Retain Member.getInitializer for Kotlin programs

I opt to identify any syntactic initializer. These are broader in scope than Java's member initializers, which are necessarily context-free, whereas in Kotlin the primary constructor's parameters can be referred to.

java/ql/lib/semmle/code/java/Expr.qll

@@ -517,6 +517,19 @@ class AssignExpr extends Assignment, @assignexpr {
   override string getAPrimaryQlClass() { result = "AssignExpr" }
 }
 
+/**
+ * A Kotlin class member initializer assignment.
+ *
+ * For example, `class X { val y = 1 }`
+ */
+class KtInitializerAssignExpr extends AssignExpr {
+  KtInitializerAssignExpr() {
+    ktInitializerAssignment(this)
+  }
+
+  override string getAPrimaryQlClass() { result = "KtInitializerAssignExpr" }
+}
+
 /**
  * A common super-class to represent compound assignments, which include an implicit operator.
  *

java/ql/lib/semmle/code/java/Member.qll

@@ -638,6 +638,16 @@ class Field extends Member, ExprParent, @field, Variable {
       // (CodeQL models explicit initializer blocks as BlockStmt in initializer methods)
       exprStmt.getParent() = im.getBody()
     )
+    or
+    // Kotlin initializers are more general than Java's, in that they may refer to
+    // primary constructor parameters. This identifies a syntactic initializer, so
+    // `class A { val y = 1 }` is an initializer, as is `class B(x: Int) { val y = x }`,
+    // but `class C { var x: Int; init { x = 1 } }` is not, and neither is
+    // `class D { var x: Int; constructor(y: Int) { x = y } }`
+    exists(KtInitializerAssignExpr e |
+      e.getDest() = this.getAnAccess() and
+      e.getSource() = result
+    )
   }
 
   /**