Fix the 918-fields test

The test relied on a synthetic field that the newer Java compiler
was not generating since the field was not being used. In order
to cause the synthetic generation of the field, which allows an
inner class to refer to its parent, the inner class has been
changed to have a reference to an outer field.

Bug: 378676805
Test: atest CtsJvmtiRunTest918HostTestCases:android.jvmti.cts.JvmtiHostTest918#testJvmti
Change-Id: I499154372fb4123c6ccd13e479cbeeb2a2ec1203

2 files changed, 14 insertions, 3 deletions

diff --git a/test/918-fields/expected-stdout.txt b/test/918-fields/expected-stdout.txt
index bd42f75f8a..0114ccc998 100644
--- a/test/918-fields/expected-stdout.txt
+++ b/test/918-fields/expected-stdout.txt
@@ -6,6 +6,10 @@ false
 class java.io.InterruptedIOException
 1
 false
+[this$0, Lart/Test918;, null]
+class art.Test918$Foo
+4112
+true
 [VAL, I, null]
 interface art.Test918$Bar
 25
diff --git a/test/918-fields/src/art/Test918.java b/test/918-fields/src/art/Test918.java
index 593c99c908..7d8050e453 100644
--- a/test/918-fields/src/art/Test918.java
+++ b/test/918-fields/src/art/Test918.java
@@ -28,8 +28,7 @@ public class Test918 {
     public static void doTest() throws Exception {
         testField(Math.class, "PI");
         testField(InterruptedIOException.class, "bytesTransferred");
-        // TODO(b/378676805): Update this check.
-        // testField(Foo.class, "this$0");
+        testField(Foo.class, "this$0");
         testField(Bar.class, "VAL");
         testField(Generics.class, "generics");
         testField(Generics.class, "privateValue");
@@ -65,7 +64,15 @@ public class Test918 {
     private static native int getFieldModifiers(Field f);
     private static native boolean isFieldSynthetic(Field f);
 
-    private class Foo {}
+    private class Foo {
+        public void inc() {
+            // Touch a field in the outer class. Needed to avoid a javac optimization which removes
+            // the synthetic field that refers to the instance of the outer class (this$0).
+            fooVal++;
+        }
+    }
+
+    private int fooVal = 0;
 
     private static interface Bar {
         public static int VAL = 1;