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" }
+}

java/ql/test/kotlin/library-tests/methods/methods.expected

@@ -1,3 +1,4 @@
+methods
 | methods2.kt:4:1:5:1 | fooBarTopLevelMethod |
 | methods2.kt:7:1:10:1 | <init> |
 | methods2.kt:7:1:10:1 | equals |
@@ -17,3 +18,6 @@
 | methods.kt:5:1:13:1 | toString |
 | methods.kt:6:5:7:5 | classMethod |
 | methods.kt:9:5:12:5 | anotherClassMethod |
+extensions
+| methods3.kt:3:1:3:39 | fooBarTopLevelMethod | file://:0:0:0:0 | int |
+| methods3.kt:6:5:6:43 | fooBarTopLevelMethod | file://:0:0:0:0 | int |

java/ql/test/kotlin/library-tests/methods/methods.ql

@@ -1,5 +1,5 @@
 import java
 
-from Method m
-select m
+query predicate methods(Method m) { any() }
 
+query predicate extensions(ExtensionMethod m, Type t) { m.getExtendedType() = t }