TS: Expose optional parameters at syntax level

javascript/ql/test/library-tests/TypeScript/OptionalParameters/OptionalParams.expected

@@ -0,0 +1,15 @@
+| tst.ts:1:23:1:23 | y |
+| tst.ts:2:16:2:16 | y |
+| tst.ts:6:28:6:28 | y |
+| tst.ts:8:12:8:12 | x |
+| tst.ts:8:24:8:24 | y |
+| tst.ts:9:13:9:13 | x |
+| tst.ts:13:7:13:7 | x |
+| tst.ts:14:13:14:13 | x |
+| tst.ts:15:17:15:17 | y |
+| tst.ts:18:26:18:26 | y |
+| tst.ts:18:30:18:30 | z |
+| tst.ts:18:34:18:34 | w |
+| tst.ts:20:40:20:45 | {x, y} |
+| tst.ts:20:49:20:51 | [w] |
+| withDefault.ts:1:22:1:22 | x |

javascript/ql/test/library-tests/TypeScript/OptionalParameters/OptionalParams.ql

@@ -0,0 +1,3 @@
+import javascript
+
+query Parameter optionalParams() { result.isDeclaredOptional() }

javascript/ql/test/library-tests/TypeScript/OptionalParameters/tst.ts

@@ -0,0 +1,20 @@
+function f(x: number, y?: string) {
+    return (x, y?) => {};
+}
+
+class C {
+    constructor(x: number, y?: string) {}
+
+    method(x?: number, y?: string) {}
+    noTypes(x?) {}
+}
+
+interface I {
+    m(x?: number);
+    field: (x?: number) => void;
+    (x: number, y?: string): void;
+}
+
+function manyDefaults(x, y?, z?, w?) {}
+
+declare function optionalDestructuring({x, y}?, [w]?);

javascript/ql/test/library-tests/TypeScript/OptionalParameters/withDefault.ts

@@ -0,0 +1 @@
+function withDefault(x? = 5) {} // not valid syntax