Add PackageJson and LiteralUnion types (#5)

Author: BendingBender

index.d.ts

@@ -1,3 +1,5 @@
+export {PackageJson} from './source/package-json';
+
 // TODO: Add more examples
 
 // TODO: This can just be `export type Primitive = not object` when the `not` keyword is out.
@@ -95,3 +97,33 @@ const ab: Merge<Foo, Bar> = {a: 1, b: 2};
 ```
 */
 export type Merge<FirstType, SecondType> = Omit<FirstType, Extract<keyof FirstType, keyof SecondType>> & SecondType;
+
+/**
+Allows creating a union type by combining primitive types and literal types without sacrificing auto-completion in IDEs for the literal type part of the union.
+
+Currently, when a union type of a primitive type is combined with literal types, TypeScript loses all information about the combined literals. Thus, when such type is used in an IDE with autocompletion, no suggestions are made for the declared literals.
+
+This type is a workaround for [Microsoft/TypeScript#29729](https://github.com/Microsoft/TypeScript/issues/29729). It will be removed as soon as it's not needed anymore.
+
+@example
+```
+import {LiteralUnion} from 'type-fest';
+
+type Pet = 'dog' | 'cat' | string;
+
+const pet: Pet = '';
+// Start typing in your TypeScript-enabled IDE.
+// You **will not** get auto-completion for `dog` and `cat` literals.
+
+// …
+
+type Pet2 = LiteralUnion<'dog' | 'cat', string>;
+
+const pet: Pet2 = '';
+// You **will** get auto-completion for `dog` and `cat` literals.
+```
+ */
+export type LiteralUnion<
+	LiteralType extends BaseType,
+	BaseType extends Primitive
+> = LiteralType | (BaseType & {_?: never});

index.test-d.ts

@@ -1,5 +1,6 @@
 /* eslint-disable import/no-unassigned-import */
 import './test/omit';
 import './test/merge';
+import './test/package-json';
 
 // TODO: Add negative tests. Blocked by: https://github.com/SamVerschueren/tsd-check/issues/2

package.json

@@ -16,7 +16,8 @@
 		"test": "xo && tsd-check"
 	},
 	"files": [
-		"index.d.ts"
+		"index.d.ts",
+		"source"
 	],
 	"keywords": [
 		"typescript",

readme.md

@@ -64,6 +64,11 @@ See the [types file](index.d.ts) for complete docs.
 
 - `Omit` - Create a type from an object type without certain keys.
 - `Merge` - Merge two types into a new type. Keys of the second type overrides keys of the first type.
+- `LiteralUnion` - Allows creating a union type by combining primitive types and literal types without sacrificing auto-completion in IDEs for the literal type part of the union. Workaround for [Microsoft/TypeScript#29729](https://github.com/Microsoft/TypeScript/issues/29729).
+
+### Miscellaneous
+
+- `PackageJson` - Type for [npm's `package.json` file](https://docs.npmjs.com/creating-a-package-json-file).
 
 
 ## Declined types