Mutare.Mutators.DefaultDrop (mutare v0.1.0)

Drops a trailing optional argument so the call uses its default value.

Not-found defaults — implicit nil

These lookups use nil when the optional fallback is removed:

• Map.get/3 → Map.get/2 Keyword.get/3 → Keyword.get/2
• Access.get/3 → Access.get/2 Access.key/2 → Access.key/1
• Map.pop/3 → Map.pop/2 Keyword.pop/3 → Keyword.pop/2
• Keyword.pop_first/3 → Keyword.pop_first/2
• Enum.at/3 → Enum.at/2
• List.pop_at/3 → List.pop_at/2
• List.keyfind/4 → List.keyfind/3
• List.flatten/2 → List.flatten/1
• List.first/2 → List.first/1 List.last/2 → List.last/1
• Map.get_lazy/3 → Map.get/2 Keyword.get_lazy/3 → Keyword.get/2
• Map.pop_lazy/3 → Map.pop/2 Keyword.pop_lazy/3 → Keyword.pop/2

The _lazy forms also change to their non-lazy counterpart.

Refinement defaults — a precision, base, separator, or fill

These calls revert to their standard precision, base, separator, fill, or trimming behavior:

• Float.round/2, Float.ceil/2, Float.floor/2 → /1 — drop the precision (implicit 0)
• Integer.to_string/2, Integer.to_charlist/2, Integer.parse/2, Integer.digits/2, Integer.undigits/2 → /1 — drop the base (implicit 10)
• Enum.join/2 → Enum.join/1 — drop the separator (implicit "")
• String.pad_leading/3, String.pad_trailing/3 → /2 — drop the fill (implicit " ")
• String.trim/2, String.trim_leading/2, String.trim_trailing/2 → /1 — drop the to-trim string, reverting to whitespace trimming

A call is skipped when its trailing literal already equals the implicit default: nil for the lookups, 0 for the rounding precision, 10 for the integer base, "" for Enum.join, " " for the pads — Map.get(m, k, nil), Float.round(x, 0), Integer.to_string(n, 10), Enum.join(xs, ""), String.pad_leading(s, n, " ") are all unchanged. List.flatten(xs, []) is also skipped because [] is the implicit tail. Non-default literals, variables, and expressions are eligible.

Lazy fallbacks are always eligible. The string argument to String.trim/2 and its directional variants is also always eligible because no string value reproduces the default whitespace behavior.

Default comparison uses the decoded value of a string literal.

This mutator is enabled by default and matches aliased and imported calls. It may produce a separate mutant alongside: Mutare.Mutators.CallRemoval removes String.trim/pad_leading/pad_trailing outright, while this family retains the call with default behavior; Mutare.Mutators.Numeric changes Float.ceil to Float.floor or vice versa while retaining the precision.