From 263a3f4cbdaef20a68f252f4ce1cd78e2d9c08c8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Thu, 7 Sep 2023 19:33:29 +0200
Subject: [PATCH 01/12] Introduce `TConfig`

---
 packages/core/src/Machine.ts | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/packages/core/src/Machine.ts b/packages/core/src/Machine.ts
index 7a3cf1afbf..65c7532335 100644
--- a/packages/core/src/Machine.ts
+++ b/packages/core/src/Machine.ts
@@ -11,6 +11,13 @@ import {
 import { TypegenConstraint, ResolveTypegenMeta } from './typegenTypes.ts';
 import { StateMachine } from './StateMachine.ts';
 
+interface StatesSchema {
+  states?: {
+    [key: string]: StatesSchema;
+  };
+  [k: string]: unknown;
+}
+
 export function createMachine<
   TContext extends MachineContext,
   TEvent extends AnyEventObject, // TODO: consider using a stricter `EventObject` here
@@ -21,7 +28,8 @@ export function createMachine<
   TTag extends string,
   TInput,
   TOutput extends NonReducibleUnknown,
-  TTypesMeta extends TypegenConstraint
+  TTypesMeta extends TypegenConstraint,
+  TConfig extends StatesSchema
 >(
   config: MachineConfig<
     TContext,
@@ -34,7 +42,8 @@ export function createMachine<
     TInput,
     TOutput,
     TTypesMeta
-  >,
+  > &
+    TConfig,
   implementations?: InternalMachineImplementations<
     TContext,
     TEvent,

From b1f54336cfc2aede045be5241072df876b97c980 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 12:10:52 +0200
Subject: [PATCH 02/12] add the index signature as it wont work without it

---
 packages/core/src/Machine.ts | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/packages/core/src/Machine.ts b/packages/core/src/Machine.ts
index 65c7532335..31d50fcf67 100644
--- a/packages/core/src/Machine.ts
+++ b/packages/core/src/Machine.ts
@@ -12,9 +12,7 @@ import { TypegenConstraint, ResolveTypegenMeta } from './typegenTypes.ts';
 import { StateMachine } from './StateMachine.ts';
 
 interface StatesSchema {
-  states?: {
-    [key: string]: StatesSchema;
-  };
+  states?: Record<string, StatesSchema>;
   [k: string]: unknown;
 }
 

From 20b70de3dfbf5c45c11b51b976a5d85ebc3b8f75 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 15:16:51 +0200
Subject: [PATCH 03/12] Use a different strategy to infer `TConfig`

---
 packages/core/src/Machine.ts                  | 33 +++++++++++--------
 packages/core/src/StateMachine.ts             |  3 +-
 packages/core/src/types.ts                    | 18 +++-------
 packages/core/test/types.test.ts              | 19 -----------
 .../test/createActorContext.test.tsx          |  4 +--
 5 files changed, 27 insertions(+), 50 deletions(-)

diff --git a/packages/core/src/Machine.ts b/packages/core/src/Machine.ts
index 31d50fcf67..e7907e4946 100644
--- a/packages/core/src/Machine.ts
+++ b/packages/core/src/Machine.ts
@@ -6,16 +6,12 @@ import {
   ProvidedActor,
   NonReducibleUnknown,
   Prop,
-  AnyEventObject
+  AnyEventObject,
+  MachineTypes
 } from './types.ts';
 import { TypegenConstraint, ResolveTypegenMeta } from './typegenTypes.ts';
 import { StateMachine } from './StateMachine.ts';
 
-interface StatesSchema {
-  states?: Record<string, StatesSchema>;
-  [k: string]: unknown;
-}
-
 export function createMachine<
   TContext extends MachineContext,
   TEvent extends AnyEventObject, // TODO: consider using a stricter `EventObject` here
@@ -27,9 +23,7 @@ export function createMachine<
   TInput,
   TOutput extends NonReducibleUnknown,
   TTypesMeta extends TypegenConstraint,
-  TConfig extends StatesSchema
->(
-  config: MachineConfig<
+  TConfig extends MachineConfig<
     TContext,
     TEvent,
     TActor,
@@ -38,10 +32,23 @@ export function createMachine<
     TDelay,
     TTag,
     TInput,
-    TOutput,
-    TTypesMeta
-  > &
-    TConfig,
+    TOutput
+  >
+>(
+  config: {
+    types?: MachineTypes<
+      TContext,
+      TEvent,
+      TActor,
+      TAction,
+      TGuard,
+      TDelay,
+      TTag,
+      TInput,
+      TOutput,
+      TTypesMeta
+    >;
+  } & TConfig,
   implementations?: InternalMachineImplementations<
     TContext,
     TEvent,
diff --git a/packages/core/src/StateMachine.ts b/packages/core/src/StateMachine.ts
index 86c2a3bc8c..da52a443ed 100644
--- a/packages/core/src/StateMachine.ts
+++ b/packages/core/src/StateMachine.ts
@@ -127,8 +127,7 @@ export class StateMachine<
       any,
       any,
       any,
-      TOutput,
-      any
+      TOutput
     >,
     implementations?: MachineImplementationsSimplified<TContext, TEvent>
   ) {
diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index 63c397796b..2cfe579f8f 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -1294,8 +1294,7 @@ export type MachineConfig<
   TDelay extends string = string,
   TTag extends string = string,
   TInput = any,
-  TOutput = unknown,
-  TTypesMeta = TypegenDisabled
+  TOutput = unknown
 > = (RootStateNodeConfig<
   NoInfer<TContext>,
   NoInfer<TEvent>,
@@ -1313,18 +1312,9 @@ export type MachineConfig<
    * The machine's own version.
    */
   version?: string;
-  types?: MachineTypes<
-    TContext,
-    TEvent,
-    TActor,
-    TAction,
-    TGuard,
-    TDelay,
-    TTag,
-    TInput,
-    TOutput,
-    TTypesMeta
-  >;
+  // we need to avoid failing the common property check for empty machine configs or ones that only contain `types` property
+  // without it whe inferred config type (like `{}` or `{ types: {} }`) fails the assignability check to its constraint
+  types?: unknown;
 }) &
   (Equals<TContext, MachineContext> extends true
     ? { context?: InitialContext<LowInfer<TContext>, TInput> }
diff --git a/packages/core/test/types.test.ts b/packages/core/test/types.test.ts
index 32a57ebd8e..f50b734fea 100644
--- a/packages/core/test/types.test.ts
+++ b/packages/core/test/types.test.ts
@@ -333,25 +333,6 @@ describe('output', () => {
   });
 });
 
-it('should infer context type from `config.context` when there is no `schema.context`', () => {
-  createMachine(
-    {
-      context: {
-        foo: 'test'
-      }
-    },
-    {
-      actions: {
-        someAction: ({ context }) => {
-          ((_accept: string) => {})(context.foo);
-          // @ts-expect-error
-          ((_accept: number) => {})(context.foo);
-        }
-      }
-    }
-  );
-});
-
 it('should not use actions as possible inference sites', () => {
   createMachine(
     {
diff --git a/packages/xstate-react/test/createActorContext.test.tsx b/packages/xstate-react/test/createActorContext.test.tsx
index 0f3ed03807..d7e28641f9 100644
--- a/packages/xstate-react/test/createActorContext.test.tsx
+++ b/packages/xstate-react/test/createActorContext.test.tsx
@@ -114,14 +114,14 @@ describe('createActorContext', () => {
       },
       on: {
         INC: {
-          actions: assign<MachineContext>(({ context }) => ({
+          actions: assign(({ context }) => ({
             obj: {
               counter: context.obj.counter + 1
             }
           }))
         },
         PUSH: {
-          actions: assign<MachineContext>(({ context }) => ({
+          actions: assign(({ context }) => ({
             arr: [...context.arr, Math.random().toString(36).slice(2)]
           }))
         }

From 6b98e33838463a501e890da874195168311d5bae Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 15:20:20 +0200
Subject: [PATCH 04/12] fix failures related to top-level context factories

---
 packages/core/src/types.ts                            |  4 ++--
 packages/core/test/invoke.test.ts                     | 11 +++++------
 packages/core/test/transient.test.ts                  |  9 +++++----
 .../xstate-react/test/createActorContext.test.tsx     |  3 ++-
 packages/xstate-react/test/useActor.test.tsx          |  7 ++++---
 5 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index 2cfe579f8f..11246ff002 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -1317,8 +1317,8 @@ export type MachineConfig<
   types?: unknown;
 }) &
   (Equals<TContext, MachineContext> extends true
-    ? { context?: InitialContext<LowInfer<TContext>, TInput> }
-    : { context: InitialContext<LowInfer<TContext>, TInput> });
+    ? { context?: InitialContext<TContext, TInput> }
+    : { context: InitialContext<TContext, TInput> });
 
 export interface ProvidedActor {
   src: string;
diff --git a/packages/core/test/invoke.test.ts b/packages/core/test/invoke.test.ts
index 28cf57a19b..48897ebcc3 100644
--- a/packages/core/test/invoke.test.ts
+++ b/packages/core/test/invoke.test.ts
@@ -768,14 +768,13 @@ describe('invoke', () => {
   promiseTypes.forEach(({ type, createPromise }) => {
     describe(`with promises (${type})`, () => {
       const invokePromiseMachine = createMachine({
-        types: {} as { context: { id: number; succeed: boolean } },
+        types: {} as {
+          context: { id: number; succeed: boolean };
+          input: { id?: number; succeed?: boolean };
+        },
         id: 'invokePromise',
         initial: 'pending',
-        context: ({
-          input
-        }: {
-          input: { id?: number; succeed?: boolean };
-        }) => ({
+        context: ({ input }) => ({
           id: 42,
           succeed: true,
           ...input
diff --git a/packages/core/test/transient.test.ts b/packages/core/test/transient.test.ts
index dac5b9045f..1ec884ae4f 100644
--- a/packages/core/test/transient.test.ts
+++ b/packages/core/test/transient.test.ts
@@ -569,13 +569,14 @@ describe('transient states (eventless transitions)', () => {
 
   it("shouldn't crash when invoking a machine with initial transient transition depending on custom data", () => {
     const timerMachine = createMachine({
+      types: {} as {
+        context: { duration: number };
+        input: { duration: number };
+      },
       initial: 'initial',
-      context: ({ input }: { input: { duration: number } }) => ({
+      context: ({ input }) => ({
         duration: input.duration
       }),
-      types: {
-        context: {} as { duration: number }
-      },
       states: {
         initial: {
           always: [
diff --git a/packages/xstate-react/test/createActorContext.test.tsx b/packages/xstate-react/test/createActorContext.test.tsx
index d7e28641f9..5082b9c603 100644
--- a/packages/xstate-react/test/createActorContext.test.tsx
+++ b/packages/xstate-react/test/createActorContext.test.tsx
@@ -446,8 +446,9 @@ describe('createActorContext', () => {
       createMachine({
         types: {} as {
           context: { doubled: number };
+          input: number;
         },
-        context: ({ input }: { input: number }) => ({
+        context: ({ input }) => ({
           doubled: input * 2
         })
       })
diff --git a/packages/xstate-react/test/useActor.test.tsx b/packages/xstate-react/test/useActor.test.tsx
index 9ecae6a4a3..e3b0ddcb11 100644
--- a/packages/xstate-react/test/useActor.test.tsx
+++ b/packages/xstate-react/test/useActor.test.tsx
@@ -836,11 +836,12 @@ describeEachReactMode('useActor (%s)', ({ suiteKey, render }) => {
 
   it('custom data should be available right away for the invoked actor', () => {
     const childMachine = createMachine({
-      types: {
-        context: {} as { value: number }
+      types: {} as {
+        context: { value: number };
+        input: { value: number };
       },
       initial: 'intitial',
-      context: ({ input }: { input: { value: number } }) => {
+      context: ({ input }) => {
         return {
           value: input.value
         };

From 2a9ef8e75aab8a446ba9617608ca8c4a48e8f681 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 15:30:41 +0200
Subject: [PATCH 05/12] fix extra test case

---
 packages/core/test/input.test.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/core/test/input.test.ts b/packages/core/test/input.test.ts
index 07d9f2b972..085432dccb 100644
--- a/packages/core/test/input.test.ts
+++ b/packages/core/test/input.test.ts
@@ -225,7 +225,8 @@ describe('input', () => {
     const spy = jest.fn();
 
     const child = createMachine({
-      context: ({ input }: { input: number }) => {
+      types: {} as { input: number },
+      context: ({ input }) => {
         spy(input);
         return {};
       }

From 2a86964dca9214456c791aeef44c55183b3bb856 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 15:39:00 +0200
Subject: [PATCH 06/12] Add explicit `types` in one of the tests

---
 packages/core/test/types.test.ts | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/packages/core/test/types.test.ts b/packages/core/test/types.test.ts
index f50b734fea..97b56d55bb 100644
--- a/packages/core/test/types.test.ts
+++ b/packages/core/test/types.test.ts
@@ -1646,12 +1646,14 @@ describe('actor types', () => {
 
   it('when some provided actors have specified ids index signature should be allowed', () => {
     const child1 = createMachine({
+      types: {} as { context: { counter: number } },
       context: {
         counter: 0
       }
     });
 
     const child2 = createMachine({
+      types: {} as { context: { answer: string } },
       context: {
         answer: ''
       }

From c0ef0cb97911f5247ce34e5af14d687e33801ec3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 20:39:49 +0200
Subject: [PATCH 07/12] skip one error

---
 packages/core/test/types.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/core/test/types.test.ts b/packages/core/test/types.test.ts
index 97b56d55bb..d4abbd3f06 100644
--- a/packages/core/test/types.test.ts
+++ b/packages/core/test/types.test.ts
@@ -3301,7 +3301,7 @@ describe('delays', () => {
         delays: 'one second' | 'one minute';
       },
       after: {
-        // @ts-expect-error
+        // @x-ts-expect-error it would be cool to error here but the added number index signature makes this non-weak type and the common property check doesn't kick in
         'unknown delay': {}
       }
     });

From 0739a1f517aadb1fa8509e5805f267b7936ed3c4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 21:29:41 +0200
Subject: [PATCH 08/12] drop redundant `NoInfer`s

---
 packages/core/src/types.ts | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index a5447b822b..a5a9a65f18 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -1296,14 +1296,14 @@ export type MachineConfig<
   TInput = any,
   TOutput = unknown
 > = (RootStateNodeConfig<
-  NoInfer<TContext>,
-  NoInfer<TEvent>,
-  NoInfer<TActor>,
-  NoInfer<TAction>,
-  NoInfer<TGuard>,
-  NoInfer<TDelay>,
-  NoInfer<TTag>,
-  NoInfer<TOutput>
+  TContext,
+  TEvent,
+  TActor,
+  TAction,
+  TGuard,
+  TDelay,
+  TTag,
+  TOutput
 > & {
   /**
    * The initial context (extended state)

From d93e70f1ad00e33006ccda8cd1b49ebe5a6ca20a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Fri, 8 Sep 2023 21:37:24 +0200
Subject: [PATCH 09/12] Move inline bit to `InferenceSources` helper

---
 packages/core/src/Machine.ts | 56 ++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 15 deletions(-)

diff --git a/packages/core/src/Machine.ts b/packages/core/src/Machine.ts
index e7907e4946..96783513bd 100644
--- a/packages/core/src/Machine.ts
+++ b/packages/core/src/Machine.ts
@@ -7,11 +7,38 @@ import {
   NonReducibleUnknown,
   Prop,
   AnyEventObject,
-  MachineTypes
+  MachineTypes,
+  EventObject
 } from './types.ts';
 import { TypegenConstraint, ResolveTypegenMeta } from './typegenTypes.ts';
 import { StateMachine } from './StateMachine.ts';
 
+interface InferenceSources<
+  TContext extends MachineContext,
+  TEvent extends EventObject,
+  TActor extends ProvidedActor,
+  TAction extends ParameterizedObject,
+  TGuard extends ParameterizedObject,
+  TDelay extends string,
+  TTag extends string,
+  TInput,
+  TOutput extends NonReducibleUnknown,
+  TTypesMeta extends TypegenConstraint
+> {
+  types?: MachineTypes<
+    TContext,
+    TEvent,
+    TActor,
+    TAction,
+    TGuard,
+    TDelay,
+    TTag,
+    TInput,
+    TOutput,
+    TTypesMeta
+  >;
+}
+
 export function createMachine<
   TContext extends MachineContext,
   TEvent extends AnyEventObject, // TODO: consider using a stricter `EventObject` here
@@ -35,20 +62,19 @@ export function createMachine<
     TOutput
   >
 >(
-  config: {
-    types?: MachineTypes<
-      TContext,
-      TEvent,
-      TActor,
-      TAction,
-      TGuard,
-      TDelay,
-      TTag,
-      TInput,
-      TOutput,
-      TTypesMeta
-    >;
-  } & TConfig,
+  config: InferenceSources<
+    TContext,
+    TEvent,
+    TActor,
+    TAction,
+    TGuard,
+    TDelay,
+    TTag,
+    TInput,
+    TOutput,
+    TTypesMeta
+  > &
+    TConfig,
   implementations?: InternalMachineImplementations<
     TContext,
     TEvent,

From ddb5388dbfded0ff1d04763c4d53c826aa903041 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Sat, 9 Sep 2023 00:38:04 +0200
Subject: [PATCH 10/12] tweak things slightly

---
 packages/core/src/Machine.ts     | 20 ++++++++++----------
 packages/core/src/types.ts       | 11 ++++++-----
 packages/core/test/types.test.ts |  2 +-
 3 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/packages/core/src/Machine.ts b/packages/core/src/Machine.ts
index 96783513bd..48f4374f63 100644
--- a/packages/core/src/Machine.ts
+++ b/packages/core/src/Machine.ts
@@ -1,19 +1,19 @@
+import { StateMachine } from './StateMachine.ts';
+import { ResolveTypegenMeta, TypegenConstraint } from './typegenTypes.ts';
 import {
+  AnyEventObject,
+  EventObject,
+  InternalMachineImplementations,
   MachineConfig,
   MachineContext,
-  InternalMachineImplementations,
-  ParameterizedObject,
-  ProvidedActor,
+  MachineTypes,
   NonReducibleUnknown,
+  ParameterizedObject,
   Prop,
-  AnyEventObject,
-  MachineTypes,
-  EventObject
+  ProvidedActor
 } from './types.ts';
-import { TypegenConstraint, ResolveTypegenMeta } from './typegenTypes.ts';
-import { StateMachine } from './StateMachine.ts';
 
-interface InferenceSources<
+interface InferenceSource<
   TContext extends MachineContext,
   TEvent extends EventObject,
   TActor extends ProvidedActor,
@@ -62,7 +62,7 @@ export function createMachine<
     TOutput
   >
 >(
-  config: InferenceSources<
+  config: InferenceSource<
     TContext,
     TEvent,
     TActor,
diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index a5a9a65f18..3cb0c6909c 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -1295,7 +1295,7 @@ export type MachineConfig<
   TTag extends string = string,
   TInput = any,
   TOutput = unknown
-> = (RootStateNodeConfig<
+> = RootStateNodeConfig<
   TContext,
   TEvent,
   TActor,
@@ -1312,13 +1312,14 @@ export type MachineConfig<
    * The machine's own version.
    */
   version?: string;
+  context?: InitialContext<TContext, TInput>;
   // we need to avoid failing the common property check for empty machine configs or ones that only contain `types` property
   // without it whe inferred config type (like `{}` or `{ types: {} }`) fails the assignability check to its constraint
   types?: unknown;
-}) &
-  (Equals<TContext, MachineContext> extends true
-    ? { context?: InitialContext<TContext, TInput> }
-    : { context: InitialContext<TContext, TInput> });
+} & ConditionalRequired<
+    { context?: unknown },
+    MachineContext extends TContext ? false : true
+  >;
 
 export interface ProvidedActor {
   src: string;
diff --git a/packages/core/test/types.test.ts b/packages/core/test/types.test.ts
index d4abbd3f06..31d27bc05b 100644
--- a/packages/core/test/types.test.ts
+++ b/packages/core/test/types.test.ts
@@ -368,7 +368,7 @@ it('should work with generic context', () => {
   createMachineWithExtras({ counter: 42 });
 });
 
-it('should not widen literal types defined in `schema.context` based on `config.context`', () => {
+it('should not widen literal types defined in `types.context` based on `config.context`', () => {
   createMachine({
     types: {
       context: {} as {

From 808f668a508ca64d832dec24ffbc696bbf0fc35c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Sat, 16 Sep 2023 09:16:02 +0200
Subject: [PATCH 11/12] Add `TStringLiteral` to fix widening issues

---
 packages/core/src/Machine.ts      |   6 +-
 packages/core/src/StateMachine.ts |   3 +-
 packages/core/src/StateNode.ts    |   5 +-
 packages/core/src/actions/pure.ts |   6 +-
 packages/core/src/stateUtils.ts   |   2 +-
 packages/core/src/types.ts        | 218 ++++++++++++++++++++++--------
 packages/xstate-test/src/types.ts |  14 +-
 7 files changed, 189 insertions(+), 65 deletions(-)

diff --git a/packages/core/src/Machine.ts b/packages/core/src/Machine.ts
index 48f4374f63..a22b8b7c6c 100644
--- a/packages/core/src/Machine.ts
+++ b/packages/core/src/Machine.ts
@@ -59,8 +59,10 @@ export function createMachine<
     TDelay,
     TTag,
     TInput,
-    TOutput
-  >
+    TOutput,
+    TStringLiteral
+  >,
+  TStringLiteral extends string
 >(
   config: InferenceSource<
     TContext,
diff --git a/packages/core/src/StateMachine.ts b/packages/core/src/StateMachine.ts
index 21a2dfd668..594f424f42 100644
--- a/packages/core/src/StateMachine.ts
+++ b/packages/core/src/StateMachine.ts
@@ -128,7 +128,8 @@ export class StateMachine<
       any,
       any,
       any,
-      TOutput
+      TOutput,
+      string
     >,
     implementations?: MachineImplementationsSimplified<TContext, TEvent>
   ) {
diff --git a/packages/core/src/StateNode.ts b/packages/core/src/StateNode.ts
index 686ea87a8f..6592c0da42 100644
--- a/packages/core/src/StateNode.ts
+++ b/packages/core/src/StateNode.ts
@@ -159,7 +159,8 @@ export class StateNode<
       TODO, // output
       TODO, // guards
       TODO, // delays
-      TODO // tags
+      TODO, // tags
+      string // TStringLiteral
     >,
     options: StateNodeOptions<TContext, TEvent>
   ) {
@@ -293,6 +294,7 @@ export class StateNode<
       ProvidedActor,
       ParameterizedObject,
       ParameterizedObject,
+      string,
       string
     >
   > {
@@ -337,6 +339,7 @@ export class StateNode<
           ProvidedActor,
           ParameterizedObject,
           ParameterizedObject,
+          string,
           string
         >;
       })
diff --git a/packages/core/src/actions/pure.ts b/packages/core/src/actions/pure.ts
index e5f39ce943..f21c77bd7d 100644
--- a/packages/core/src/actions/pure.ts
+++ b/packages/core/src/actions/pure.ts
@@ -65,7 +65,8 @@ export function pure<
   TActor extends ProvidedActor = ProvidedActor,
   TAction extends ParameterizedObject = ParameterizedObject,
   TGuard extends ParameterizedObject = ParameterizedObject,
-  TDelay extends string = string
+  TDelay extends string = string,
+  TStringLiteral extends string = string
 >(
   getActions: ({
     context,
@@ -82,7 +83,8 @@ export function pure<
         TActor,
         NoInfer<TAction>,
         NoInfer<TGuard>,
-        TDelay
+        TDelay,
+        TStringLiteral
       >
     | undefined
 ): PureAction<
diff --git a/packages/core/src/stateUtils.ts b/packages/core/src/stateUtils.ts
index 0d25737c22..febbf6f194 100644
--- a/packages/core/src/stateUtils.ts
+++ b/packages/core/src/stateUtils.ts
@@ -460,7 +460,7 @@ export function formatInitialTransition<
   stateNode: AnyStateNode,
   _target:
     | SingleOrArray<string>
-    | InitialTransitionConfig<TContext, TEvent, TODO, TODO, TODO, TODO>
+    | InitialTransitionConfig<TContext, TEvent, TODO, TODO, TODO, TODO, string>
 ): InitialTransitionDefinition<TContext, TEvent> {
   if (typeof _target === 'string' || isArray(_target)) {
     const targets = toArray(_target).map((t) => {
diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index d514b878f4..8855bd1d7e 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -158,7 +158,8 @@ export interface ChooseBranch<
   TActor extends ProvidedActor = ProvidedActor,
   TAction extends ParameterizedObject = ParameterizedObject,
   TGuard extends ParameterizedObject = ParameterizedObject,
-  TDelay extends string = string
+  TDelay extends string = string,
+  TStringLiteral extends string = string
 > {
   guard?: Guard<TContext, TExpressionEvent, undefined, TGuard>;
   actions: Actions<
@@ -169,7 +170,8 @@ export interface ChooseBranch<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   >;
 }
 
@@ -213,7 +215,8 @@ export type Action<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > =
   // TODO: consider merging `NoRequiredParams` and `WithDynamicParams` into one
   // this way we could iterate over `TAction` (and `TGuard` in the `Guard` type) once and not twice
@@ -238,6 +241,7 @@ export type UnknownAction = Action<
   ProvidedActor,
   ParameterizedObject,
   ParameterizedObject,
+  string,
   string
 >;
 
@@ -249,7 +253,8 @@ export type Actions<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > = SingleOrArray<
   Action<
     TContext,
@@ -259,7 +264,8 @@ export type Actions<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   >
 >;
 
@@ -286,7 +292,8 @@ export interface TransitionConfig<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > {
   guard?: Guard<TContext, TExpressionEvent, undefined, TGuard>;
   actions?: Actions<
@@ -297,7 +304,8 @@ export interface TransitionConfig<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   >;
   reenter?: boolean;
   target?: TransitionTarget | undefined;
@@ -311,7 +319,8 @@ export interface InitialTransitionConfig<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > extends TransitionConfig<
     TContext,
     TEvent,
@@ -319,7 +328,8 @@ export interface InitialTransitionConfig<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   > {
   target: TransitionTarget;
 }
@@ -331,7 +341,8 @@ export type AnyTransitionConfig = TransitionConfig<
   any,
   any,
   any,
-  any
+  any,
+  string
 >;
 
 export interface InvokeDefinition<
@@ -340,7 +351,8 @@ export interface InvokeDefinition<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > {
   id: string;
 
@@ -364,7 +376,8 @@ export interface InvokeDefinition<
           TActor,
           TAction,
           TGuard,
-          TDelay
+          TDelay,
+          TStringLiteral
         >
       >;
   /**
@@ -380,7 +393,8 @@ export interface InvokeDefinition<
           TActor,
           TAction,
           TGuard,
-          TDelay
+          TDelay,
+          TStringLiteral
         >
       >;
 
@@ -394,12 +408,13 @@ export interface InvokeDefinition<
           TActor,
           TAction,
           TGuard,
-          TDelay
+          TDelay,
+          TStringLiteral
         >
       >;
 
   toJSON: () => Omit<
-    InvokeDefinition<TContext, TEvent, TActor, TAction, TGuard, TDelay>,
+    InvokeDefinition<TContext, TEvent, TActor, TAction, TGuard, TDelay, string>,
     'onDone' | 'onError' | 'toJSON'
   >;
 }
@@ -412,7 +427,8 @@ export type DelayedTransitions<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > =
   | {
       [K in Delay<TDelay>]?:
@@ -425,7 +441,8 @@ export type DelayedTransitions<
               TActor,
               TAction,
               TGuard,
-              TDelay
+              TDelay,
+              TStringLiteral
             >
           >;
     }
@@ -437,7 +454,8 @@ export type DelayedTransitions<
         TActor,
         TAction,
         TGuard,
-        TDelay
+        TDelay,
+        TStringLiteral
       > & {
         delay:
           | Delay<TDelay>
@@ -470,7 +488,8 @@ export type StatesConfig<
   TGuard extends ParameterizedObject,
   TDelay extends string,
   TTag extends string,
-  TOutput
+  TOutput,
+  TStringLiteral extends string
 > = {
   [K in string]: StateNodeConfig<
     TContext,
@@ -480,7 +499,8 @@ export type StatesConfig<
     TGuard,
     TDelay,
     TTag,
-    TOutput
+    TOutput,
+    TStringLiteral
   >;
 };
 
@@ -500,7 +520,8 @@ export type TransitionConfigOrTarget<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > = SingleOrArray<
   | TransitionConfigTarget
   | TransitionConfig<
@@ -510,7 +531,8 @@ export type TransitionConfigOrTarget<
       TActor,
       TAction,
       TGuard,
-      TDelay
+      TDelay,
+      TStringLiteral
     >
 >;
 
@@ -520,7 +542,8 @@ export type TransitionsConfig<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > =
   | {
       [K in EventDescriptor<TEvent>]?: TransitionConfigOrTarget<
@@ -530,7 +553,8 @@ export type TransitionsConfig<
         TActor,
         TAction,
         TGuard,
-        TDelay
+        TDelay,
+        TStringLiteral
       >;
     };
 
@@ -559,7 +583,8 @@ type DistributeActors<
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
   TDelay extends string,
-  TSpecificActor extends ProvidedActor
+  TSpecificActor extends ProvidedActor,
+  TStringLiteral extends string
 > = TSpecificActor extends { src: infer TSrc }
   ? Compute<
       {
@@ -588,7 +613,8 @@ type DistributeActors<
                 TActor,
                 TAction,
                 TGuard,
-                TDelay
+                TDelay,
+                TStringLiteral
               >
             >;
         /**
@@ -604,7 +630,8 @@ type DistributeActors<
                 TActor,
                 TAction,
                 TGuard,
-                TDelay
+                TDelay,
+                TStringLiteral
               >
             >;
 
@@ -618,7 +645,8 @@ type DistributeActors<
                 TActor,
                 TAction,
                 TGuard,
-                TDelay
+                TDelay,
+                TStringLiteral
               >
             >;
       } & (TSpecificActor['id'] extends string
@@ -645,21 +673,31 @@ export type InvokeConfig<
   TActor extends ProvidedActor,
   TAction extends ParameterizedObject,
   TGuard extends ParameterizedObject,
-  TDelay extends string
+  TDelay extends string,
+  TStringLiteral extends string
 > = IsLiteralString<TActor['src']> extends true
-  ? DistributeActors<TContext, TEvent, TActor, TAction, TGuard, TDelay, TActor>
+  ? DistributeActors<
+      TContext,
+      TEvent,
+      TActor,
+      TAction,
+      TGuard,
+      TDelay,
+      TActor,
+      TStringLiteral
+    >
   : {
       /**
        * The unique identifier for the invoked machine. If not specified, this
        * will be the machine's own `id`, or the URL (from `src`).
        */
-      id?: string;
+      id?: TStringLiteral;
 
       systemId?: string;
       /**
        * The source of the machine to be invoked, or the machine itself.
        */
-      src: AnyActorLogic | string; // TODO: fix types
+      src: AnyActorLogic | TStringLiteral; // TODO: fix types
 
       input?:
         | Mapper<TContext, TEvent, NonReducibleUnknown>
@@ -677,7 +715,8 @@ export type InvokeConfig<
               TActor,
               TAction,
               TGuard,
-              TDelay
+              TDelay,
+              TStringLiteral
             >
           >;
       /**
@@ -693,7 +732,8 @@ export type InvokeConfig<
               TActor,
               TAction,
               TGuard,
-              TDelay
+              TDelay,
+              TStringLiteral
             >
           >;
 
@@ -707,12 +747,21 @@ export type InvokeConfig<
               TActor,
               TAction,
               TGuard,
-              TDelay
+              TDelay,
+              TStringLiteral
             >
           >;
     };
 
-export type AnyInvokeConfig = InvokeConfig<any, any, any, any, any, any>;
+export type AnyInvokeConfig = InvokeConfig<
+  any,
+  any,
+  any,
+  any,
+  any,
+  any,
+  string
+>;
 
 export interface StateNodeConfig<
   TContext extends MachineContext,
@@ -722,13 +771,22 @@ export interface StateNodeConfig<
   TGuard extends ParameterizedObject,
   TDelay extends string,
   TTag extends string,
-  TOutput
+  TOutput,
+  TStringLiteral extends string
 > {
   /**
    * The initial state transition.
    */
   initial?:
-    | InitialTransitionConfig<TContext, TEvent, TActor, TAction, TGuard, TDelay>
+    | InitialTransitionConfig<
+        TContext,
+        TEvent,
+        TActor,
+        TAction,
+        TGuard,
+        TDelay,
+        TStringLiteral
+      >
     | SingleOrArray<string>
     | undefined;
   /**
@@ -759,19 +817,36 @@ export interface StateNodeConfig<
         TGuard,
         TDelay,
         TTag,
-        NonReducibleUnknown
+        NonReducibleUnknown,
+        TStringLiteral
       >
     | undefined;
   /**
    * The services to invoke upon entering this state node. These services will be stopped upon exiting this state node.
    */
   invoke?: SingleOrArray<
-    InvokeConfig<TContext, TEvent, TActor, TAction, TGuard, TDelay>
+    InvokeConfig<
+      TContext,
+      TEvent,
+      TActor,
+      TAction,
+      TGuard,
+      TDelay,
+      TStringLiteral
+    >
   >;
   /**
    * The mapping of event types to their potential transition(s).
    */
-  on?: TransitionsConfig<TContext, TEvent, TActor, TAction, TGuard, TDelay>;
+  on?: TransitionsConfig<
+    TContext,
+    TEvent,
+    TActor,
+    TAction,
+    TGuard,
+    TDelay,
+    TStringLiteral
+  >;
   /**
    * The action(s) to be executed upon entering the state node.
    */
@@ -783,7 +858,8 @@ export interface StateNodeConfig<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   >;
   /**
    * The action(s) to be executed upon exiting the state node.
@@ -796,7 +872,8 @@ export interface StateNodeConfig<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   >;
   /**
    * The potential transition(s) to be taken upon reaching a final child state node.
@@ -813,7 +890,8 @@ export interface StateNodeConfig<
           TActor,
           TAction,
           TGuard,
-          TDelay
+          TDelay,
+          TStringLiteral
         >
       >
     | undefined;
@@ -821,7 +899,15 @@ export interface StateNodeConfig<
    * The mapping (or array) of delays (in milliseconds) to their potential transition(s).
    * The delayed transitions are taken after the specified delay in an interpreter.
    */
-  after?: DelayedTransitions<TContext, TEvent, TActor, TAction, TGuard, TDelay>;
+  after?: DelayedTransitions<
+    TContext,
+    TEvent,
+    TActor,
+    TAction,
+    TGuard,
+    TDelay,
+    TStringLiteral
+  >;
 
   /**
    * An eventless transition that is always taken when this state node is active.
@@ -833,7 +919,8 @@ export interface StateNodeConfig<
     TActor,
     TAction,
     TGuard,
-    TDelay
+    TDelay,
+    TStringLiteral
   >;
   /**
    * @private
@@ -883,7 +970,8 @@ export type AnyStateNodeConfig = StateNodeConfig<
   any,
   any,
   any,
-  any
+  any,
+  string
 >;
 
 export interface StateNodeDefinition<
@@ -905,7 +993,9 @@ export interface StateNodeDefinition<
   meta: any;
   order: number;
   output?: FinalStateNodeConfig<TContext, TEvent>['output'];
-  invoke: Array<InvokeDefinition<TContext, TEvent, TODO, TODO, TODO, TODO>>;
+  invoke: Array<
+    InvokeDefinition<TContext, TEvent, TODO, TODO, TODO, TODO, string>
+  >;
   description?: string;
   tags: string[];
 }
@@ -954,7 +1044,8 @@ export interface AtomicStateNodeConfig<
     TODO,
     TODO,
     TODO,
-    TODO
+    TODO,
+    string
   > {
   initial?: undefined;
   parallel?: false | undefined;
@@ -987,7 +1078,17 @@ export type SimpleOrStateNodeConfig<
   TEvent extends EventObject
 > =
   | AtomicStateNodeConfig<TContext, TEvent>
-  | StateNodeConfig<TContext, TEvent, TODO, TODO, TODO, TODO, TODO, TODO>;
+  | StateNodeConfig<
+      TContext,
+      TEvent,
+      TODO,
+      TODO,
+      TODO,
+      TODO,
+      TODO,
+      TODO,
+      string
+    >;
 
 export type ActionFunctionMap<
   TContext extends MachineContext,
@@ -1320,7 +1421,8 @@ type RootStateNodeConfig<
   TGuard extends ParameterizedObject,
   TDelay extends string,
   TTag extends string,
-  TOutput
+  TOutput,
+  TStringLiteral extends string
 > = Omit<
   StateNodeConfig<
     TContext,
@@ -1330,7 +1432,8 @@ type RootStateNodeConfig<
     TGuard,
     TDelay,
     TTag,
-    TOutput
+    TOutput,
+    TStringLiteral
   >,
   'states'
 > & {
@@ -1343,7 +1446,8 @@ type RootStateNodeConfig<
         TGuard,
         TDelay,
         TTag,
-        TOutput
+        TOutput,
+        TStringLiteral
       >
     | undefined;
 };
@@ -1357,7 +1461,8 @@ export type MachineConfig<
   TDelay extends string = string,
   TTag extends string = string,
   TInput = any,
-  TOutput = unknown
+  TOutput = unknown,
+  TStringLiteral extends string = string
 > = RootStateNodeConfig<
   TContext,
   TEvent,
@@ -1366,7 +1471,8 @@ export type MachineConfig<
   TGuard,
   TDelay,
   TTag,
-  TOutput
+  TOutput,
+  TStringLiteral
 > & {
   /**
    * The initial context (extended state)
@@ -1598,7 +1704,7 @@ export interface TransitionDefinition<
   TContext extends MachineContext,
   TEvent extends EventObject
 > extends Omit<
-    TransitionConfig<TContext, TEvent, TEvent, TODO, TODO, TODO, TODO>,
+    TransitionConfig<TContext, TEvent, TEvent, TODO, TODO, TODO, TODO, string>,
     | 'target'
     // `guard` is correctly rejected by `extends` here and `actions` should be too
     // however, `any` passed to `TransitionConfig` as `TAction` collapses its `.actions` to `any` and it's accidentally allowed here
diff --git a/packages/xstate-test/src/types.ts b/packages/xstate-test/src/types.ts
index 7b23c0b001..45944e947d 100644
--- a/packages/xstate-test/src/types.ts
+++ b/packages/xstate-test/src/types.ts
@@ -55,7 +55,8 @@ export interface TestStateNodeConfig<
       ParameterizedObject,
       TODO,
       TODO,
-      TODO
+      TODO,
+      string
     >,
     | 'type'
     | 'history'
@@ -169,7 +170,16 @@ export interface TestTransitionConfig<
   TContext extends MachineContext,
   TEvent extends EventObject,
   TTestContext
-> extends TransitionConfig<TContext, TEvent, TEvent, TODO, TODO, TODO, string> {
+> extends TransitionConfig<
+    TContext,
+    TEvent,
+    TEvent,
+    TODO,
+    TODO,
+    TODO,
+    string,
+    string
+  > {
   test?: (
     state: State<TContext, TEvent, any, any, any, any>,
     testContext: TTestContext

From c4cad266c25d8c31eb57fd0929cc4395f1231cca Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Sat, 16 Sep 2023 09:28:35 +0200
Subject: [PATCH 12/12] Actually utilize `TStringLiteral` for typing actions

---
 packages/core/src/guards.ts | 25 +++++++++++++------
 packages/core/src/types.ts  | 50 +++++++++++++++++++++----------------
 2 files changed, 46 insertions(+), 29 deletions(-)

diff --git a/packages/core/src/guards.ts b/packages/core/src/guards.ts
index 466129a048..d05c651141 100644
--- a/packages/core/src/guards.ts
+++ b/packages/core/src/guards.ts
@@ -35,10 +35,11 @@ export type Guard<
   TContext extends MachineContext,
   TExpressionEvent extends EventObject,
   TExpressionGuard extends ParameterizedObject | undefined,
-  TGuard extends ParameterizedObject
+  TGuard extends ParameterizedObject,
+  TStringLiteral extends string
 > =
   | NoRequiredParams<TGuard>
-  | WithDynamicParams<TContext, TExpressionEvent, TGuard>
+  | WithDynamicParams<TContext, TExpressionEvent, TGuard, TStringLiteral>
   | GuardPredicate<TContext, TExpressionEvent, TExpressionGuard, TGuard>;
 
 export type UnknownGuard = UnknownReferencedGuard | UnknownInlineGuard;
@@ -47,14 +48,16 @@ type UnknownReferencedGuard = Guard<
   MachineContext,
   EventObject,
   ParameterizedObject,
-  ParameterizedObject
+  ParameterizedObject,
+  string
 >;
 
 type UnknownInlineGuard = Guard<
   MachineContext,
   EventObject,
   undefined,
-  ParameterizedObject
+  ParameterizedObject,
+  string
 >;
 
 interface BuiltinGuard {
@@ -114,7 +117,15 @@ export function not<
   TExpressionEvent extends EventObject,
   TExpressionGuard extends ParameterizedObject | undefined,
   TGuard extends ParameterizedObject
->(guard: Guard<TContext, TExpressionEvent, TExpressionGuard, NoInfer<TGuard>>) {
+>(
+  guard: Guard<
+    TContext,
+    TExpressionEvent,
+    TExpressionGuard,
+    NoInfer<TGuard>,
+    string
+  >
+) {
   function not(_: GuardArgs<TContext, TExpressionEvent, TExpressionGuard>) {
     if (isDevelopment) {
       throw new Error(`This isn't supposed to be called`);
@@ -148,7 +159,7 @@ export function and<
   TGuard extends ParameterizedObject
 >(
   guards: ReadonlyArray<
-    Guard<TContext, TExpressionEvent, TExpressionGuard, NoInfer<TGuard>>
+    Guard<TContext, TExpressionEvent, TExpressionGuard, NoInfer<TGuard>, string>
   >
 ) {
   function and(_: GuardArgs<TContext, TExpressionEvent, TExpressionGuard>) {
@@ -184,7 +195,7 @@ export function or<
   TGuard extends ParameterizedObject
 >(
   guards: ReadonlyArray<
-    Guard<TContext, TExpressionEvent, TExpressionGuard, NoInfer<TGuard>>
+    Guard<TContext, TExpressionEvent, TExpressionGuard, NoInfer<TGuard>, string>
   >
 ) {
   function or(_: GuardArgs<TContext, TExpressionEvent, TExpressionGuard>) {
diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index 8855bd1d7e..dbf1ca6ca6 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -161,7 +161,7 @@ export interface ChooseBranch<
   TDelay extends string = string,
   TStringLiteral extends string = string
 > {
-  guard?: Guard<TContext, TExpressionEvent, undefined, TGuard>;
+  guard?: Guard<TContext, TExpressionEvent, undefined, TGuard, TStringLiteral>;
   actions: Actions<
     TContext,
     TExpressionEvent,
@@ -188,24 +188,29 @@ type ConditionalRequired<T, Condition extends boolean> = Condition extends true
 export type WithDynamicParams<
   TContext extends MachineContext,
   TExpressionEvent extends EventObject,
-  T extends ParameterizedObject
-> = T extends any
-  ? ConditionalRequired<
-      {
-        type: T['type'];
-        params?:
-          | T['params']
-          | (({
-              context,
-              event
-            }: {
-              context: TContext;
-              event: TExpressionEvent;
-            }) => T['params']);
-      },
-      undefined extends T['params'] ? false : true
-    >
-  : never;
+  T extends ParameterizedObject,
+  TStringLiteral extends string
+> = T['type'] extends any
+  ? T extends any
+    ? ConditionalRequired<
+        {
+          type: T['type'];
+          params?:
+            | T['params']
+            | (({
+                context,
+                event
+              }: {
+                context: TContext;
+                event: TExpressionEvent;
+              }) => T['params']);
+        },
+        undefined extends T['params'] ? false : true
+      >
+    : never
+  : {
+      type: TStringLiteral;
+    };
 
 export type Action<
   TContext extends MachineContext,
@@ -221,7 +226,7 @@ export type Action<
   // TODO: consider merging `NoRequiredParams` and `WithDynamicParams` into one
   // this way we could iterate over `TAction` (and `TGuard` in the `Guard` type) once and not twice
   | NoRequiredParams<TAction>
-  | WithDynamicParams<TContext, TExpressionEvent, TAction>
+  | WithDynamicParams<TContext, TExpressionEvent, TAction, TStringLiteral>
   | ActionFunction<
       TContext,
       TExpressionEvent,
@@ -295,7 +300,7 @@ export interface TransitionConfig<
   TDelay extends string,
   TStringLiteral extends string
 > {
-  guard?: Guard<TContext, TExpressionEvent, undefined, TGuard>;
+  guard?: Guard<TContext, TExpressionEvent, undefined, TGuard, TStringLiteral>;
   actions?: Actions<
     TContext,
     TExpressionEvent,
@@ -1262,7 +1267,8 @@ type MachineImplementationsGuards<
     TContext,
     MaybeNarrowedEvent<TIndexedEvents, TEventsCausingGuards, K>,
     Cast<TIndexedGuards[K], ParameterizedObject>,
-    Cast<Prop<TIndexedGuards, keyof TIndexedGuards>, ParameterizedObject>
+    Cast<Prop<TIndexedGuards, keyof TIndexedGuards>, ParameterizedObject>,
+    string
   >;
 };