45 lines
1.8 KiB
Text
45 lines
1.8 KiB
Text
/-
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Copyright (c) 2020 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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import Lean.Meta.Tactic.Clear
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namespace Lean.Meta
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def revert (mvarId : MVarId) (fvarIds : Array FVarId) (preserveOrder : Bool := false) : MetaM (Array FVarId × MVarId) := do
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if fvarIds.isEmpty then
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pure (#[], mvarId)
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else withMVarContext mvarId do
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checkNotAssigned mvarId `revert
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for fvarId in fvarIds do
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if (← getLocalDecl fvarId) |>.isAuxDecl then
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throwError "failed to revert {mkFVar fvarId}, it is an auxiliary declaration created to represent recursive definitions"
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let fvars := fvarIds.map mkFVar
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match MetavarContext.MkBinding.collectForwardDeps (← getMCtx) (← getLCtx) fvars preserveOrder with
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| Except.error _ => throwError "failed to revert variables {fvars}"
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| Except.ok toRevert =>
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/- We should clear any `auxDecl` in `toRevert` -/
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let mut mvarId := mvarId
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let mut toRevertNew := #[]
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for x in toRevert do
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if (← getLocalDecl x.fvarId!) |>.isAuxDecl then
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mvarId ← clear mvarId x.fvarId!
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else
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toRevertNew := toRevertNew.push x
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let tag ← getMVarTag mvarId
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-- TODO: the following code can be optimized because `MetavarContext.revert` will compute `collectDeps` again.
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-- We should factor out the relevat part
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-- Set metavariable kind to natural to make sure `revert` will assign it.
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setMVarKind mvarId MetavarKind.natural
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let (e, toRevert) ←
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try
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liftMkBindingM <| MetavarContext.revert toRevertNew mvarId preserveOrder
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finally
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setMVarKind mvarId MetavarKind.syntheticOpaque
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let mvar := e.getAppFn
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setMVarTag mvar.mvarId! tag
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return (toRevert.map Expr.fvarId!, mvar.mvarId!)
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end Lean.Meta
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