Added tree-shaking to the compiler.

21 files changed, 728 insertions, 353 deletions

diff --git a/documentation/bookmark/error_messages.md b/documentation/bookmark/error_messages.md
index 9ad8c04f2..f3b7a3120 100644
--- a/documentation/bookmark/error_messages.md
+++ b/documentation/bookmark/error_messages.md
@@ -1,4 +1,5 @@
 # Reference
 
+1. [Error Messages in Haskell, and how to Improve them](https://anthony.noided.media/blog/haskell/programming/2020/05/14/haskell-errors.html)
 1. [The Futhark Error Index](https://futhark-lang.org/blog/2021-09-24-the-futhark-error-index.html)
 
diff --git a/documentation/bookmark/scheduling.md b/documentation/bookmark/scheduling.md
new file mode 100644
index 000000000..1b09091b6
--- /dev/null
+++ b/documentation/bookmark/scheduling.md
@@ -0,0 +1,4 @@
+# Reference
+
+1. [The Many Uses of Schedulers](https://eruhinim.com/post/many-uses-of-schedulers/)
+
diff --git a/documentation/bookmark/tool/text_editor.md b/documentation/bookmark/tool/text_editor.md
index 2142fa0be..f835ab41f 100644
--- a/documentation/bookmark/tool/text_editor.md
+++ b/documentation/bookmark/tool/text_editor.md
@@ -169,6 +169,7 @@
 
 ## General
 
+1. https://texteditors.org/cgi-bin/wiki.pl?EditorIndex
 1. [Slate: A completely customizable framework for building rich text editors.](https://github.com/ianstormtaylor/slate)
 1. [Trix: A rich text editor for everyday writing.](https://trix-editor.org/)
 1. [Left](https://100r.co/site/left.html)
diff --git a/lux-jvm/source/luxc/lang/directive/jvm.lux b/lux-jvm/source/luxc/lang/directive/jvm.lux
index 60032010d..3c384b475 100644
--- a/lux-jvm/source/luxc/lang/directive/jvm.lux
+++ b/lux-jvm/source/luxc/lang/directive/jvm.lux
@@ -20,7 +20,8 @@
       [array {"+" Array}]
       ["[0]" list ("[1]#[0]" mix functor monoid)]
       ["[0]" dictionary {"+" Dictionary}]
-      ["[0]" sequence {"+" Sequence} ("[1]#[0]" functor mix)]]]
+      ["[0]" sequence {"+" Sequence} ("[1]#[0]" functor mix)]
+      ["[0]" set {"+" Set}]]]
     [math
      [number
       ["[0]" nat]]]
@@ -28,7 +29,7 @@
      ["/" jvm
       [encoding
        ["[0]" name {"+" External}]]
-      ["[1][0]" type {"+" Type Constraint}
+      ["[1][0]" type {"+" Type Typed Constraint}
        [category {"+" Void Value Return Primitive Object Class Var Parameter}]
        ["[0]" parser]
        ["[0]T" lux]
@@ -54,7 +55,9 @@
           [directive
            ["[0]/" lux]]]]]]
       [meta
-       [archive {"+" Archive}]]]]]]
+       [archive {"+" Archive}
+        ["[0]" artifact]
+        ["[0]" dependency]]]]]]]
   [///
    [host
     ["[0]" jvm {"+" Inst}
@@ -692,7 +695,7 @@
 
 (type: (Constructor a)
   [Privacy Bit (List Annotation) (List (Type Var)) (List (Type Class))
-   Text (List Argument) (List [(Type Value) a])
+   Text (List Argument) (List (Typed a))
    a])
 
 (type: (Override a)
@@ -722,6 +725,35 @@
    {#Static (Static a)}
    {#Abstract Abstract}))
 
+(def: (method_dependencies archive method)
+  (-> Archive (Method Synthesis)
+      (generation.Operation jvm.Anchor jvm.Inst jvm.Definition
+                            (Set artifact.Dependency)))
+  (case method
+    {#Constructor [privacy strict_floating_point? annotations variables exceptions
+                   self arguments constructor_arguments
+                   body]}
+    (do [! phase.monad]
+      [all_super_ctor_dependencies (monad.each ! (|>> product.right (dependency.dependencies archive))
+                                               constructor_arguments)
+       body_dependencies (dependency.dependencies archive body)]
+      (in (dependency.all (list& body_dependencies all_super_ctor_dependencies))))
+    
+    
+    (^or {#Override [[parent_name parent_variables] name strict_floating_point? annotations variables
+                     self arguments return exceptions
+                     body]}
+         {#Virtual [name privacy final? strict_floating_point? annotations variables
+                    self arguments return exceptions
+                    body]}
+         {#Static [name privacy strict_floating_point? annotations variables
+                   arguments return exceptions
+                   body]})
+    (dependency.dependencies archive body)
+    
+    {#Abstract _}
+    (# phase.monad in artifact.no_dependencies)))
+
 (def: constructor
   (Parser (Constructor Code))
   (let [constructor_argument (: (Parser [(Type Value) Code])
@@ -1434,6 +1466,10 @@
          methodsA (monad.each ! (method_analysis archive declaration supers) methodsC)
          methodsS (monad.each ! (method_synthesis archive) methodsA)
          methodsG (monad.each ! (method_generation archive super_class) methodsS)
+         all_dependencies (|> methodsS
+                              (monad.each ! (method_dependencies archive))
+                              (# ! each dependency.all)
+                              directive.lifted_generation)
          .let [directive [class_name
                           (def.class {jvm.#V1_6} {jvm.#Public} jvm.noneC class_name
                                      (list#each ..constraint type_variables)
@@ -1443,7 +1479,7 @@
                                                                methodsG)))]]]
         (directive.lifted_generation
          (do !
-           [artifact_id (generation.learn_custom class_name)
+           [artifact_id (generation.learn_custom class_name all_dependencies)
             _ (generation.execute! directive)
             _ (generation.save! artifact_id {.#Some class_name} directive)
             _ (generation.log! (format "JVM Class " (%.text class_name)))]
@@ -1470,7 +1506,7 @@
                                              def.fuse))]]]
         (directive.lifted_generation
          (do !
-           [artifact_id (generation.learn_custom class_name)
+           [artifact_id (generation.learn_custom class_name artifact.no_dependencies)
             _ (generation.execute! directive)
             _ (generation.save! artifact_id {.#Some class_name} directive)
             _ (generation.log! (format "JVM Interface " (%.text class_name)))]
diff --git a/lux-jvm/source/luxc/lang/translation/jvm/extension/host.lux b/lux-jvm/source/luxc/lang/translation/jvm/extension/host.lux
index bbc8920f6..ee4096fe1 100644
--- a/lux-jvm/source/luxc/lang/translation/jvm/extension/host.lux
+++ b/lux-jvm/source/luxc/lang/translation/jvm/extension/host.lux
@@ -1,71 +1,73 @@
 (.using
-  [library
-   [lux {"-" Type Label Primitive int char type}
-    [ffi {"+" import:}]
-    [abstract
-     ["[0]" monad {"+" do}]]
-    [control
-     ["[0]" maybe ("[1]#[0]" functor)]
-     ["[0]" exception {"+" exception:}]
-     ["[0]" function]
-     ["<>" parser ("[1]#[0]" monad)
-      ["<[0]>" text]
-      ["<[0]>" synthesis {"+" Parser}]]]
-    [data
-     ["[0]" product]
-     ["[0]" text ("[1]#[0]" equivalence)
-      ["%" format {"+" format}]]
-     [collection
-      ["[0]" list ("[1]#[0]" monad mix)]
-      ["[0]" dictionary {"+" Dictionary}]
-      ["[0]" set]]]
-    [macro
-     ["[0]" template]]
-    [math
-     [number
-      ["n" nat]]]
-    [target
-     [jvm
-      ["[0]" type {"+" Type Typed Argument}
-       ["[0]" category {"+" Void Value Return Primitive Object Class Array Var Parameter Method}]
-       ["[0]" box]
-       ["[0]" reflection]
-       ["[0]" signature]
-       ["[0]" descriptor]
-       ["[0]" parser]]]]
-    [tool
-     [compiler
-      ["[0]" phase ("[1]#[0]" monad)]
-      [reference {"+" }
-       ["[0]" variable {"+" Variable Register}]]
-      [meta
-       [archive {"+" Archive}]]
-      [language
-       [lux
-        [analysis {"+" Environment}]
-        ["[0]" synthesis {"+" Synthesis Path %synthesis}]
-        ["[0]" generation]
-        [phase
-         [generation
-          [extension {"+" Nullary Unary Binary
-                      nullary unary binary}]]
+ [library
+  [lux {"-" Type Label Primitive int char type}
+   [ffi {"+" import:}]
+   [abstract
+    ["[0]" monad {"+" do}]]
+   [control
+    ["[0]" maybe ("[1]#[0]" functor)]
+    ["[0]" exception {"+" exception:}]
+    ["[0]" function]
+    ["<>" parser ("[1]#[0]" monad)
+     ["<[0]>" text]
+     ["<[0]>" synthesis {"+" Parser}]]]
+   [data
+    ["[0]" product]
+    ["[0]" text ("[1]#[0]" equivalence)
+     ["%" format {"+" format}]]
+    [collection
+     ["[0]" list ("[1]#[0]" monoid mix monad)]
+     ["[0]" dictionary {"+" Dictionary}]
+     ["[0]" set {"+" Set}]]]
+   [macro
+    ["[0]" template]]
+   [math
+    [number
+     ["n" nat]]]
+   [target
+    [jvm
+     ["[0]" type {"+" Type Typed Argument}
+      ["[0]" category {"+" Void Value Return Primitive Object Class Array Var Parameter Method}]
+      ["[0]" box]
+      ["[0]" reflection]
+      ["[0]" signature]
+      ["[0]" descriptor]
+      ["[0]" parser]]]]
+   [tool
+    [compiler
+     ["[0]" phase ("[1]#[0]" monad)]
+     [reference {"+" }
+      ["[0]" variable {"+" Variable Register}]]
+     [meta
+      [archive {"+" Archive}
+       ["[0]" artifact]
+       ["[0]" dependency]]]
+     [language
+      [lux
+       [analysis {"+" Environment}]
+       ["[0]" synthesis {"+" Synthesis Path %synthesis}]
+       ["[0]" generation]
+       [phase
+        [generation
+         [extension {"+" Nullary Unary Binary
+                     nullary unary binary}]]
+        [analysis
+         ["[0]A" reference]]
+        ["[0]" extension
+         ["[0]" bundle]
          [analysis
-          ["[0]A" reference]]
-         ["[0]" extension
-          ["[0]" bundle]
-          [analysis
-           ["/" jvm]]]]]]]]]]
-  [luxc
-   [lang
-    [host
-     ["$" jvm {"+" Label Inst Def Handler Bundle Operation Phase}
-      ["_" inst]
-      ["_[0]" def]]]]]
-  ["[0]" // "_"
-   [common {"+" custom}]
-   ["/[1]" //
-    ["[1][0]" reference]
-    ["[1][0]" function]]])
+          ["/" jvm]]]]]]]]]]
+ [luxc
+  [lang
+   [host
+    ["$" jvm {"+" Label Inst Def Handler Bundle Operation Phase}
+     ["_" inst]
+     ["_[0]" def]]]]]
+ ["[0]" // "_"
+  [common {"+" custom}]
+  ["/[1]" //
+   ["[1][0]" reference]
+   ["[1][0]" function]]])
 
 (template [<name> <category> <parser>]
   [(def: .public <name>
@@ -1073,6 +1075,13 @@
                   ... (# type.equivalence = type.double returnT)
                   (unwrap_primitive _.DRETURN type.double)))))))
 
+(def: (method_dependencies archive method)
+  (-> Archive (/.Overriden_Method Synthesis) (Operation (Set artifact.Dependency)))
+  (let [[_super _name _strict_fp? _annotations
+         _t_vars _this _arguments _return _exceptions
+         bodyS] method]
+    (dependency.dependencies archive bodyS)))
+
 (def: class::anonymous
   Handler
   (..custom
@@ -1086,72 +1095,86 @@
                                                   inputsTS
                                                   overriden_methods])
       (do [! phase.monad]
-        [[context _] (generation.with_new_context archive (in []))
-         .let [[module_id artifact_id] context
-               anonymous_class_name (///.class_name context)
-               class (type.class anonymous_class_name (list))
-               total_environment (|> overriden_methods
-                                     ... Get all the environments.
-                                     (list#each product.left)
-                                     ... Combine them.
-                                     list#conjoint
-                                     ... Remove duplicates.
-                                     (set.of_list synthesis.hash)
-                                     set.list)
-               global_mapping (|> total_environment
-                                  ... Give them names as "foreign" variables.
-                                  list.enumeration
-                                  (list#each (function (_ [id capture])
-                                               [capture {variable.#Foreign id}]))
-                                  (dictionary.of_list synthesis.hash))
-               normalized_methods (list#each (function (_ [environment
-                                                           [ownerT name
-                                                            strict_fp? annotations vars
-                                                            self_name arguments returnT exceptionsT
-                                                            body]])
-                                               (let [local_mapping (|> environment
-                                                                       list.enumeration
-                                                                       (list#each (function (_ [foreign_id capture])
-                                                                                    [(synthesis.variable/foreign foreign_id)
-                                                                                     (|> global_mapping
-                                                                                         (dictionary.value capture)
-                                                                                         maybe.trusted)]))
-                                                                       (dictionary.of_list synthesis.hash))]
-                                                 [ownerT name
-                                                  strict_fp? annotations vars
-                                                  self_name arguments returnT exceptionsT
-                                                  (normalize_method_body local_mapping body)]))
-                                             overriden_methods)]
-         inputsTI (monad.each ! (generate_input generate archive) inputsTS)
-         method_definitions (|> normalized_methods
-                                (monad.each ! (function (_ [ownerT name
-                                                            strict_fp? annotations varsT
-                                                            self_name arguments returnT exceptionsT
-                                                            bodyS])
-                                                (do !
-                                                  [bodyG (generation.with_context artifact_id
-                                                           (generate archive bodyS))
-                                                   .let [argumentsT (list#each product.right arguments)]]
-                                                  (in (_def.method {$.#Public}
-                                                                   (if strict_fp?
-                                                                     ($_ $.++M $.finalM $.strictM)
-                                                                     $.finalM)
-                                                                   name
-                                                                   (type.method [varsT argumentsT returnT exceptionsT])
-                                                                   (|>> (prepare_arguments 1 argumentsT)
-                                                                        bodyG
-                                                                        (returnI returnT)))))))
-                                (# ! each _def.fuse))
-         .let [directive [anonymous_class_name
-                          (_def.class {$.#V1_6} {$.#Public} $.finalC
-                                      anonymous_class_name (list)
-                                      super_class super_interfaces
-                                      (|>> (///function.with_environment total_environment)
-                                           (..with_anonymous_init class total_environment super_class inputsTI)
-                                           method_definitions))]]
-         _ (generation.execute! directive)
-         _ (generation.save! artifact_id {.#None} directive)]
-        (..anonymous_instance generate archive class total_environment)))]))
+        [all_input_dependencies (monad.each ! (|>> product.right (dependency.dependencies archive)) inputsTS)
+         all_closure_dependencies (|> overriden_methods
+                                      (list#each product.left)
+                                      list.together
+                                      (monad.each ! (dependency.dependencies archive)))
+         all_method_dependencies (monad.each ! (|>> product.right (method_dependencies archive)) overriden_methods)
+         .let [all_dependencies (dependency.all ($_ list#composite
+                                                    all_input_dependencies
+                                                    all_closure_dependencies
+                                                    all_method_dependencies))]]
+        (do [! phase.monad]
+          [[context _] (generation.with_new_context
+                         archive
+                         all_dependencies
+                         (in []))
+           .let [[module_id artifact_id] context
+                 anonymous_class_name (///.class_name context)
+                 class (type.class anonymous_class_name (list))
+                 total_environment (|> overriden_methods
+                                       ... Get all the environments.
+                                       (list#each product.left)
+                                       ... Combine them.
+                                       list#conjoint
+                                       ... Remove duplicates.
+                                       (set.of_list synthesis.hash)
+                                       set.list)
+                 global_mapping (|> total_environment
+                                    ... Give them names as "foreign" variables.
+                                    list.enumeration
+                                    (list#each (function (_ [id capture])
+                                                 [capture {variable.#Foreign id}]))
+                                    (dictionary.of_list synthesis.hash))
+                 normalized_methods (list#each (function (_ [environment
+                                                             [ownerT name
+                                                              strict_fp? annotations vars
+                                                              self_name arguments returnT exceptionsT
+                                                              body]])
+                                                 (let [local_mapping (|> environment
+                                                                         list.enumeration
+                                                                         (list#each (function (_ [foreign_id capture])
+                                                                                      [(synthesis.variable/foreign foreign_id)
+                                                                                       (|> global_mapping
+                                                                                           (dictionary.value capture)
+                                                                                           maybe.trusted)]))
+                                                                         (dictionary.of_list synthesis.hash))]
+                                                   [ownerT name
+                                                    strict_fp? annotations vars
+                                                    self_name arguments returnT exceptionsT
+                                                    (normalize_method_body local_mapping body)]))
+                                               overriden_methods)]
+           inputsTI (monad.each ! (generate_input generate archive) inputsTS)
+           method_definitions (|> normalized_methods
+                                  (monad.each ! (function (_ [ownerT name
+                                                              strict_fp? annotations varsT
+                                                              self_name arguments returnT exceptionsT
+                                                              bodyS])
+                                                  (do !
+                                                    [bodyG (generation.with_context artifact_id
+                                                             (generate archive bodyS))
+                                                     .let [argumentsT (list#each product.right arguments)]]
+                                                    (in (_def.method {$.#Public}
+                                                                     (if strict_fp?
+                                                                       ($_ $.++M $.finalM $.strictM)
+                                                                       $.finalM)
+                                                                     name
+                                                                     (type.method [varsT argumentsT returnT exceptionsT])
+                                                                     (|>> (prepare_arguments 1 argumentsT)
+                                                                          bodyG
+                                                                          (returnI returnT)))))))
+                                  (# ! each _def.fuse))
+           .let [directive [anonymous_class_name
+                            (_def.class {$.#V1_6} {$.#Public} $.finalC
+                                        anonymous_class_name (list)
+                                        super_class super_interfaces
+                                        (|>> (///function.with_environment total_environment)
+                                             (..with_anonymous_init class total_environment super_class inputsTI)
+                                             method_definitions))]]
+           _ (generation.execute! directive)
+           _ (generation.save! artifact_id {.#None} directive)]
+          (..anonymous_instance generate archive class total_environment))))]))
 
 (def: class_bundle
   Bundle
diff --git a/lux-jvm/source/luxc/lang/translation/jvm/function.lux b/lux-jvm/source/luxc/lang/translation/jvm/function.lux
index 6d2d3e8f9..7932360a3 100644
--- a/lux-jvm/source/luxc/lang/translation/jvm/function.lux
+++ b/lux-jvm/source/luxc/lang/translation/jvm/function.lux
@@ -33,7 +33,8 @@
         [synthesis {"+" Synthesis Abstraction Apply}]
         ["[0]" generation {"+" Context}]]]
       [meta
-       [archive {"+" Archive}]]]]]]
+       [archive {"+" Archive}
+        ["[0]" dependency]]]]]]]
   [luxc
    [lang
     [host
@@ -307,6 +308,7 @@
   (-> (Maybe Context) (Generator Abstraction))
   (do [! phase.monad]
     [@begin _.make_label
+     dependencies (dependency.dependencies archive bodyS)
      [function_context bodyI] (case forced_context
                                 {.#Some function_context}
                                 (do !
@@ -316,7 +318,7 @@
                                        without_context]))
                                 
                                 {.#None}
-                                (generation.with_new_context archive
+                                (generation.with_new_context archive dependencies
                                   (generation.with_anchor [@begin 1]
                                     (generate archive bodyS))))
      .let [function_class (//.class_name function_context)]
diff --git a/lux-jvm/source/luxc/lang/translation/jvm/runtime.lux b/lux-jvm/source/luxc/lang/translation/jvm/runtime.lux
index dc2cb5053..33cf199ea 100644
--- a/lux-jvm/source/luxc/lang/translation/jvm/runtime.lux
+++ b/lux-jvm/source/luxc/lang/translation/jvm/runtime.lux
@@ -11,7 +11,8 @@
       ["%" format {"+" format}]]
      [collection
       ["[0]" list ("[1]@[0]" functor)]
-      ["[0]" sequence]]]
+      ["[0]" sequence]
+      ["[0]" set]]]
     ["[0]" math
      [number
       ["n" nat]]]
@@ -411,10 +412,11 @@
      ... function_payload ..translate_function
      ]
     (in [(|> artifact.empty
-             artifact.resource
+             (artifact.resource true artifact.no_dependencies)
              product.right
-             artifact.resource
-             product.right)
+             ... (artifact.resource true artifact.no_dependencies)
+             ... product.right
+             )
          (sequence.sequence runtime_payload
                             ... function_payload
                             )])))
diff --git a/stdlib/commands.md b/stdlib/commands.md
index 37241c077..79982596b 100644
--- a/stdlib/commands.md
+++ b/stdlib/commands.md
@@ -36,8 +36,8 @@ cd ~/lux/stdlib/ && lein install
 cd ~/lux/stdlib/ && mvn install:install-file -Dfile=target/library.tar -DgroupId=com.github.luxlang -DartifactId=stdlib -Dversion=0.6.0-SNAPSHOT -Dpackaging=tar
 
 cd ~/lux/stdlib/ && mvn deploy:deploy-file \
--Durl=https://<username>:<password>@oss.sonatype.org/content/repositories/snapshots/ \
--Dfile=target/library.tar \
+-Durl=https://USERNAME:PASSWORD@oss.sonatype.org/content/repositories/snapshots/ \
+-Dfile=library.tar \
 -DgroupId=com.github.luxlang \
 -DartifactId=stdlib \
 -Dversion=0.6.5-SNAPSHOT \
diff --git a/stdlib/source/library/lux/data/collection/dictionary.lux b/stdlib/source/library/lux/data/collection/dictionary.lux
index ac9fe8002..ee7b7cb7d 100644
--- a/stdlib/source/library/lux/data/collection/dictionary.lux
+++ b/stdlib/source/library/lux/data/collection/dictionary.lux
@@ -534,29 +534,34 @@
     (array.size colls)
     ))
 
-(def: (node#entries node)
-  (All (_ k v) (-> (Node k v) (List [k v])))
+(def: (node#mix f init node)
+  (All (_ k v a) (-> (-> [k v] a a) a (Node k v) a))
   (case node
     {#Hierarchy _size hierarchy}
-    (array#mix (function (_ sub_node tail) (list#composite (node#entries sub_node) tail))
-               {.#End}
+    (array#mix (function (_ sub_node current)
+                 (node#mix f current sub_node))
+               init
                hierarchy)
 
     {#Base bitmap base}
-    (array#mix (function (_ branch tail)
+    (array#mix (function (_ branch current)
                  (case branch
                    {.#Left sub_node}
-                   (list#composite (node#entries sub_node) tail)
+                   (node#mix f current sub_node)
 
-                   {.#Right [key' val']}
-                   {.#Item [key' val'] tail}))
-               {.#End}
+                   {.#Right kv}
+                   (f kv current)))
+               init
                base)
     
     {#Collisions hash colls}
-    (array#mix (function (_ [key' val'] tail) {.#Item [key' val'] tail})
-               {.#End}
-               colls)))
+    (array#mix f init colls)))
+
+(def: node#entries
+  (All (_ k v) (-> (Node k v) (List [k v])))
+  (node#mix (function (_ head tail)
+              {.#Item head tail})
+            {.#End}))
 
 (type: .public (Dictionary k v)
   (Record
@@ -619,7 +624,7 @@
 
 (def: .public size
   (All (_ k v) (-> (Dictionary k v) Nat))
-  (|>> product.right ..node#size))
+  (|>> (value@ #root) ..node#size))
 
 (def: .public empty?
   (All (_ k v) (-> (Dictionary k v) Bit))
@@ -627,7 +632,7 @@
 
 (def: .public entries
   (All (_ k v) (-> (Dictionary k v) (List [k v])))
-  (|>> product.right ..node#entries))
+  (|>> (value@ #root) ..node#entries))
 
 (def: .public (of_list key_hash kvs)
   (All (_ k v) (-> (Hash k) (List [k v]) (Dictionary k v)))
@@ -639,8 +644,8 @@
 (template [<side> <name>]
   [(def: .public <name>
      (All (_ k v) (-> (Dictionary k v) (List <side>)))
-     (|>> ..entries
-          (list#mix (function (_ [k v] bundle)
+     (|>> (value@ #root)
+          (node#mix (function (_ [k v] bundle)
                       {.#Item <side> bundle})
                     {.#End})))]
 
@@ -650,13 +655,14 @@
 
 (def: .public (merged dict2 dict1)
   (All (_ k v) (-> (Dictionary k v) (Dictionary k v) (Dictionary k v)))
-  (list#mix (function (_ [key val] dict) (has key val dict))
+  (node#mix (function (_ [key val] dict)
+              (has key val dict))
             dict1
-            (entries dict2)))
+            (value@ #root dict2)))
 
 (def: .public (merged_with f dict2 dict1)
   (All (_ k v) (-> (-> v v v) (Dictionary k v) (Dictionary k v) (Dictionary k v)))
-  (list#mix (function (_ [key val2] dict)
+  (node#mix (function (_ [key val2] dict)
               (case (value key dict)
                 {.#None}
                 (has key val2 dict)
@@ -664,7 +670,7 @@
                 {.#Some val1}
                 (has key (f val2 val1) dict)))
             dict1
-            (entries dict2)))
+            (value@ #root dict2)))
 
 (def: .public (re_bound from_key to_key dict)
   (All (_ k v) (-> k k (Dictionary k v) (Dictionary k v)))
diff --git a/stdlib/source/library/lux/program.lux b/stdlib/source/library/lux/program.lux
index 0d9576d79..469aa68e6 100644
--- a/stdlib/source/library/lux/program.lux
+++ b/stdlib/source/library/lux/program.lux
@@ -1,19 +1,19 @@
 (.using
-  [library
-   [lux "*"
-    ["@" target]
-    [abstract
-     [monad {"+" do}]]
-    [control
-     ["[0]" io]
-     [concurrency
-      ["[0]" thread]]
-     ["<>" parser
-      ["<[0]>" code]
-      ["<[0]>" cli]]]
-    [macro {"+" with_symbols}
-     [syntax {"+" syntax:}]
-     ["[0]" code]]]])
+ [library
+  [lux "*"
+   ["@" target]
+   [abstract
+    [monad {"+" do}]]
+   [control
+    ["[0]" io]
+    [concurrency
+     ["[0]" thread]]
+    ["<>" parser
+     ["<[0]>" code]
+     ["<[0]>" cli]]]
+   [macro {"+" with_symbols}
+    [syntax {"+" syntax:}]
+    ["[0]" code]]]])
 
 (type: Arguments
   (Variant
@@ -28,15 +28,14 @@
 (syntax: .public (program: [args ..arguments^
                             body <code>.any])
   (with_symbols [g!program g!args g!_ g!output g!message]
-    (let [initialization+event_loop
-          (` ((~! do) (~! io.monad)
-              [(~ g!output) (~ body)
-               (~+ (for [@.old (list)
-                         @.jvm (list)
-                         @.js (list)
-                         @.python (list)]
-                        (list g!_ (` (~! thread.run!)))))]
-              ((~' in) (~ g!output))))]
+    (let [initialization+event_loop (for [@.old body
+                                          @.jvm body
+                                          @.js body
+                                          @.python body]
+                                         (` ((~! do) (~! io.monad)
+                                             [(~ g!output) (~ body)
+                                              (~ g!_) (~! thread.run!)]
+                                             ((~' in) (~ g!output)))))]
       (in (list (` ("lux def program"
                     (~ (case args
                          {#Raw args}
diff --git a/stdlib/source/library/lux/tool/compiler/language/lux/generation.lux b/stdlib/source/library/lux/tool/compiler/language/lux/generation.lux
index b2a99c6a4..ac37f48aa 100644
--- a/stdlib/source/library/lux/tool/compiler/language/lux/generation.lux
+++ b/stdlib/source/library/lux/tool/compiler/language/lux/generation.lux
@@ -1,35 +1,38 @@
 (.using
-  [library
-   [lux {"-" Module symbol}
-    [abstract
-     [monad {"+" do}]]
-    [control
-     ["[0]" try {"+" Try}]
-     ["[0]" exception {"+" exception:}]
-     ["[0]" function]]
-    [data
-     [binary {"+" Binary}]
-     ["[0]" product]
-     ["[0]" text ("[1]#[0]" equivalence)
-      ["%" format {"+" format}]]
-     [collection
-      ["[0]" sequence {"+" Sequence}]
-      ["[0]" list ("[1]#[0]" functor)]]]
-    [math
-     [number
-      ["n" nat]]]
-    [meta
-     ["[0]" symbol]]]]
-  [//
-   [synthesis {"+" Synthesis}]
-   [phase
-    ["[0]" extension]]
-   [///
-    ["[0]" phase]
-    [meta
-     ["[0]" archive {"+" Archive}
-      ["[0]" descriptor {"+" Module}]
-      ["[0]" artifact]]]]])
+ [library
+  [lux {"-" Module symbol}
+   [abstract
+    [monad {"+" do}]]
+   [control
+    ["[0]" try {"+" Try}]
+    ["[0]" exception {"+" exception:}]
+    ["[0]" function]]
+   [data
+    [binary {"+" Binary}]
+    ["[0]" product]
+    ["[0]" text ("[1]#[0]" equivalence)
+     ["%" format {"+" format}]]
+    [collection
+     ["[0]" sequence {"+" Sequence}]
+     ["[0]" list ("[1]#[0]" functor mix)]
+     ["[0]" set {"+" Set}]]]
+   [macro
+    ["[0]" template]]
+   [math
+    [number
+     ["n" nat]]]
+   [meta
+    ["[0]" symbol]]]]
+ [//
+  [synthesis {"+" Synthesis}]
+  [phase
+   ["[0]" extension]]
+  [///
+   ["[0]" phase]
+   [meta
+    ["[0]" archive {"+" Archive}
+     ["[0]" descriptor {"+" Module}]
+     ["[0]" artifact]]]]])
 
 (type: .public Context
   [archive.ID artifact.ID])
@@ -75,7 +78,8 @@
     #registry artifact.Registry
     #counter Nat
     #context (Maybe artifact.ID)
-    #log (Sequence Text)]))
+    #log (Sequence Text)
+    #interim_artifacts (List artifact.ID)]))
 
 (template [<special> <general>]
   [(type: .public (<special> anchor expression directive)
@@ -101,7 +105,8 @@
    #registry artifact.empty
    #counter 0
    #context {.#None}
-   #log sequence.empty])
+   #log sequence.empty
+   #interim_artifacts (list)])
 
 (def: .public empty_buffer
   Buffer
@@ -241,21 +246,21 @@
       {.#None}
       (phase.except ..no_buffer_for_saving_code [artifact_id]))))
 
-(template [<name> <artifact>]
-  [(def: .public (<name> name)
-     (All (_ anchor expression directive)
-       (-> Text (Operation anchor expression directive artifact.ID)))
-     (function (_ (^@ stateE [bundle state]))
-       (let [[id registry'] (<artifact> name (value@ #registry state))]
-         {try.#Success [[bundle (with@ #registry registry' state)]
-                        id]})))]
-
-  [learn artifact.definition]
-  [learn_custom artifact.custom]
-  [learn_analyser artifact.analyser]
-  [learn_synthesizer artifact.synthesizer]
-  [learn_generator artifact.generator]
-  [learn_directive artifact.directive]
+(template [<mandatory?> <inputs> <input_types> <name> <artifact>]
+  [(`` (def: .public (<name> name (~~ (template.spliced <inputs>)) dependencies)
+         (All (_ anchor expression directive)
+           (-> Text (~~ (template.spliced <input_types>)) (Set artifact.Dependency) (Operation anchor expression directive artifact.ID)))
+         (function (_ (^@ stateE [bundle state]))
+           (let [[id registry'] (<artifact> name <mandatory?> dependencies (value@ #registry state))]
+             {try.#Success [[bundle (with@ #registry registry' state)]
+                            id]}))))]
+
+  [mandatory? [mandatory?] [Bit] learn artifact.definition]
+  [#1 [] [] learn_custom artifact.custom]
+  [#0 [] [] learn_analyser artifact.analyser]
+  [#0 [] [] learn_synthesizer artifact.synthesizer]
+  [#0 [] [] learn_generator artifact.generator]
+  [#0 [] [] learn_directive artifact.directive]
   )
 
 (exception: .public (unknown_definition [name Symbol
@@ -318,16 +323,17 @@
       (in [[bundle' (with@ #context (value@ #context state) state')]
            output]))))
 
-(def: .public (with_new_context archive body)
+(def: .public (with_new_context archive dependencies body)
   (All (_ anchor expression directive a)
-    (-> Archive (Operation anchor expression directive a)
+    (-> Archive (Set artifact.Dependency) (Operation anchor expression directive a)
         (Operation anchor expression directive [Context a])))
   (function (_ (^@ stateE [bundle state]))
-    (let [[id registry'] (artifact.resource (value@ #registry state))]
+    (let [[id registry'] (artifact.resource false dependencies (value@ #registry state))]
       (do try.monad
         [[[bundle' state'] output] (body [bundle (|> state
                                                      (with@ #registry registry')
-                                                     (with@ #context {.#Some id}))])
+                                                     (with@ #context {.#Some id})
+                                                     (revised@ #interim_artifacts (|>> {.#Item id})))])
          module_id (archive.id (value@ #module state) archive)]
         (in [[bundle' (with@ #context (value@ #context state) state')]
              [[module_id id]
@@ -340,3 +346,21 @@
     {try.#Success [[bundle
                     (revised@ #log (sequence.suffix message) state)]
                    []]}))
+
+(def: .public (with_interim_artifacts archive body)
+  (All (_ anchor expression directive a)
+    (-> Archive (Operation anchor expression directive a)
+        (Operation anchor expression directive [(Set Context) a])))
+  (do phase.monad
+    [module (extension.read (value@ #module))]
+    (function (_ state+)
+      (do try.monad
+        [module_id (archive.id module archive)
+         [[bundle' state'] output] (body state+)]
+        (in [[bundle'
+              (with@ #interim_artifacts (list) state')]
+             [(list#mix (function (_ artifact_id dependencies)
+                          (set.has [module_id artifact_id] dependencies))
+                        artifact.no_dependencies
+                        (value@ #interim_artifacts state'))
+              output]])))))
diff --git a/stdlib/source/library/lux/tool/compiler/language/lux/phase/extension/directive/lux.lux b/stdlib/source/library/lux/tool/compiler/language/lux/phase/extension/directive/lux.lux
index 12a13781c..49e889381 100644
--- a/stdlib/source/library/lux/tool/compiler/language/lux/phase/extension/directive/lux.lux
+++ b/stdlib/source/library/lux/tool/compiler/language/lux/phase/extension/directive/lux.lux
@@ -1,51 +1,54 @@
 (.using
-  [library
-   [lux "*"
-    ["@" target]
-    ["[0]" meta]
-    [abstract
-     ["[0]" monad {"+" do}]]
-    [control
-     [io {"+" IO}]
-     ["[0]" try]
-     ["[0]" exception {"+" exception:}]
-     ["<>" parser
-      ["<[0]>" code {"+" Parser}]]]
-    [data
-     ["[0]" binary]
-     ["[0]" product]
-     ["[0]" text
-      ["%" format {"+" format}]]
-     [collection
-      ["[0]" dictionary]
-      ["[0]" array]
-      ["[0]" list ("[1]#[0]" functor)]]]
-    [macro
-     ["[0]" code]]
-    [math
-     [number
-      ["n" nat]]]
-    ["[0]" type {"+" :sharing} ("[1]#[0]" equivalence)
-     ["[0]" check]]]]
-  ["[0]" /// {"+" Extender}
-   ["[1][0]" bundle]
-   ["[1][0]" analysis]
+ [library
+  [lux "*"
+   ["@" target]
+   ["[0]" meta]
+   [abstract
+    ["[0]" monad {"+" do}]]
+   [control
+    [io {"+" IO}]
+    ["[0]" try]
+    ["[0]" exception {"+" exception:}]
+    ["<>" parser
+     ["<[0]>" code {"+" Parser}]]]
+   [data
+    ["[0]" binary]
+    ["[0]" product]
+    ["[0]" text
+     ["%" format {"+" format}]]
+    [collection
+     ["[0]" dictionary]
+     ["[0]" array]
+     ["[0]" list ("[1]#[0]" functor mix)]
+     ["[0]" set {"+" Set}]]]
+   [macro
+    ["[0]" code]]
+   [math
+    [number
+     ["n" nat]]]
+   ["[0]" type {"+" :sharing} ("[1]#[0]" equivalence)
+    ["[0]" check]]]]
+ ["[0]" /// {"+" Extender}
+  ["[1][0]" bundle]
+  ["[1][0]" analysis]
+  ["/[1]" // "_"
+   [analysis
+    ["[0]" module]
+    ["[0]A" type]]
    ["/[1]" // "_"
-    [analysis
-     ["[0]" module]
-     ["[0]A" type]]
-    ["/[1]" // "_"
-     ["[1][0]" analysis
-      [macro {"+" Expander}]
-      ["[1]/[0]" evaluation]]
-     ["[1][0]" synthesis {"+" Synthesis}]
-     ["[1][0]" generation {"+" Context}]
-     ["[1][0]" directive {"+" Import Requirements Phase Operation Handler Bundle}]
-     ["[1][0]" program {"+" Program}]
-     [///
-      ["[0]" phase]
-      [meta
-       ["[0]" archive {"+" Archive}]]]]]])
+    ["[1][0]" analysis
+     [macro {"+" Expander}]
+     ["[1]/[0]" evaluation]]
+    ["[1][0]" synthesis {"+" Synthesis}]
+    ["[1][0]" generation {"+" Context}]
+    ["[1][0]" directive {"+" Import Requirements Phase Operation Handler Bundle}]
+    ["[1][0]" program {"+" Program}]
+    [///
+     ["[0]" phase]
+     [meta
+      ["[0]" archive {"+" Archive}
+       ["[0]" artifact]
+       ["[0]" dependency]]]]]]])
 
 (def: .public (custom [syntax handler])
   (All (_ anchor expression directive s)
@@ -114,9 +117,11 @@
         (Operation anchor expression directive [Type expression Any])))
   (/////directive.lifted_generation
    (do phase.monad
-     [codeG (generate archive codeS)
-      id (/////generation.learn name)
+     [[interim_artifacts codeG] (/////generation.with_interim_artifacts archive
+                                  (generate archive codeS))
+      dependencies (dependency.dependencies archive codeS)
       module_id (phase.lifted (archive.id module archive))
+      id (/////generation.learn name false (set.union interim_artifacts dependencies))
       [target_name value directive] (/////generation.define! [module_id id] {.#None} codeG)
       _ (/////generation.save! id {.#None} directive)]
      (in [code//type codeG value]))))
@@ -166,9 +171,11 @@
                         (///.lifted meta.current_module_name))]
        (/////directive.lifted_generation
         (do phase.monad
-          [codeG (generate archive codeS)
+          [[interim_artifacts codeG] (/////generation.with_interim_artifacts archive
+                                       (generate archive codeS))
+           dependencies (dependency.dependencies archive codeS)
            module_id (phase.lifted (archive.id current_module archive))
-           id (<learn> extension)
+           id (<learn> extension (set.union interim_artifacts dependencies))
            [target_name value directive] (/////generation.define! [module_id id] {.#None} codeG)
            _ (/////generation.save! id {.#None} directive)]
           (in [codeG value])))))
@@ -489,8 +496,10 @@
         Synthesis
         (/////generation.Operation anchor expression directive Any)))
   (do phase.monad
-    [programG (generate archive programS)
-     artifact_id (/////generation.learn /////program.name)]
+    [[interim_artifacts programG] (/////generation.with_interim_artifacts archive
+                                    (generate archive programS))
+     dependencies (dependency.dependencies archive programS)
+     artifact_id (/////generation.learn /////program.name true (set.union interim_artifacts dependencies))]
     (/////generation.save! artifact_id {.#None} (program [module_id artifact_id] programG))))
 
 (def: (def::program program)
diff --git a/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/function.lux b/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/function.lux
index 32c78830d..1c4bee276 100644
--- a/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/function.lux
+++ b/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/function.lux
@@ -29,7 +29,8 @@
       [variable {"+" Register Variable}]]
      [meta
       [archive {"+" Archive}
-       ["[0]" artifact]]]]]]])
+       ["[0]" artifact]
+       ["[0]" dependency]]]]]]])
 
 (def: .public (apply expression archive [functionS argsS+])
   (Generator (Application Synthesis))
@@ -66,7 +67,8 @@
 (def: .public (function statement expression archive [environment arity bodyS])
   (-> Phase! (Generator (Abstraction Synthesis)))
   (do [! ///////phase.monad]
-    [[[function_module function_artifact] body!] (/////generation.with_new_context archive
+    [dependencies (dependency.dependencies archive bodyS)
+     [[function_module function_artifact] body!] (/////generation.with_new_context archive dependencies
                                                    (/////generation.with_anchor 1
                                                      (statement expression archive bodyS)))
      closureO+ (monad.each ! (expression archive) environment)
diff --git a/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/runtime.lux b/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/runtime.lux
index 19ef21fbf..936d40b2e 100644
--- a/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/runtime.lux
+++ b/stdlib/source/library/lux/tool/compiler/language/lux/phase/generation/ruby/runtime.lux
@@ -283,13 +283,16 @@
   (|>> (_.bit_and (_.manual "+0x80000000"))
        (_.= (_.int +0))))
 
+(def: i32##up
+  (_.bit_shl (_.int +32)))
+
 (template: (i64 @high @low)
   [(|> (_.? (i32##positive? @high)
             @high
             (|> (_.manual "+0xFFFFFFFF")
                 (_.- @high)
                 _.bit_not))
-       (_.bit_shl (_.int +32))
+       i32##up
        (_.bit_or @low))])
 
 (template [<runtime> <host>]
@@ -347,11 +350,9 @@
                   (_.set (list low) (|> input i32##low (_.bit_shr shift)
                                         (_.bit_or (|> input i32##high (_.bit_shl (_.- shift (_.int +32)))))))
                   (_.return (..i64 high low))))
-            ($_ _.then
-                (_.set (list low) (_.? (|> shift (_.= (_.int +32)))
-                                       (i32##high input)
-                                       (|> input i32##high (_.bit_shr (_.- (_.int +32) shift)))))
-                (_.return (..i64 (_.int +0) low)))))))
+            (_.return (_.? (|> shift (_.= (_.int +32)))
+                           (i32##high input)
+                           (|> input i32##high (_.bit_shr (_.- (_.int +32) shift)))))))))
 
 (runtime: (i64##/ parameter subject)
   (let [extra (_.do "remainder" (list parameter) {.#None} subject)]
@@ -580,7 +581,7 @@
     [_ (/////generation.execute! ..runtime)
      _ (/////generation.save! ..module_id {.#None} ..runtime)]
     (in [(|> artifact.empty
-             artifact.resource
+             (artifact.resource true artifact.no_dependencies)
              product.right)
          (sequence.sequence [..module_id
                              {.#None}
diff --git a/stdlib/source/library/lux/tool/compiler/meta/archive.lux b/stdlib/source/library/lux/tool/compiler/meta/archive.lux
index cbcdd36b3..c09aff7e6 100644
--- a/stdlib/source/library/lux/tool/compiler/meta/archive.lux
+++ b/stdlib/source/library/lux/tool/compiler/meta/archive.lux
@@ -5,6 +5,7 @@
      ["[0]" equivalence {"+" Equivalence}]
      ["[0]" monad {"+" do}]]
     [control
+     ["[0]" maybe]
      ["[0]" try {"+" Try}]
      ["[0]" exception {"+" exception:}]
      ["[0]" function]
@@ -132,6 +133,14 @@
         {.#None}
         (exception.except ..module_must_be_reserved_before_it_can_be_added [module]))))
 
+  (def: .public entries
+    (-> Archive (List [Module [ID [Descriptor (Document Any) Output]]]))
+    (|>> :representation
+         (value@ #resolver)
+         dictionary.entries
+         (list.all (function (_ [module [module_id entry]])
+                     (# maybe.monad each (|>> [module_id] [module]) entry)))))
+
   (def: .public (find module archive)
     (-> Module Archive (Try [Descriptor (Document Any) Output]))
     (let [(^open "_[0]") (:representation archive)]
diff --git a/stdlib/source/library/lux/tool/compiler/meta/archive/artifact.lux b/stdlib/source/library/lux/tool/compiler/meta/archive/artifact.lux
index 9bb7c3914..8f636a0b2 100644
--- a/stdlib/source/library/lux/tool/compiler/meta/archive/artifact.lux
+++ b/stdlib/source/library/lux/tool/compiler/meta/archive/artifact.lux
@@ -1,25 +1,29 @@
 (.using
-  [library
-   [lux "*"
-    [abstract
-     [monad {"+" do}]]
-    [control
-     [pipe {"+" case>}]
-     ["[0]" exception {"+" exception:}]
-     ["<>" parser
-      ["<[0]>" binary {"+" Parser}]]]
-    [data
-     ["[0]" product]
-     ["[0]" text
-      ["%" format {"+" format}]]
-     [collection
-      ["[0]" list]
-      ["[0]" sequence {"+" Sequence} ("[1]#[0]" functor mix)]
-      ["[0]" dictionary {"+" Dictionary}]]
-     [format
-      ["[0]" binary {"+" Writer}]]]
-    [type
-     abstract]]])
+ [library
+  [lux "*"
+   [abstract
+    [monad {"+" do}]]
+   [control
+    [pipe {"+" case>}]
+    ["[0]" exception {"+" exception:}]
+    ["<>" parser
+     ["<[0]>" binary {"+" Parser}]]]
+   [data
+    ["[0]" product]
+    ["[0]" text
+     ["%" format {"+" format}]]
+    [collection
+     ["[0]" list]
+     ["[0]" sequence {"+" Sequence} ("[1]#[0]" functor mix)]
+     ["[0]" dictionary {"+" Dictionary}]
+     ["[0]" set {"+" Set}]]
+    [format
+     ["[0]" binary {"+" Writer}]]]
+   [math
+    [number
+     ["[0]" nat]]]
+   [type
+    abstract]]])
 
 (type: .public ID
   Nat)
@@ -34,10 +38,22 @@
    {#Directive Text}
    {#Custom Text}))
 
+(type: .public Dependency
+  [Nat ID])
+
+(def: dependency_hash
+  (product.hash nat.hash nat.hash))
+
+(def: .public no_dependencies
+  (Set Dependency)
+  (set.empty dependency_hash))
+
 (type: .public Artifact
   (Record
    [#id ID
-    #category Category]))
+    #category Category
+    #mandatory? Bit
+    #dependencies (Set Dependency)]))
 
 (abstract: .public Registry
   (Record
@@ -57,25 +73,29 @@
     (-> Registry ID)
     (|>> ..artifacts sequence.size))
 
-  (def: .public (resource registry)
-    (-> Registry [ID Registry])
+  (def: .public (resource mandatory? dependencies registry)
+    (-> Bit (Set Dependency) Registry [ID Registry])
     (let [id (..next registry)]
       [id
        (|> registry
            :representation
            (revised@ #artifacts (sequence.suffix [#id id
-                                                  #category {#Anonymous}]))
+                                                  #category {#Anonymous}
+                                                  #mandatory? mandatory?
+                                                  #dependencies dependencies]))
            :abstraction)]))
 
   (template [<tag> <create> <fetch>]
-    [(def: .public (<create> name registry)
-       (-> Text Registry [ID Registry])
+    [(def: .public (<create> name mandatory? dependencies registry)
+       (-> Text Bit (Set Dependency) Registry [ID Registry])
        (let [id (..next registry)]
          [id
           (|> registry
               :representation
               (revised@ #artifacts (sequence.suffix [#id id
-                                                     #category {<tag> name}]))
+                                                     #category {<tag> name}
+                                                     #mandatory? mandatory?
+                                                     #dependencies dependencies]))
               (revised@ #resolver (dictionary.has name id))
               :abstraction)]))
 
@@ -118,11 +138,19 @@
                            [4 #Generator binary.text] 
                            [5 #Directive binary.text]
                            [6 #Custom binary.text]))))
-          artifacts (: (Writer (Sequence Category))
-                       (binary.sequence/64 category))]
+          mandatory? binary.bit
+          dependency (: (Writer Dependency)
+                        (binary.and binary.nat binary.nat))
+          dependencies (: (Writer (Set Dependency))
+                          (binary.set dependency))
+          artifacts (: (Writer (Sequence [Category Bit (Set Dependency)]))
+                       (binary.sequence/64 ($_ binary.and category mandatory? dependencies)))]
       (|>> :representation
            (value@ #artifacts)
-           (sequence#each (value@ #category))
+           (sequence#each (function (_ it)
+                            [(value@ #category it)
+                             (value@ #mandatory? it)
+                             (value@ #dependencies it)]))
            artifacts)))
 
   (exception: .public (invalid_category [tag Nat])
@@ -146,17 +174,22 @@
                            [5 #Directive <binary>.text]
                            [6 #Custom <binary>.text])
                           
-                          _ (<>.failure (exception.error ..invalid_category [tag])))))]
-      (|> (<binary>.sequence/64 category)
-          (# <>.monad each (sequence#mix (function (_ artifact registry)
+                          _ (<>.failure (exception.error ..invalid_category [tag])))))
+          mandatory? <binary>.bit
+          dependency (: (Parser Dependency)
+                        (<>.and <binary>.nat <binary>.nat))
+          dependencies (: (Parser (Set Dependency))
+                          (<binary>.set ..dependency_hash dependency))]
+      (|> (<binary>.sequence/64 ($_ <>.and category mandatory? dependencies))
+          (# <>.monad each (sequence#mix (function (_ [category mandatory? dependencies] registry)
                                            (product.right
-                                            (case artifact
+                                            (case category
                                               {#Anonymous}
-                                              (..resource registry)
+                                              (..resource mandatory? dependencies registry)
 
                                               (^template [<tag> <create>]
                                                 [{<tag> name}
-                                                 (<create> name registry)])
+                                                 (<create> name mandatory? dependencies registry)])
                                               ([#Definition ..definition]
                                                [#Analyser ..analyser]
                                                [#Synthesizer ..synthesizer]
diff --git a/stdlib/source/library/lux/tool/compiler/meta/archive/dependency.lux b/stdlib/source/library/lux/tool/compiler/meta/archive/dependency.lux
new file mode 100644
index 000000000..70f5b5744
--- /dev/null
+++ b/stdlib/source/library/lux/tool/compiler/meta/archive/dependency.lux
@@ -0,0 +1,215 @@
+... https://en.wikipedia.org/wiki/Tree_shaking
+(.using
+ [library
+  [lux "*"
+   [abstract
+    [hash {"+" Hash}]
+    ["[0]" monad {"+" do}]]
+   [data
+    ["[0]" product]
+    [collection
+     ["[0]" list ("[1]#[0]" monoid mix monad)]
+     ["[0]" set {"+" Set}]
+     ["[0]" dictionary {"+" Dictionary}]
+     ["[0]" sequence]]]
+   [math
+    [number
+     ["[0]" nat]]]
+   [meta
+    ["[0]" symbol]]
+   [tool
+    [compiler
+     ["[0]" phase]
+     ["[0]" reference {"+" Constant}]
+     [language
+      [lux
+       ["[0]" analysis]
+       ["[0]" synthesis {"+" Synthesis Path}]
+       ["[0]" generation {"+" Context Operation}]]]
+     [meta
+      ["[0]" archive {"+" Archive}
+       ["[0]" artifact]
+       ["[0]" descriptor]]]]]]])
+
+(def: (path_references references)
+  (-> (-> Synthesis (List Constant))
+      (-> Path (List Constant)))
+  (function (again path)
+    (case path
+      (^or {synthesis.#Pop}
+           {synthesis.#Access _}
+           {synthesis.#Bind _})
+      (list)
+
+      (^template [<tag>]
+        [{<tag> left right}
+         ($_ list#composite
+             (again left)
+             (again right))])
+      ([synthesis.#Alt]
+       [synthesis.#Seq])
+      
+      {synthesis.#Bit_Fork when then else}
+      (case else
+        {.#Some else}
+        ($_ list#composite
+            (again then)
+            (again else))
+        
+        {.#None}
+        (again then))
+
+      (^template [<tag>]
+        [{<tag> fork}
+         (|> {.#Item fork}
+             (list#each (|>> product.right again))
+             list#conjoint)])
+      ([synthesis.#I64_Fork]
+       [synthesis.#F64_Fork]
+       [synthesis.#Text_Fork])
+      
+      {synthesis.#Then then}
+      (references then))))
+
+(def: (references value)
+  (-> Synthesis (List Constant))
+  (case value
+    {synthesis.#Primitive value}
+    (list)
+    
+    {synthesis.#Structure value}
+    (case value
+      {analysis.#Variant value}
+      (|> value
+          (value@ analysis.#value)
+          references)
+      
+      {analysis.#Tuple value}
+      (|> value
+          (list#each references)
+          list#conjoint))
+
+    {synthesis.#Reference value}
+    (case value
+      {reference.#Variable _}
+      (list)
+      
+      {reference.#Constant value}
+      (list value))
+    
+    {synthesis.#Control value}
+    (case value
+      {synthesis.#Branch value}
+      (case value
+        {synthesis.#Let input _ body}
+        ($_ list#composite
+            (references input)
+            (references body))
+        
+        {synthesis.#If test then else}
+        ($_ list#composite
+            (references test)
+            (references then)
+            (references else))
+        
+        {synthesis.#Get _ record}
+        (references record)
+        
+        {synthesis.#Case input path}
+        ($_ list#composite
+            (references input)
+            (path_references references path)))
+      
+      {synthesis.#Loop value}
+      (case value
+        {synthesis.#Scope value}
+        (|> value
+            (value@ synthesis.#iteration)
+            references)
+        
+        {synthesis.#Again value}
+        (|> value
+            (list#each references)
+            list#conjoint))
+      
+      {synthesis.#Function value}
+      (case value
+        {synthesis.#Abstraction value}
+        (|> value
+            (value@ synthesis.#body)
+            references)
+        
+        {synthesis.#Apply function arguments}
+        (|> (list& function arguments)
+            (list#each references)
+            list#conjoint)))
+    
+    {synthesis.#Extension [name parameters]}
+    (|> parameters
+        (list#each references)
+        list#conjoint)))
+
+(def: context_hash
+  (Hash Context)
+  (product.hash nat.hash nat.hash))
+
+(def: .public (dependencies archive value)
+  (All (_ anchor expression directive)
+    (-> Archive Synthesis (Operation anchor expression directive (Set artifact.Dependency))))
+  (let [! phase.monad]
+    (|> value
+        ..references
+        (set.of_list symbol.hash)
+        set.list
+        (monad.each ! (generation.remember archive))
+        (# ! each (set.of_list context_hash)))))
+
+(def: .public all
+  (-> (List (Set artifact.Dependency))
+      (Set artifact.Dependency))
+  (list#mix set.union artifact.no_dependencies))
+
+(def: (immediate_dependencies archive)
+  (-> Archive [(List artifact.Dependency)
+               (Dictionary artifact.Dependency (Set artifact.Dependency))])
+  (|> archive
+      archive.entries
+      (list#each (function (_ [module [module_id [descriptor document output]]])
+                   (|> descriptor
+                       (value@ descriptor.#registry)
+                       artifact.artifacts
+                       sequence.list
+                       (list#each (function (_ artifact)
+                                    [[module_id (value@ artifact.#id artifact)]
+                                     (value@ artifact.#mandatory? artifact)
+                                     (value@ artifact.#dependencies artifact)])))))
+      list.together
+      (list#mix (function (_ [artifact_id mandatory? dependencies]
+                             [mandatory_dependencies
+                              all_dependencies])
+                  [(if mandatory?
+                     (list& artifact_id mandatory_dependencies)
+                     mandatory_dependencies)
+                   (dictionary.has artifact_id dependencies all_dependencies)])
+                [(list)
+                 (dictionary.empty context_hash)])))
+
+(def: .public (necessary_dependencies archive)
+  (-> Archive (Set artifact.Dependency))
+  (let [[mandatory immediate] (immediate_dependencies archive)]
+    (loop [pending mandatory
+           minimum artifact.no_dependencies]
+      (case pending
+        {.#Item head tail}
+        (if (set.member? minimum head)
+          (again tail minimum)
+          (again (case (dictionary.value head immediate)
+                   {.#Some additional}
+                   (list#composite (set.list additional) tail)
+
+                   {.#None}
+                   tail)
+                 (set.has head minimum)))
+        
+        {.#End}
+        minimum))))
diff --git a/stdlib/source/library/lux/tool/compiler/meta/cache/dependency.lux b/stdlib/source/library/lux/tool/compiler/meta/cache/dependency.lux
index 1cf11fda6..6e8a800ec 100644
--- a/stdlib/source/library/lux/tool/compiler/meta/cache/dependency.lux
+++ b/stdlib/source/library/lux/tool/compiler/meta/cache/dependency.lux
@@ -7,7 +7,7 @@
      ["[0]" maybe ("[1]#[0]" functor)]
      ["[0]" try {"+" Try}]
      ["[0]" state]
-     ["[0]" function
+     [function
       ["[0]" memo {"+" Memo}]]]
     [data
      ["[0]" text
diff --git a/stdlib/source/library/lux/tool/compiler/meta/io/archive.lux b/stdlib/source/library/lux/tool/compiler/meta/io/archive.lux
index f5243e5d2..ee222ea36 100644
--- a/stdlib/source/library/lux/tool/compiler/meta/io/archive.lux
+++ b/stdlib/source/library/lux/tool/compiler/meta/io/archive.lux
@@ -223,7 +223,7 @@
                                      output (: Output sequence.empty)]
                                 (let [[analysers synthesizers generators directives] bundles]
                                   (case input
-                                    {.#Item [[artifact_id artifact_category] input']}
+                                    {.#Item [[artifact_id artifact_category mandatory_artifact? artifact_dependencies] input']}
                                     (case (do !
                                             [data (try.of_maybe (dictionary.value (format (%.nat artifact_id) extension) actual))
                                              .let [context [module_id artifact_id]
diff --git a/stdlib/source/library/lux/tool/compiler/meta/packager/jvm.lux b/stdlib/source/library/lux/tool/compiler/meta/packager/jvm.lux
index af39e83e9..bab2f6ed9 100644
--- a/stdlib/source/library/lux/tool/compiler/meta/packager/jvm.lux
+++ b/stdlib/source/library/lux/tool/compiler/meta/packager/jvm.lux
@@ -33,7 +33,8 @@
   [//
    ["[0]" archive {"+" Output}
     ["[0]" descriptor {"+" Module}]
-    ["[0]" artifact]]
+    ["[0]" artifact]
+    ["tree_shaking" dependency]]
    [cache
     ["[0]" dependency]]
    ["[0]" io "_"
@@ -151,14 +152,17 @@
             (java/io/Flushable::flush)
             (java/util/zip/ZipOutputStream::closeEntry))))))
 
-(def: (write_module static [module output] sink)
-  (-> Static [archive.ID Output] java/util/jar/JarOutputStream
+(def: (write_module static necessary_dependencies [module output] sink)
+  (-> Static (Set Context) [archive.ID Output] java/util/jar/JarOutputStream
       (Try java/util/jar/JarOutputStream))
-  (monad.mix try.monad
-             (function (_ [artifact custom content] sink)
-               (..write_class static module artifact custom content sink))
-             sink
-             (sequence.list output)))
+  (let [! try.monad]
+    (monad.mix try.monad
+               (function (_ [artifact custom content] sink)
+                 (if (set.member? necessary_dependencies [module artifact])
+                   (..write_class static module artifact custom content sink)
+                   (# ! in sink)))
+               sink
+               (sequence.list output))))
 
 (def: (read_jar_entry_with_unknown_size input)
   (-> java/util/jar/JarInputStream [Nat Binary])
@@ -248,12 +252,13 @@
   (-> Static Packager)
   (function (_ host_dependencies archive program)
     (do [! try.monad]
-      [order (dependency.load_order $.key archive)
+      [.let [necessary_dependencies (tree_shaking.necessary_dependencies archive)]
+       order (dependency.load_order $.key archive)
        .let [buffer (java/io/ByteArrayOutputStream::new (.int ..mebi_byte))]
        sink (|> order
                 (list#each (function (_ [module [module_id [descriptor document output]]])
                              [module_id output]))
-                (monad.mix ! (..write_module static)
+                (monad.mix ! (..write_module static necessary_dependencies)
                            (java/util/jar/JarOutputStream::new buffer (..manifest program))))
        [entries duplicates sink] (|> host_dependencies
                                      dictionary.values
diff --git a/stdlib/source/test/lux/extension.lux b/stdlib/source/test/lux/extension.lux
index 1fcec22de..7422823e9 100644
--- a/stdlib/source/test/lux/extension.lux
+++ b/stdlib/source/test/lux/extension.lux
@@ -34,6 +34,9 @@
    [tool
     [compiler
      ["[0]" phase]
+     [meta
+      [archive
+       ["[0]" artifact]]]
      [language
       [lux
        ["[0]" analysis]
@@ -139,7 +142,7 @@
                         (generation_phase archive expressionS))
            
            _ (directive.lifted_generation
-              (generation.with_new_context archive
+              (generation.with_new_context archive artifact.no_dependencies
                 (do !
                   [[module_id artifact_id] (generation.context archive)
                    .let [commentary (format "Successfully installed directive " (%.text self) "!")]