1 files changed, 77 insertions, 0 deletions
diff --git a/test-suite/complexity/evars_subst.v b/test-suite/complexity/evars_subst.v
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index 0000000000..58a09dd3f6
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+++ b/test-suite/complexity/evars_subst.v
@@ -0,0 +1,77 @@
+(* Bug report #932 *)
+(* Expected time < 1.00s *)
+
+(* Let n be the number of let-in. The complexity comes from the fact
+that each implicit arguments of f was in a larger and larger
+context. To compute the type of "let _ := f ?Tn 0 in f ?T 0", "f ?Tn
+0" is substituted in the type of "f ?T 0" which is ?T. This type is an
+evar instantiated on the n variables denoting the "f ?Ti 0".  One
+obtain "?T[1;...;n-1;f ?Tn[1;...;n-1] 0]". To compute the type of "let
+_ := f ?Tn-1 0 in let _ := f ?Tn 0 in f ?T 0", another substitution is
+done leading to ?T[1;...;n-2;f ?Tn[1;...;n-2] 0;f ?Tn[1;...;n-2;f
+?Tn[1;...;n-2] 0] 0]" and so on. At the end, we get a term of
+exponential size *)
+
+(* A way to cut the complexity is to remove the dependency in
+   anonymous variables in evars; another approach would be to
+   substitute lazily and/or to simultaneously substitute let binders
+   and evars *)
+
+Variable P : Set -> Set.
+Variable f : forall A : Set, A -> P A.
+
+Check
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+ 
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+ 
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+  let _ := f _ 0 in
+
+    f _ 0.
+