Function rustc_builtin_macros::deriving::generic::find_type_parameters

pub(in deriving::generic) fn find_type_parameters(
    ty: &Ty, 
    ty_param_names: &[Symbol], 
    cx: &ExtCtxt<'_>
) -> Vec<P<Ty>>

This method helps to extract all the type parameters referenced from a type. For a type parameter <T>, it looks for either a TyPath that is not global and starts with T, or a TyQPath.