Ts 3.4 inference improvements

__tests__/draft.ts

@@ -1,4 +1,4 @@
-import {Draft, DraftArray} from "../dist/immer.js"
+import {Draft} from "../dist/immer.js"
 
 // For checking if a type is assignable to its draft type (and vice versa)
 declare const toDraft: <T>(value: T) => Draft<T>
@@ -23,7 +23,6 @@ declare const _: any
     // NOTE: As of 3.2.2, everything fails without "extends any"
     const $ = <Value extends any>(val: ReadonlyArray<Value>) => {
         val = _ as Draft<typeof val>
-        val = _ as DraftArray<typeof val>
         let elem: Value = _ as Draft<Value>
     }
 }

package.json

@@ -67,7 +67,7 @@
     "regenerator-runtime": "^0.11.1",
     "rimraf": "^2.6.2",
     "seamless-immutable": "^7.1.3",
-    "typescript": "3.1.1",
+    "typescript": "3.4.3",
     "yarn-or-npm": "^2.0.4"
   },
   "jest": {

src/immer.d.ts

@@ -12,27 +12,17 @@ type AtomicObject =
     | Number
     | String
 
-type ArrayMethod = Exclude<keyof [], number>
-type Indices<T> = Exclude<keyof T, ArrayMethod>
-
-export type DraftArray<T extends ReadonlyArray<any>> = Array<
-    {[P in Indices<T>]: Draft<T[P]>}[Indices<T>]
->
-
-export type DraftTuple<T extends ReadonlyArray<any>> = {
-    [P in keyof T]: P extends Indices<T> ? Draft<T[P]> : never
-}
-
-export type Draft<T> = T extends never[]
+export type Draft<T> = T extends AtomicObject
     ? T
-    : T extends ReadonlyArray<any>
-    ? T[number][] extends T
-        ? DraftArray<T>
-        : DraftTuple<T>
-    : T extends AtomicObject
+    : T extends object
+    ? {-readonly [K in keyof T]: Draft<T[K]>}
+    : T // mostly: unknown & any
+
+/** Convert a mutable type into a readonly type */
+export type Immutable<T> = T extends AtomicObject
     ? T
     : T extends object
-    ? {-readonly [P in keyof T]: Draft<T[P]>}
+    ? {readonly [K in keyof T]: Immutable<T[K]>}
     : T
 
 export interface Patch {
@@ -52,26 +42,6 @@ export type Produced<Base, Return> = Return extends void
     : Return extends Promise<infer Result>
     ? Promise<Result extends void ? Base : FromNothing<Result>>
     : FromNothing<Return>
-
-type ImmutableArray<T extends ReadonlyArray<any>> = {
-    [P in Extract<keyof T, number>]: ReadonlyArray<Immutable<T[number]>>
-}[Extract<keyof T, number>]
-
-type ImmutableTuple<T extends ReadonlyArray<any>> = {
-    readonly [P in keyof T]: Immutable<T[P]>
-}
-
-/** Convert a mutable type into a readonly type */
-export type Immutable<T> = T extends object
-    ? T extends AtomicObject
-        ? T
-        : T extends ReadonlyArray<any>
-        ? Array<T[number]> extends T
-            ? ImmutableArray<T>
-            : ImmutableTuple<T>
-        : {readonly [P in keyof T]: Immutable<T[P]>}
-    : T
-
 export interface IProduce {
     /**
      * The `produce` function takes a value and a "recipe function" (whose

yarn.lock

@@ -6049,10 +6049,10 @@ type-check@~0.3.2:
   dependencies:
     prelude-ls "~1.1.2"
 
-typescript@3.1.1:
-  version "3.1.1"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.1.1.tgz#3362ba9dd1e482ebb2355b02dfe8bcd19a2c7c96"
-  integrity sha512-Veu0w4dTc/9wlWNf2jeRInNodKlcdLgemvPsrNpfu5Pq39sgfFjvIIgTsvUHCoLBnMhPoUA+tFxsXjU6VexVRQ==
+typescript@3.4.3:
+  version "3.4.3"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.4.3.tgz#0eb320e4ace9b10eadf5bc6103286b0f8b7c224f"
+  integrity sha512-FFgHdPt4T/duxx6Ndf7hwgMZZjZpB+U0nMNGVCYPq0rEzWKjEDobm4J6yb3CS7naZ0yURFqdw9Gwc7UOh/P9oQ==
 
 uglify-js@^3.1.4:
   version "3.5.3"