        self.0.as_os_str()
    }
    pub fn as_str(&self) -> &str {
        self.0.as_str()
    }
    #[deprecated(note = "use Display instead")]
    pub fn display(&self) -> ! {
        unimplemented!()
    }
    #[deprecated(note = "use std::fs::metadata().is_ok() instead")]
    pub fn exists(&self) -> ! {
        unimplemented!()
    }

    pub fn components(&self) -> Utf8Components<'_> {
        self.0.components()
    }
    // endregion:delegate-methods
}

impl fmt::Display for AbsPath {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        fmt::Display::fmt(&self.0, f)
    }
}

View on GitHub (pinned to e8f7e90aa3)

Solutions

Replace .display() with the Display trait, e.g. format!("{}", path) or write!(out, "{}", path)
Use path.as_str() when a &str is needed
Fix the deprecation warning so the call is removed before shipping

Example fix

// before
println!("{}", abs_path.display());
// after
println!("{}", abs_path); // or abs_path.as_str()

Defensive patterns

Strategy: try-catch

Try / catch

// This panics and cannot be caught; fix at the source.
// Avoid: path.display()
// Use instead:
let s: &str = path.as_str();
let rendered: String = path.to_string(); // via Display

Prevention

Deny deprecation warnings (#![deny(deprecated)]) so calls fail at compile time
Use Display formatting (format!/println!) for AbsPath values
Use as_str() when a &str is needed
Never port std::path::Path method calls mechanically onto AbsPath

When it happens

Trigger: Calling abs_path.display() on an AbsPath/AbsPathBuf value in any code linked against this crate; compiling with the deprecation warning ignored (deny nothing) and running the code path that calls it.

Common situations: Migrating code from std::path::PathBuf to AbsPathBuf and mechanically keeping .display() calls; following older rust-analyzer example code that predates the Display-based API.

Related errors

AI-assisted analysis of rust-lang/rust-analyzer@e8f7e90aa3 (2026-09-03). Data as JSON: /api/errors/9f7012cab50d7601. Report an issue: GitHub.