add prelude test

tests/python/relay/test_type_infer.py

@@ -399,6 +399,54 @@ def body(var, call_func):
     tvm.ir.assert_structural_equal(mod[f_gv].checked_type, expected)
     tvm.ir.assert_structural_equal(mod[g_gv].checked_type, expected)
 
+def test_mutual_recursion_list_sum():
+    # f[A](x: List[A]) = match x {
+    #   Cons(a, Nil) => a
+    #   Cons(_, b) => g(b)
+    # }
+    # g[B](y: List[B]) = match y {
+    #   Cons(a, Nil) => a
+    #   Cons(_, b) => f(b)
+    # }
+    p = Prelude()
+    l = p.l
+    A = relay.TypeVar("x")
+    B = relay.TypeVar("y")
+
+    x = relay.Var("x", l(A))
+    y = relay.Var("y", l(B))
+
+    f_gv = relay.GlobalVar('f')
+    g_gv = relay.GlobalVar('g')
+
+    def body(var, call_func, type_param):
+        a = relay.Var("a")
+        b = relay.Var("b")
+        body = relay.Match(
+            var, 
+            [
+                relay.Clause(relay.PatternConstructor(p.cons, [relay.PatternVar(a), relay.PatternConstructor(p.nil)]), a),
+                relay.Clause(relay.PatternConstructor(p.cons, [relay.PatternWildcard(), relay.PatternVar(b)]), relay.Call(call_func, [b]))
+            ],
+            complete=False
+        )
+        func = relay.Function([var], body, type_params=type_param)
+        return func
+
+    f = body(x, g_gv, [A])
+    g = body(y, f_gv, [B])
+
+    mod = p.mod
+    mod.add_unchecked(f_gv, f)
+    mod.add_unchecked(g_gv, g)
+    mod = transform.InferTypeAll()(mod)
+
+    tv = relay.TypeVar("test")
+    expected = relay.FuncType([l(tv)], tv, [tv])
+    tvm.ir.assert_structural_equal(mod[f_gv].checked_type, expected)
+    tvm.ir.assert_structural_equal(mod[g_gv].checked_type, expected)
+
+
 def test_id_mutual():
     # f(x) = g(x)
     # g(y) = f(y)
@@ -455,4 +503,4 @@ def test_if():
     # test_let_polymorphism()
     # test_if()
     # test_id_mutual()
-    test_mutual_recursion2()
+    test_mutual_recursion_list_sum()