External class extraction prototype

java/kotlin-extractor/src/main/kotlin/utils/AutoCloseableUse.kt

@@ -0,0 +1,43 @@
+package com.github.codeql
+
+// Functions copied from stdlib/jdk7/src/kotlin/AutoCloseable.kt, which is not available within kotlinc,
+// but allows the `.use` pattern to be applied to JDK7 AutoCloseables:
+
+/**
+ * Executes the given [block] function on this resource and then closes it down correctly whether an exception
+ * is thrown or not.
+ *
+ * In case if the resource is being closed due to an exception occurred in [block], and the closing also fails with an exception,
+ * the latter is added to the [suppressed][java.lang.Throwable.addSuppressed] exceptions of the former.
+ *
+ * @param block a function to process this [AutoCloseable] resource.
+ * @return the result of [block] function invoked on this resource.
+ */
+public inline fun <T : AutoCloseable?, R> T.useAC(block: (T) -> R): R {
+  var exception: Throwable? = null
+  try {
+      return block(this)
+  } catch (e: Throwable) {
+      exception = e
+      throw e
+  } finally {
+      this.closeFinallyAC(exception)
+  }
+}
+
+/**
+* Closes this [AutoCloseable], suppressing possible exception or error thrown by [AutoCloseable.close] function when
+* it's being closed due to some other [cause] exception occurred.
+*
+* The suppressed exception is added to the list of suppressed exceptions of [cause] exception.
+*/
+fun AutoCloseable?.closeFinallyAC(cause: Throwable?) = when {
+  this == null -> {}
+  cause == null -> close()
+  else ->
+      try {
+          close()
+      } catch (closeException: Throwable) {
+          cause.addSuppressed(closeException)
+      }
+}