diff --git a/corral.json b/corral.json
index 0abae3c..e57c146 100644
--- a/corral.json
+++ b/corral.json
@@ -5,7 +5,7 @@
   "deps": [
     {
       "locator": "github.com/chalcolith/kiuatan.git",
-      "version": "1.6.0"
+      "version": "1.6.1"
     },
     {
       "locator": "github.com/ponylang/appdirs.git",
diff --git a/eohippus/analyzer/eohippus_analyzer.pony b/eohippus/analyzer/eohippus_analyzer.pony
index a46d96a..65c635c 100644
--- a/eohippus/analyzer/eohippus_analyzer.pony
+++ b/eohippus/analyzer/eohippus_analyzer.pony
@@ -1101,7 +1101,7 @@ actor EohippusAnalyzer is Analyzer
       | let file: File =>
         let json_str = recover val file.read_string(file.size()) end
         match json.Parse(json_str)
-        | let obj: json.Object =>
+        | let obj: json.Object val =>
           match ast.ParseNode(src_file.canonical_path.path, obj)
           | let node: ast.Node =>
             _log(Fine) and _log.log(
@@ -1114,7 +1114,7 @@ actor EohippusAnalyzer is Analyzer
               src_file.task_id.string() + ": error loading " +
               syntax_path.path + ": " + err)
           end
-        | let item: json.Item =>
+        | let item: json.Item val =>
           _log(Error) and _log.log(
             src_file.task_id.string() + ": error loading " + syntax_path.path +
             ": a syntax tree must be an object")
@@ -1184,7 +1184,7 @@ actor EohippusAnalyzer is Analyzer
       match OpenFile(scope_path)
       | let file: File =>
         let json_str = recover val file.read_string(file.size()) end
-        match recover val json.Parse(json_str) end
+        match json.Parse(json_str)
         | let obj: json.Object val =>
           match recover val ParseScopeJson(_context.file_auth, obj, None) end
           | let scope: Scope val =>
diff --git a/eohippus/analyzer/scope.pony b/eohippus/analyzer/scope.pony
index 1a6fc24..33e085e 100644
--- a/eohippus/analyzer/scope.pony
+++ b/eohippus/analyzer/scope.pony
@@ -1,5 +1,6 @@
 use "collections"
 use "files"
+use "itertools"
 
 use ast = "../ast"
 use json = "../json"
@@ -102,7 +103,6 @@ class val Scope
 
   fun get_json(): json.Object =>
     let props = [ as (String, json.Item): ("index", I128.from[USize](index)) ]
-
     let kind_string =
       match kind
       | PackageScope =>
@@ -124,23 +124,26 @@ class val Scope
       props.push(("canonical_path", canonical_path.path))
     end
     props.push(
-      ( "range",
-        json.Sequence(
+      ( "range"
+      , json.Sequence(
           [ as I128:
             I128.from[USize](range._1)
             I128.from[USize](range._2)
             I128.from[USize](range._3)
             I128.from[USize](range._4)
-          ])) )
+          ]) ))
     if imports.size() > 0 then
       let import_items = Array[json.Item]
       for (node_index, identifier, path) in imports.values() do
-        import_items.push(json.Object(
-          [ as (String, json.Item):
-            ("node", I128.from[USize](node_index))
-            ("identifier", identifier)
-            ("path", path)
-          ]))
+        import_items.push(
+          recover val
+            json.Object(
+              [ as (String, json.Item):
+                ("node", I128.from[USize](node_index))
+                ("identifier", identifier)
+                ("path", path)
+              ])
+          end)
       end
       props.push(("imports", json.Sequence(import_items)))
     end
@@ -148,33 +151,34 @@ class val Scope
       let def_items = Array[json.Item]
       for def_array in definitions.values() do
         for (node_index, identifier, doc_string) in def_array.values() do
-          def_items.push(json.Object(
-            [ as (String, json.Item):
-              ("node", I128.from[USize](node_index))
-              ("identifier", identifier)
-              ("doc_string", doc_string) ]))
+          def_items.push(
+            json.Object(
+              [ as (String, json.Item):
+                ("node", I128.from[USize](node_index))
+                ("identifier", identifier)
+                ("doc_string", doc_string) ]))
         end
       end
       props.push(("definitions", json.Sequence(def_items)))
     end
     if children.size() > 0 then
-      let children_items = Array[json.Item]
-      for child in children.values() do
-        children_items.push(child.get_json())
-      end
-      props.push(("children", json.Sequence(children_items)))
+      let child_items =
+        Iter[Scope box](children.values())
+          .map[json.Item]({(child) => child.get_json() })
+          .collect(Array[json.Item](children.size()))
+      props.push(("children", json.Sequence(child_items)))
     end
-    json.Object(consume props)
+    json.Object(props)
 
 primitive ParseScopeJson
   fun apply(
     auth: FileAuth,
-    scope_item: json.Item,
+    scope_item: json.Item val,
     parent: (Scope ref | None))
     : (Scope ref | String)
   =>
     match scope_item
-    | let scope_obj: json.Object =>
+    | let scope_obj: json.Object val =>
       let kind =
         match try scope_obj("kind")? end
         | "PackageScope" =>
@@ -194,14 +198,14 @@ primitive ParseScopeJson
         end
       let name =
         match try scope_obj("name")? end
-        | let str: String box =>
+        | let str: String val =>
           str
         else
           return "scope.name must be a string"
         end
       let canonical_path =
         match try scope_obj("canonical_path")? end
-        | let str: String box =>
+        | let str: String val =>
           FilePath(auth, str.clone())
         else
           match parent
@@ -213,7 +217,7 @@ primitive ParseScopeJson
         end
       let range =
         match try scope_obj("range")? end
-        | let seq: json.Sequence box =>
+        | let seq: json.Sequence val =>
           match try (seq(0)?, seq(1)?, seq(2)?, seq(3)?) end
           | (let l: I128, let c: I128, let nl: I128, let nc: I128) =>
             ( USize.from[I128](l),
@@ -239,10 +243,10 @@ primitive ParseScopeJson
         kind, name.clone(), canonical_path, range, index, parent)
 
       match try scope_obj("imports")? end
-      | let seq: json.Sequence =>
+      | let seq: json.Sequence val =>
         for item in seq.values() do
           match item
-          | let obj: json.Object =>
+          | let obj: json.Object val =>
             try
               let node_index = USize.from[I128](obj("node")? as I128)
               let identifier = obj("identifier")? as String box
@@ -255,10 +259,10 @@ primitive ParseScopeJson
         end
       end
       match try scope_obj("definitions")? end
-      | let seq: json.Sequence =>
+      | let seq: json.Sequence val =>
         for item in seq.values() do
           match item
-          | let obj: json.Object =>
+          | let obj: json.Object val =>
             try
               let node_index = USize.from[I128](obj("node")? as I128)
               let identifier = obj("identifier")? as String box
@@ -272,7 +276,7 @@ primitive ParseScopeJson
         end
       end
       match try scope_obj("children")? end
-      | let seq: json.Sequence =>
+      | let seq: json.Sequence val =>
         for item in seq.values() do
           match ParseScopeJson(auth, item, scope)
           | let child: Scope ref =>
diff --git a/eohippus/ast/annotation.pony b/eohippus/ast/annotation.pony
index 800fd7e..a81873a 100644
--- a/eohippus/ast/annotation.pony
+++ b/eohippus/ast/annotation.pony
@@ -17,7 +17,7 @@ class val Annotation is NodeData
     props.push(("identifiers", node.child_refs(identifiers)))
 
 primitive ParseAnnotation
-  fun apply(obj: json.Object, children: NodeSeq): (Annotation | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (Annotation | String) =>
     let identifiers =
       match ParseNode._get_seq_with[Identifier](
         obj,
diff --git a/eohippus/ast/call_args.pony b/eohippus/ast/call_args.pony
index d461420..55f2db6 100644
--- a/eohippus/ast/call_args.pony
+++ b/eohippus/ast/call_args.pony
@@ -32,7 +32,7 @@ class val CallArgs is NodeData
     end
 
 primitive ParseCallArgs
-  fun apply(obj: json.Object, children: NodeSeq): (CallArgs | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (CallArgs | String) =>
     let positional =
       match ParseNode._get_seq_with[Expression](
         obj,
diff --git a/eohippus/ast/doc_string.pony b/eohippus/ast/doc_string.pony
index aa71051..2f4478c 100644
--- a/eohippus/ast/doc_string.pony
+++ b/eohippus/ast/doc_string.pony
@@ -17,7 +17,7 @@ class val DocString is NodeData
     props.push(("string", node.child_ref(string)))
 
 primitive ParseDocString
-  fun apply(obj: json.Object, children: NodeSeq): (DocString | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (DocString | String) =>
     let string =
       match ParseNode._get_child_with[LiteralString](
         obj,
diff --git a/eohippus/ast/error_section.pony b/eohippus/ast/error_section.pony
index 2254371..8beadfc 100644
--- a/eohippus/ast/error_section.pony
+++ b/eohippus/ast/error_section.pony
@@ -21,7 +21,7 @@ class val ErrorSection is NodeData
     props.push(("message", message))
 
 primitive ParseErrorSection
-  fun apply(obj: json.Object, children: NodeSeq): (ErrorSection | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ErrorSection | String) =>
     let message =
       match try obj("message")? end
       | let message': String box =>
diff --git a/eohippus/ast/exp_array.pony b/eohippus/ast/exp_array.pony
index 91f413e..5d6d43e 100644
--- a/eohippus/ast/exp_array.pony
+++ b/eohippus/ast/exp_array.pony
@@ -34,7 +34,7 @@ class val ExpArray is NodeData
     end
 
 primitive ParseExpArray
-  fun apply(obj: json.Object, children: NodeSeq): (ExpArray | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpArray | String) =>
     let array_type =
       match ParseNode._get_child_with[TypeType](
         obj,
diff --git a/eohippus/ast/exp_atom.pony b/eohippus/ast/exp_atom.pony
index f6e6e59..0e44e10 100644
--- a/eohippus/ast/exp_atom.pony
+++ b/eohippus/ast/exp_atom.pony
@@ -21,7 +21,7 @@ class val ExpAtom is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseExpAtom
-  fun apply(obj: json.Object, children: NodeSeq): (ExpAtom | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpAtom | String) =>
     let body =
       match ParseNode._get_child(
         obj,
diff --git a/eohippus/ast/exp_call.pony b/eohippus/ast/exp_call.pony
index b83db50..7081504 100644
--- a/eohippus/ast/exp_call.pony
+++ b/eohippus/ast/exp_call.pony
@@ -37,7 +37,7 @@ class val ExpCall is NodeData
     end
 
 primitive ParseExpCall
-  fun apply(obj: json.Object, children: NodeSeq): (ExpCall | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpCall | String) =>
     let lhs =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_consume.pony b/eohippus/ast/exp_consume.pony
index eb77e78..568e92c 100644
--- a/eohippus/ast/exp_consume.pony
+++ b/eohippus/ast/exp_consume.pony
@@ -28,7 +28,7 @@ class val ExpConsume is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseExpConsume
-  fun apply(obj: json.Object, children: NodeSeq): (ExpConsume | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpConsume | String) =>
     let cap =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/exp_decl.pony b/eohippus/ast/exp_decl.pony
index 0075687..f54f5cb 100644
--- a/eohippus/ast/exp_decl.pony
+++ b/eohippus/ast/exp_decl.pony
@@ -38,7 +38,7 @@ class val ExpDecl is NodeData
     end
 
 primitive ParseExpDecl
-  fun apply(obj: json.Object, children: NodeSeq): (ExpDecl | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpDecl | String) =>
     let kind =
       match ParseNode._get_child_with[Keyword](
         obj, children, "kind", "ExpDecl.kind must be a Keyword")
diff --git a/eohippus/ast/exp_ffi.pony b/eohippus/ast/exp_ffi.pony
index ca120b2..46540d0 100644
--- a/eohippus/ast/exp_ffi.pony
+++ b/eohippus/ast/exp_ffi.pony
@@ -48,7 +48,7 @@ class val ExpFfi is NodeData
 primitive ParseExpFfi
   fun help_id(): String => "ExpFfi.identifier must be an Identifier or Literal"
 
-  fun apply(obj: json.Object, children: NodeSeq): (ExpFfi | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpFfi | String) =>
     let identifier =
       match ParseNode._get_child(obj, children, "identifier", help_id())
       | let node: Node =>
diff --git a/eohippus/ast/exp_for.pony b/eohippus/ast/exp_for.pony
index f1279d1..7d6af2e 100644
--- a/eohippus/ast/exp_for.pony
+++ b/eohippus/ast/exp_for.pony
@@ -40,7 +40,7 @@ class val ExpFor is NodeData
     end
 
 primitive ParseExpFor
-  fun apply(obj: json.Object, children: NodeSeq): (ExpFor | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpFor | String) =>
     let pattern =
       match ParseNode._get_child_with[TuplePattern](
         obj,
diff --git a/eohippus/ast/exp_generic.pony b/eohippus/ast/exp_generic.pony
index 06a5eb7..72ba685 100644
--- a/eohippus/ast/exp_generic.pony
+++ b/eohippus/ast/exp_generic.pony
@@ -24,7 +24,7 @@ class val ExpGeneric is NodeData
     props.push(("type_args", node.child_ref(type_args)))
 
 primitive ParseExpGeneric
-  fun apply(obj: json.Object, children: NodeSeq): (ExpGeneric | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpGeneric | String) =>
     let lhs =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_hash.pony b/eohippus/ast/exp_hash.pony
index 5e246e9..d8ac736 100644
--- a/eohippus/ast/exp_hash.pony
+++ b/eohippus/ast/exp_hash.pony
@@ -19,7 +19,7 @@ class val ExpHash is NodeData
     props.push(("rhs", node.child_ref(rhs)))
 
 primitive ParseExpHash
-  fun apply(obj: json.Object, children: NodeSeq): (ExpHash | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpHash | String) =>
     let rhs =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_if.pony b/eohippus/ast/exp_if.pony
index 9dc752d..2714402 100644
--- a/eohippus/ast/exp_if.pony
+++ b/eohippus/ast/exp_if.pony
@@ -48,7 +48,7 @@ class val ExpIf is NodeData
     end
 
 primitive ParseExpIf
-  fun apply(obj: json.Object, children: NodeSeq): (ExpIf | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpIf | String) =>
     let kind =
       match try obj("kind")? end
       | let str: String box =>
@@ -117,7 +117,7 @@ class val IfCondition is NodeData
     props.push(("then_block", node.child_ref(then_block)))
 
 primitive ParseIfCondition
-  fun apply(obj: json.Object, children: NodeSeq): (IfCondition | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (IfCondition | String) =>
     let if_true =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_jump.pony b/eohippus/ast/exp_jump.pony
index ff225e7..f578c21 100644
--- a/eohippus/ast/exp_jump.pony
+++ b/eohippus/ast/exp_jump.pony
@@ -32,7 +32,7 @@ class val ExpJump is NodeData
     end
 
 primitive ParseExpJump
-  fun apply(obj: json.Object, children: NodeSeq): (ExpJump | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpJump | String) =>
     let keyword =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/exp_lambda.pony b/eohippus/ast/exp_lambda.pony
index ac40a68..27df25a 100644
--- a/eohippus/ast/exp_lambda.pony
+++ b/eohippus/ast/exp_lambda.pony
@@ -90,7 +90,7 @@ class val ExpLambda is NodeData
     end
 
 primitive ParseExpLambda
-  fun apply(obj: json.Object, children: NodeSeq): (ExpLambda | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpLambda | String) =>
     let bare =
       match try obj("bare")? end
       | let bool: Bool =>
diff --git a/eohippus/ast/exp_match.pony b/eohippus/ast/exp_match.pony
index 8f66a97..d80e18f 100644
--- a/eohippus/ast/exp_match.pony
+++ b/eohippus/ast/exp_match.pony
@@ -34,7 +34,7 @@ class val ExpMatch is NodeData
     end
 
 primitive ParseExpMatch
-  fun apply(obj: json.Object, children: NodeSeq): (ExpMatch | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpMatch | String) =>
     let expression =
       match ParseNode._get_child_with[Expression](
         obj,
@@ -99,7 +99,7 @@ class val MatchPattern is NodeData
     end
 
 primitive ParseMatchPattern
-  fun apply(obj: json.Object, children: NodeSeq): (MatchPattern | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (MatchPattern | String) =>
     let pattern =
       match ParseNode._get_child_with[Expression](
         obj,
@@ -152,7 +152,7 @@ class val MatchCase is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseMatchCase
-  fun apply(obj: json.Object, children: NodeSeq): (MatchCase | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (MatchCase | String) =>
     let patterns =
       match ParseNode._get_seq_with[MatchPattern](
         obj,
diff --git a/eohippus/ast/exp_object.pony b/eohippus/ast/exp_object.pony
index 956b78a..2645468 100644
--- a/eohippus/ast/exp_object.pony
+++ b/eohippus/ast/exp_object.pony
@@ -36,7 +36,7 @@ class val ExpObject is NodeData
     props.push(("members", node.child_ref(members)))
 
 primitive ParseExpObject
-  fun apply(obj: json.Object, children: NodeSeq): (ExpObject | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpObject | String) =>
     let cap =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/exp_operation.pony b/eohippus/ast/exp_operation.pony
index f6b5483..7a3ee83 100644
--- a/eohippus/ast/exp_operation.pony
+++ b/eohippus/ast/exp_operation.pony
@@ -69,7 +69,7 @@ class val ExpOperation is NodeData
     end
 
 primitive ParseExpOperation
-  fun apply(obj: json.Object, children: NodeSeq): (ExpOperation | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpOperation | String) =>
     let lhs =
       match ParseNode._get_child(
         obj,
diff --git a/eohippus/ast/exp_recover.pony b/eohippus/ast/exp_recover.pony
index 7a20114..9954393 100644
--- a/eohippus/ast/exp_recover.pony
+++ b/eohippus/ast/exp_recover.pony
@@ -28,7 +28,7 @@ class val ExpRecover is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseExpRecover
-  fun apply(obj: json.Object, children: NodeSeq): (ExpRecover | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpRecover | String) =>
     let cap =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/exp_repeat.pony b/eohippus/ast/exp_repeat.pony
index af773ae..3f8d775 100644
--- a/eohippus/ast/exp_repeat.pony
+++ b/eohippus/ast/exp_repeat.pony
@@ -33,7 +33,7 @@ class val ExpRepeat is NodeData
     end
 
 primitive ParseExpRepeat
-  fun apply(obj: json.Object, children: NodeSeq): (ExpRepeat | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpRepeat | String) =>
     let body =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_sequence.pony b/eohippus/ast/exp_sequence.pony
index 899afa2..272bd5c 100644
--- a/eohippus/ast/exp_sequence.pony
+++ b/eohippus/ast/exp_sequence.pony
@@ -19,7 +19,7 @@ class val ExpSequence is NodeData
     props.push(("expressions", node.child_refs(expressions)))
 
 primitive ParseExpSequence
-  fun apply(obj: json.Object, children: NodeSeq): (ExpSequence | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpSequence | String) =>
     let expressions =
       match ParseNode._get_seq_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_try.pony b/eohippus/ast/exp_try.pony
index 1f82435..6827321 100644
--- a/eohippus/ast/exp_try.pony
+++ b/eohippus/ast/exp_try.pony
@@ -31,7 +31,7 @@ class val ExpTry is NodeData
     end
 
 primitive ParseExpTry
-  fun apply(obj: json.Object, children: NodeSeq): (ExpTry | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpTry | String) =>
     let body =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_tuple.pony b/eohippus/ast/exp_tuple.pony
index a8b6c44..f5b88fe 100644
--- a/eohippus/ast/exp_tuple.pony
+++ b/eohippus/ast/exp_tuple.pony
@@ -19,7 +19,7 @@ class val ExpTuple is NodeData
     end
 
 primitive ParseExpTuple
-  fun apply(obj: json.Object, children: NodeSeq): (ExpTuple | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpTuple | String) =>
     let sequences =
       match ParseNode._get_seq_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_while.pony b/eohippus/ast/exp_while.pony
index 52c98fc..dea718c 100644
--- a/eohippus/ast/exp_while.pony
+++ b/eohippus/ast/exp_while.pony
@@ -33,7 +33,7 @@ class val ExpWhile is NodeData
     end
 
 primitive ParseExpWhile
-  fun apply(obj: json.Object, children: NodeSeq): (ExpWhile | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpWhile | String) =>
     let condition =
       match ParseNode._get_child_with[Expression](
         obj,
diff --git a/eohippus/ast/exp_with.pony b/eohippus/ast/exp_with.pony
index c3200e8..a79596a 100644
--- a/eohippus/ast/exp_with.pony
+++ b/eohippus/ast/exp_with.pony
@@ -27,7 +27,7 @@ class val ExpWith is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseExpWith
-  fun apply(obj: json.Object, children: NodeSeq): (ExpWith | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (ExpWith | String) =>
     let elements =
       match ParseNode._get_seq_with[WithElement](
         obj,
@@ -80,7 +80,7 @@ class val WithElement is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseWithElement
-  fun apply(obj: json.Object, children: NodeSeq): (WithElement | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (WithElement | String) =>
     let pattern =
       match ParseNode._get_child_with[TuplePattern](
         obj,
diff --git a/eohippus/ast/identifier.pony b/eohippus/ast/identifier.pony
index 89dd789..6ac85e3 100644
--- a/eohippus/ast/identifier.pony
+++ b/eohippus/ast/identifier.pony
@@ -15,7 +15,7 @@ class val Identifier is NodeData
     props.push(("string", string))
 
 primitive ParseIdentifier
-  fun apply(obj: json.Object, children: NodeSeq): (Identifier | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (Identifier | String) =>
     let string =
       match try obj("string")? end
       | let s: String box =>
diff --git a/eohippus/ast/keyword.pony b/eohippus/ast/keyword.pony
index 2e1708c..417ccfd 100644
--- a/eohippus/ast/keyword.pony
+++ b/eohippus/ast/keyword.pony
@@ -82,7 +82,7 @@ class val Keyword is NodeData
     props.push(("string", string))
 
 primitive ParseKeyword
-  fun apply(obj: json.Object, children: NodeSeq): (Keyword | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (Keyword | String) =>
     let string =
       match try obj("string")? end
       | let str: String box =>
diff --git a/eohippus/ast/literal_bool.pony b/eohippus/ast/literal_bool.pony
index e56a253..4ab216d 100644
--- a/eohippus/ast/literal_bool.pony
+++ b/eohippus/ast/literal_bool.pony
@@ -17,7 +17,7 @@ class val LiteralBool is NodeDataWithValue[LiteralBool, Bool]
   fun value(): Bool => _value
 
 primitive ParseLiteralBool
-  fun apply(obj: json.Object, children: NodeSeq): (LiteralBool | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (LiteralBool | String) =>
     let value =
       match try obj("value")? end
       | let bool: Bool =>
diff --git a/eohippus/ast/literal_char.pony b/eohippus/ast/literal_char.pony
index b7e29da..ff63186 100644
--- a/eohippus/ast/literal_char.pony
+++ b/eohippus/ast/literal_char.pony
@@ -39,7 +39,7 @@ class val LiteralChar is NodeDataWithValue[LiteralChar, U32]
   fun value(): U32 => _value
 
 primitive ParseLiteralChar
-  fun apply(obj: json.Object, children: NodeSeq): (LiteralChar | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (LiteralChar | String) =>
     let kind =
       match try obj("kind")? end
       | let str: String box =>
diff --git a/eohippus/ast/literal_float.pony b/eohippus/ast/literal_float.pony
index 1a8fbbc..efd185b 100644
--- a/eohippus/ast/literal_float.pony
+++ b/eohippus/ast/literal_float.pony
@@ -17,7 +17,7 @@ class val LiteralFloat is NodeDataWithValue[LiteralFloat, F64]
   fun value(): F64 => _value
 
 primitive ParseLiteralFloat
-  fun apply(obj: json.Object, children: NodeSeq): (LiteralFloat | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (LiteralFloat | String) =>
     let value =
       match try obj("value")? end
       | let float: F64 =>
diff --git a/eohippus/ast/literal_integer.pony b/eohippus/ast/literal_integer.pony
index 228528d..c44ec69 100644
--- a/eohippus/ast/literal_integer.pony
+++ b/eohippus/ast/literal_integer.pony
@@ -31,7 +31,9 @@ class val LiteralInteger is NodeDataWithValue[LiteralInteger, U128]
   fun value(): U128 => _value
 
 primitive ParseLiteralInteger
-  fun apply(obj: json.Object, children: NodeSeq): (LiteralInteger | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq)
+    : (LiteralInteger | String)
+  =>
     let value =
       match try obj("value")? end
       | let n: I128 =>
diff --git a/eohippus/ast/literal_string.pony b/eohippus/ast/literal_string.pony
index 23414e7..49d6a34 100644
--- a/eohippus/ast/literal_string.pony
+++ b/eohippus/ast/literal_string.pony
@@ -30,7 +30,9 @@ class val LiteralString is NodeDataWithValue[LiteralString, String]
   fun value(): String => _value
 
 primitive ParseLiteralString
-  fun apply(obj: json.Object, children: NodeSeq): (LiteralString | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq)
+    : (LiteralString | String)
+  =>
     let value =
       match try obj("value")? end
       | let str: String box =>
diff --git a/eohippus/ast/method_params.pony b/eohippus/ast/method_params.pony
index 39a6b18..2f70239 100644
--- a/eohippus/ast/method_params.pony
+++ b/eohippus/ast/method_params.pony
@@ -21,7 +21,7 @@ class val MethodParams is NodeData
     end
 
 primitive ParseMethodParams
-  fun apply(obj: json.Object, children: NodeSeq): (MethodParams | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (MethodParams | String) =>
     let params =
       match ParseNode._get_seq_with[MethodParam](
         obj,
@@ -70,7 +70,7 @@ class val MethodParam is NodeData
     end
 
 primitive ParseMethodParam
-  fun apply(obj: json.Object, children: NodeSeq): (MethodParam | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (MethodParam | String) =>
     let identifier =
       match ParseNode._get_child_with[Identifier](
         obj,
diff --git a/eohippus/ast/node.pony b/eohippus/ast/node.pony
index 43cedde..cc8b860 100644
--- a/eohippus/ast/node.pony
+++ b/eohippus/ast/node.pony
@@ -52,8 +52,7 @@ trait val Node
 
   fun scope_index(): (USize | None)
 
-  fun get_json()
-    : json.Object
+  fun get_json() : json.Object
     """Get a JSON representation of the node."""
 
   fun map[D: NodeData val](seq: NodeSeqWith[D], updates: ChildUpdateMap)
@@ -80,11 +79,11 @@ trait val Node
     I128.from[ISize](-1)
 
   fun child_refs(childs: NodeSeq): json.Item =>
-    let items: Array[json.Item] = Array[json.Item](childs.size())
+    let seq = Array[json.Item](childs.size())
     for child in childs.values() do
-      items.push(child_ref(child))
+      seq.push(child_ref(child))
     end
-    json.Sequence(consume items)
+    json.Sequence(seq)
 
   fun string(): String iso^
 
diff --git a/eohippus/ast/node_with.pony b/eohippus/ast/node_with.pony
index b4c2e3d..e78f498 100644
--- a/eohippus/ast/node_with.pony
+++ b/eohippus/ast/node_with.pony
@@ -304,9 +304,7 @@ class val NodeWith[D: NodeData val] is Node
   fun scope_index(): (USize | None) =>
     _scope_index
 
-  fun get_json()
-    : json.Object
-  =>
+  fun get_json() : json.Object =>
     """Get a JSON representation of the node."""
     let props = [ as (String, json.Item): ("name", name()) ]
     match (_src_info.line, _src_info.column)
@@ -341,9 +339,9 @@ class val NodeWith[D: NodeData val] is Node
       props.push(("post_trivia", child_refs(_post_trivia)))
     end
     if _children.size() > 0 then
-      let child_json = json.Sequence.from_iter(
-        Iter[Node](_children.values()).map[json.Item](
-          {(child) => child.get_json()}))
+      let child_json =
+        json.Sequence.from_iter[Node](
+          children().values(), {(child) => child.get_json() })
       props.push(("children", child_json))
     end
     json.Object(props)
diff --git a/eohippus/ast/parse_node.pony b/eohippus/ast/parse_node.pony
index 3cf7886..a1c895b 100644
--- a/eohippus/ast/parse_node.pony
+++ b/eohippus/ast/parse_node.pony
@@ -2,7 +2,7 @@ use json = "../json"
 use parser = "../parser"
 
 primitive ParseNode
-  fun apply(locator: parser.Locator, obj: json.Object): (Node | String) =>
+  fun apply(locator: parser.Locator, obj: json.Object val): (Node | String) =>
     let name =
       match try obj("name")? end
       | let str: String box =>
@@ -12,7 +12,7 @@ primitive ParseNode
       end
     let src_info =
       match try obj("src_info")? end
-      | let src_info_obj: json.Object box =>
+      | let src_info_obj: json.Object val =>
         let line' =
           match try src_info_obj("line")? end
           | let n: I128 =>
@@ -57,10 +57,10 @@ primitive ParseNode
 
     let children': Array[Node] trn = Array[Node]
     match try obj("children")? end
-    | let children_seq: json.Sequence =>
+    | let children_seq: json.Sequence val =>
       for child_item in children_seq.values() do
         match child_item
-        | let child_obj: json.Object =>
+        | let child_obj: json.Object val =>
           match ParseNode(locator, child_obj)
           | let n: Node =>
             children'.push(n)
@@ -72,7 +72,7 @@ primitive ParseNode
         end
       end
     end
-    let children: Array[Node] val = consume children'
+    let children: ReadSeq[Node] val = consume children'
 
     let annotation =
       match try obj("annotation")? end
@@ -88,7 +88,6 @@ primitive ParseNode
       else
         return "annotation must refer to an Annotation"
       end
-
     let doc_strings =
       match _get_seq_with[DocString](
         obj,
@@ -267,8 +266,38 @@ primitive ParseNode
       "unknown node data type " + name
     end
 
+  fun _ctor[D: NodeData val](
+    ctor: {ref (): (D | String)},
+    src_info: SrcInfo,
+    children: NodeSeq,
+    annotation: (NodeWith[Annotation] | None),
+    doc_strings: NodeSeqWith[DocString],
+    pre_trivia: NodeSeqWith[Trivia],
+    post_trivia: NodeSeqWith[Trivia],
+    scope_index: (USize | None))
+    : (Node | String)
+  =>
+    let data =
+      match ctor()
+      | let data': D =>
+        data'
+      | let err: String =>
+        return err
+      end
+
+    NodeWith[D](
+      src_info,
+      children,
+      data,
+      annotation,
+      doc_strings,
+      pre_trivia,
+      post_trivia,
+      None,
+      scope_index)
+
   fun _get_child(
-    obj: json.Object,
+    obj: json.Object val,
     children: NodeSeq,
     key: String,
     help: String,
@@ -290,7 +319,7 @@ primitive ParseNode
     end
 
   fun _get_child_with[D: NodeData val](
-    obj: json.Object,
+    obj: json.Object val,
     children: NodeSeq,
     key: String,
     help: String,
@@ -316,7 +345,7 @@ primitive ParseNode
     end
 
   fun _get_seq_with[D: NodeData val](
-    obj: json.Object,
+    obj: json.Object val,
     children: NodeSeq,
     key: String,
     help: String,
@@ -324,7 +353,7 @@ primitive ParseNode
     : (NodeSeqWith[D] | String)
   =>
     match try obj(key)? end
-    | let seq: json.Sequence =>
+    | let seq: json.Sequence box =>
       let nodes: Array[NodeWith[D]] trn = Array[NodeWith[D]]
       for item in seq.values() do
         match item
@@ -349,42 +378,13 @@ primitive ParseNode
       end
     end
 
-  fun _ctor[D: NodeData val](
-    ctor: {(): (D | String)} box,
-    src_info: SrcInfo,
-    children: NodeSeq,
-    annotation: (NodeWith[Annotation] | None),
-    doc_strings: NodeSeqWith[DocString],
-    pre_trivia: NodeSeqWith[Trivia],
-    post_trivia: NodeSeqWith[Trivia],
-    scope_index: (USize | None))
-    : (Node | String)
-  =>
-    let data =
-      match ctor()
-      | let data': D =>
-        data'
-      | let err: String =>
-        return err
-      end
-
-    NodeWith[D](
-      src_info,
-      children,
-      data,
-      annotation,
-      doc_strings,
-      pre_trivia,
-      post_trivia,
-      None,
-      scope_index)
-
 type _NodeConstructor is
-  {(SrcInfo,
-    NodeSeq,
-    (NodeWith[Annotation] | None),
-    NodeSeqWith[DocString],
-    NodeSeqWith[Trivia],
-    NodeSeqWith[Trivia],
-    (USize | None))
-    : (Node | String)} box
+  { ref
+    ( SrcInfo
+    , NodeSeq
+    , (NodeWith[Annotation] | None)
+    , NodeSeqWith[DocString]
+    , NodeSeqWith[Trivia]
+    , NodeSeqWith[Trivia]
+    , (USize | None) )
+    : (Node | String) }
diff --git a/eohippus/ast/span.pony b/eohippus/ast/span.pony
index 1986e7d..e029875 100644
--- a/eohippus/ast/span.pony
+++ b/eohippus/ast/span.pony
@@ -15,5 +15,5 @@ class val Span is NodeData
     None
 
 primitive ParseSpan
-  fun apply(obj: json.Object, children: NodeSeq): (Span | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (Span | String) =>
     recover Span end
diff --git a/eohippus/ast/src_file.pony b/eohippus/ast/src_file.pony
index c57a814..0c78b72 100644
--- a/eohippus/ast/src_file.pony
+++ b/eohippus/ast/src_file.pony
@@ -37,7 +37,7 @@ class val SrcFile is NodeData
     end
 
 primitive ParseSrcFile
-  fun apply(obj: json.Object, children: NodeSeq): (SrcFile | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (SrcFile | String) =>
     let locator =
       match try obj("locator")? end
       | let str: String box =>
diff --git a/eohippus/ast/syntax_tree.pony b/eohippus/ast/syntax_tree.pony
index 98979aa..7dc81bd 100644
--- a/eohippus/ast/syntax_tree.pony
+++ b/eohippus/ast/syntax_tree.pony
@@ -63,40 +63,44 @@ primitive SyntaxTree
         // we inside-out these matches, because we still want to populate
         // new_children if there's a None new child, to record that the children
         // changed
-        match (new_children, update_map)
-        | (let nc: Array[Node] trn, let um: ChildUpdateMap trn) =>
-          match new_child
-          | let new_child': Node =>
-            nc.push(new_child')
-            um(child) = new_child'
-          end
-        | (None, None) if new_child isnt child =>
-          let nc: Array[Node] trn = Array[Node](node.children().size())
-          let um: ChildUpdateMap trn = ChildUpdateMap(node.children().size())
+        (new_children, update_map) =
+          match (consume new_children, consume update_map)
+          | (let nc: Array[Node] trn, let um: ChildUpdateMap trn) =>
+            match new_child
+            | let new_child': Node =>
+              nc.push(new_child')
+              um.update(child, new_child')
+            end
+            (consume nc, consume um)
+          | (None, None) if new_child isnt child =>
+            let nc: Array[Node] trn = Array[Node](node.children().size())
+            let um: ChildUpdateMap trn = ChildUpdateMap(node.children().size())
 
-          // if we haven't seen any changes until now, fill up our new_children
-          // with the old ones
-          for j in col.Range(0, i) do
-            try
-              let old_child = node.children()(j)?
-              nc.push(old_child)
-              um(old_child) = old_child
+            // if we haven't seen any changes until now, fill up our new_children
+            // with the old ones
+            for j in col.Range(0, i) do
+              try
+                let old_child = node.children()(j)?
+                nc.push(old_child)
+                um(old_child) = old_child
+              end
             end
-          end
 
-          match new_child
-          | let new_child': Node =>
-            nc.push(new_child')
-            um(child) = new_child'
+            match new_child
+            | let new_child': Node =>
+              nc.push(new_child')
+              um(child) = new_child'
+            end
+            (consume nc, consume um)
+          | ( let nc: (Array[Node] trn | None)
+            , let um: (ChildUpdateMap trn | None))
+          =>
+            (consume nc, consume um)
           end
-
-          new_children = consume nc
-          update_map = consume um
-        end
         i = i + 1
       end
 
-      match (new_children, update_map)
+      match (consume new_children, consume update_map)
       | (let nc: Array[Node] trn, let um: ChildUpdateMap trn) =>
         (node_state, let new_node, errors') = visitor.visit_post(
             node_state,
diff --git a/eohippus/ast/token.pony b/eohippus/ast/token.pony
index b32f3bc..7ad1ea6 100644
--- a/eohippus/ast/token.pony
+++ b/eohippus/ast/token.pony
@@ -76,7 +76,7 @@ class val Token is NodeData
     props.push(("string", string))
 
 primitive ParseToken
-  fun apply(obj: json.Object, children: NodeSeq): (Token | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (Token | String) =>
     let string =
       match try obj("string")? end
       | let s: String box =>
diff --git a/eohippus/ast/trivia.pony b/eohippus/ast/trivia.pony
index 6225a74..11aeccb 100644
--- a/eohippus/ast/trivia.pony
+++ b/eohippus/ast/trivia.pony
@@ -41,7 +41,7 @@ class val Trivia is NodeData
     props.push(("string", string))
 
 primitive ParseTrivia
-  fun apply(obj: json.Object, children: NodeSeq): (Trivia | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (Trivia | String) =>
     let kind: TriviaKind =
       match try obj("kind")? end
       | "LineCommentTrivia" =>
diff --git a/eohippus/ast/tuple_pattern.pony b/eohippus/ast/tuple_pattern.pony
index 54c8838..56dd9ca 100644
--- a/eohippus/ast/tuple_pattern.pony
+++ b/eohippus/ast/tuple_pattern.pony
@@ -35,11 +35,11 @@ primitive ParseTuplePattern
   fun _help(): String => "TuplePattern.elements must be a sequence of " +
     "(Identifier | TuplePattern)"
 
-  fun apply(obj: json.Object, children: NodeSeq): (TuplePattern | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TuplePattern | String) =>
     let elements: Array[(NodeWith[Identifier] | NodeWith[TuplePattern])] trn =
       Array[(NodeWith[Identifier] | NodeWith[TuplePattern])]
     match try obj("elements")? end
-    | let seq: json.Sequence =>
+    | let seq: json.Sequence val =>
       for item in seq.values() do
         match item
         | let i: I128 =>
diff --git a/eohippus/ast/type_args.pony b/eohippus/ast/type_args.pony
index aa7c48b..1f422d9 100644
--- a/eohippus/ast/type_args.pony
+++ b/eohippus/ast/type_args.pony
@@ -19,7 +19,7 @@ class val TypeArgs is NodeData
     props.push(("types", node.child_refs(types)))
 
 primitive ParseTypeArgs
-  fun apply(obj: json.Object, children: NodeSeq): (TypeArgs | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeArgs | String) =>
     let types =
       match ParseNode._get_seq_with[TypeType](
         obj,
diff --git a/eohippus/ast/type_arrow.pony b/eohippus/ast/type_arrow.pony
index f65e4a7..72446c4 100644
--- a/eohippus/ast/type_arrow.pony
+++ b/eohippus/ast/type_arrow.pony
@@ -28,7 +28,7 @@ class val TypeArrow is NodeData
     end
 
 primitive ParseTypeArrow
-  fun apply(obj: json.Object, children: NodeSeq): (TypeArrow | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeArrow | String) =>
     let lhs =
       match ParseNode._get_child(
         obj,
diff --git a/eohippus/ast/type_atom.pony b/eohippus/ast/type_atom.pony
index 7d6b66c..4bc0629 100644
--- a/eohippus/ast/type_atom.pony
+++ b/eohippus/ast/type_atom.pony
@@ -17,7 +17,7 @@ class val TypeAtom is NodeData
     props.push(("body", node.child_ref(body)))
 
 primitive ParseTypeAtom
-  fun apply(obj: json.Object, children: NodeSeq): (TypeAtom | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeAtom | String) =>
     let body =
       match ParseNode._get_child(
         obj,
diff --git a/eohippus/ast/type_infix.pony b/eohippus/ast/type_infix.pony
index 4a5b507..fb0d25f 100644
--- a/eohippus/ast/type_infix.pony
+++ b/eohippus/ast/type_infix.pony
@@ -31,7 +31,7 @@ class val TypeInfix is NodeData
     end
 
 primitive ParseTypeInfix
-  fun apply(obj: json.Object, children: NodeSeq): (TypeInfix | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeInfix | String) =>
     let types =
       match ParseNode._get_seq_with[TypeType](
         obj,
diff --git a/eohippus/ast/type_lambda.pony b/eohippus/ast/type_lambda.pony
index 06fa2a8..0357774 100644
--- a/eohippus/ast/type_lambda.pony
+++ b/eohippus/ast/type_lambda.pony
@@ -82,7 +82,7 @@ class val TypeLambda is NodeData
     end
 
 primitive ParseTypeLambda
-  fun apply(obj: json.Object, children: NodeSeq): (TypeLambda | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeLambda | String) =>
     let bare =
       match try obj("bare")? end
       | let bool: Bool =>
diff --git a/eohippus/ast/type_nominal.pony b/eohippus/ast/type_nominal.pony
index 04d8a1b..86cdf65 100644
--- a/eohippus/ast/type_nominal.pony
+++ b/eohippus/ast/type_nominal.pony
@@ -54,7 +54,7 @@ class val TypeNominal is NodeData
     end
 
 primitive ParseTypeNominal
-  fun apply(obj: json.Object, children: NodeSeq): (TypeNominal | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeNominal | String) =>
     let lhs =
       match ParseNode._get_child_with[Identifier](
         obj,
diff --git a/eohippus/ast/type_params.pony b/eohippus/ast/type_params.pony
index 2e7613d..15f0cab 100644
--- a/eohippus/ast/type_params.pony
+++ b/eohippus/ast/type_params.pony
@@ -19,7 +19,7 @@ class val TypeParams is NodeData
     end
 
 primitive ParseTypeParams
-  fun apply(obj: json.Object, children: NodeSeq): (TypeParams | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeParams | String) =>
     let params =
       match ParseNode._get_seq_with[TypeParam](
         obj,
@@ -71,7 +71,7 @@ class val TypeParam is NodeData
     end
 
 primitive ParseTypeParam
-  fun apply(obj: json.Object, children: NodeSeq): (TypeParam | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeParam | String) =>
     let identifier =
       match ParseNode._get_child_with[Identifier](
         obj,
diff --git a/eohippus/ast/type_tuple.pony b/eohippus/ast/type_tuple.pony
index 05f2018..cedb2f1 100644
--- a/eohippus/ast/type_tuple.pony
+++ b/eohippus/ast/type_tuple.pony
@@ -18,7 +18,7 @@ class val TypeTuple is NodeData
     end
 
 primitive ParseTypeTuple
-  fun apply(obj: json.Object, children: NodeSeq): (TypeTuple | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypeTuple | String) =>
     let types =
       match ParseNode._get_seq_with[TypeType](
         obj,
diff --git a/eohippus/ast/typedef_alias.pony b/eohippus/ast/typedef_alias.pony
index fdb4287..43a5908 100644
--- a/eohippus/ast/typedef_alias.pony
+++ b/eohippus/ast/typedef_alias.pony
@@ -33,7 +33,7 @@ class val TypedefAlias is NodeData
     props.push(("type", node.child_ref(type_type)))
 
 primitive ParseTypedefAlias
-  fun apply(obj: json.Object, children: NodeSeq): (TypedefAlias | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypedefAlias | String) =>
     let identifier =
       match ParseNode._get_child_with[Identifier](
         obj,
diff --git a/eohippus/ast/typedef_class.pony b/eohippus/ast/typedef_class.pony
index 27e9a57..77a680e 100644
--- a/eohippus/ast/typedef_class.pony
+++ b/eohippus/ast/typedef_class.pony
@@ -67,7 +67,7 @@ class val TypedefClass is NodeData
     end
 
 primitive ParseTypedefClass
-  fun apply(obj: json.Object, children: NodeSeq): (TypedefClass | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypedefClass | String) =>
     let kind =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/typedef_field.pony b/eohippus/ast/typedef_field.pony
index 970de94..3717067 100644
--- a/eohippus/ast/typedef_field.pony
+++ b/eohippus/ast/typedef_field.pony
@@ -44,7 +44,7 @@ class val TypedefField is NodeData
     end
 
 primitive ParseTypedefField
-  fun apply(obj: json.Object, children: NodeSeq): (TypedefField | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypedefField | String) =>
     let kind =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/typedef_members.pony b/eohippus/ast/typedef_members.pony
index 663f892..d5a7d94 100644
--- a/eohippus/ast/typedef_members.pony
+++ b/eohippus/ast/typedef_members.pony
@@ -31,7 +31,9 @@ class val TypedefMembers is NodeData
     end
 
 primitive ParseTypedefMembers
-  fun apply(obj: json.Object, children: NodeSeq): (TypedefMembers | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq)
+    : (TypedefMembers | String)
+  =>
     let fields =
       match ParseNode._get_seq_with[TypedefField](
         obj,
diff --git a/eohippus/ast/typedef_method.pony b/eohippus/ast/typedef_method.pony
index e0f2260..49e2646 100644
--- a/eohippus/ast/typedef_method.pony
+++ b/eohippus/ast/typedef_method.pony
@@ -83,7 +83,9 @@ class val TypedefMethod is NodeData
     end
 
 primitive ParseTypedefMethod
-  fun apply(obj: json.Object, children: NodeSeq): (TypedefMethod | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq)
+    : (TypedefMethod | String)
+  =>
     let kind =
       match ParseNode._get_child_with[Keyword](
         obj,
diff --git a/eohippus/ast/typedef_primitive.pony b/eohippus/ast/typedef_primitive.pony
index 523ec99..ffc35b7 100644
--- a/eohippus/ast/typedef_primitive.pony
+++ b/eohippus/ast/typedef_primitive.pony
@@ -44,7 +44,7 @@ class val TypedefPrimitive is NodeData
     end
 
 primitive ParseTypedefPrimitive
-  fun apply(obj: json.Object, children: NodeSeq): (TypedefPrimitive | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (TypedefPrimitive | String) =>
     let identifier =
       match ParseNode._get_child_with[Identifier](
         obj,
diff --git a/eohippus/ast/using.pony b/eohippus/ast/using.pony
index 6828eb9..2df94ac 100644
--- a/eohippus/ast/using.pony
+++ b/eohippus/ast/using.pony
@@ -47,7 +47,7 @@ class val UsingPony is NodeData
     end
 
 primitive ParseUsingPony
-  fun apply(obj: json.Object, children: NodeSeq): (UsingPony | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (UsingPony | String) =>
     let identifier =
       match ParseNode._get_child_with[Identifier](
         obj,
@@ -170,7 +170,7 @@ class val UsingFFI is NodeData
     end
 
 primitive ParseUsingFFI
-  fun apply(obj: json.Object, children: NodeSeq): (UsingFFI | String) =>
+  fun apply(obj: json.Object val, children: NodeSeq): (UsingFFI | String) =>
     let identifier =
       match ParseNode._get_child_with[Identifier](
         obj,
diff --git a/eohippus/json/item.pony b/eohippus/json/item.pony
index d35181f..88e4660 100644
--- a/eohippus/json/item.pony
+++ b/eohippus/json/item.pony
@@ -4,25 +4,21 @@ use ".."
 primitive Null
   fun string(): String iso^ => "null".clone()
 
-type Item is (Object | Sequence | String box | I128 | F64 | Bool | Null)
+type Item is (Object box | Sequence box | String box | I128 | F64 | Bool | Null)
 
 primitive Clone
-  fun apply(item: Item): Item val =>
+  fun apply(item: Item)
+    : (Object ref | Sequence ref | String ref | I128 | F64 | Bool | Null)
+  =>
     match item
-    | let obj: Object =>
-      let props: Seq[(String, Item val)] trn = Array[(String, Item val)]
+    | let obj: Object box =>
+      let props = Array[(String, Item)]
       for (k, v) in obj.pairs() do
         props.push((k, Clone(v)))
       end
-      let props': Seq[(String, Item val)] val = consume props
-      recover Object(props') end
-    | let seq: Sequence =>
-      let items: Seq[Item val] trn = Array[Item val]
-      for v in items.values() do
-        items.push(Clone(v))
-      end
-      let items': Seq[Item val] val = consume items
-      recover Sequence(items') end
+      Object(props)
+    | let seq: Sequence box =>
+      Sequence.from_iter[Item](seq.values(), {(i) => Clone(i) })
     | let str: String box =>
       str.clone()
     | let int: I128 =>
diff --git a/eohippus/json/object.pony b/eohippus/json/object.pony
index 43d86e3..cc773fa 100644
--- a/eohippus/json/object.pony
+++ b/eohippus/json/object.pony
@@ -2,12 +2,16 @@ use "collections"
 use "itertools"
 use ".."
 
-class box Object
-  embed _items: Array[(String, Item)] = _items.create()
+class Object
+  embed _items: Array[(String, Item)]
 
-  new create(items: ReadSeq[(String, Item)] box = Array[(String, Item)]) =>
-    for (key, value) in items.values() do
-      _items.push((key, value))
+  new create(items: (ReadSeq[(String, Item)] | None) = None) =>
+    match items
+    | let items': ReadSeq[(String, Item)] =>
+      _items = _items.create(items'.size())
+      _items.append(items')
+    else
+      _items = _items.create()
     end
 
   fun contains(key: (String | USize)): Bool =>
@@ -70,11 +74,11 @@ class box Object
         result.append("\"" + key + "\":")
         if pretty then result.append(" ") end
         match value
-        | let obj: this->Object box =>
+        | let obj: Object box =>
           result.append(obj.get_string(pretty, indent'))
-        | let seq: this->Sequence box =>
+        | let seq: Sequence box =>
           result.append(seq.get_string(pretty, indent'))
-        | let str: this->String box =>
+        | let str: String box =>
           result.append("\"" + StringUtil.escape(str) + "\"")
         | let int: I128 =>
           result.append(int.string())
diff --git a/eohippus/json/parse.pony b/eohippus/json/parse.pony
index f9febdc..a36250c 100644
--- a/eohippus/json/parse.pony
+++ b/eohippus/json/parse.pony
@@ -1,15 +1,15 @@
 
 primitive Parse
-  fun apply(str: String): (Item | ParseError) =>
+  fun apply(str: String): (Item val | ParseError) =>
     let parser = Parser
     for ch in str.values() do
       match parser.parse_char(ch)
-      | let item: (Item | ParseError) =>
+      | let item: (Item val | ParseError) =>
         return item
       end
     end
     match parser.parse_char(0)
-    | let item: (Item | ParseError) =>
+    | let item: (Item val | ParseError) =>
       return item
     end
     ParseError(str.size(), "unknown error")
@@ -51,7 +51,7 @@ type _ParseState is
   | _InFalse
   | _InNull )
 
-type _TempItem is
+type _StackItem is
   ( Object trn
   | Sequence trn
   | String trn
@@ -60,9 +60,9 @@ type _TempItem is
   | Bool
   | Null
   | U32
-  | (String trn, None)
-  | (F64, F64) // frac; floating point, next fractional power of 10
-  | (F64, I32) ) // exp; floating point, exponent (∞ or -∞ to start)
+  | (String, None) // property to be filled
+  | (F64, F64)     // frac; floating point, next fractional power of 10
+  | (F64, I32) )   // exp; floating point, exponent (∞ or -∞ to start)
 
 type _TrnItem is
   ( Object trn
@@ -75,7 +75,7 @@ type _TrnItem is
 
 class Parser
   let _ten: F64 = 10.0
-  let _value_stack: Array[_TempItem] = _value_stack.create()
+  let _value_stack: Array[_StackItem] = _value_stack.create()
   var _state: _ParseState = _ExpectItem
   var _index: USize = 0
   var _line: USize = 1
@@ -316,7 +316,7 @@ class Parser
   fun ref _expect_next(): _ParseState ? =>
     if _value_stack.size() > 0 then
       match _value_stack(_value_stack.size() - 1)?
-      | let _: Object trn =>
+      | let _: Object tag =>
         return _ExpectName
       end
     end
@@ -412,7 +412,8 @@ class Parser
   fun ref _handle_in_string(is_name: Bool): (ParseError | None) ? =>
     if _ch == '"' then
       if is_name then
-        _value_stack.push((_value_stack.pop()? as String trn^, None))
+        let name = _value_stack.pop()? as String trn^
+        _value_stack.push((consume name, None))
         _state = _ExpectColon
       else
         _add_item(_value_stack.pop()? as String trn^)?
@@ -421,7 +422,7 @@ class Parser
     elseif (_ch == '\\') and (not is_name) then
       _state = _InEscape
     else
-      (_value_stack(_value_stack.size() - 1)? as String trn^).push(_ch)
+      (_value_stack(_value_stack.size() - 1)? as String trn).push(_ch)
     end
     None
 
@@ -443,7 +444,7 @@ class Parser
       if _expect_hex > 0 then
         _value_stack.push(cur)
       else
-        (_value_stack(_value_stack.size() - 1)? as String trn^).push_utf32(cur)
+        (_value_stack(_value_stack.size() - 1)? as String trn).push_utf32(cur)
         _state = _InString
       end
     else
@@ -471,7 +472,7 @@ class Parser
         else
           _ch
         end
-      (_value_stack(_value_stack.size() - 1)? as String trn^).push(ch')
+      (_value_stack(_value_stack.size() - 1)? as String trn).push(ch')
       _state = _InString
     end
     None
@@ -580,13 +581,15 @@ class Parser
     if _value_stack.size() == 0 then
       _value_stack.push(consume item)
     else
-      match _value_stack(_value_stack.size() - 1)?
+      let top = _value_stack.pop()?
+      match consume top
       | let seq: Sequence trn =>
         seq.push(consume item)
-      | (let name: String trn, _) =>
-        (_value_stack(_value_stack.size() - 2)? as Object trn)
-          .update(consume name, consume item)
-        _value_stack.pop()?
+        _value_stack.push(consume seq)
+      | (let name: String, _) =>
+        let obj = _value_stack.pop()? as Object trn^
+        obj.update(consume name, consume item)
+        _value_stack.push(consume obj)
       else
         error
       end
diff --git a/eohippus/json/sequence.pony b/eohippus/json/sequence.pony
index d63fb2f..a23859e 100644
--- a/eohippus/json/sequence.pony
+++ b/eohippus/json/sequence.pony
@@ -1,14 +1,22 @@
 use "collections"
+use "itertools"
 use ".."
 
-class box Sequence
-  embed _items: Array[Item] = _items.create()
+class Sequence
+  embed _items: Array[Item]
 
-  new create(items: ReadSeq[this->Item] box = Array[this->Item]) =>
-    _items.append(items)
+  new create(items: (ReadSeq[Item] | None) = None) =>
+    match items
+    | let items': ReadSeq[Item] =>
+      _items = _items.create(items'.size())
+      _items.append(items')
+    else
+      _items = Array[Item](0)
+    end
 
-  new from_iter(items: Iterator[this->Item]) =>
-    _items.concat(items)
+  new from_iter[T](items: Iterator[T], f: {(T!): Item } box) =>
+    _items = Array[Item]
+    Iter[T](items).map[Item](f).collect(_items)
 
   fun size(): USize => _items.size()
 
@@ -44,11 +52,11 @@ class box Sequence
         end
         if pretty then result.append(indent') end
         match item
-        | let obj: this->Object box =>
+        | let obj: Object box =>
           result.append(obj.get_string(pretty, indent'))
-        | let seq: this->Sequence box =>
+        | let seq: Sequence box =>
           result.append(seq.get_string(pretty, indent'))
-        | let str: this->String box =>
+        | let str: String box =>
           result.append("\"" + StringUtil.escape(str) + "\"")
         | let int: I128 =>
           result.append(int.string())
diff --git a/eohippus/json/subsumes.pony b/eohippus/json/subsumes.pony
index 6eae986..7f9f544 100644
--- a/eohippus/json/subsumes.pony
+++ b/eohippus/json/subsumes.pony
@@ -65,10 +65,10 @@ primitive Subsumes
       if a_str == b_str then
         return (true, "")
       else
-        return (
-          false,
-          "'" + StringUtil.escape(a_str) + "' at " + p + " != '" +
-            StringUtil.escape(b_str) + "'")
+        return
+          ( false
+          , "'" + StringUtil.escape(a_str) + "' at " + p + " != '" +
+              StringUtil.escape(b_str) + "'" )
       end
     end
     (false, "rhs at " + p + " is not a string")
diff --git a/eohippus/server/rpc/data/client_capabilities/client_capabilities.pony b/eohippus/server/rpc/data/client_capabilities/client_capabilities.pony
index dc00a3e..bf3d426 100644
--- a/eohippus/server/rpc/data/client_capabilities/client_capabilities.pony
+++ b/eohippus/server/rpc/data/client_capabilities/client_capabilities.pony
@@ -4,7 +4,7 @@ interface val ClientCapabilities
   fun val workspace(): (WorkspaceClientCapabilities | None)
   fun val textDocument(): (TextDocumentClientCapabilities | None)
   fun val general(): (GeneralClientCapabilities | None)
-  fun val experimental(): (json.Item val | None)
+  fun val experimental(): (json.Item | None)
 
 primitive ParseClientCapabilities
   fun apply(obj: json.Object val): (ClientCapabilities | String) =>
@@ -50,11 +50,14 @@ primitive ParseClientCapabilities
           return "clientCapabilities.general must be a JSON object"
         end
       end
-    let experimental' = try json.Clone(obj("experimental")?) end
+    let experimental': (json.Item val | None) =
+      try
+        recover val json.Clone(obj("experimental")?) end
+      end
     object val is ClientCapabilities
       fun val workspace(): (WorkspaceClientCapabilities | None) => workspace'
       fun val textDocument(): (TextDocumentClientCapabilities | None) =>
         textDocument'
       fun val general(): (GeneralClientCapabilities | None) => general'
-      fun val experimental(): (json.Item val | None) => experimental'
+      fun val experimental(): (json.Item | None) => experimental'
     end
diff --git a/eohippus/server/rpc/data/client_capabilities/general_client_capabilities.pony b/eohippus/server/rpc/data/client_capabilities/general_client_capabilities.pony
index 00cc0f2..24d6578 100644
--- a/eohippus/server/rpc/data/client_capabilities/general_client_capabilities.pony
+++ b/eohippus/server/rpc/data/client_capabilities/general_client_capabilities.pony
@@ -88,7 +88,7 @@ interface val StaleRequestSupport
   fun val retryOnContentModified(): Array[String] val
 
 primitive ParseStaleRequestSupport
-  fun apply(obj: json.Object): (StaleRequestSupport | String) =>
+  fun apply(obj: json.Object val): (StaleRequestSupport | String) =>
     let cancel' =
       try
         match obj("cancel")?
@@ -103,7 +103,7 @@ primitive ParseStaleRequestSupport
     let retryOnContentModified': Array[String] val =
       try
         match obj("retryOnContentModified")?
-        | let r_seq: json.Sequence =>
+        | let r_seq: json.Sequence val =>
           let reqs: Array[String] trn = Array[String]
           for r_item in r_seq.values() do
             match r_item
diff --git a/eohippus/server/rpc/data/client_capabilities/regular_expressions_client_capabilities.pony b/eohippus/server/rpc/data/client_capabilities/regular_expressions_client_capabilities.pony
index 37e6b47..0d7da50 100644
--- a/eohippus/server/rpc/data/client_capabilities/regular_expressions_client_capabilities.pony
+++ b/eohippus/server/rpc/data/client_capabilities/regular_expressions_client_capabilities.pony
@@ -11,7 +11,7 @@ primitive ParseRegularExpressionsClientCapabilities
     let engine': String =
       try
         match obj("engine")?
-        | let e: String =>
+        | let e: String val =>
           e.clone()
         else
           return "regularExpressions.engine must be of type string"
@@ -22,7 +22,7 @@ primitive ParseRegularExpressionsClientCapabilities
     let version': (String | None) =
       try
         match obj("version")?
-        | let v: String =>
+        | let v: String val =>
           v.clone()
         else
           return "regularExpressions.version must be of type string"
diff --git a/eohippus/server/rpc/data/client_capabilities/text_document_client_capabilities.pony b/eohippus/server/rpc/data/client_capabilities/text_document_client_capabilities.pony
index a0717d3..d2bc943 100644
--- a/eohippus/server/rpc/data/client_capabilities/text_document_client_capabilities.pony
+++ b/eohippus/server/rpc/data/client_capabilities/text_document_client_capabilities.pony
@@ -115,7 +115,7 @@ primitive ParseTagSupport
     let valueSet': Array[DiagnosticTag] val =
       try
         match obj("valueSet")?
-        | let vs_seq: json.Sequence =>
+        | let vs_seq: json.Sequence val =>
           let values: Array[DiagnosticTag] trn = Array[DiagnosticTag]
           for item in vs_seq.values() do
             values.push(
diff --git a/eohippus/server/rpc/data/client_capabilities/workspace_client_capabilities.pony b/eohippus/server/rpc/data/client_capabilities/workspace_client_capabilities.pony
index 065eb3d..d377722 100644
--- a/eohippus/server/rpc/data/client_capabilities/workspace_client_capabilities.pony
+++ b/eohippus/server/rpc/data/client_capabilities/workspace_client_capabilities.pony
@@ -19,7 +19,7 @@ interface val WorkspaceClientCapabilities
   // fun val diagnostics(): (DiagnosticWorkspaceClientCapabilities | None)
 
 primitive ParseWorkspaceClientCapabilities
-  fun apply(obj: json.Object): (WorkspaceClientCapabilities | String) =>
+  fun apply(obj: json.Object val): (WorkspaceClientCapabilities | String) =>
     let applyEdit' =
       try
         match obj("applyEdit")?
@@ -32,7 +32,7 @@ primitive ParseWorkspaceClientCapabilities
     let workspaceEdit' =
       try
         match obj("workspaceEdit")?
-        | let we_obj: json.Object =>
+        | let we_obj: json.Object val =>
           match ParseWorkspaceEditClientCapabilities(we_obj)
           | let we: WorkspaceEditClientCapabilities =>
             we
diff --git a/eohippus/server/rpc/data/client_capabilities/workspace_edit_client_capabilities.pony b/eohippus/server/rpc/data/client_capabilities/workspace_edit_client_capabilities.pony
index cd6c42e..665bb9a 100644
--- a/eohippus/server/rpc/data/client_capabilities/workspace_edit_client_capabilities.pony
+++ b/eohippus/server/rpc/data/client_capabilities/workspace_edit_client_capabilities.pony
@@ -11,7 +11,7 @@ interface val WorkspaceEditClientCapabilities
   //   (ChangeAnnotationSupportClientCapability | None)
 
 primitive ParseWorkspaceEditClientCapabilities
-  fun apply(obj: json.Object): (WorkspaceEditClientCapabilities | String) =>
+  fun apply(obj: json.Object val): (WorkspaceEditClientCapabilities | String) =>
     let documentChanges' =
       try
         match obj("documentChanges")?
@@ -24,7 +24,7 @@ primitive ParseWorkspaceEditClientCapabilities
     let resourceOperations': (Array[ResourceOperationKind] val | None)  =
       try
         match obj("resourceOperations")?
-        | let ro_seq: json.Sequence =>
+        | let ro_seq: json.Sequence val =>
           let ops: Array[ResourceOperationKind] trn =
             Array[ResourceOperationKind]
           for item in ro_seq.values() do
@@ -50,7 +50,7 @@ interface val ChangeAnnotationSupportClientCapability
   fun val groupsOnLabel(): (Bool | None)
 
 primitive ParseChangeAnnotationSupportClientCapability
-  fun apply(obj: json.Object):
+  fun apply(obj: json.Object val):
     (ChangeAnnotationSupportClientCapability | String)
   =>
     let groupsOnLabel' =
diff --git a/eohippus/server/rpc/data/document.pony b/eohippus/server/rpc/data/document.pony
index e71bac1..acc5647 100644
--- a/eohippus/server/rpc/data/document.pony
+++ b/eohippus/server/rpc/data/document.pony
@@ -21,4 +21,4 @@ interface val DocumentFilter is SendData
     end
     json.Object(props)
 
-type DocumentSelector is Seq[DocumentFilter]
+type DocumentSelector is Seq[DocumentFilter] val
diff --git a/eohippus/server/rpc/data/initialize_params.pony b/eohippus/server/rpc/data/initialize_params.pony
index 2f8e085..93cb9a5 100644
--- a/eohippus/server/rpc/data/initialize_params.pony
+++ b/eohippus/server/rpc/data/initialize_params.pony
@@ -55,7 +55,7 @@ primitive ParseInitializeParams
     let locale': (String | None) =
       try
         match obj("locale")?
-        | let str: String =>
+        | let str: String val =>
           str.clone()
         else
           return "initializeParams.locale must be of type string"
@@ -64,7 +64,7 @@ primitive ParseInitializeParams
     let rootPath': (String | None) =
       try
         match obj("rootPath")?
-        | let str: String =>
+        | let str: String val =>
           str.clone()
         | json.Null =>
           None
@@ -75,7 +75,7 @@ primitive ParseInitializeParams
     let rootUri': (String | None) =
       try
         match obj("rootUri")?
-        | let str: String =>
+        | let str: String val =>
           str.clone()
         | json.Null =>
           None
@@ -87,7 +87,7 @@ primitive ParseInitializeParams
       end
     let initializationOptions': (json.Item val | None) =
       try
-        json.Clone(obj("initializationOptions")?)
+        recover val json.Clone(obj("initializationOptions")?) end
       end
     let capabilities' =
       try
@@ -96,7 +96,7 @@ primitive ParseInitializeParams
           match c_caps.ParseClientCapabilities(cap_obj)
           | let client_caps: c_caps.ClientCapabilities =>
             client_caps
-          | let err: String =>
+          | let err: String val =>
             return err
           end
         else
@@ -112,7 +112,7 @@ primitive ParseInitializeParams
           match ParseTraceValue(str)
           | let tv: TraceValue =>
             tv
-          | let err: String =>
+          | let err: String val =>
             return err
           end
         else
@@ -149,7 +149,7 @@ primitive ParseInitializeParams
       fun val locale(): (String | None) => locale'
       fun val rootPath(): (String | None) => rootPath'
       fun val rootUri(): (DocumentUri | None) => rootUri'
-      fun val initializationOptions(): (json.Item val | None) =>
+      fun val initializationOptions(): (json.Item | None) =>
         initializationOptions'
       fun val capabilities(): c_caps.ClientCapabilities => capabilities'
       fun val trace(): (TraceValue | None) => trace'
@@ -197,7 +197,7 @@ primitive TraceVerbose
 type TraceValue is (TraceOff | TraceMessages | TraceVerbose)
 
 primitive ParseTraceValue
-  fun apply(item: json.Item): (TraceValue | String) =>
+  fun apply(item: json.Item val): (TraceValue | String) =>
     match item
     | "off" =>
       TraceOff
diff --git a/eohippus/server/rpc/data/initialize_result.pony b/eohippus/server/rpc/data/initialize_result.pony
index d3f41d0..7b8a84e 100644
--- a/eohippus/server/rpc/data/initialize_result.pony
+++ b/eohippus/server/rpc/data/initialize_result.pony
@@ -7,27 +7,23 @@ interface val InitializeResult is ResultData
   fun val capabilities(): s_caps.ServerCapabilities
   fun val serverInfo(): (ServerInfo | None)
 
-  fun val get_json(): json.Item val =>
-    recover val
-      let props =
-        [ as (String, json.Item): ("capabilities", capabilities().get_json()) ]
-      match serverInfo()
-      | let si: ServerInfo =>
-        props.push(("serverInfo", si.get_json()))
-      end
-      json.Object(props)
+  fun val get_json(): json.Item =>
+    let props =
+      [ as (String, json.Item): ("capabilities", capabilities().get_json()) ]
+    match serverInfo()
+    | let si: ServerInfo =>
+      props.push(("serverInfo", si.get_json()))
     end
+    json.Object(props)
 
 interface val ServerInfo is ResultData
   fun val name(): String
   fun val version(): (String | None)
 
-  fun val get_json(): json.Item val =>
-    recover val
-      let props = [ as (String, json.Item): ("name", name()) ]
-      match version()
-      | let v: String =>
-        props.push(("version", v))
-      end
-      json.Object(props)
+  fun val get_json(): json.Item =>
+    let props = [ as (String, json.Item): ("name", name()) ]
+    match version()
+    | let v: String =>
+      props.push(("version", v))
     end
+    json.Object(props)
diff --git a/eohippus/server/rpc/data/misc_message_stuff.pony b/eohippus/server/rpc/data/misc_message_stuff.pony
index 38afc9f..fbde1eb 100644
--- a/eohippus/server/rpc/data/misc_message_stuff.pony
+++ b/eohippus/server/rpc/data/misc_message_stuff.pony
@@ -11,7 +11,7 @@ interface val Notification is Message
   fun val params(): NotificationParams
 
 interface val NotificationParams
-  fun val get_json(): json.Item val
+  fun val get_json(): json.Item
 
 interface val RequestMessage is Message
   fun val id(): (I128 | String val)
@@ -129,24 +129,20 @@ interface val Location
   fun val range(): Range
 
   fun val get_json(): json.Item =>
-    recover val
-      json.Object(
-        [ as (String, json.Item):
-          ("uri", uri())
-          ("range", range().get_json()) ])
-    end
+    json.Object(
+      [ as (String, json.Item):
+        ("uri", uri())
+        ("range", range().get_json()) ])
 
 interface val Range
   fun val start(): Position
   fun val endd(): Position
 
   fun val get_json(): json.Item =>
-    recover val
-      json.Object(
-        [ as (String, json.Item):
-          ("start", start().get_json())
-          ("end", endd().get_json()) ])
-    end
+    json.Object(
+      [ as (String, json.Item):
+        ("start", start().get_json())
+        ("end", endd().get_json()) ])
 
 primitive ParseRange
   fun apply(obj: json.Object val): (Range | String) =>
@@ -184,12 +180,10 @@ interface val Position
   fun val character(): I128
 
   fun val get_json(): json.Item =>
-    recover val
-      json.Object(
-        [ as (String, json.Item):
-          ("line", line())
-          ("character", character()) ])
-    end
+    json.Object(
+      [ as (String, json.Item):
+        ("line", line())
+        ("character", character()) ])
 
 primitive ParsePosition
   fun apply(obj: json.Object val): (Position | String) =>
diff --git a/eohippus/server/rpc/data/publish_diagnostics_params.pony b/eohippus/server/rpc/data/publish_diagnostics_params.pony
index 6a10431..35a1290 100644
--- a/eohippus/server/rpc/data/publish_diagnostics_params.pony
+++ b/eohippus/server/rpc/data/publish_diagnostics_params.pony
@@ -1,3 +1,5 @@
+use "itertools"
+
 use json = "../../../json"
 
 interface val PublishDiagnosticsParams is NotificationParams
@@ -5,20 +7,19 @@ interface val PublishDiagnosticsParams is NotificationParams
   fun val version(): (I128 | None) => None
   fun val diagnostics(): Array[Diagnostic] val
 
-  fun val get_json(): json.Item val =>
-    recover val
-      let props = [ as (String, json.Item): ("uri", uri()) ]
-      match version()
-      | let n: I128 =>
-        props.push(("version", n))
-      end
-      let diag_items = Array[json.Item val]
-      for diag in diagnostics().values() do
-        diag_items.push(diag.get_json())
-      end
-      props.push(("diagnostics", json.Sequence(diag_items)))
-      json.Object(props)
+  fun val get_json(): json.Item =>
+    let props = [ as (String, json.Item): ("uri", uri()) ]
+    match version()
+    | let n: I128 =>
+      props.push(("version", n))
     end
+    props.push(
+      ( "diagnostics"
+      , recover val
+          json.Sequence.from_iter[Diagnostic](
+            diagnostics().values(), { (diag) => diag.get_json() })
+        end ))
+    json.Object(props)
 
 primitive DiagnosticError
   fun apply(): I128 => 1
@@ -50,13 +51,11 @@ interface val DiagnosticRelatedInformation
   fun val location(): Location
   fun val message(): String
 
-  fun val get_json(): json.Item val =>
-    recover val
-      json.Object(
-        [ as (String, json.Item):
-          ("location", location().get_json())
-          ("message", message()) ])
-    end
+  fun val get_json(): json.Item =>
+    json.Object(
+      [ as (String, json.Item):
+        ("location", location().get_json())
+        ("message", message()) ])
 
 interface val Diagnostic
   fun val range(): Range
@@ -70,55 +69,51 @@ interface val Diagnostic
     : (Array[DiagnosticRelatedInformation] val | None)
   =>
     None
-  fun val data(): (json.Item val | None) => None
-
-  fun val get_json(): json.Item val =>
-    recover val
-      let props = [ as (String, json.Item): ("range", range().get_json()) ]
-      match severity()
-      | let s: DiagnosticSeverity =>
-        props.push(("severity", s()))
-      end
-      match code()
-      | let item: (I128 | String) =>
-        props.push(("code", item))
-      end
-      match codeDescription()
-      | let cd: CodeDescription =>
-        props.push(("codeDescription", cd.get_json()))
-      end
-      match source()
-      | let str: String =>
-        props.push(("source", str))
-      end
-      props.push(("message", message()))
-      match tags()
-      | let tags_arr: Array[DiagnosticTag] val =>
-        let items = Array[json.Item]
-        for t in tags_arr.values() do
-          items.push(t())
-        end
-        props.push(("tags", json.Sequence(items)))
-      end
-      match relatedInformation()
-      | let ri_arr: Array[DiagnosticRelatedInformation] val =>
-        let items = Array[json.Item]
-        for ri in ri_arr.values() do
-          items.push(ri.get_json())
+  fun val data(): (json.Item | None) => None
+
+  fun val get_json(): json.Item =>
+    let props = [ as (String, json.Item): ("range", range().get_json()) ]
+    match severity()
+    | let s: DiagnosticSeverity =>
+      props.push(("severity", s()))
+    end
+    match code()
+    | let item: (I128 | String) =>
+      props.push(("code", item))
+    end
+    match codeDescription()
+    | let cd: CodeDescription =>
+      props.push(("codeDescription", cd.get_json()))
+    end
+    match source()
+    | let str: String =>
+      props.push(("source", str))
+    end
+    props.push(("message", message()))
+    match tags()
+    | let tags_arr: Array[DiagnosticTag] val =>
+      let seq =
+        recover val
+          json.Sequence.from_iter[DiagnosticTag](
+            tags_arr.values(), {(t) => t() })
         end
-        props.push(("relatedInformation", json.Sequence(items)))
-      end
-      match data()
-      | let d: json.Item =>
-        props.push(("data", d))
-      end
-      json.Object(props)
+      props.push(("tags", seq))
+    end
+    match relatedInformation()
+    | let ri_arr: Array[DiagnosticRelatedInformation] val =>
+      let seq =
+        json.Sequence.from_iter[DiagnosticRelatedInformation](
+          ri_arr.values(), {(ri) => ri.get_json() })
+      props.push(("relatedInformation", seq))
     end
+    match data()
+    | let d: json.Item =>
+      props.push(("data", d))
+    end
+    json.Object(props)
 
 interface val CodeDescription
   fun val href(): String
 
-  fun val get_json(): json.Item val =>
-    recover val
-      json.Object([ as (String, json.Item): ("href", href()) ])
-    end
+  fun val get_json(): json.Item =>
+    json.Object([ as (String, json.Item): ("href", href()) ])
diff --git a/eohippus/server/rpc/data/server_capabilities/notebook_document_sync_options.pony b/eohippus/server/rpc/data/server_capabilities/notebook_document_sync_options.pony
index 53b30f5..de6dd63 100644
--- a/eohippus/server/rpc/data/server_capabilities/notebook_document_sync_options.pony
+++ b/eohippus/server/rpc/data/server_capabilities/notebook_document_sync_options.pony
@@ -1,5 +1,6 @@
-use json = "../../../../json"
+use "itertools"
 
+use json = "../../../../json"
 use ".."
 
 interface val NotebookDocumentSyncOptions is SendData
@@ -7,17 +8,20 @@ interface val NotebookDocumentSyncOptions is SendData
   fun val save(): (Bool | None) => None
 
   fun val get_json_props(): Array[(String, json.Item)] =>
-    let selector_values = Array[json.Item]
-    for selector in notebookSelector().values() do
-      let sv = selector.get_json()
-      if sv isnt json.Null then
-        selector_values.push(sv)
-      end
-    end
-
-    let props =
-      [ as (String, json.Item):
-        ("notebookSelector", json.Sequence(selector_values)) ]
+    let seq =
+      json.Sequence(
+        Iter[NotebookSelectorData](notebookSelector().values())
+          .filter_map[json.Item](
+            { (selector) =>
+              let sj = selector.get_json()
+              if sj isnt json.Null then
+                sj
+              else
+                None
+              end
+            })
+          .collect(Array[json.Item]))
+    let props = [ as (String, json.Item): ("notebookSelector", seq) ]
     match save()
     | let s: Bool =>
       props.push(("save", s))
@@ -29,17 +33,16 @@ interface val NotebookDocumentSyncOptions is SendData
 
 interface val NotebookSelectorData is SendData
   fun val notebook(): (String | NotebookDocumentFilter | None) => None
-  fun val cells(): (Array[NotebookCell] | None) => None
+  fun val cells(): (Array[NotebookCell] val | None) => None
 
   fun val get_json(): json.Item =>
     let cells_value =
       match cells()
-      | let arr: Array[NotebookCell] =>
-        let cell_items = Array[json.Item]
-        for cell in arr.values() do
-          cell_items.push(cell.get_json())
+      | let arr: Array[NotebookCell] val =>
+        recover val
+          json.Sequence.from_iter[NotebookCell](
+            arr.values(), {(cell) => cell.get_json() })
         end
-        json.Sequence(cell_items)
       end
 
     let props = Array[(String, json.Item)]
@@ -50,7 +53,7 @@ interface val NotebookSelectorData is SendData
       props.push(("notebook", ndf.get_json()))
     end
     match cells_value
-    | let cv: json.Sequence =>
+    | let cv: json.Sequence val =>
       props.push(("cells", cv))
     end
     if props.size() > 0 then
diff --git a/eohippus/server/rpc/data/server_capabilities/semantic_tokens_options.pony b/eohippus/server/rpc/data/server_capabilities/semantic_tokens_options.pony
index b49fae4..fc7f98a 100644
--- a/eohippus/server/rpc/data/server_capabilities/semantic_tokens_options.pony
+++ b/eohippus/server/rpc/data/server_capabilities/semantic_tokens_options.pony
@@ -42,11 +42,10 @@ interface val SemanticTokensRegistrationOptions is
     end
     match documentSelector()
     | let ds: DocumentSelector =>
-      let items = Array[json.Item]
-      for filter in ds.values() do
-        items.push(filter.get_json())
-      end
-      props.push(("documentSelector", json.Sequence(items)))
+      let seq =
+        json.Sequence.from_iter[DocumentFilter](
+          ds.values(), {(filter) => filter.get_json() })
+      props.push(("documentSelector", seq))
     end
     props.append(get_json_props())
     json.Object(props)
@@ -58,8 +57,8 @@ interface val SemanticTokensLegend
   fun val get_json(): json.Item =>
     json.Object(
       [ as (String, json.Item):
-        ("tokenTypes", json.Sequence(tokenTypes()))
-        ("tokenModifiers", json.Sequence(tokenModifiers())) ])
+        ("tokenTypes", recover val json.Sequence(tokenTypes()) end)
+        ("tokenModifiers", recover val json.Sequence(tokenModifiers()) end) ])
 
 interface val SemanticTokensFullOptions
   fun val delta(): (Bool | None)
diff --git a/eohippus/server/rpc/data/server_capabilities/text_document_registration_options.pony b/eohippus/server/rpc/data/server_capabilities/text_document_registration_options.pony
index 78e9c42..66cbbc1 100644
--- a/eohippus/server/rpc/data/server_capabilities/text_document_registration_options.pony
+++ b/eohippus/server/rpc/data/server_capabilities/text_document_registration_options.pony
@@ -9,10 +9,11 @@ interface val TextDocumentRegistrationOptions is SendData
     let props = Array[(String, json.Item)]
     match documentSelector()
     | let ds: DocumentSelector =>
-      let items = Array[json.Item]
-      for filter in ds.values() do
-        items.push(filter.get_json())
-      end
-      props.push(("documentSelector", json.Sequence(items)))
+      let seq =
+        recover val
+          json.Sequence.from_iter[DocumentFilter](
+            ds.values(), {(filter) => filter.get_json() })
+        end
+      props.push(("documentSelector", seq))
     end
-    json.Object(props)
+    json.Object(consume props)
diff --git a/eohippus/server/rpc/handler.pony b/eohippus/server/rpc/handler.pony
index 8d124ca..0f5d439 100644
--- a/eohippus/server/rpc/handler.pony
+++ b/eohippus/server/rpc/handler.pony
@@ -57,7 +57,7 @@ actor EohippusHandler is Handler
   let _log: Logger[String]
   let _server: Server
   let _channel: Channel
-  let _json_parser: json.Parser
+  let _json_parser: json.Parser iso
 
   var _state: _HandlerState
   var _current_header_name: String ref
@@ -514,7 +514,7 @@ actor EohippusHandler is Handler
     _state = _NotConnected
     _server.rpc_closed()
 
-  fun ref _write_message(obj: json.Object) =>
+  fun ref _write_message(obj: json.Object box) =>
     let body = recover val obj.get_string(false) end
     let message: String trn = String
     message.append("Content-Length:")
diff --git a/eohippus/test/_test_ast_parse_node.pony b/eohippus/test/_test_ast_parse_node.pony
index 4640418..da66e35 100644
--- a/eohippus/test/_test_ast_parse_node.pony
+++ b/eohippus/test/_test_ast_parse_node.pony
@@ -35,7 +35,7 @@ class iso _TestAstParseNodeAnnotation is UnitTest
         }
       """
     match json.Parse(src)
-    | let obj: json.Object =>
+    | let obj: json.Object val =>
       match ast.ParseNode(name(), obj)
       | let ann: ast.NodeWith[ast.Annotation] =>
         h.assert_is[(USize | None)](4, ann.src_info().line, "line")
diff --git a/eohippus/test/_test_json.pony b/eohippus/test/_test_json.pony
index 9dedebc..23d611c 100644
--- a/eohippus/test/_test_json.pony
+++ b/eohippus/test/_test_json.pony
@@ -132,6 +132,7 @@ class iso _TestJsonSubsumes is UnitTest
 
       let exp5 = json.Object(
         [ as (String, json.Item):
-          ("foo", json.Sequence([ as json.Item: I128(1); I128(2) ])) ])
+          ( "foo"
+          , recover val json.Sequence([ as json.Item: I128(1); I128(2) ]) end) ])
       let source5 = """{"foo":[1,2]}"""
       _test(h, source5, exp5)
diff --git a/eohippus/test/lsp/test_stream.pony b/eohippus/test/lsp/test_stream.pony
index d65e1a7..add84d5 100644
--- a/eohippus/test/lsp/test_stream.pony
+++ b/eohippus/test/lsp/test_stream.pony
@@ -22,9 +22,9 @@ actor TestInputStream is InputStream
     if not _valid then return end
     match _notify
     | let notify: InputNotify iso =>
-      match data
-      | let str: String =>
-        notify(str.clone().iso_array())
+      match consume data
+      | let str: String iso =>
+        notify((consume str).iso_array())
       | let arr: Array[U8] iso =>
         notify(consume arr)
       end