Function function_signature_params 

pub fn function_signature_params<'db>(
    diagnostics: &mut SemanticDiagnostics<'db>,
    db: &'db dyn Database,
    resolver: &mut Resolver<'db>,
    params: impl Iterator<Item = Param<'db>>,
    function_title_id: Option<FunctionTitleId<'db>>,
    env: &mut Environment<'db>,
) -> Vec<Parameter<'db>>

Returns the parameters of the given function signature’s AST.