Clarify relationship of isFromSource and Element::fromSource.

Author: Max Schaefer

java/ql/automodel/src/AutomodelJavaUtil.qll

@@ -86,8 +86,15 @@ predicate includeAutomodelCandidate(string package, string type, string name, st
 /**
  * Holds if the given program element corresponds to a piece of source code,
  * that is, it is not compiler-generated.
+ *
+ * Note: This is a stricter check than `Element::fromSource`, which simply
+ * checks whether the element is in a source file as opposed to a JAR file.
+ * There can be compiler-generated elements in source files (especially for
+ * Kotlin), which we also want to exclude.
  */
 predicate isFromSource(Element e) {
+  // from a source file (not a JAR)
+  e.fromSource() and
   // not explicitly marked as compiler-generated
   not e.isCompilerGenerated() and
   // does not have a dummy location