Add ExtensionMethod class

java/ql/lib/config/semmlecode.dbscheme

@@ -1059,3 +1059,7 @@ ktBreakContinueTarget(
   unique int id: @breakcontinuestmt ref,
   int target: @ktloopstmt ref
 )
+
+ktExtensionFunctions(
+  unique int id: @method ref
+)

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

@@ -670,3 +670,13 @@ class Field extends Member, ExprParent, @field, Variable {
 class InstanceField extends Field {
   InstanceField() { not this.isStatic() }
 }
+
+/** A Kotlin extension function. */
+class ExtensionMethod extends Method {
+  ExtensionMethod() { ktExtensionFunctions(this) }
+
+  /** Gets the type being extended by this method. */
+  Type getExtendedType() { result = getParameter(-1).getType() }
+
+  override string getAPrimaryQlClass() { result = "ExtensionMethod" }
+}