lean4-htt/tests/elab/1692.lean
Sebastian Ullrich db6aa9d8d3
feat: move instance-class check to declaration site (#12325)
This PR adds a warning to any `def` of class type that does not also
declare an appropriate reducibility.

The warning check runs after elaboration (checking the actual
reducibility status via `getReducibilityStatus`) rather than
syntactically checking modifiers before elaboration. This is necessary
to accommodate patterns like `@[to_additive (attr :=
implicit_reducible)]` in Mathlib, where the reducibility attribute is
applied during `.afterCompilation` by another attribute, and would be
missed by a purely syntactic check.

---------

Co-authored-by: Paul Reichert <6992158+datokrat@users.noreply.github.com>
Co-authored-by: Kim Morrison <kim@tqft.net>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
2026-03-06 03:23:27 +00:00

23 lines
642 B
Text
Raw Permalink Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

import Lean.Hygiene
set_option warn.classDefReducibility false
def otherInhabited : Inhabited Nat := ⟨42⟩
def f := Id.run do
let ⟨n⟩ ← pure otherInhabited
-- do-notation expands to `pure otherInhabited >>= fun x : Inhabited Nat => ...`
-- the `x : Inhabited Nat` should not be available for TC synth (i.e., `default` should be 0)
return default + n
example : f = 42 := rfl
open Lean
def g : Syntax :=
let rec stx : Syntax := Unhygienic.run `(f 0 1)
let stx := stx
match stx with
| `(f $_args*) => Syntax -- should not resolve to tmp var created by stx matcher
| _ => default
example : g = g.stx := rfl