Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
3acd77a154
Floris van Doorn [reported on Zulip](https://leanprover.zulipchat.com/#narrow/stream/270676-lean4/topic/have.20tactic.20error.20recovery/near/425283053) that it is confusing that the `have : T := e` tactic completely fails if the body `e` is not of type `T`. This is in contrast to `have : T := by exact e`, which does not completely fail when `e` is not of type `T`. This ends up being caused by `elabTermEnsuringType` throwing an error when it fails to insert a coercion. Now, it detects this case, and it checks the `errToSorry` flag to decide whether to throw the error or to log the error and insert a `sorry`. This is justified by `elabTermEnsuringType` being a frontend to `elabTerm`, which inserts `sorry` on error. An alternative would be to make `ensureType` respect `errToSorry`, but there exists code that expects being able to catch when `ensureType` fails. Making such code manipulate `errToSorry` seems error prone, and this function is not a main entry point to the term elaborator, unlike `elabTermEnsuringType`. |
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This is the repository for Lean 4.
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