Merge pull request #18962 from asgerf/js/local-type-indirection

JS: Unfold local type aliases in getAnUnderlyingType

Author: asgerf

javascript/ql/lib/semmle/javascript/TypeScript.qll

@@ -773,6 +773,17 @@ class LocalTypeAccess extends @local_type_access, TypeAccess, Identifier, Lexica
    */
   LocalTypeName getLocalTypeName() { result.getAnAccess() = this }
 
+  private TypeAliasDeclaration getAlias() {
+    this.getLocalTypeName().getADeclaration() = result.getIdentifier()
+  }
+
+  override TypeExpr getAnUnderlyingType() {
+    result = this.getAlias().getDefinition().getAnUnderlyingType()
+    or
+    not exists(this.getAlias()) and
+    result = this
+  }
+
   override string getAPrimaryQlClass() { result = "LocalTypeAccess" }
 }
 

javascript/ql/test/library-tests/frameworks/HTTP/RemoteRequestInput.expected

@@ -1,5 +1,7 @@
 | connect.js:6:5:6:11 | req.url | url |
 | connect.js:7:5:7:21 | req.cookies.get() | cookie |
+| express-typed.ts:4:5:4:12 | req.body | body |
+| express-typed.ts:10:5:10:12 | req.body | body |
 | express.js:12:5:12:19 | req.param("p1") | parameter |
 | express.js:13:5:13:17 | req.params.p2 | parameter |
 | express.js:14:5:14:16 | req.query.p3 | parameter |

javascript/ql/test/library-tests/frameworks/HTTP/express-typed.ts

@@ -0,0 +1,11 @@
+import { Request } from "express";
+
+export function f1(req: Request) {
+    req.body;
+}
+
+type Alias = Request & { foo: string };
+
+export function f2(req: Alias) {
+    req.body;
+}