101 lines
4.4 KiB
Text
101 lines
4.4 KiB
Text
/-
|
||
Copyright (c) 2020 Microsoft Corporation. All rights reserved.
|
||
Released under Apache 2.0 license as described in the file LICENSE.
|
||
Authors: Leonardo de Moura
|
||
-/
|
||
import Lean.Meta.Tactic.Subst
|
||
import Lean.Meta.Tactic.Clear
|
||
|
||
namespace Lean.Meta
|
||
|
||
structure CaseValueSubgoal where
|
||
mvarId : MVarId
|
||
newH : FVarId
|
||
subst : FVarSubst := {}
|
||
|
||
instance : Inhabited CaseValueSubgoal :=
|
||
⟨{ mvarId := arbitrary, newH := arbitrary }⟩
|
||
|
||
/--
|
||
Split goal `... |- C x` into two subgoals
|
||
`..., (h : x = value) |- C value`
|
||
`..., (h : x != value) |- C x`
|
||
where `fvarId` is `x`s id.
|
||
The type of `x` must have decidable equality.
|
||
|
||
Remark: `subst` field of the second subgoal is equal to the input `subst`. -/
|
||
def caseValueAux (mvarId : MVarId) (fvarId : FVarId) (value : Expr) (hName : Name := `h) (subst : FVarSubst := {})
|
||
: MetaM (CaseValueSubgoal × CaseValueSubgoal) :=
|
||
withMVarContext mvarId do
|
||
let tag ← getMVarTag mvarId
|
||
checkNotAssigned mvarId `caseValue
|
||
let target ← getMVarType mvarId
|
||
let xEqValue ← mkEq (mkFVar fvarId) value
|
||
let xNeqValue := mkApp (mkConst `Not) xEqValue
|
||
let thenTarget := Lean.mkForall hName BinderInfo.default xEqValue target
|
||
let elseTarget := Lean.mkForall hName BinderInfo.default xNeqValue target
|
||
let thenMVar ← mkFreshExprSyntheticOpaqueMVar thenTarget tag
|
||
let elseMVar ← mkFreshExprSyntheticOpaqueMVar elseTarget tag
|
||
let val ← mkAppOptM `dite #[none, xEqValue, none, thenMVar, elseMVar]
|
||
assignExprMVar mvarId val
|
||
let (elseH, elseMVarId) ← intro1P elseMVar.mvarId!
|
||
let elseSubgoal := { mvarId := elseMVarId, newH := elseH, subst := subst : CaseValueSubgoal }
|
||
let (thenH, thenMVarId) ← intro1P thenMVar.mvarId!
|
||
let symm := false
|
||
let clearH := false
|
||
let (thenSubst, thenMVarId) ← substCore thenMVarId thenH symm subst clearH
|
||
withMVarContext thenMVarId do
|
||
trace[Meta]! "subst domain: {thenSubst.domain}"
|
||
let thenH := (thenSubst.get thenH).fvarId!
|
||
trace[Meta]! "searching for decl"
|
||
let decl ← getLocalDecl thenH
|
||
trace[Meta]! "found decl"
|
||
let thenSubgoal := { mvarId := thenMVarId, newH := (thenSubst.get thenH).fvarId!, subst := thenSubst : CaseValueSubgoal }
|
||
pure (thenSubgoal, elseSubgoal)
|
||
|
||
def caseValue (mvarId : MVarId) (fvarId : FVarId) (value : Expr) : MetaM (CaseValueSubgoal × CaseValueSubgoal) := do
|
||
let s ← caseValueAux mvarId fvarId value
|
||
appendTagSuffix s.1.mvarId `thenBranch
|
||
appendTagSuffix s.2.mvarId `elseBranch
|
||
pure s
|
||
|
||
structure CaseValuesSubgoal where
|
||
mvarId : MVarId
|
||
newHs : Array FVarId := #[]
|
||
subst : FVarSubst := {}
|
||
|
||
instance : Inhabited CaseValuesSubgoal :=
|
||
⟨{ mvarId := arbitrary }⟩
|
||
|
||
/--
|
||
Split goal `... |- C x` into values.size + 1 subgoals
|
||
1) `..., (h_1 : x = value[0]) |- C value[0]`
|
||
...
|
||
n) `..., (h_n : x = value[n - 1]) |- C value[n - 1]`
|
||
n+1) `..., (h_1 : x != value[0]) ... (h_n : x != value[n-1]) |- C x`
|
||
where `n = values.size`
|
||
where `fvarId` is `x`s id.
|
||
The type of `x` must have decidable equality.
|
||
|
||
Remark: the last subgoal is for the "else" catchall case, and its `subst` is `{}`.
|
||
Remark: the fiels `newHs` has size 1 forall but the last subgoal. -/
|
||
def caseValues (mvarId : MVarId) (fvarId : FVarId) (values : Array Expr) (hNamePrefix := `h) : MetaM (Array CaseValuesSubgoal) :=
|
||
let rec loop : Nat → MVarId → List Expr → Array FVarId → Array CaseValuesSubgoal → MetaM (Array CaseValuesSubgoal)
|
||
| i, mvarId, [], hs, subgoals => throwTacticEx `caseValues mvarId "list of values must not be empty"
|
||
| i, mvarId, v::vs, hs, subgoals => do
|
||
let (thenSubgoal, elseSubgoal) ← caseValueAux mvarId fvarId v (hNamePrefix.appendIndexAfter i) {}
|
||
appendTagSuffix thenSubgoal.mvarId ((`case).appendIndexAfter i)
|
||
let thenMVarId ← hs.foldlM
|
||
(fun thenMVarId h => match thenSubgoal.subst.get h with
|
||
| Expr.fvar fvarId _ => tryClear thenMVarId fvarId
|
||
| _ => pure thenMVarId)
|
||
thenSubgoal.mvarId
|
||
let subgoals := subgoals.push { mvarId := thenMVarId, newHs := #[thenSubgoal.newH], subst := thenSubgoal.subst }
|
||
match vs with
|
||
| [] => do
|
||
appendTagSuffix elseSubgoal.mvarId ((`case).appendIndexAfter (i+1))
|
||
pure $ subgoals.push { mvarId := elseSubgoal.mvarId, newHs := hs.push elseSubgoal.newH, subst := {} }
|
||
| vs => loop (i+1) elseSubgoal.mvarId vs (hs.push elseSubgoal.newH) subgoals
|
||
loop 1 mvarId values.toList #[] #[]
|
||
|
||
end Lean.Meta
|