Fix dataflow for kotlin.Array.iterator()

Author: tamasvajk

java/ql/lib/semmle/code/java/dataflow/ExternalFlow.qll

@@ -143,6 +143,7 @@ private module Frameworks {
   private import semmle.code.java.frameworks.JMS
   private import semmle.code.java.frameworks.RabbitMQ
   private import semmle.code.java.regex.RegexFlowModels
+  private import semmle.code.java.frameworks.KotlinStdLib
 }
 
 private predicate sourceModelCsv(string row) {

java/ql/lib/semmle/code/java/dataflow/internal/DataFlowPrivate.qll

@@ -205,6 +205,11 @@ private predicate canContainBool(Type t) {
   any(BooleanType b).(RefType).getASourceSupertype+() = t
 }
 
+private predicate isArray(Type t) {
+  t instanceof Array or
+  t.(RefType).getSourceDeclaration().hasQualifiedName("kotlin", "Array")
+}
+
 /**
  * Holds if `t1` and `t2` are compatible, that is, whether data can flow from
  * a node of type `t1` to a node of type `t2`.
@@ -221,6 +226,9 @@ predicate compatibleTypes(Type t1, Type t2) {
     erasedHaveIntersection(e1, e2)
     or
     canContainBool(e1) and canContainBool(e2)
+    or
+    // Make java array and `kotlin.Array` types compatible.
+    isArray(e1) and isArray(e2)
   )
 }
 

java/ql/lib/semmle/code/java/frameworks/KotlinStdLib.qll

@@ -0,0 +1,10 @@
+/** Definitions of taint steps in the KotlinStdLib framework */
+
+import java
+private import semmle.code.java.dataflow.ExternalFlow
+
+private class KotlinStdLibSummaryCsv extends SummaryModelCsv {
+  override predicate row(string row) {
+    row = ["kotlin;Array;false;iterator;();;Argument[-1].ArrayElement;ReturnValue.Element;value"]
+  }
+}

java/ql/test/kotlin/library-tests/dataflow/foreach/test.expected

@@ -5,3 +5,4 @@
 | C2.kt:8:32:8:32 | a | C2.kt:9:14:9:14 | l |
 | C2.kt:8:32:8:32 | a | C2.kt:10:14:10:17 | ...[...] |
 | C2.kt:8:32:8:32 | a | C2.kt:12:18:12:21 | ...[...] |
+| C2.kt:8:32:8:32 | a | C2.kt:15:18:15:18 | s |