diff --git a/toy-impl/examples/a.py b/toy-impl/examples/a.py
index 11616ff..3b65f29 100644
--- a/toy-impl/examples/a.py
+++ b/toy-impl/examples/a.py
@@ -13,6 +13,9 @@ class Vec:
         else:
             return Vec([self.v[i] + other.v[i] for i in range(len(self.v))])
 
+    def get(self, index: int32) -> int32:
+        return self.v.head()
+
 
 T = TypeVar('T', int32, list[int32])
 
diff --git a/toy-impl/inference.py b/toy-impl/inference.py
index 0195f80..02af224 100644
--- a/toy-impl/inference.py
+++ b/toy-impl/inference.py
@@ -88,8 +88,10 @@ def resolve_call(obj,
     # TODO: we may want to return the substitution, for monomorphization...
     f_args = None
     f_result = None
+    subst = {}
     if obj is not None:
         obj = obj.subst(assumptions)
+        subst = obj.get_subst()
     if obj is None:
         if fn in ctx.functions:
             f = ctx.functions[fn]
@@ -107,7 +109,8 @@ def resolve_call(obj,
                 f_args, f_result = TupleType([]), c
         else:
             raise CustomError(f"No such function {fn}")
-    elif isinstance(obj, PrimitiveType) or isinstance(obj, ClassType):
+    elif isinstance(obj, PrimitiveType) or isinstance(obj, ClassType) \
+            or isinstance(obj, ParametricType):
         if fn in obj.methods:
             f = obj.methods[fn]
             if len(f[0]) == 0 or (not isinstance(f[0][0], SelfType) and \
@@ -154,7 +157,7 @@ def resolve_call(obj,
         raise CustomError("Divergent type after constraints substitution")
 
     a = TupleType(args)
-    subst = find_subst(assumptions, {}, a, f_args)
+    subst = find_subst(assumptions, subst, a, f_args)
     if isinstance(subst, str):
         raise CustomError(f"type check failed: {subst}")
     result = f_result.subst(subst)
diff --git a/toy-impl/primitives.py b/toy-impl/primitives.py
index 5b3edd6..e609a7f 100644
--- a/toy-impl/primitives.py
+++ b/toy-impl/primitives.py
@@ -66,6 +66,11 @@ i32.methods['__init__'] = ([SelfType(), I], None, {'I'})
 i64.methods['__init__'] = ([SelfType(), I], None, {'I'})
 f32.methods['__init__'] = ([SelfType(), I], None, {'I'})
 
+ParametricType.method_table['list'] = {
+    'get': ([SelfType(), i32], TypeVariable('T1', []), set()),
+    'head': ([SelfType()], TypeVariable('T1', []), set())
+}
+
 simplest_ctx = Context({}, types)
 simplest_ctx.functions['len'] = ([ListType(A)], i32, {'A'})
 simplest_ctx.functions['range'] = ([i32], ListType(i32), set())
diff --git a/toy-impl/type_def.py b/toy-impl/type_def.py
index 024000b..47b2e58 100644
--- a/toy-impl/type_def.py
+++ b/toy-impl/type_def.py
@@ -23,6 +23,9 @@ class Type:
                 return tv
         return self
 
+    def get_subst(self):
+        return {}
+
 
 class BotType:
     def __eq__(self, other):
@@ -113,10 +116,16 @@ class VirtualClassType(Type):
 
 class ParametricType(Type):
     params: list[Type]
+    name: str
 
-    def __init__(self, params: list[Type]):
+    method_table = {}
+
+    def __init__(self, name, params: list[Type]):
         super().__init__()
         self.params = params
+        self.name = name
+        if name in ParametricType.method_table:
+            self.methods = ParametricType.method_table[name]
 
     def __eq__(self, other):
         if type(self) != type(other) or len(self.params) != len(other.params):
@@ -148,9 +157,12 @@ class ParametricType(Type):
         s.params = [v.inv_subst(subst) for v in self.params]
         return s
 
+    def get_subst(self):
+        return {f'T{i + 1}': v for i, v in enumerate(self.params)}
+
 class ListType(ParametricType):
     def __init__(self, param: Type):
-        super().__init__([param])
+        super().__init__('list', [param])
 
     def __str__(self):
         return f"list[{self.params[0]}]"
@@ -158,7 +170,7 @@ class ListType(ParametricType):
 
 class TupleType(ParametricType):
     def __init__(self, params: list[Type]):
-        super().__init__(params)
+        super().__init__('tuple', params)
 
     def __str__(self):
         return f"tuple[{', '.join([str(v) for v in self.params])}]"