Function remap_rustc_diagnostics 

pub fn remap_rustc_diagnostics(
    diagnostics: &[RustcDiagnostic],
    source_map: &SourceMap,
    file_of: &dyn Fn(usize) -> Option<String>,
) -> Vec<RemappedError>

Remap every rustc error diagnostic to its originating LOGOS line via the SourceMap. Diagnostics whose Rust line can’t be mapped are dropped (better silent than pointing at generated Rust). Uses each diagnostic’s PRIMARY span.