2907df22ec
This PR implements RFC #12216: native computation (`native_decide`, `bv_decide`) is represented in the logic as one axiom per computation, asserting the equality that was obtained from the native computation. `#print axiom` will no longer show `Lean.trustCompiler`, but rather the auto-generated names of these axioms (with, for example, `._native.bv_decide.` in the name). See the RFC for more information. This PR introduces a common MetaM helper (`nativeEqTrue`) used by `native_decide` and `bv_decide` alike that runs the computation and then asserts the result using an axiom. It also deprecated the `ofReduceBool` axioms etc. Not included in this PR is infrastructure for enumerating these axioms, prettier `#print axioms` (should we want his) and tactic concurrency. Fixes #12216.
85 lines
3 KiB
Text
85 lines
3 KiB
Text
/-
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Copyright (c) 2025 Lean FRO, LLC. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Joachim Breitner
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-/
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module
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prelude
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public import Lean.Meta.Basic
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import Lean.Util.CollectLevelParams
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import Lean.AddDecl
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import Lean.Meta.AppBuilder
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import Lean.Elab.DeclarationRange
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open Lean Meta
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namespace Lean.Meta
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/-!
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This module contains infrastructure for proofs by native evaluation (`native decide`, `bv_decide`).
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Such proofs involve a native computation using the Lean kernel, and then asserting the result
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of that computation as an axiom towards the logic.
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-/
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public inductive NativeEqTrueResult where
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/-- The given expression `e` evalutes to true. `prf` is a proof of `e = true`. -/
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| success (prf : Expr)
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/-- The given expression `e` evalutes to false. -/
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| notTrue
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/--
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A call to `nativeEqTrue tacName e`, where `e` is a closed value of type `Bool`, will compile and run
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that value, check that it evaluates to `true`, and if so, will add an axiom asserting `e = true` and
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return that axiom.
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It is the basis for `native_decide` and `bv_decide` tactics.
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-/
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public def nativeEqTrue (tacticName : Name) (e : Expr) (axiomDeclRange? : Option Syntax := none) : MetaM NativeEqTrueResult := do
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let e ← instantiateMVars e
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if e.hasFVar then
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throwError m!"Tactic `{tacticName}` failed: Cannot native decide proposition with free variables:{indentExpr e}"
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if e.hasMVar then
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throwError m!"Tactic `{tacticName}` failed: Cannot native decide proposition with metavariables:{indentExpr e}"
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let levels := (collectLevelParams {} e).params.toList
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let isTrue ← withoutModifyingEnv do
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let auxDeclName ← mkAuxDeclName <| `_native ++ tacticName ++ `decl
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let decl := Declaration.defnDecl {
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name := auxDeclName
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levelParams := levels
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type := mkConst ``Bool
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value := e
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hints := .abbrev
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safety := .safe
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}
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try
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-- disable async codegen so we can catch its exceptions; we don't want to report `evalConst`
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-- failures below when the actual reason was a codegen failure
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withOptions (Elab.async.set · false) do
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addAndCompile decl
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catch ex =>
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throwError m!"Tactic `{tacticName}` failed. Error: {ex.toMessageData}"
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-- Now evaluate the constant, and check that it is true.
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try
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unsafe evalConst Bool auxDeclName
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catch ex =>
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throwError m!"\
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Tactic `{tacticName}` failed: Could not evaluate decidable instance. \
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Error: {ex.toMessageData}"
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unless isTrue do return .notTrue
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let auxAxiomName ← mkAuxDeclName <| `_native ++ tacticName ++ `ax
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let axDecl := Declaration.axiomDecl {
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name := auxAxiomName
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levelParams := levels
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type := mkApp3 (mkConst ``Eq [1]) (mkConst ``Bool) e (mkConst ``Bool.true)
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isUnsafe := false
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}
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addDecl axDecl
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if let some ref := axiomDeclRange? then
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Elab.addDeclarationRangesFromSyntax auxAxiomName ref
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let levelParams := levels.map mkLevelParam
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return .success <| mkConst auxAxiomName levelParams
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