Fix detecting an existing Map/Set

This didn't affect compilation to CJS since that sets `exports.Map`
instead of creating a global.

Author: elibarzilay

src/compiler/corePublic.ts

@@ -117,22 +117,30 @@ namespace ts {
         declare const Map: MapConstructor | undefined;
         declare const Set: SetConstructor | undefined;
 
+        const globals = typeof globalThis !== "undefined" ? globalThis
+                  : typeof global !== "undefined" ? global
+                  // @ts-ignore
+                  : typeof window !== "undefined" ? window
+                  : undefined;
+
         /**
          * Returns the native Map implementation if it is available and compatible (i.e. supports iteration).
          */
         export function tryGetNativeMap(): MapConstructor | undefined {
             // Internet Explorer's Map doesn't support iteration, so don't use it.
+            const gMap = globals.Map;
             // eslint-disable-next-line no-in-operator
-            return typeof Map !== "undefined" && "entries" in Map.prototype && new Map([[0, 0]]).size === 1 ? Map : undefined;
+            return typeof gMap !== "undefined" && "entries" in gMap.prototype && new gMap([[0, 0]]).size === 1 ? gMap : undefined;
         }
 
         /**
          * Returns the native Set implementation if it is available and compatible (i.e. supports iteration).
          */
         export function tryGetNativeSet(): SetConstructor | undefined {
             // Internet Explorer's Set doesn't support iteration, so don't use it.
+            const gSet = globals.Set;
             // eslint-disable-next-line no-in-operator
-            return typeof Set !== "undefined" && "entries" in Set.prototype && new Set([0]).size === 1 ? Set : undefined;
+            return typeof gSet !== "undefined" && "entries" in gSet.prototype && new gSet([0]).size === 1 ? gSet : undefined;
         }
     }