implement recursion properly with closures

1 files changed, 17 insertions, 7 deletions

diff --git a/src/lang/ks-lang/index.ts b/src/lang/ks-lang/index.ts
index e5a78b9..772c9c9 100644
--- a/src/lang/ks-lang/index.ts
+++ b/src/lang/ks-lang/index.ts
@@ -23,13 +23,23 @@ export const createFn =
   <ArgsConstraint extends any[]>() =>
   <Program extends string>(
     program: Program
-  ): Evaluate<Parse<Lex<Program>>> extends [infer ProgramFn extends FnPrim]
-    ? TransformArgs<ProgramFn["args"]> extends ArgsConstraint
-      ? <const Args extends ArgsConstraint>(
-          ...args: Args
-        ) => CallFn<ProgramFn, Args, EmptyStackFrame>
-      : EvalError<`Program's args do not extend args constraint`>
-    : EvalError<"Cannot create a function from a program that does not eval to a function"> => {
+  ): Evaluate<Parse<Lex<Program>>> extends infer E
+    ? E extends [infer ProgramFn extends FnPrim]
+      ? TransformArgs<ProgramFn["args"]> extends ArgsConstraint
+        ? <const Args extends ArgsConstraint>(
+            ...args: Args
+          ) => CallFn<ProgramFn, Args, EmptyStackFrame, []>
+        : EvalError<`Program's args do not extend args constraint`>
+      : E extends readonly [
+          readonly [infer Prim extends FnPrim, infer StackFrame, infer Name]
+        ]
+      ? TransformArgs<Prim["args"]> extends ArgsConstraint
+        ? <const Args extends ArgsConstraint>(
+            ...args: Args
+          ) => CallFn<E[0], Args, EmptyStackFrame, []>
+        : EvalError<`Program's args do not extend args constraint`>
+      : EvalError<"Cannot create a function from a program that does not eval to a function">
+    : never => {
     const [programFn] = evaluate(parse(lex(program))) as Array<FnPrim>;
     if (!programFn.fn) {
       throw new Error(