Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
4213862b0e
This PR removes the `[grind_norm]` attribute. The normalization theorems used by `grind` are now fixed and cannot be modified by users. We use normalization theorems to ensure the built-in procedures receive term wish expected "shapes". We use it for types that have built-in support in grind. Users could misuse this feature as a simplification rule. For example, consider the following example: ```lean def replicate : (n : Nat) → (a : α) → List α | 0, _ => [] | n+1, a => a :: replicate n a -- I want `grind` to instantiate the equations theorems for me. attribute [grind] replicate -- I want it to use the equation theorems as simplication rules too. attribute [grind_norm] replicate /-- info: [grind.assert] n = 0 [grind.assert] ¬replicate n xs = [] [grind.ematch.instance] replicate.eq_1: replicate 0 xs = [] [grind.assert] True -/ set_option trace.grind.ematch.instance true in set_option trace.grind.assert true in example (xs : List α) : n = 0 → replicate n xs = [] := by grind -- fails :( ``` In this example, `grind` starts by asserting the two propositions as expected: `n = 0`, and `¬replicate n xs = []`. The normalizer cannot reduce `replicate n xs` as expected. Then, the E-matching module finds the instance `replicate 0 xs = []` for the equation theorem `replicate.eq_1` also as expected. But, then the normalizer kicks in and reduces the new instance to `True`. By removing `[grind_norm]` we elimninate this kind of misuse. Users that want to preprocess a formula before invoking `grind` should use `simp` instead. |
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