Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
26ad4d6972
This PR extracts the functional (lambda) passed to `brecOn` in structural recursion into a named `_f` helper definition (e.g. `foo._f`), similar to how well-founded recursion uses `._unary`. This way the functional shows up with a helpful name in kernel diagnostics rather than as an anonymous lambda. The `_f` definition is added with `.abbrev` kernel reducibility hints and the `@[reducible]` elaborator attribute, so the kernel unfolds it eagerly after `brecOn` iota-reduces. For inductive predicates, the previous inline lambda behavior is kept. To ensure that parent definitions still get the correct reducibility height (since `getMaxHeight` ignores `.abbrev` definitions), each `_f`'s body height is registered via a new `defHeightOverrideExt` environment extension. `getMaxHeight` checks this extension for all definitions, making the height computation transparent to the extraction. This change improves code size (a bit). It may regress kernel reduction times, especially if a function defined by structural recursion is used in kernel reduction proofs on the hot path. Functions defined by structural recursion are not particularly fast to reduce anyways (due to the `.brecOn` construction), so already now it may be worth writing a kernel-reduction-friendly function manually (using the recursor directly, avoiding overloaded operations). This change will guide you in knowing which function to optimize. 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com> |
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