This PR makes an empty `by` block run `try?` in the background and
surface its suggestions, while still producing the usual unsolved-goals
diagnostic. The implicit `try?` is informational only — it does not
change elaboration behavior beyond emitting messages. Behaviour is
controlled by a new option `tactic.tryOnEmptyBy`, disabled by default
for now; set it to `true` to opt in. The default may flip in a future
release.
Behaviour summary, when the option is enabled:
* The empty `by` reports unsolved goals immediately, before the
(possibly slow) `try?` has finished.
* The `try?` work is spawned as an asynchronous snapshot task
(`Term.wrapAsyncAsSnapshot` + `Core.logSnapshotTask`), so subsequent
elaboration is not blocked and the suggestions arrive when ready.
* `try?` is gated on its parser infrastructure being available, so
working on the prelude (before `Init.Try` is imported) keeps the regular
empty-`by` behaviour.
* No effect when the empty `by` appears inside a backtracking combinator
(e.g. `first | exact (by) | …`) or when `try?` finds no applicable
suggestion.
Implementation notes:
* `elabEmptyByAsTry` (in `Lean.Elab.Tactic.Try`) is registered as a
second `@[builtin_term_elab byTactic]`, alongside the existing
`elabByTactic` in `Lean.Elab.BuiltinTerm`. The gate
`shouldElabEmptyByAsTry` is checked in both elaborators so the
empty-`by` path takes the `try?` route while non-empty `by` follows the
regular path. The body shared between them is factored as
`elabByTacticCore`. The two-elaborator setup avoids a circular module
dependency between `BuiltinTerm.lean` and `Tactic/Try.lean`; an inline
comment in `Try.lean` explains this.
* A latent bug from #13229 is fixed along the way: `evalSepTactics`
returned at the very top for an empty tactic sequence without resolving
the `tacSnap` promise that `MutualDef.mkTacTask` sets up for `:= by …`
bodies. The dangling promise was harmless in typical use because the
cmd's cancellation token would fire shortly after elaboration and drop
it, but with a slow async snapshot task in the same command (as the
implicit `try?` here) the language-server info-tree walk would block on
it and the editor's Messages view would only update once the task
finished. Resolved at the early-return in `evalSepTactics`.
* The test infrastructure in `Lean.Server.Test.Cancel` gains a
label-keyed `testTasksRef` registry plus `mkTestTask` /
`wait_for_test_task`. The pre-existing `block_until_cancelled` is
reimplemented on top of `mkTestTask` and the redundant
`blockUntilCancelledOnce` ref is removed.
Tests:
* `tests/elab/tryOnEmptyBy.lean`, `tests/elab/try_prelude.lean` —
feature behaviour and prelude gating.
* `tests/server_interactive/cancellation_empty_by.lean` — verifies that
on document re-elaboration `cancelRec` reaches the empty-`by` snapshot's
cancel token registered with `Core.logSnapshotTask`. A
`[try_suggestion]` generator wires the outer cancel token's `onSet` to
resolve a `mkTestTask "T_outer"` promise, and the candidate
`wait_for_test_task "T_outer"` waits on it. If `cancelTk? := none` is
passed to `Core.logSnapshotTask`, `cancelRec` cannot reach the token,
the wait blocks, and the runner times out. If `cancelTk? := none` is
also passed to `wrapAsyncAsSnapshot`, no `onSet` resolver is registered,
the promise drops without resolution, and `wait_for_test_task` surfaces
a `"task dropped"` diagnostic on stderr.
* `tests/server_interactive/cancellation_try_plain.lean` — verifies
cancellation of plain `try?` (no `=>`) when its `[try_suggestion]`
candidate runs synchronously inside `expandUserTactic`, by chaining
through `wait_for_cancel_once_async`'s shared promise. Breaking
`SnapshotTask.cancelRec` to skip walking children causes a runner
timeout.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
This PR adds high priority to instances for `OfSemiring.Q` in the grind
ring envelope. When Mathlib is imported, instance synthesis for types
like `OfSemiring.Q Nat` becomes very expensive because the solver
explores many irrelevant paths before finding the correct instances. By
marking these instances as high priority and adding shortcut instances
for basic operations (`Add`, `Sub`, `Mul`, `Neg`, `OfNat`, `NatCast`,
`IntCast`, `HPow`), instance synthesis resolves quickly.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Kim Morrison <kim@tqft.net>
This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.
For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
2026-02-25 13:51:53 +00:00
Renamed from tests/lean/run/info_trees.lean (Browse further)
