diff --git a/core/Array.carp b/core/Array.carp
index a18e8853..a952dd71 100644
--- a/core/Array.carp
+++ b/core/Array.carp
@@ -105,6 +105,7 @@ Returns `Nothing` if the array is empty.")
               (set! eq false)
               (break))))
         eq)))
+   (implements = Array.=)
 
   (doc maximum "gets the maximum in an array (elements must support `<`) and wraps it in a `Just`.
 
@@ -144,6 +145,7 @@ If the array is empty, returns `Nothing`")
       (for [i start-index end-index]
         (set! result (push-back result @(unsafe-nth xs i))))
       result))
+  (implements slice Array.slice)
 
   (doc prefix "gets a prefix array to `end-index`.")
   (defn prefix [xs end-index]
diff --git a/core/Bool.carp b/core/Bool.carp
index dbaed50b..edb64ad3 100644
--- a/core/Bool.carp
+++ b/core/Bool.carp
@@ -13,6 +13,8 @@
 
 (defmodule RefBool
   (defn = [a b]
-    (Bool.= @a @b)))
+    (Bool.= @a @b))
+  (implements = RefBool.=)
+  )
 
 (defn not [a] (Bool.not a))
diff --git a/core/Char.carp b/core/Char.carp
index 73150cfb..bc514cc0 100644
--- a/core/Char.carp
+++ b/core/Char.carp
@@ -58,11 +58,15 @@
 (defmodule CharRef
   (defn = [a b]
     (Char.= @a @b))
+  (implements = CharRef.=)
   (defn < [a b]
     (Char.< @a @b))
+  (implements < CharRef.<)
   (defn > [a b]
     (Char.> @a @b))
+  (implements > CharRef.>)
 )
 
 (defmodule PtrChar
-  (register str (Fn [(Ptr Char)] String)))
+  (register str (Fn [(Ptr Char)] String))
+  (implements str PtrChar.str))
diff --git a/core/Collection.carp b/core/Collection.carp
index be4b0038..aff8abd1 100644
--- a/core/Collection.carp
+++ b/core/Collection.carp
@@ -1,5 +1,9 @@
 (definterface unsafe-nth (Fn [(Ref (a b) c) Int] &b))
+(implements unsafe-nth Array.unsafe-nth)
+(implements unsafe-nth StaticArray.unsafe-nth)
 (definterface length (Fn [(Ref (a b))] Int))
+(implements unsafe-nth Array.length)
+(implements unsafe-nth StaticArray.length)
 
 (defmodule Collections
   (defn empty? [a] 
diff --git a/core/Color.carp b/core/Color.carp
index 5cbe6823..50d3b247 100644
--- a/core/Color.carp
+++ b/core/Color.carp
@@ -27,8 +27,10 @@
   (use Id)
   (defn hash [k]
     (get-tag k))
+  (implements hash Color.hash)
   (defn = [a b]
     (= (hash (the (Ref Id) a)) (hash b)))
+  (implements = Color.=)
 
   (def table
     {(Black) @"30"
diff --git a/core/Double.carp b/core/Double.carp
index 3abd2ad0..0711ed44 100644
--- a/core/Double.carp
+++ b/core/Double.carp
@@ -68,7 +68,8 @@
   (implements floor Double.floor)
   (implements frexp Double.frexp)
   (implements ldexp Double.ldexp)
-  (implements log Double.log10)
+  (implements log Double.log)
+  (implements log10 Double.log10)
   (implements mod Double.mod)
   (implements modf Double.modf)
   (implements pow Double.pow)
@@ -95,7 +96,7 @@ The margin of error is `0.00001`.")
 
   (defn dec [x]
     (- x 1.0))
-  (implements inc Double.dec)
+  (implements dec Double.dec)
 
   (defn add-ref [x y]
     (Double.+ @x @y))
@@ -105,10 +106,13 @@ The margin of error is `0.00001`.")
 (defmodule DoubleRef
   (defn = [a b]
     (Double.= @a @b))
+  (implements = DoubleRef.=)
 
   (defn < [a b]
     (Double.< @a @b))
+  (implements < DoubleRef.<)
 
   (defn > [a b]
     (Double.> @a @b))
+  (implements > DoubleRef.>)
 )
diff --git a/core/Float.carp b/core/Float.carp
index 16ef1851..c4527e83 100644
--- a/core/Float.carp
+++ b/core/Float.carp
@@ -79,7 +79,8 @@ The margin of error is 0.00001.")
   (implements floor Float.floor)
   (implements frexp Float.frexp)
   (implements ldexp Float.ldexp)
-  (implements log Float.log10)
+  (implements log Float.log)
+  (implements log10 Float.log10)
   (implements mod Float.mod)
   (implements modf Float.modf)
   (implements pow Float.pow)
diff --git a/core/Int.carp b/core/Int.carp
index 1db8607c..7859f637 100644
--- a/core/Int.carp
+++ b/core/Int.carp
@@ -95,10 +95,13 @@
 (defmodule IntRef
   (defn = [a b]
     (Int.= @a @b))
+  (implements = IntRef.=)
 
   (defn < [a b]
     (Int.< @a @b))
+  (implements < IntRef.<)
 
   (defn > [a b]
     (Int.> @a @b))
+  (implements > IntRef.>)
 )
diff --git a/core/Map.carp b/core/Map.carp
index 730e19b4..7f879e57 100644
--- a/core/Map.carp
+++ b/core/Map.carp
@@ -11,66 +11,82 @@
           (set! a (* a b))
           (set! x (Int.inc x))))
       (Int.abs vh)))
+   (implements hash String.hash)
 )
 
 (defmodule Int
   (defn hash [k] (the Int @k))
+   (implements hash Int.hash)
 )
 
 (defmodule Long
   (defn hash [k] (to-int (the Long @k)))
+   (implements hash Long.hash)
 )
 
 (defmodule Bool
   (defn hash [k] (if (the Bool @k) 1 0))
+  (implements hash Bool.hash)
 )
 
 (defmodule Char
   (defn hash [k] (to-int (the Char @k)))
+  (implements hash Char.hash)
 )
 
 (defmodule Byte
   (defn hash [k] (to-int (the Byte @k)))
+  (implements hash Byte.hash)
 )
 
 (defmodule Float
   (defn hash [k] (Float.to-bytes @k))
+  (implements hash Float.hash)
 )
 
 (defmodule Double
   (defn hash [k] (Long.to-int (Double.to-bytes @k)))
+  (implements hash Double.hash)
 )
 
 (defmodule Int8
   (defn hash [k] (Long.to-int (Int8.to-long @k)))
+  (implements hash Int8.hash)
 )
 
 (defmodule Int16
   (defn hash [k] (Long.to-int (Int16.to-long @k)))
+  (implements hash Int16.hash)
 )
 
 (defmodule Int32
   (defn hash [k] (Long.to-int (Int32.to-long @k)))
+  (implements hash Int32.hash)
 )
 
 (defmodule Int64
   (defn hash [k] (Long.to-int (Int64.to-long @k)))
+  (implements hash Int64.hash)
 )
 
 (defmodule Uint8
   (defn hash [k] (Long.to-int (Uint8.to-long @k)))
+  (implements hash Uint8.hash)
 )
 
 (defmodule Uint16
   (defn hash [k] (Long.to-int (Uint16.to-long @k)))
+  (implements hash Uint16.hash)
 )
 
 (defmodule Uint32
   (defn hash [k] (Long.to-int (Uint32.to-long @k)))
+  (implements hash Uint32.hash)
 )
 
 (defmodule Uint64
   (defn hash [k] (Long.to-int (Uint64.to-long @k)))
+  (implements hash Uint64.hash)
 )
 
 (defmodule Pair
@@ -79,6 +95,7 @@
       (set! code (+ (* 31 code) (hash (Pair.a pair))))
       (set! code (+ (* 31 code) (hash (Pair.b pair))))
       code))
+  (implements hash Pair.hash)
 )
 
 (deftype (Bucket a b) [entries (Array (Pair a b))])
@@ -261,6 +278,7 @@
     (and (= (length m1) (length m2))
          ;; we could use contains? and get-with-default here to avoid requiring a (zero) for the value type
          (all? &(fn [k v] (= v &(get m2 k))) m1)))
+  (implements = Map.=)
 
   (doc for-each "Execute the binary function f for all keys and values in the map m.")
   (defn for-each [m f]
@@ -449,6 +467,7 @@
   (defn = [set-a set-b]
     (and (= (Set.length set-a) (Set.length set-b))
          (subset? set-a set-b)))
+  (implements = Set.=)
 
   (doc for-each "Execute the unary function f for each element in the set s.")
   (defn for-each [s f]
@@ -507,4 +526,5 @@
                       @"{"
                       set)]
       (String.append &res " }")))
+  (implements str Set.str)
 )
diff --git a/core/Maybe.carp b/core/Maybe.carp
index 231d0631..1431bfae 100644
--- a/core/Maybe.carp
+++ b/core/Maybe.carp
@@ -51,6 +51,7 @@ It is the inverse of [`just?`](#just?).")
         (match-ref b
           (Nothing) false
           (Just y) (= x y))))
+  (implements = Maybe.=)
 
   (doc unsafe-ptr "Creates a `(Ptr a)` from a `(Maybe a)`. If the `Maybe` was
 `Nothing`, this function will return a `NULL` value.")
@@ -69,4 +70,5 @@ It is the inverse of [`just?`](#just?).")
 
   (doc zero "returns `Nothing`.")
   (defn zero [] (Nothing))
+  (implements zero Maybe.zero)
 )
diff --git a/core/Pattern.carp b/core/Pattern.carp
index ac2406df..6a849b87 100644
--- a/core/Pattern.carp
+++ b/core/Pattern.carp
@@ -29,12 +29,16 @@ If you want to replace all occurrences of the pattern, use `-1`.")
   (defn matches? [pat s] (/= (find pat s) -1))
 
   (register str (Fn [&Pattern] String))
+  (implements str Pattern.str)
   (register prn (Fn [&Pattern] String))
+  (implements prn Pattern.prn)
 
   (register init (Fn [&String] Pattern))
   (register =    (Fn [&Pattern &Pattern] Bool))
+  (implements = Pattern.=)
   (register delete     (Fn [Pattern] ()))
   (register copy       (Fn [&Pattern] Pattern))
+  (implements copy Pattern.copy)
 
   (doc from-chars "creates a pattern that matches a group of characters from a list of those characters.")
   (defn from-chars [chars]
diff --git a/core/Pointer.carp b/core/Pointer.carp
index e175ba03..30e93032 100644
--- a/core/Pointer.carp
+++ b/core/Pointer.carp
@@ -1,4 +1,6 @@
 (defmodule Pointer
   (defn inc [a] (Pointer.add a 1l))
+  (implements inc Pointer.inc)
   (defn dec [a] (Pointer.sub a 1l))
+  (implements dec Pointer.dec)
 )
diff --git a/core/Result.carp b/core/Result.carp
index f9b69c8e..41fec174 100644
--- a/core/Result.carp
+++ b/core/Result.carp
@@ -106,6 +106,7 @@ It is the inverse of [`success?`](#success?).")
         (match-ref b
           (Success _) false
           (Error y) (= x y))))
+  (implements = Result.=)
 )
 
 (defmodule Maybe
diff --git a/core/StdInt.carp b/core/StdInt.carp
index b2de6c73..3dfe354b 100644
--- a/core/StdInt.carp
+++ b/core/StdInt.carp
@@ -50,6 +50,9 @@
   (defn prn [a] (Int8.prn @a))
   (defn str [a] (Int8.str @a))
   (defn = [a b] (Int8.= @a @b))
+  (implements prn Int8Extra.prn)
+  (implements str Int8Extra.str)
+  (implements = Int8Extra.=)
 )
 
 (defmodule Int16
@@ -93,6 +96,9 @@
   (defn prn [a] (Int16.prn @a))
   (defn str [a] (Int16.str @a))
   (defn = [a b] (Int16.= @a @b))
+  (implements prn Int16Extra.prn)
+  (implements str Int16Extra.str)
+  (implements = Int16Extra.=)
 )
 
 (defmodule Int32
@@ -136,6 +142,9 @@
   (defn prn [a] (Int32.prn @a))
   (defn str [a] (Int32.str @a))
   (defn = [a b] (Int32.= @a @b))
+  (implements prn Int32Extra.prn)
+  (implements str Int32Extra.str)
+  (implements = Int32Extra.=)
 )
 
 (defmodule Int64
@@ -179,6 +188,9 @@
   (defn prn [a] (Int64.prn @a))
   (defn str [a] (Int64.str @a))
   (defn = [a b] (Int64.= @a @b))
+  (implements prn Int64Extra.prn)
+  (implements str Int64Extra.str)
+  (implements = Int64Extra.=)
 )
 
 (defmodule Uint8
@@ -222,6 +234,9 @@
   (defn prn [a] (Uint8.prn @a))
   (defn str [a] (Uint8.str @a))
   (defn = [a b] (Uint8.= @a @b))
+  (implements prn Uint8Extra.prn)
+  (implements str Uint8Extra.str)
+  (implements = Uint8Extra.=)
 )
 
 (defmodule Uint16
@@ -265,6 +280,9 @@
   (defn prn [a] (Uint16.prn @a))
   (defn str [a] (Uint16.str @a))
   (defn = [a b] (Uint16.= @a @b))
+  (implements prn Uint16Extra.prn)
+  (implements str Uint16Extra.str)
+  (implements = Uint16Extra.=)
 )
 
 (defmodule Uint32
@@ -308,6 +326,9 @@
   (defn prn [a] (Uint32.prn @a))
   (defn str [a] (Uint32.str @a))
   (defn = [a b] (Uint32.= @a @b))
+  (implements prn Uint32Extra.prn)
+  (implements str Uint32Extra.str)
+  (implements = Uint32Extra.=)
 )
 
 (defmodule Uint64
@@ -351,4 +372,7 @@
   (defn prn [a] (Uint64.prn @a))
   (defn str [a] (Uint64.str @a))
   (defn = [a b] (Uint64.= @a @b))
+  (implements prn Uint64Extra.prn)
+  (implements str Uint64Extra.str)
+  (implements = Uint64Extra.=)
 )
diff --git a/core/String.carp b/core/String.carp
index 098b8f98..17b89c48 100644
--- a/core/String.carp
+++ b/core/String.carp
@@ -20,6 +20,7 @@
   (register from-chars (Fn [&(Array Char)] String))
   (register tail (λ [(Ref String)] String))
   (register format (Fn [&String &String] String))
+  (implements format String.format)
   (register string-set! (Fn [&String Int Char] ()))
   (register string-set-at! (Fn [&String Int &String] ()))
   (register allocate (Fn [Int Char] String))
@@ -171,14 +172,15 @@
 
   (defn < [a b]
     (String.< &a &b))
-  (implements = StringCopy.<)
+  (implements < StringCopy.<)
 
   (defn > [a b]
     (String.> &a &b))
-  (implements = StringCopy.>)
+  (implements > StringCopy.>)
 
   (defn prn [s]
     (prn &(the String s)))
+  (implements prn StringCopy.prn)
 
   (defn str [s]
     (str &(the String s)))
@@ -187,12 +189,14 @@
 
 (defmodule Bool
   (register str (Fn [Bool] String))
+  (implements str Bool.str)
   (register format (Fn [&String Bool] String))
   (implements format Bool.format)
 )
 
 (defmodule Int
   (register str (Fn [Int] String))
+  (implements str Int.str)
   (register format (Fn [&String Int] String))
   (implements format Int.format)
   (register from-string (λ [&String] Int))
@@ -201,6 +205,7 @@
 
 (defmodule Byte
   (register str (Fn [Byte] String))
+  (implements str Byte.str)
   (register format (Fn [&String Byte] String))
   (implements format Byte.format)
   (register from-string (λ [&String] Byte))
@@ -209,6 +214,7 @@
 
 (defmodule Float
   (register str (Fn [Float] String))
+  (implements str Float.str)
   (register format (Fn [&String Float] String))
   (implements format Float.format)
   (register from-string (λ [&String] Float))
@@ -217,6 +223,7 @@
 
 (defmodule Long
   (register str (Fn [Long] String))
+  (implements str Long.str)
   (register format (Fn [&String Long] String))
   (implements format Long.format)
   (register from-string (λ [&String] Long))
@@ -225,6 +232,7 @@
 
 (defmodule Double
   (register str (Fn [Double] String))
+  (implements str Double.str)
   (register format (Fn [&String Double] String))
   (implements format Double.format)
   (register from-string (λ [&String] Double))
@@ -233,6 +241,7 @@
 
 (defmodule Char
   (register str (Fn [Char] String))
+  (implements str Char.str)
   (register prn (Fn [Char] String))
   (implements prn Char.prn)
   (register format (Fn [&String Char] String))
@@ -245,17 +254,21 @@
   (defn prn [x] (Int.str @x))
   (implements prn IntRef.prn)
   (defn str [x] (Int.str @x))
+  (implements str IntRef.str)
   )
 
 (defmodule BoolRef
   (defn prn [x] (Bool.str @x))
   (implements prn BoolRef.prn)
-  (defn str [x] (Bool.str @x)))
+  (defn str [x] (Bool.str @x))
+  (implements str BoolRef.str)
+  )
 
 (defmodule ByteRef
   (defn prn [x] (Byte.str @x))
   (implements prn ByteRef.prn)
   (defn str [x] (Byte.str @x))
+  (implements str ByteRef.str)
   )
 
 (defmodule Long (defn prn [x] (Long.str x)) (implements prn Long.prn))
diff --git a/core/Tuples.carp b/core/Tuples.carp
index cd6fd832..738665ca 100644
--- a/core/Tuples.carp
+++ b/core/Tuples.carp
@@ -4,14 +4,17 @@
   (defn = [p1 p2]
     (and (= (Pair.a p1) (Pair.a p2))
          (= (Pair.b p1) (Pair.b p2))))
+  (implements = PairRef.=)
 
   (defn < [p1 p2]
     (if (= (Pair.a p1) (Pair.a p2))
       (< (Pair.b p1) (Pair.b p2))
       (< (Pair.a p1) (Pair.a p2))))
+  (implements < PairRef.<)
 
   (defn > [p1 p2]
     (PairRef.< p2 p1)))
+  (implements > PairRef.=)
 
 (defmodule Pair
   (defn init-from-refs [r1 r2]
@@ -20,12 +23,15 @@
   (defn = [p1 p2]
     (and (= (Pair.a &p1) (Pair.a &p2))
          (= (Pair.b &p1) (Pair.b &p2))))
+  (implements = Pair.=)
 
   (defn < [p1 p2]
     (PairRef.< &p1 &p2))
+  (implements < Pair.<)
 
   (defn > [p1 p2]
     (PairRef.> &p1 &p2))
+  (implements > Pair.>)
 
   (doc reverse "reverses a `Pair` `p` such that its first member is its second member and vice versa.")
   (defn reverse [p]
diff --git a/examples/functor.carp b/examples/functor.carp
index 56052b58..68c904a2 100644
--- a/examples/functor.carp
+++ b/examples/functor.carp
@@ -7,13 +7,15 @@
 
 (defmodule ArrayExtension
   (defn fmap [f a] (Array.endo-map f a))
+  (implements fmap ArrayExtension.fmap)
   )
 
 (deftype Box [x Int])
 
 (defmodule Box
   (defn fmap [f box] (let [new-x (~f @(Box.x &box))]
-                       (Box.set-x box new-x))))
+                       (Box.set-x box new-x)))
+  (implements fmap Box.fmap))
 
 (use Box)
 (use ArrayExtension)
diff --git a/examples/sorting.carp b/examples/sorting.carp
index 24451b06..16f07c37 100644
--- a/examples/sorting.carp
+++ b/examples/sorting.carp
@@ -9,7 +9,12 @@
   (defn > [a b]
     (> (Age.x a) (Age.x b)))
   (defn < [a b]
-    (< (Age.x a) (Age.x b))))
+    (< (Age.x a) (Age.x b)))
+
+  (implements = Age.=)
+  (implements > Age.>)
+  (implements < Age.<)
+  )
 
 (defn main []
   (let-do [ints (Array.sort [10 3 75 40])
diff --git a/test/memory.carp b/test/memory.carp
index 6a33950b..4733ef89 100644
--- a/test/memory.carp
+++ b/test/memory.carp
@@ -291,9 +291,11 @@
   (defn < [a b]
     (< (Array.length a)
        (Array.length b)))
+  (implements < ArrayCompareExtension.<)
   (defn > [a b]
     (> (Array.length a)
        (Array.length b))))
+  (implements > ArrayCompareExtension.>)
 (defn array-sort-1 []
   (let [xs [[0 0] [0 0 0] [0 0 0 0] [0]]
         ys (Array.sort xs)]
diff --git a/test/nested.carp b/test/nested.carp
index dc5a9b78..1f042cf5 100644
--- a/test/nested.carp
+++ b/test/nested.carp
@@ -15,11 +15,13 @@
 ;; A function with correct nr of args but just generic types used to really confuse the type checker:
 (defmodule Confuse
   (defn = [a b]
-    true))
+    true)
+  (implements = Confuse.=))
 
 (defmodule Young
   (defn = [y1 y2]
-    (Int.= @(age y1) @(age y2))))
+    (Int.= @(age y1) @(age y2)))
+  (implements = Young.=))
 
 ;; Now I want to use 'Young.=' in with 'Ur.compare'
 (defn f []