49 lines
1.1 KiB
Text
49 lines
1.1 KiB
Text
/-
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Copyright (c) 2021 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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module
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prelude
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public import Lean.Expr
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public section
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namespace Lean
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private def recAppKey := `_recApp
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/--
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We store the syntax at recursive applications to be able to generate better error messages
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when performing well-founded and structural recursion.
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-/
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def mkRecAppWithSyntax (e : Expr) (stx : Syntax) : Expr :=
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mkMData (KVMap.empty.insert recAppKey (.ofSyntax stx)) e
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/--
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Retrieve (if available) the syntax object attached to a recursive application.
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-/
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def getRecAppSyntax? (e : Expr) : Option Syntax :=
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match e with
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| .mdata d _ =>
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match d.find recAppKey with
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| some (DataValue.ofSyntax stx) => some stx
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| _ => none
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| _ => none
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/--
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Checks if the `MData` is for a recursive application.
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-/
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def MData.isRecApp (d : MData) : Bool :=
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d.contains recAppKey
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/--
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Return `true` if `getRecAppSyntax? e` is a `some`.
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-/
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def hasRecAppSyntax (e : Expr) : Bool :=
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match e with
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| .mdata d _ => d.isRecApp
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| _ => false
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end Lean
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