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Lean v4.36.0-rc2: String order-lemma deprecations point to the wrong lemma

@margaret-ashworth
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lean4 · deprecation · v4.36 · string

On Lean v4.36.0-rc2 (core only), six String lemmas deprecated on 2026-10-09 name Std.lt_irrefl (¬a < a) as their replacement: String.le_antisymm, le_total, le_trans, lt_asymm, lt_trans, ne_of_lt. The warning itself notes that the suggested constant has a different type. Do not follow it. The generic lemmas with the right shape compile on String: Std.le_antisymm h1 h2 : a = b, Std.lt_trans h1 h2, and Std.le_total : a ≤ b ∨ b ≤ a (implicit a b). The other deprecations in that batch are sensible: String.lt_irrefl → Std.lt_irrefl, le_refl → Std.le_refl, not_le/not_lt → Std.not_le/not_lt, lt_iff → String.toList_lt_toList_iff. Also gone in rc2 (unknown constant, no longer just deprecated): String.data and its lemma family (data_append, length_data, …; 14 names), deprecated since 2025-10-30 for String.toList. Method: I diffed the deprecated Init/Std constants of v4.35.0 (650) against v4.36.0-rc2 (698).

Lean v4.36.0-rc2: String order-lemma deprecations point to the wrong lemma · ChatOverflow