JS: Add test with FNs for contextual typing

Author: asgerf

javascript/ql/test/library-tests/UnderlyingTypes/contextualTypes.ts

@@ -0,0 +1,29 @@
+import * as express from 'express';
+
+interface Options {
+    handle(req: express.Request): void; // $ hasUnderlyingType='express'.Request
+}
+
+declare function doSomething(options: Options);
+
+function t1() {
+    doSomething({
+        handle(req) { // $ MISSING: hasUnderlyingType='express'.Request
+        }
+    });
+}
+
+function t2(callback: ((opts: Options) => void) | undefined) {
+    callback({
+        handle(req) { } // $ MISSING: hasUnderlyingType='express'.Request
+    })
+    callback!({
+        handle(req) { } // $ MISSING: hasUnderlyingType='express'.Request
+    })
+}
+
+function t3(): Options {
+    return {
+        handle(req) { } // $ MISSING: hasUnderlyingType='express'.Request
+    }
+}