This PR adds the new attributes `[grind =>]` and `[grind <=]` for
controlling pattern selection and minimizing the number of places where
we have to use verbose `grind_pattern` command. It also fixes a bug in
the new pattern selection procedure, and improves the automatic pattern
selection for local lemmas.
The tests `grind_constProp.lean` and `no_grind_constProp.lean` are the
same use case with and without `grind`.
This PR adds a simple strategy to the (WIP) `grind` tactic. It just
keeps internalizing new theorem instances found by E-matching. The
simple strategy can solve examples such as:
```lean
grind_pattern Array.size_set => Array.set a i v h
grind_pattern Array.get_set_eq => a.set i v h
grind_pattern Array.get_set_ne => (a.set i v hi)[j]
example (as bs : Array α) (v : α)
(i : Nat)
(h₁ : i < as.size)
(h₂ : bs = as.set i v)
: as.size = bs.size := by
grind
example (as bs cs : Array α) (v : α)
(i : Nat)
(h₁ : i < as.size)
(h₂ : bs = as.set i v)
(h₃ : cs = bs)
(h₄ : i ≠ j)
(h₅ : j < cs.size)
(h₆ : j < as.size)
: cs[j] = as[j] := by
grind
opaque R : Nat → Nat → Prop
theorem Rtrans (a b c : Nat) : R a b → R b c → R a c := sorry
grind_pattern Rtrans => R a b, R b c
example : R a b → R b c → R c d → R d e → R a d := by
grind
```
This PR adds support for activating relevant theorems for the (WIP)
`grind` tactic. We say a theorem is relevant to a `grind` goal if the
symbols occurring in its patterns also occur in the goal.
