rust-lang/rust-analyzer · error

Cannot rename builtin type

Error message

Cannot rename builtin type

What it means

rust_analyzer's `Definition::rename` refuses to rename any `Definition::BuiltinType` (e.g. `u32`, `bool`, `str`). Builtin types are provided by the language/core crate and have no single definitional site to rewrite, so every reference would be ambiguous. The library deliberately bails instead of producing an incorrect SourceChange.

Solutions

1. Rename the user-defined item instead; builtin types cannot be renamed.
2. To alias a builtin, introduce a type alias (`type MyInt = i32;`) manually.
3. In client code, check `matches!(def, Definition::BuiltinType(_))` before calling rename and surface a user-friendly message.

Example fix

// before (rename request on builtin)
definition.rename(sema, "i64", ...); // Err: Cannot rename builtin type
// after
if matches!(definition, Definition::BuiltinType(_)) {
    return; // skip rename, show "builtin types cannot be renamed"
}
definition.rename(sema, "i64", ...)?;

fn can_rename(def: &Definition) -> bool {
    !matches!(def, Definition::BuiltinType(_) | Definition::BuiltinAttr(_) | Definition::SelfType(_) | Definition::ToolModule(_))
}

fn is_renamable(def: &Definition) -> bool {
    !matches!(def, Definition::BuiltinType(_))
}

match def.rename(sema, new_name, ...) {
    Err(e) if e.to_string().contains("Cannot rename builtin type") => eprintln!("builtin types cannot be renamed"),
    Err(e) => return Err(e),
    Ok(change) => apply(change),
}

When it happens

Trigger: Calling `Definition::rename` (public API, crates/ide-db/src/rename.rs:114) on a definition resolved to a builtin type, e.g. when the user invokes rename on the `i32` token in `let x: i32 = 0;`.

Common situations: Cursor placed on a primitive type name in source code and the editor issues a `textDocument/rename` LSP request; IDE plugins resolving the token to `hir::Namespace`-style builtin types rather than a user item.

Related errors

• Can't rename local that is defined in a macro declaration
• Cannot rename a builtin attr.
• Cannot rename parameter to self for trait functions
• Cannot rename reference to `_` as it is being referenced…
• Cannot rename `Self`

AI-assisted analysis of rust-lang/rust-analyzer@e8f7e90aa3 (2026-09-03). Data as JSON: /api/errors/0e3a6164d6e8eb7a. Report an issue: GitHub.

Appendix: source

Thrown at crates/ide-db/src/rename.rs:114

        // cases where self.krate() is None is handled below.
        let edition = if let Some(krate) = self.krate(sema.db) {
            // Can we not rename non-local items?
            // Then bail if non-local
            if !krate.origin(sema.db).is_local() {
                bail!("Cannot rename a non-local definition")
            }
            krate.edition(sema.db)
        } else {
            Edition::LATEST
        };

        match *self {
            Definition::Module(module) => rename_mod(sema, module, new_name),
            Definition::ToolModule(_) => {
                bail!("Cannot rename a tool module")
            }
            Definition::BuiltinType(_) => {
                bail!("Cannot rename builtin type")
            }
            Definition::BuiltinAttr(_) => {
                bail!("Cannot rename a builtin attr.")
            }
            Definition::SelfType(_) => bail!("Cannot rename `Self`"),
            Definition::Macro(mac) => rename_reference(
                sema,
                Definition::Macro(mac),
                new_name,
                rename_definition,
                edition,
                config,
            ),
            def => rename_reference(sema, def, new_name, rename_definition, edition, config),
        }
    }

    /// Textual range of the identifier which will change when renaming this

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