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perf: use lean_instantiate_expr_mvars at instantiateExprMVars #4922

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Aug 5, 2024
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perf: use lean_instantiate_expr_mvars at instantiateExprMVars #4922

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77 changes: 4 additions & 73 deletions src/Lean/MetavarContext.lean
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Original file line number Diff line number Diff line change
Expand Up @@ -550,79 +550,10 @@ partial def instantiateLevelMVars [Monad m] [MonadMCtx m] (l : Level) : m Level
opaque instantiateExprMVarsImp (mctx : MetavarContext) (e : Expr) : MetavarContext × Expr

/-- instantiateExprMVars main function -/
partial def instantiateExprMVars [Monad m] [MonadMCtx m] [STWorld ω m] [MonadLiftT (ST ω) m] (e : Expr) : MonadCacheT ExprStructEq Expr m Expr :=
if !e.hasMVar then
pure e
else checkCache { val := e : ExprStructEq } fun _ => do match e with
| .proj _ _ s => return e.updateProj! (← instantiateExprMVars s)
| .forallE _ d b _ => return e.updateForallE! (← instantiateExprMVars d) (← instantiateExprMVars b)
| .lam _ d b _ => return e.updateLambdaE! (← instantiateExprMVars d) (← instantiateExprMVars b)
| .letE _ t v b _ => return e.updateLet! (← instantiateExprMVars t) (← instantiateExprMVars v) (← instantiateExprMVars b)
| .const _ lvls => return e.updateConst! (← lvls.mapM instantiateLevelMVars)
| .sort lvl => return e.updateSort! (← instantiateLevelMVars lvl)
| .mdata _ b => return e.updateMData! (← instantiateExprMVars b)
| .app .. => e.withApp fun f args => do
let instArgs (f : Expr) : MonadCacheT ExprStructEq Expr m Expr := do
let args ← args.mapM instantiateExprMVars
pure (mkAppN f args)
let instApp : MonadCacheT ExprStructEq Expr m Expr := do
let wasMVar := f.isMVar
let f ← instantiateExprMVars f
if wasMVar && f.isLambda then
/- Some of the arguments in `args` are irrelevant after we beta
reduce. Also, it may be a bug to not instantiate them, since they
may depend on free variables that are not in the context (see
issue #4375). So we pass `useZeta := true` to ensure that they are
instantiated. -/
instantiateExprMVars (f.betaRev args.reverse (useZeta := true))
else
instArgs f
match f with
| .mvar mvarId =>
match (← getDelayedMVarAssignment? mvarId) with
| none => instApp
| some { fvars, mvarIdPending } =>
/-
Apply "delayed substitution" (i.e., delayed assignment + application).
That is, `f` is some metavariable `?m`, that is delayed assigned to `val`.
If after instantiating `val`, we obtain `newVal`, and `newVal` does not contain
metavariables, we replace the free variables `fvars` in `newVal` with the first
`fvars.size` elements of `args`. -/
if fvars.size > args.size then
/- We don't have sufficient arguments for instantiating the free variables `fvars`.
This can only happen if a tactic or elaboration function is not implemented correctly.
We decided to not use `panic!` here and report it as an error in the frontend
when we are checking for unassigned metavariables in an elaborated term. -/
instArgs f
else
let newVal ← instantiateExprMVars (mkMVar mvarIdPending)
if newVal.hasExprMVar then
instArgs f
else do
let args ← args.mapM instantiateExprMVars
/-
Example: suppose we have
`?m t1 t2 t3`
That is, `f := ?m` and `args := #[t1, t2, t3]`
Moreover, `?m` is delayed assigned
`?m #[x, y] := f x y`
where, `fvars := #[x, y]` and `newVal := f x y`.
After abstracting `newVal`, we have `f (Expr.bvar 0) (Expr.bvar 1)`.
After `instantiaterRevRange 0 2 args`, we have `f t1 t2`.
After `mkAppRange 2 3`, we have `f t1 t2 t3` -/
let newVal := newVal.abstract fvars
let result := newVal.instantiateRevRange 0 fvars.size args
let result := mkAppRange result fvars.size args.size args
pure result
| _ => instApp
| e@(.mvar mvarId) => checkCache { val := e : ExprStructEq } fun _ => do
match (← getExprMVarAssignment? mvarId) with
| some newE => do
let newE' ← instantiateExprMVars newE
mvarId.assign newE'
pure newE'
| none => pure e
| e => pure e
def instantiateExprMVars [Monad m] [MonadMCtx m] (e : Expr) : m Expr := do
let (mctx, eNew) := instantiateExprMVarsImp (← getMCtx) e
setMCtx mctx
return eNew

instance : MonadMCtx (StateRefT MetavarContext (ST ω)) where
getMCtx := get
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