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TypeClass.lean
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TypeClass.lean
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/-
Copyright (c) 2022 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.
Authors: Gabriel Ebner
-/
import Lean.Meta.Instances
import Batteries.Tactic.Lint.Basic
namespace Std.Tactic.Lint
open Lean Meta
/--
Lints for instances with arguments that cannot be filled in, like
```
instance {α β : Type} [Group α] : Mul α where ...
```
-/
@[env_linter] def impossibleInstance : Linter where
noErrorsFound := "No instance has arguments that are impossible to infer"
errorsFound := "SOME INSTANCES HAVE ARGUMENTS THAT ARE IMPOSSIBLE TO INFER
These are arguments that are not instance-implicit and do not appear in
another instance-implicit argument or the return type."
test declName := do
unless ← isInstance declName do return none
forallTelescopeReducing (← inferType (← mkConstWithLevelParams declName)) fun args ty => do
let argTys ← args.mapM inferType
let impossibleArgs ← args.zipWithIndex.filterMapM fun (arg, i) => do
let fv := arg.fvarId!
if (← fv.getDecl).binderInfo.isInstImplicit then return none
if ty.containsFVar fv then return none
if argTys[i+1:].any (·.containsFVar fv) then return none
return some m!"argument {i+1} {arg} : {← inferType arg}"
if impossibleArgs.isEmpty then return none
addMessageContextFull <| .joinSep impossibleArgs.toList ", "
/--
A linter for checking if any declaration whose type is not a class is marked as an instance.
-/
@[env_linter] def nonClassInstance : Linter where
noErrorsFound := "No instances of non-classes"
errorsFound := "INSTANCES OF NON-CLASSES"
test declName := do
if !(← isInstance declName) then return none
let info ← getConstInfo declName
if !(← isClass? info.type).isSome then return "should not be an instance"
return none