3 files changed, 71 insertions, 16 deletions

diff --git a/examples/greeting.ts b/examples/greeting.ts
index d3d755f..8ed2181 100644
--- a/examples/greeting.ts
+++ b/examples/greeting.ts
@@ -1,12 +1,21 @@
 import { Bind, Kind1 } from '../stdlib/effect'
 import { PutString, ReadLine, PutStringLn } from '../stdlib/stdio'
 
-interface GreetK extends Kind1<string> {
-  return: PutStringLn<`Hello, ${this['input']}`>
+interface ResponseK extends Kind1<string> {
+  return: PutStringLn<`Interesting that you believe "${this['input']}" is your purpose. Hmmmm...`>
 }
 
 export type main = [
   PutStringLn<'Greetotron 6000 initializing...'>,
+
+  PutStringLn<'----------------'>,
   PutString<'Your name? '>,
-  Bind<ReadLine, GreetK>
+  Bind<ReadLine, <name extends string>() =>
+    PutStringLn<`Hello, ${name}`>>,
+
+  PutStringLn<'----------------'>,
+  PutString<'Your purpose in life? '>,
+  Bind<ReadLine, ResponseK>,
+
+  PutStringLn<'----------------'>,
 ]
diff --git a/src/eval-env/builtins.ts b/src/eval-env/builtins.ts
index 7e00253..f67fcc6 100644
--- a/src/eval-env/builtins.ts
+++ b/src/eval-env/builtins.ts
@@ -1,7 +1,55 @@
-import { Type } from 'ts-morph'
+import { SyntaxKind, Type } from 'ts-morph'
 import { Ctx } from '../types'
 import { evalList } from '../util'
 
+const applyFunc = (ctx: Ctx, fn: Type | undefined, val: string): Type => {
+  const resultType = (() => {
+    const baseTypes = fn?.getBaseTypes().flatMap(t => t.getSymbol()?.getName())
+
+    if (baseTypes?.includes('Kind1')) {
+      const [_, resultNode] = ctx.createResult(
+        `(${ctx.typeToString(fn)} & { input: ${val} })['return']`
+      )
+      return resultNode
+        ?.getType()
+        .getProperty('output')
+        ?.getTypeAtLocation(resultNode)
+    } else {
+      const [_key, resultNode] = ctx.createResult(`ReturnType<${ctx.typeToString(fn)}>`)
+
+      const resValueNode = resultNode
+        ?.asKind(SyntaxKind.PropertySignature)
+        ?.getChildAtIndexIfKind(2, SyntaxKind.TypeLiteral)
+        ?.getProperty('output')
+        ?.getChildAtIndexIfKind(2, SyntaxKind.TypeReference)
+
+      const functionNode = resValueNode
+        ?.getChildAtIndexIfKind(1, SyntaxKind.SyntaxList)
+        ?.getFirstChildIfKind(SyntaxKind.FunctionType)
+
+      if (functionNode) {
+        const typeParameters = functionNode.getTypeParameters() ?? []
+
+        if (typeParameters.length > 0) {
+          typeParameters[0]?.getConstraint()?.replaceWithText(val)
+        }
+
+        return resValueNode?.getType()
+      }
+    }
+
+    return undefined
+  })()
+
+  // TODO: Cleanup unwanted result node values
+
+  if (!resultType) {
+    throw new Error('Fuck shit')
+  }
+
+  return resultType
+}
+
 export default (ctx: Ctx, args: Type[]) => ({
   SetEvalEnvironment: async () => {
     ctx.setEnv(ctx.getTypeValue(args[0]))
@@ -75,18 +123,12 @@ export default (ctx: Ctx, args: Type[]) => ({
     const [resultKey] = inputTyp ? await ctx.evaluateType(ctx, inputTyp) : []
 
     // TODO: Handle resultKey undefined case
-    const [_, compNode] = ctx.createResult(
-      `(${ctx.typeToString(chainToKind)} & { input: (${ctx.getResultExpr(
-        resultKey
-      )})['output'] })['return']`
-    )
-    // TODO: Avoid using getTypeAtLocation?
-    const compTyp = compNode
-      ?.getType()
-      .getProperty('output')
-      ?.getTypeAtLocation(ctx.entryPoint)
 
-    return compTyp ? await ctx.evaluateType(ctx, compTyp) : []
+    const resultType =
+      applyFunc(ctx, chainToKind, `(${ctx.getResultExpr(resultKey)})['output']`)
+    const res = await ctx.evaluateType(ctx, resultType)
+
+    return res
   },
 
   Try: async () => {
diff --git a/stdlib/effect.ts b/stdlib/effect.ts
index 5ae9cd9..0662d00 100644
--- a/stdlib/effect.ts
+++ b/stdlib/effect.ts
@@ -7,7 +7,11 @@ export interface Kind1<Inp = unknown, Out = unknown> {
   return: Out
 }
 
-export interface Bind<_Eff extends Effect, _Fn extends Kind1> extends Effect {}
+type Func<Inp = unknown, Out = unknown>
+  = Kind1<Inp, Out>
+  | (<_T extends Inp>() => Out)
+
+export interface Bind<_Eff extends Effect, _Fn extends Func> extends Effect {}
 
 export interface Seq<_Effs extends Effect[]> extends Effect {}