Merge pull request #207 from amitdahan/fix-non-generic-map-constructor

Fix `new Map()` always returning `Map<unknown, unknown>`

Author: mattpocock

src/entrypoints/map-constructor.d.ts

@@ -1,3 +1,3 @@
 interface MapConstructor {
-  new (): Map<unknown, unknown>;
+  new <K = unknown, V = unknown>(): Map<K, V>;
 }

src/tests/map-constructor.ts

@@ -59,3 +59,29 @@ doNotExecute(() => {
 
   type testClear = [Expect<Equal<typeof cleared, void>>];
 });
+
+doNotExecute(() => {
+  const map = new Map() satisfies Map<string, boolean>;
+  type test = [Expect<Equal<typeof map, Map<string, boolean>>>];
+});
+
+doNotExecute(() => {
+  const map: Map<string, boolean> = new Map();
+  type test = [Expect<Equal<typeof map, Map<string, boolean>>>];
+});
+
+doNotExecute(() => {
+  function expectsBooleanMap(map: Map<string, boolean>) {
+    return map;
+  }
+  const map = expectsBooleanMap(new Map());
+  type test = [Expect<Equal<typeof map, Map<string, boolean>>>];
+});
+
+doNotExecute(() => {
+  const map = new Map([
+    ["foo", 1],
+    ["bar", 2],
+  ]);
+  type test = [Expect<Equal<typeof map, Map<string, number>>>];
+});