I made a modification to the `mkLambdaFVars` function, adding a
`etaReduce : Bool` parameter that determines whether a new lambda of the
form `fun x => f x` should be replaced by `f`. I then set this option to
true at `isDefEq` when processing metavariable assignments.
This means that many unnecessary eta unreduced expression are now
reduced. This is beneficial for users, so that they do not have to deal
with such unreduced expressions. It is also beneficial for performance,
leading to a 0.6% improvement in build instructions. Most notably,
`Mathlib.Algebra.DirectLimit`, previously a top 50 slowest file, has
sped up by 40%.
Quite a number of proof in mathlib broke. Many of these involve removing
a now unnecessary `simp only`. In other cases, a simp or rewrite doesn't
work anymore, such as a `simp_rw [mul_comm]` that was used to rewrite
`fun x => 2*x`, but now this term has turned into `HMul.hMul 2`.
Closes#4386
The `save` happened in a slightly different context from the restore,
which a refinement of the `saveOrRestoreFull` signature now makes
impossible.
Fixes#4328
Extends Lean's incremental reporting and reuse between commands into
various steps inside declarations:
* headers and bodies of each (mutual) definition/theorem
* `theorem ... := by` for each contained tactic step, including
recursively inside supported combinators currently consisting of
* `·` (cdot), `case`, `next`
* `induction`, `cases`
* macros such as `next` unfolding to the above
*Incremental reuse* means not recomputing any such steps if they are not
affected by a document change. *Incremental reporting* includes the
parts seen in the recording above: the progress bar and messages. Other
language server features such as hover etc. are *not yet* supported
incrementally, i.e. they are shown only when the declaration has been
fully processed as before.
---------
Co-authored-by: Scott Morrison <scott.morrison@gmail.com>
### Explanation
In the case that `assignSyntheticOpaque := true` and the given
metavariable is `syntheticOpaque` and the depth of the metavariable is
not the current depth, `isReadOnlyOrSyntheticOpaque` returns false, even
though the metavariable is read-only because of being declared at a
smaller depth. This causes the metavariable to (wrongly) be able to be
instantiated by `isDefEq`.
This bug was found at the proof of
[RingHom.PropertyIsLocal.sourceAffineLocally_of_source_openCover](https://leanprover-community.github.io/mathlib4_docs/Mathlib/AlgebraicGeometry/Morphisms/RingHomProperties.html#RingHom.PropertyIsLocal.sourceAffineLocally_of_source_openCover),
which involves a type class synthesis for `CommRing ?m.2404`, and the
synthesis manages to instantiate this metavariable into different
values, even though `synthInstance?` increases the metavariable depth.
This synthesis fails after 1 second.
I found the bug while modifying the instance synthesis code: the
modified code spent several minutes on this failed synthesis.
### Test
The problem can be verified with the test:
```
run_meta do
let m ← mkFreshExprMVar (Expr.sort levelOne) MetavarKind.syntheticOpaque
withAssignableSyntheticOpaque do
withNewMCtxDepth do
let eq ← isDefEq m (.const ``Nat [])
Lean.logInfo m! "{eq}"
```
this unification used to succeed, giving `true`, and this fix makes it
return `false`.
### Impact on Mathlib
This fix causes a change in the behaviour of `congr`, `convert` and
friends, which breaks a couple of proofs in mathlib. Most of these are
fixed by supplying more arguments.
I fixed these proofs, and
[benched](http://speed.lean-fro.org/mathlib4/compare/b821bfd9-3769-4930-b77f-0adc6f9d218f/to/e7b27246-a3e6-496a-b552-ff4b45c7236e?hash2=4f3c460cc1668820c9af8418a87a23db44c7acab)
mathlib. The result is that most files are unaffected, but some files
are significantly improved. This is most prominent in
Mathlib.RingTheory.Jacobson, where the number of instructions has
decreased by 28%. The overall improvement is a 0.3% reduction in
instructions.
[Zulip
message](https://leanprover.zulipchat.com/#narrow/stream/287929-mathlib4/topic/Ways.20to.20speed.20up.20Mathlib/near/439218960)
Summary:
- Take `synthPendingDepth` into account when caching TC results
- Add `maxSynthPendingDepth` option with default := 2.
- Add support for tracking `synthPending` failures when using
`set_option diagnostics true`
closes#2522closes#3313closes#3927
Identical to #4114 but with `maxSynthPendingDepth := 1`
closes#4114
cc @semorrison
It currently only reports how many times each declaration has been
unfolded, and how often the `isDefEq` heuristic for `f a =?= f b` has
been used. Only counters above the threshold are reported.
We add a new configuration flag for `isDefEq`:
`Meta.Config.univApprox`.
When it is true, we approximate the solution for universe constraints
such as
- `u =?= max u ?v`, we use `?v := u`, and ignore the solution `?v := 0`.
- `max u v =?= max u ?w`, we use `?w := v`, and ignore the solution `?w
:= max u v`.
We only apply these approximations when there the contraints cannot be
postponed anymore. These approximations prevent error messages such as
```
error: stuck at solving universe constraint
max u ?u.3430 =?= u
```
This kind of error seems to appear in several Mathlib files.
We currently do not use these approximations while synthesizing type
class instances.
Part of the retreat Hackathon.
---------
Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>
Co-authored-by: Mario Carneiro <di.gama@gmail.com>
This is a rewrite of the `UnusedVariables` lint to inline and simplify
many of the dependent functions to try to improve the performance of
this lint, which quite often shows up in perf reports.
* The mvar assignment scanning is one of the most expensive parts of the
process, so we do two things to improve this:
* Lazily perform the scan only if we need it
* Use an object-pointer hashmap to ensure that we don't have quadratic
behavior when there are many mvar assignments with slight differences.
* The dependency on `Lean.Server` is removed, meaning we don't need to
do the LSP conversion stuff anymore. The main logic of reference finding
is inlined.
* We take `fvarAliases` into account, and union together fvars which are
aliases of a base fvar. (It would be great if we had `UnionFind` here.)
More docs will be added once we confirm an actual perf improvement.
---------
Co-authored-by: Sebastian Ullrich <sebasti@nullri.ch>
This adds the concept of **functional induction** to lean.
Derived from the definition of a (possibly mutually) recursive function,
a **functional
induction principle** is tailored to proofs about that function. For
example from:
```
def ackermann : Nat → Nat → Nat
| 0, m => m + 1
| n+1, 0 => ackermann n 1
| n+1, m+1 => ackermann n (ackermann (n + 1) m)
derive_functional_induction ackermann
```
we get
```
ackermann.induct (motive : Nat → Nat → Prop) (case1 : ∀ (m : Nat), motive 0 m)
(case2 : ∀ (n : Nat), motive n 1 → motive (Nat.succ n) 0)
(case3 : ∀ (n m : Nat), motive (n + 1) m → motive n (ackermann (n + 1) m) → motive (Nat.succ n) (Nat.succ m))
(x x : Nat) : motive x x
```
At the moment, the user has to ask for the functional induction
principle explicitly using
```
derive_functional_induction ackermann
```
The module docstring of `Lean/Meta/Tactic/FunInd.lean` contains more
details on the
design and implementation of this command.
More convenience around this (e.g. a `functional induction` tactic) will
follow eventually.
This PR includes a bunch of `PSum`/`PSigma` related functions in the
`Lean.Tactic.FunInd`
namespace. I plan to move these to `PackArgs`/`PackMutual` afterwards,
and do some cleaning
up as I do that.
---------
Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>
Co-authored-by: Leonardo de Moura <leomoura@amazon.com>
This is still a draft PR, but includes the core exact? and apply?
tactics.
Still need to convert to builtin syntax and test on Std.
---------
Co-authored-by: David Thrane Christiansen <david@davidchristiansen.dk>
This commit also removes parameter `simpleReduce` from discrimination
trees, and take WHNF configuration options.
Reason: it is more dynamic now. For example, the simplifier
will be able to use different configurations for discrimination tree insertion
and retrieval. We need this feature to address issues #2669 and #2281
This commit also removes the dead Meta.Config field `zetaNonDep`.
