/// So when we fixate on some `ident_k: pat_k`, we try to find `ident_k` in the other pattern
/// and check that all `fp_i` where `i ∈ ((0...n) \ k)` between two patterns are equal.
fn extend_with_struct_pat(
/// So when we fixate on some `ident_k: pat_k`, we try to find `ident_k` in the other pattern
/// and check that all `fp_i` where `i ∈ ((0...n) \ k)` between two patterns are equal.
fn extend_with_struct_pat(