Function build_dots_validation_stmt 

pub(crate) fn build_dots_validation_stmt(
    dots_param: &Ident,
    spec_tokens: &TokenStream,
) -> Stmt

Builds the let dots_typed = <dots>.typed(<spec>)... statement injected at the start of a function body when #[miniextendr(dots = typed_list!(...))] is used.

Raises through arg_error! so validation keeps the argument-condition kind, the R parameter name (...), and the crate’s configured classes. Display formatting preserves TypedListError’s human-readable diagnostics.