[ssr] avoid HO unif when doing truncation analysis

Eliminators can be:
- dependent: ... -> forall x (y : I x), P x y
- truncated: ... -> forall x (y : I x), P x
- funind like: ..-> forall x, P t
The user may provide a term t in `elim: t`
- t may be the last argument
- t may be the last "pattern" (standing for the last
argument of P)

We use unification to see if t (and its type) fits
in one of these cases (and/or to infer t).

This patch refuses to use unification in the HO case
eg `?T a = t` since the result is too often a false
positive.

1 files changed, 29 insertions, 0 deletions

diff --git a/test-suite/ssr/elim_noquant.v b/test-suite/ssr/elim_noquant.v
new file mode 100644
index 0000000000..e6662203e9
--- /dev/null
+++ b/test-suite/ssr/elim_noquant.v
@@ -0,0 +1,29 @@
+Require Import ssreflect.
+
+
+Axiom app : forall T, list T -> list T -> list T.
+Arguments app {_}.
+Infix "++" := app.
+
+Lemma test (aT rT : Type)
+           (pmap : (aT -> option rT) -> list aT -> list rT)
+           (perm_eq : list rT -> list rT -> Prop)
+           (f : aT -> option rT)
+           (g : rT -> aT)
+           (s t : list aT)
+           (E : forall T : list aT -> Type,
+               (forall s1 s2 s3 : list aT,
+                  T (s1 ++ s2 ++ s3) -> T (s2 ++ s1 ++ s3)) ->
+                 T s -> T t) :
+        perm_eq (pmap f s) (pmap f t).
+Proof.
+elim/E: (t).
+Admitted.
+
+
+Lemma test2 (a b : nat) : a = b -> b = 1.
+Proof.
+elim.
+match goal with |- a = 1 => idtac end.
+Admitted.
+