This PR extends the procedure behind `inferInstanceAs`/`def ...
deriving` to continue recursion through the class graph even when a
(local) instance to wrap was found in order to re-use already-wrapped
instance of subclasses.
This PR ensures that if wrapInstance encounters an instance that cannot
be reduced to a constructor, the wrapping definition is left at
semireducible transparency to avoid leakage.
Instead of unconditionally wrapping value of fields that were copied
from flattened parent structures, try finding an existing instance and
projecting it first.
This PR updates the `inferInstanceAs` docstring to reflect current
behavior: it requires an
expected type from context and should not be used as a simple
`inferInstance` synonym. The
old example (`#check inferInstanceAs (Inhabited Nat)`) no longer works,
so it's replaced
with one demonstrating the intended transport use case.
Additionally, renames `InstanceNormalForm.lean` to `WrapInstance.lean`,
`normalizeInstance`
to `wrapInstance`, and the trace class `Meta.instanceNormalForm` to
`Meta.wrapInstance`,
removing the "instance normal form" terminology from both documentation
and code.
Context:
https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/inferInstanceAs.20is.20broken/near/581449313🤖 Prepared with Claude Code
---------
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-25 02:20:49 +00:00
Renamed from src/Lean/Meta/InstanceNormalForm.lean (Browse further)
