Function validate_coerce_shared_fields 

fn validate_coerce_shared_fields<'tcx>(
    infcx: &InferCtxt<'tcx>,
    impl_did: LocalDefId,
    param_env: ParamEnv<'tcx>,
    coerce_shared_trait: DefId,
    trait_name: &'static str,
    span: Span,
    diagnostic_context: CoerceSharedDiagnosticContext,
    source_def: AdtDef<'tcx>,
    source_args: GenericArgsRef<'tcx>,
    target_def: AdtDef<'tcx>,
    target_args: GenericArgsRef<'tcx>,
) -> Result<(), ErrorGuaranteed>