[nullsafe] Repro for wrong nullability of $bcvarN in try-with-resource

Summary:
Although try-with-resource is supported by nullsafe this code pattern
throws it off and make nullsafe report on a virtual **b**yte-**c**ode
variable.

Check out debug output from `TryWithResource` (or attached
visualisation of CFG):
0. node14: $bcvar2=null (on entry to try-with-resource).
1. node16: n$14=$bcvar2, but **also** PRUNE(!(n$14 == null), true). Then we go to
2. node18: do something here and in case of exception go to
3. node25->node23->node19->node20: and here we do
$bcvar2->addSuppressed(...).

Because on step 1 we refined nullability of n$14, but didn't refine
nullability of $bcvar20, on step 3 we are sure that $bcvar is null and
therefore issue an error.

Reviewed By: mityal

Differential Revision: D20558343

fbshipit-source-id: 520505039

infer/tests/codetoanalyze/java/nullsafe-default/TryWithResource.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package codetoanalyze.java.nullsafe_default;
+
+import java.io.IOException;
+import java.io.StringWriter;
+
+public class TryWithResource {
+  private static final int[] KEYS = {1};
+
+  private void FP_OK_StringWriterInTWRBlock() throws IOException {
+    // IMPORTANT: this for-loop is needed for issue to manifest.
+    for (int key : KEYS) {
+      // no-op
+    }
+
+    try (StringWriter stringWriter = new StringWriter()) {
+      // no-op
+    }
+  }
+}

infer/tests/codetoanalyze/java/nullsafe-default/issues.exp

@@ -395,4 +395,6 @@ codetoanalyze/java/nullsafe-default/TrueFalseOnNull.java, codetoanalyze.java.nul
 codetoanalyze/java/nullsafe-default/TrueFalseOnNull.java, codetoanalyze.java.nullsafe_default.TrueFalseOnNull$TestStaticOneParam.notAnnotatedNegativeBranchIsBAD(java.lang.String):void, 1, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`s` is nullable and is not locally checked for null when calling `toString()`.]
 codetoanalyze/java/nullsafe-default/TrueFalseOnNull.java, codetoanalyze.java.nullsafe_default.TrueFalseOnNull$TestStaticOneParam.notAnnotatedPositiveBranchIsBAD(java.lang.String):void, 1, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`s` is nullable and is not locally checked for null when calling `toString()`.]
 codetoanalyze/java/nullsafe-default/TrueFalseOnNull.java, codetoanalyze.java.nullsafe_default.TrueFalseOnNull$TestStaticOneParam.trueOnNullPositiveBranchIsBAD(java.lang.String):void, 1, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [`s` is nullable and is not locally checked for null when calling `toString()`.]
+codetoanalyze/java/nullsafe-default/TryWithResource.java, Linters_dummy_method, 1, ERADICATE_META_CLASS_NEEDS_FIXING, no_bucket, INFO, []
+codetoanalyze/java/nullsafe-default/TryWithResource.java, codetoanalyze.java.nullsafe_default.TryWithResource.FP_OK_StringWriterInTWRBlock():void, 6, ERADICATE_NULLABLE_DEREFERENCE, no_bucket, WARNING, [NullPointerException will be thrown at this line! Object is `null` and is dereferenced via calling `addSuppressed(...)`: null constant at line 22.]
 codetoanalyze/java/nullsafe-default/third-party-test-code/some/test/pckg/ThirdPartyTestClass.java, some.test.pckg.ThirdPartyTestClass.returnSpecifiedAsNullable():java.lang.String, 0, ERADICATE_RETURN_OVER_ANNOTATED, no_bucket, ADVICE, [Method `returnSpecifiedAsNullable()` is annotated with `@Nullable` but never returns null.]