Downgrade to Checker Framework 3.40.0 (#895)

This fixes a regression where we were seeing a crash in CFG
construction. Reported upstream as
typetools/checker-framework#6396.

gradle/dependencies.gradle

@@ -40,7 +40,7 @@ if (project.hasProperty("epApiVersion")) {
 
 def versions = [
     asm                    : "9.3",
-    checkerFramework       : "3.41.0",
+    checkerFramework       : "3.40.0",
     // for comparisons in other parts of the build
     errorProneLatest       : latestErrorProneVersion,
     // The version of Error Prone used to check NullAway's code.

nullaway/build.gradle

@@ -65,6 +65,9 @@ dependencies {
     testImplementation deps.test.mockito
     testImplementation deps.test.javaxAnnotationApi
     testImplementation deps.test.assertJ
+    // This is for a test exposing a CFG construction failure in the Checker Framework.  We can probably remove it once
+    // the issue is fixed upstream and we update. See https://github.com/typetools/checker-framework/issues/6396.
+    testImplementation 'org.apache.spark:spark-sql_2.12:3.3.2'
 
     errorProneOldest deps.build.errorProneCheckApiOld
     errorProneOldest(deps.build.errorProneTestHelpersOld) {

nullaway/src/test/java/com/uber/nullaway/NullAwayCoreTests.java

@@ -960,4 +960,29 @@ public void primitiveCastsRememberNullChecks() {
             "}")
         .doTest();
   }
+
+  /**
+   * This test exposes a failure in CFG construction in Checker Framework 3.41.0 and above. Once a
+   * fix for this issue makes it to a Checker Framework release, we can probably remove this test.
+   * See https://github.com/typetools/checker-framework/issues/6396.
+   */
+  @Test
+  public void cfgConstructionSymbolCompletionFailure() {
+    defaultCompilationHelper
+        .addSourceLines(
+            "Test.java",
+            "package com.uber;",
+            "import org.apache.spark.sql.SparkSession;",
+            "class Test {",
+            "  static class X {",
+            "    X(SparkSession session) {}",
+            "  }",
+            "  X run() {",
+            "    try (SparkSession session = SparkSession.builder().getOrCreate()) {",
+            "      return new X(session);",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
 }