fix(remix-server-runtime): disallow incompatible return types of TypedResponse

.changeset/light-sheep-give.md

@@ -0,0 +1,26 @@
+---
+"remix": patch
+"@remix-run/serve": patch
+"@remix-run/server-runtime": patch
+---
+
+Fix `TypedResponse` so that Typescript correctly shows errors for incompatible types in loaders and actions.
+
+Previously, when the return type of a loader or action was explicitly set to `TypedResponse<SomeType>`,
+Typescript would not show errors when the loader or action returned an incompatible type.
+
+For example:
+
+```ts
+export const action = async (args: ActionArgs): Promise<TypedResponse<string>> => {
+    return json(42);
+};
+```
+
+In this case, Typescript would now show an error even though `42` is clearly not a `string`.
+
+In this case, happens because `json` returns a `TypedResponse<string>`,
+but because `TypedReponse<string>` is just `Response & { json: () => Promise<string> }`
+and `Response` already defines `{ json: () => Promise<any> }`, then type erasure caused `Promise<any>` to be used for `42`.
+
+To fix this, we explicitly omit the `Response`'s `json` property before intersecting with `{ json: () => Promise<T> }`.