infra: update file structure for util/internal (#3141)

1 files changed, 39 insertions, 0 deletions

diff --git a/src/internal/types.ts b/src/internal/types.ts
new file mode 100644
index 00000000..affdda7e
--- /dev/null
+++ b/src/internal/types.ts
@@ -0,0 +1,39 @@
+/**
+ * Type that provides auto-suggestions but also any string.
+ *
+ * @see https://github.com/microsoft/TypeScript/issues/29729#issuecomment-471566609
+ */
+export type LiteralUnion<TSuggested extends TBase, TBase = string> =
+  | TSuggested
+  | (TBase & { zz_IGNORE_ME?: never });
+
+/**
+ * A function that returns a value.
+ *
+ * `Function` cannot be used instead because it doesn't accept class declarations.
+ * These would fail when invoked since they are invoked without the `new` keyword.
+ */
+export type Callable = (
+  // TODO @Shinigami92 2023-02-14: This `any` type can be fixed by anyone if they want to.
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  ...args: any[]
+) => unknown;
+
+/**
+ * Type that represents a single method/function name of the given type.
+ */
+export type MethodOf<TObjectType, TSignature extends Callable = Callable> = {
+  [Key in keyof TObjectType]: TObjectType[Key] extends TSignature
+    ? Key extends string
+      ? Key
+      : never
+    : never;
+}[keyof TObjectType];
+
+/**
+ * Type that represents all method/function names of the given type.
+ */
+export type MethodsOf<
+  TObjectType,
+  TSignature extends Callable = Callable,
+> = ReadonlyArray<MethodOf<TObjectType, TSignature>>;