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.

Uses unwrap_or_else(|e| panic!("...: {e}")) rather than Result::expect, which formats the error with Debug instead of Display — for TypedListError that leaks PascalCase enum-variant names (Missing { name: "x" }) into the R-visible message instead of the human-phrased text (missing required field: "x") that the direct typed_list! path already produces via Display. See audit A8.