5f4d724c2d
This PR improves `match` generalization such that it abstracts metavariables in types of local variables and in the result type of the match over the match discriminants. Previously, a metavariable in the result type would silently default to the behavior of `generalizing := false`, and a metavariable in the type of a free variable would lead to an error (#8099). Example of a `match` that elaborates now but previously wouldn't: ```lean example (a : Nat) (ha : a = 37) := (match a with | 42 => by contradiction | n => n) = 37 ``` This is because the result type of the `match` is a metavariable that was not abstracted over `a` and hence generalization failed; the result is that `contradiction` cannot pick up the proof `ha : 42 = 37`. The old behavior can be recovered by passing `(generalizing := false)` to the `match`. Furthermore, programs such as the following can now be elaborated: ```lean example (n : Nat) : Id (Fin (n + 1)) := have jp : ?m := ?rhs match n with | 0 => ?jmp1 | n + 1 => ?jmp2 where finally case m => exact Fin (n + 1) → Id (Fin (n + 1)) case jmp1 => exact jp ⟨0, by decide⟩ case jmp2 => exact jp ⟨n, by omega⟩ case rhs => exact pure ``` This is useful for the `do` elaborator. Fixes #8099.
29 lines
775 B
Text
29 lines
775 B
Text
/--
|
|
info: Try this:
|
|
[apply] simp only [ha, Nat.reduceEqDiff, imp_self]
|
|
-/
|
|
#guard_msgs in
|
|
example (a : Nat) (ha : a = 37) :
|
|
(match (generalizing := false) h : a with | 42 => by simp_all | n => n) = 37 := by
|
|
simp? [ha]
|
|
|
|
example (a : Nat) (ha : a = 37) (hb : b = 37) :
|
|
(match (generalizing := false) h : a with | 42 => by simp_all | n => n) = b := by
|
|
simp only [ha, Nat.reduceEqDiff, imp_self]
|
|
guard_target =ₛ 37 = b
|
|
rw [hb]
|
|
|
|
/--
|
|
info: Try this:
|
|
[apply] simp only [ha]
|
|
-/
|
|
#guard_msgs in
|
|
example (a : Nat) (ha : a = 37) :
|
|
(match a with | 42 => by simp_all | n => n) = 37 := by
|
|
simp? [ha]
|
|
|
|
example (a : Nat) (ha : a = 37) (hb : b = 37) :
|
|
(match a with | 42 => by simp_all | n => n) = b := by
|
|
simp only [ha]
|
|
guard_target =ₛ 37 = b
|
|
rw [hb]
|