Adds support for symbols as keys in Maps.

__tests__/Map.ts

@@ -387,4 +387,24 @@ describe('Map', () => {
     expect(map.toString()).toEqual('Map { 2: 2 }');
   });
 
+  it('supports symbols as keys', () => {
+    const symbolA = Symbol('A');
+    const symbolB = Symbol('B');
+    const symbolC = Symbol('C');
+    const m = Map({[symbolA]: 'A', [symbolB]: 'B', [symbolC]: 'C'});
+    expect(m.size).toBe(3);
+    expect(m.get(symbolA)).toBe('A');
+    expect(m.get(symbolB)).toBe('B');
+    expect(m.get(symbolC)).toBe('C');
+  });
+
+  it('symbol keys are unique', () => {
+    const symbolA = Symbol('FooBar');
+    const symbolB = Symbol('FooBar');
+    const m = Map({[symbolA]: 'FizBuz', [symbolB]: 'FooBar'});
+    expect(m.size).toBe(2);
+    expect(m.get(symbolA)).toBe('FizBuz');
+    expect(m.get(symbolB)).toBe('FooBar');
+  });
+
 });

src/Seq.js

@@ -192,7 +192,11 @@ export class ArraySeq extends IndexedSeq {
 
 class ObjectSeq extends KeyedSeq {
   constructor(object) {
-    const keys = Object.keys(object);
+    let symbols = [];
+    if (typeof Object.getOwnPropertySymbols === 'function') {
+      symbols = Object.getOwnPropertySymbols(object);
+    }
+    const keys = Object.keys(object).concat(symbols);
     this._object = object;
     this._keys = keys;
     this.size = keys.length;