Fix #115: indexing type with generic

Author: SebastienGllmt

src/transform-inline/visitor-indexed-access.ts

@@ -87,6 +87,9 @@ function visitObjectType(type: ts.ObjectType, indexType: ts.Type, visitorContext
     } else if (visitorContext.checker.getIndexTypeOfType(type, ts.IndexKind.Number)) {
         // Index type is number -> array type.
         return visitArrayObjectType(type, indexType, visitorContext);
+    } else if ((ts.TypeFlags.TypeParameter & indexType.symbol?.flags) !== 0) {
+       // Index type is type -> type
+        return VisitorTypeCheck.visitType(indexType, visitorContext);
     } else {
         // Index type is string -> regular object type.
         return visitRegularObjectType(type, indexType, visitorContext);

test/issue-115.ts

@@ -0,0 +1,24 @@
+import * as assert from 'assert';
+import { is } from '../index';
+
+/* https://github.com/woutervh-/typescript-is/issues/115 */
+
+export const Status = {
+    enable: 'enable',
+    disable: 'disable'
+} as const;
+
+type StatusObject<Key extends keyof typeof Status> = {
+    status: (typeof Status)[Key];
+};
+
+describe('is', () => {
+    describe('Accessing generic member of a type', () => {
+        it('should return true for the right member', () => {
+            assert.deepStrictEqual(is<StatusObject<'enable'>>({ status: Status.enable }), true);
+        });
+        it('should return false for the wrong member', () => {
+           assert.deepStrictEqual(is<StatusObject<'enable'>>({ status: Status.disable }), false);
+        });
+    });
+});