diff --git a/prototyping/FFI/Data/List.agda b/prototyping/FFI/Data/List.agda
deleted file mode 100644
index e35c464c..00000000
--- a/prototyping/FFI/Data/List.agda
+++ /dev/null
@@ -1,8 +0,0 @@
-module FFI.Data.Maybe where
-
-{-# FOREIGN GHC import qualified Data.Maybe #-}
-
-data Maybe (A : Set) : Set where
-  Nothing : Maybe A
-  Just : A → Maybe A
-{-# COMPILE GHC Maybe = data Data.Maybe.Maybe (Data.Maybe.Nothing|Data.Maybe.Just) #-}
diff --git a/prototyping/Luau/Syntax/FromJSON.agda b/prototyping/Luau/Syntax/FromJSON.agda
index 93514044..2c09f02f 100644
--- a/prototyping/Luau/Syntax/FromJSON.agda
+++ b/prototyping/Luau/Syntax/FromJSON.agda
@@ -2,15 +2,78 @@ module Luau.Syntax.FromJSON where
 
 open import Luau.Syntax using (Type; Block; Stat ; Expr; nil; return; _∙; _∙_)
 
+open import Agda.Builtin.List using (List; _∷_; [])
+
 open import FFI.Data.Aeson using (Value; Array; Object; object; array; fromString; lookup)
 open import FFI.Data.Bool using (true; false)
 open import FFI.Data.Either using (Either; Left; Right)
-open import FFI.Data.Maybe using (nothing; just)
+open import FFI.Data.Maybe using (Maybe; nothing; just)
 open import FFI.Data.String using (String; _++_)
 open import FFI.Data.Vector using (head; tail; null; empty)
 
-AstExprConstantNil = fromString "AstExprConstantNil"
-AstStatReturn = fromString "AstStatReturn"
+AstExprKeys =
+  "AstExprBinary" ∷
+  "AstExprCall" ∷
+  "AstExprConstantBool" ∷
+  "AstExprConstantNil" ∷
+  "AstExprConstantNumber" ∷
+  "AstExprConstantString" ∷
+  "AstExprError" ∷
+  "AstExprFunction" ∷
+  "AstExprGlobal" ∷
+  "AstExprGroup" ∷
+  "AstExprIndexExpr" ∷
+  "AstExprIndexName" ∷
+  "AstExprLocal" ∷
+  "AstExprTable" ∷
+  "AstExprTypeAssertion" ∷
+  "AstExprUnary" ∷
+  []
+
+AstStatKeys =
+  "AstStatAssign" ∷
+  "AstStatBlock" ∷
+  "AstStatBreak" ∷
+  "AstStatCompoundAssign" ∷
+  "AstStatContinue" ∷
+  "AstStatDeclareClass" ∷
+  "AstStatDeclareFunction" ∷
+  "AstStatDeclareGlobal" ∷
+  "AstStatError" ∷
+  "AstStatExpr" ∷
+  "AstStatFor" ∷
+  "AstStatForIn" ∷
+  "AstStatFunction" ∷
+  "AstStatIf" ∷
+  "AstStatLocal" ∷
+  "AstStatLocalFunction" ∷
+  "AstStatRepeat" ∷
+  "AstStatReturn" ∷
+  "AstStatTypeAlias" ∷
+  []
+
+AstTypeKeys =
+  "AstTypeError" ∷
+  "AstTypeFunction" ∷
+  "AstTypeIntersection" ∷
+  "AstTypePackExplicit" ∷
+  "AstTypePackGeneric" ∷
+  "AstTypePackVariadic" ∷
+  "AstTypeReference" ∷
+  "AstTypeTable" ∷
+  "AstTypeTypeof" ∷
+  "AstTypeUnion" ∷
+  []
+
+data Lookup : Set where
+  _,_ : String → Value → Lookup
+  nil : Lookup
+
+lookupIn : List String → Object → Lookup
+lookupIn [] obj = nil
+lookupIn (key ∷ keys) obj with lookup (fromString key) obj
+lookupIn (key ∷ keys) obj | nothing = lookupIn keys obj
+lookupIn (key ∷ keys) obj | just value = (key , value)
 
 exprFromJSON : Value → Either String Expr
 exprFromObject : Object → Either String Expr
@@ -22,19 +85,21 @@ blockFromArray : Array → Either String Block
 exprFromJSON (object obj) = exprFromObject obj
 exprFromJSON val = Left "Expr should be an object"
 
-exprFromObject obj with lookup AstExprConstantNil obj
-exprFromObject obj | just val = Right nil
-exprFromObject obj | nothing = Left "Unsupported Expr"
+exprFromObject obj with lookupIn AstExprKeys obj
+exprFromObject obj | ("AstExprConstantNil" , value) = Right nil
+exprFromObject obj | (key , value) = Left ("Unsupported " ++ key)
+exprFromObject obj | nil = Left "Unexpected Expr object"
 
 {-# NON_TERMINATING #-}
 statFromJSON (object obj) = statFromObject obj
 statFromJSON _ = Left "Stat should be an object"
 
-statFromObject obj with lookup AstStatReturn obj
-statFromObject obj | just val with exprFromJSON val
-statFromObject obj | just val | Left err = Left err
-statFromObject obj | just val | Right exp = Right (return exp)
-statFromObject obj | nothing = Left "Unsupported Stat"
+statFromObject obj with lookupIn AstStatKeys obj
+statFromObject obj | ("AstStatReturn" , value) with exprFromJSON value
+statFromObject obj | ("AstStatReturn" , value) | Left err = Left err
+statFromObject obj | ("AstStatReturn" , value) | Right expr = Right (return expr)
+statFromObject obj | (key , value) = Left ("Unsupported " ++ key)
+statFromObject obj | nil = Left "Unexpected Stat object"
 
 blockFromJSON (array arr) = blockFromArray arr
 blockFromJSON _ = Left "Block should be an array"