chore: typos / improvements to grind messages (#6561)

This PR fixes some typos and makes minor improvements to grind
doc-strings and messages.

src/Init/Grind/Tactics.lean

@@ -21,7 +21,7 @@ end Lean.Parser.Attr
 namespace Lean.Grind
 /--
 The configuration for `grind`.
-Passed to `grind` using, for example, the `grind (config := { eager := true })` syntax.
+Passed to `grind` using, for example, the `grind (config := { matchEqs := true })` syntax.
 -/
 structure Config where
   /-- Maximum number of case-splits in a proof search branch. It does not include splits performed during normalization. -/

src/Init/Grind/Util.lean

@@ -21,8 +21,6 @@ def doNotSimp {α : Sort u} (a : α) : α := a
 /-- Gadget for representing offsets `t+k` in patterns. -/
 def offset (a b : Nat) : Nat := a + b
 
-set_option pp.proofs true
-
 theorem nestedProof_congr (p q : Prop) (h : p = q) (hp : p) (hq : q) : HEq (nestedProof p hp) (nestedProof q hq) := by
   subst h; apply HEq.refl
 

src/Lean/Meta/Tactic/Grind/Canon.lean

@@ -22,7 +22,7 @@ to detect when two structurally different atoms are definitionally equal.
 The `grind` tactic, on the other hand, uses congruence closure. Moreover, types, type formers, proofs, and instances
 are considered supporting elements and are not factored into congruence detection.
 
-This module minimizes the number of `isDefEq` checks by comparing two terms `a` and `b` only if they instances,
+This module minimizes the number of `isDefEq` checks by comparing two terms `a` and `b` only if they are instances,
 types, or type formers and are the `i`-th arguments of two different `f`-applications. This approach is
 sufficient for the congruence closure procedure used by the `grind` tactic.
 
@@ -129,17 +129,17 @@ where
         else
           let pinfos := (← getFunInfo f).paramInfo
           let mut modified := false
-          let mut args := args
-          for i in [:args.size] do
-            let arg := args[i]!
+          let mut args := args.toVector
+          for h : i in [:args.size] do
+            let arg := args[i]
             let arg' ← match (← shouldCanon pinfos i arg) with
             | .canonType  => canonType f i arg
             | .canonInst  => canonInst f i arg
             | .visit      => visit arg
             unless ptrEq arg arg' do
-              args := args.set! i arg'
+              args := args.set i arg'
               modified := true
-          pure <| if modified then mkAppN f args else e
+          pure <| if modified then mkAppN f args.toArray else e
       | .forallE _ d b _ =>
         -- Recall that we have `ForallProp.lean`.
         let d' ← visit d

src/Lean/Meta/Tactic/Grind/EMatchTheorem.lean

@@ -218,7 +218,7 @@ private def getPatternFn? (pattern : Expr) : Option Expr :=
     | _ => none
 
 /--
-Returns a bit-mask `mask` s.t. `mask[i]` is true if the the corresponding argument is
+Returns a bit-mask `mask` s.t. `mask[i]` is true if the corresponding argument is
 - a type (that is not a proposition) or type former, or
 - a proof, or
 - an instance implicit argument
@@ -248,13 +248,13 @@ private partial def go (pattern : Expr) (root := false) : M Expr := do
     | throwError "invalid pattern, (non-forbidden) application expected{indentExpr pattern}"
   assert! f.isConst || f.isFVar
   saveSymbol f.toHeadIndex
-  let mut args := pattern.getAppArgs
+  let mut args := pattern.getAppArgs.toVector
   let supportMask ← getPatternSupportMask f args.size
-  for i in [:args.size] do
-    let arg := args[i]!
+  for h : i in [:args.size] do
+    let arg := args[i]
     let isSupport := supportMask[i]?.getD false
-    args := args.set! i (← goArg arg isSupport)
-  return mkAppN f args
+    args := args.set i (← goArg arg isSupport)
+  return mkAppN f args.toArray
 where
   goArg (arg : Expr) (isSupport : Bool) : M Expr := do
     if !arg.hasLooseBVars then
@@ -556,8 +556,8 @@ private partial def collect (e : Expr) : CollectorM Unit := do
         -- restore state and continue search
         set saved
       catch _ =>
-        -- restore state and continue search
         trace[grind.ematch.pattern.search] "skip, exception during normalization"
+        -- restore state and continue search
         set saved
     let args := e.getAppArgs
     for arg in args, flag in (← NormalizePattern.getPatternSupportMask f args.size) do
@@ -592,7 +592,7 @@ private def mkEMatchTheoremWithKind? (origin : Origin) (levelParams : Array Name
       | .fwd =>
         let ps ← getPropTypes xs
         if ps.isEmpty then
-          throwError "invalid `grind` forward theorem, theorem `{← origin.pp}` does not have proposional hypotheses"
+          throwError "invalid `grind` forward theorem, theorem `{← origin.pp}` does not have propositional hypotheses"
         pure ps
       | .bwd => pure #[type]
       | .default => pure <| #[type] ++ (← getPropTypes xs)
@@ -623,7 +623,7 @@ private def getKind (stx : Syntax) : TheoremKind :=
   else
     .bwd
 
-private def addGrindEqAttr (declName : Name) (attrKind : AttributeKind) (useLhs := true) : MetaM Unit := do
+private def addGrindEqAttr (declName : Name) (attrKind : AttributeKind) (thmKind : TheoremKind) (useLhs := true) : MetaM Unit := do
   if (← getConstInfo declName).isTheorem then
     ematchTheoremsExt.add (← mkEMatchEqTheorem declName (normalizePattern := true) (useLhs := useLhs)) attrKind
   else if let some eqns ← getEqnsFor? declName then
@@ -632,18 +632,18 @@ private def addGrindEqAttr (declName : Name) (attrKind : AttributeKind) (useLhs
     for eqn in eqns do
       ematchTheoremsExt.add (← mkEMatchEqTheorem eqn) attrKind
   else
-    throwError "`[grind_eq]` attribute can only be applied to equational theorems or function definitions"
+    throwError s!"`{thmKind.toAttribute}` attribute can only be applied to equational theorems or function definitions"
 
 private def addGrindAttr (declName : Name) (attrKind : AttributeKind) (thmKind : TheoremKind) : MetaM Unit := do
   if thmKind == .eqLhs then
-    addGrindEqAttr declName attrKind (useLhs := true)
+    addGrindEqAttr declName attrKind thmKind (useLhs := true)
   else if thmKind == .eqRhs then
-    addGrindEqAttr declName attrKind (useLhs := false)
+    addGrindEqAttr declName attrKind thmKind (useLhs := false)
   else if thmKind == .eqBoth then
-    addGrindEqAttr declName attrKind (useLhs := true)
-    addGrindEqAttr declName attrKind (useLhs := false)
+    addGrindEqAttr declName attrKind thmKind (useLhs := true)
+    addGrindEqAttr declName attrKind thmKind (useLhs := false)
   else if !(← getConstInfo declName).isTheorem then
-    addGrindEqAttr declName attrKind
+    addGrindEqAttr declName attrKind thmKind
   else
     let some thm ← mkEMatchTheoremWithKind? (.decl declName) #[] (← getProofFor declName) thmKind
       | throwError "`@{thmKind.toAttribute} theorem {declName}` {thmKind.explainFailure}, consider using different options or the `grind_pattern` command"
@@ -653,11 +653,21 @@ builtin_initialize
   registerBuiltinAttribute {
     name := `grind
     descr :=
-      "The `[grind_eq]` attribute is used to annotate equational theorems and functions.\
-      When applied to an equational theorem, it marks the theorem for use in heuristic instantiations by the `grind` tactic.\
-      When applied to a function, it automatically annotates the equational theorems associated with that function.\
+      "The `[grind]` attribute is used to annotate declarations.\
+      \
+      When applied to an equational theorem, `[grind =]`, `[grind =_]`, or `[grind _=_]`\
+      will mark the theorem for use in heuristic instantiations by the `grind` tactic,
+      using respectively the left-hand side, the right-hand side, or both sides of the theorem.\
+      When applied to a function, `[grind =]` automatically annotates the equational theorems associated with that function.\
+      When applied to a theorem `[grind ←]` will instantiate the theorem whenever it encounters the conclusion of the theorem
+      (that is, it will use the theorem for backwards reasoning).\
+      When applied to a theorem `[grind →]` will instantiate the theorem whenever it encounters sufficiently many of the propositional hypotheses
+      (that is, it will use the theorem for forwards reasoning).\
+      \
+      The attribute `[grind]` by itself will effectively try `[grind ←]` (if the conclusion is sufficient for instantiation) and then `[grind →]`.\
+      \
       The `grind` tactic utilizes annotated theorems to add instances of matching patterns into the local context during proof search.\
-      For example, if a theorem `@[grind_eq] theorem foo_idempotent : foo (foo x) = foo x` is annotated,\
+      For example, if a theorem `@[grind =] theorem foo_idempotent : foo (foo x) = foo x` is annotated,\
       `grind` will add an instance of this theorem to the local context whenever it encounters the pattern `foo (foo x)`."
     applicationTime := .afterCompilation
     add := fun declName stx attrKind => do

src/Lean/Meta/Tactic/Grind/Internalize.lean

@@ -47,13 +47,13 @@ private def updateAppMap (e : Expr) : GoalM Unit := do
 /-- Inserts `e` into the list of case-split candidates. -/
 private def addSplitCandidate (e : Expr) : GoalM Unit := do
   trace[grind.split.candidate] "{e}"
-  modify fun s => { s with splitCadidates := e :: s.splitCadidates }
+  modify fun s => { s with splitCandidates := e :: s.splitCandidates }
 
 -- TODO: add attribute to make this extensible
 private def forbiddenSplitTypes := [``Eq, ``HEq, ``True, ``False]
 
 /-- Inserts `e` into the list of case-split candidates if applicable. -/
-private def checkAndaddSplitCandidate (e : Expr) : GoalM Unit := do
+private def checkAndAddSplitCandidate (e : Expr) : GoalM Unit := do
   unless e.isApp do return ()
   if e.isIte || e.isDIte then
     addSplitCandidate e
@@ -148,7 +148,7 @@ partial def internalize (e : Expr) (generation : Nat) : GoalM Unit := do
       -- We do not want to internalize the components of a literal value.
       mkENode e generation
     else e.withApp fun f args => do
-      checkAndaddSplitCandidate e
+      checkAndAddSplitCandidate e
       addMatchEqns f generation
       if f.isConstOf ``Lean.Grind.nestedProof && args.size == 2 then
         -- We only internalize the proposition. We can skip the proof because of

src/Lean/Meta/Tactic/Grind/Split.lean

@@ -52,23 +52,23 @@ private def checkCaseSplitStatus (e : Expr) : GoalM CaseSplitStatus := do
     if (← isResolvedCaseSplit e) then
       return .resolved
     if (← isMatcherApp e) then
-      return .notReady -- TODO: implement splittes for `match`
+      return .notReady -- TODO: implement splitters for `match`
       -- return .ready
     let .const declName .. := e.getAppFn | unreachable!
     if (← isInductivePredicate declName <&&> isEqTrue e) then
       return .ready
     return .notReady
 
-/-- Returns the next case-split to be peformed. It uses a very simple heuristic. -/
+/-- Returns the next case-split to be performed. It uses a very simple heuristic. -/
 private def selectNextSplit? : GoalM (Option Expr) := do
   if (← isInconsistent) then return none
   if (← checkMaxCaseSplit) then return none
-  go (← get).splitCadidates none []
+  go (← get).splitCandidates none []
 where
   go (cs : List Expr) (c? : Option Expr) (cs' : List Expr) : GoalM (Option Expr) := do
     match cs with
     | [] =>
-      modify fun s => { s with splitCadidates := cs'.reverse }
+      modify fun s => { s with splitCandidates := cs'.reverse }
       if c?.isSome then
         -- Remark: we reset `numEmatch` after each case split.
         -- We should consider other strategies in the future.

src/Lean/Meta/Tactic/Grind/Types.lean

@@ -29,7 +29,7 @@ def congrPlaceholderProof := mkConst (Name.mkSimple "[congruence]")
 
 /--
 Returns `true` if `e` is `True`, `False`, or a literal value.
-See `LitValues` for supported literals.
+See `Lean.Meta.LitValues` for supported literals.
 -/
 def isInterpreted (e : Expr) : MetaM Bool := do
   if e.isTrue || e.isFalse then return true
@@ -59,11 +59,11 @@ structure CongrTheoremCacheKey where
   f       : Expr
   numArgs : Nat
 
--- We manually define `BEq` because we wannt to use pointer equality.
+-- We manually define `BEq` because we want to use pointer equality.
 instance : BEq CongrTheoremCacheKey where
   beq a b := isSameExpr a.f b.f && a.numArgs == b.numArgs
 
--- We manually define `Hashable` because we wannt to use pointer equality.
+-- We manually define `Hashable` because we want to use pointer equality.
 instance : Hashable CongrTheoremCacheKey where
   hash a := mixHash (unsafe ptrAddrUnsafe a.f).toUInt64 (hash a.numArgs)
 
@@ -123,7 +123,7 @@ def abstractNestedProofs (e : Expr) : GrindM Expr := do
 
 /--
 Applies hash-consing to `e`. Recall that all expressions in a `grind` goal have
-been hash-consing. We perform this step before we internalize expressions.
+been hash-consed. We perform this step before we internalize expressions.
 -/
 def shareCommon (e : Expr) : GrindM Expr := do
   modifyGet fun { canon, scState, nextThmIdx, congrThms, trueExpr, falseExpr, simpStats } =>
@@ -193,7 +193,7 @@ structure ENode where
   interpreted : Bool := false
   /-- `ctor := true` if the head symbol is a constructor application. -/
   ctor : Bool := false
-  /-- `hasLambdas := true` if equivalence class contains lambda expressions. -/
+  /-- `hasLambdas := true` if the equivalence class contains lambda expressions. -/
   hasLambdas : Bool := false
   /--
   If `heqProofs := true`, then some proofs in the equivalence class are based
@@ -383,7 +383,7 @@ structure Goal where
   /-- `match` auxiliary functions whose equations have already been created and activated. -/
   matchEqNames : PHashSet Name := {}
   /-- Case-split candidates. -/
-  splitCadidates : List Expr := []
+  splitCandidates : List Expr := []
   /-- Number of splits performed to get to this goal. -/
   numSplits : Nat := 0
   /-- Case-splits that do not have to be performed anymore. -/