Error Prone: Enable and fix NarrowingCompoundAssignment

I'm not going to pretend I understand the code in IdGenerator; the
replacement was exactly what was suggested by Error Prone, and based on
the documentation[1], this construction is just making explicit the way
that Java was already interpreting it.

[1] https://github.com/google/error-prone/blob/master/docs/bugpattern/NarrowingCompoundAssignment.md

Change-Id: I2437b71e774b607871916c4386ee9e42e75554cd

java/com/google/gerrit/server/index/change/AllChangesIndexer.java

@@ -23,6 +23,7 @@ import static com.google.gerrit.server.git.QueueProvider.QueueType.BATCH;
 import com.google.common.base.Stopwatch;
 import com.google.common.collect.ComparisonChain;
 import com.google.common.flogger.FluentLogger;
+import com.google.common.primitives.Ints;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.ListeningExecutorService;
 import com.google.gerrit.index.SiteIndexer;
@@ -108,7 +109,7 @@ public class AllChangesIndexer extends SiteIndexer<Change.Id, ChangeData, Change
     int projectsFailed = 0;
     for (Project.NameKey name : projectCache.all()) {
       try (Repository repo = repoManager.openRepository(name)) {
-        long size = estimateSize(repo);
+        int size = estimateSize(repo);
         changeCount += size;
         projects.add(new ProjectHolder(name, size));
       } catch (IOException e) {
@@ -126,15 +127,17 @@ public class AllChangesIndexer extends SiteIndexer<Change.Id, ChangeData, Change
     return indexAll(index, projects);
   }
 
-  private long estimateSize(Repository repo) throws IOException {
+  private int estimateSize(Repository repo) throws IOException {
     // Estimate size based on IDs that show up in ref names. This is not perfect, since patch set
     // refs may exist for changes whose metadata was never successfully stored. But that's ok, as
     // the estimate is just used as a heuristic for sorting projects.
-    return repo.getRefDatabase().getRefsByPrefix(RefNames.REFS_CHANGES).stream()
-        .map(r -> Change.Id.fromRef(r.getName()))
-        .filter(Objects::nonNull)
-        .distinct()
-        .count();
+    long size =
+        repo.getRefDatabase().getRefsByPrefix(RefNames.REFS_CHANGES).stream()
+            .map(r -> Change.Id.fromRef(r.getName()))
+            .filter(Objects::nonNull)
+            .distinct()
+            .count();
+    return Ints.saturatedCast(size);
   }
 
   private SiteIndexer.Result indexAll(ChangeIndex index, SortedSet<ProjectHolder> projects) {

java/com/google/gerrit/server/util/IdGenerator.java

@@ -45,8 +45,8 @@ public class IdGenerator {
   public static int mix(int salt, int in) {
     short v0 = hi16(in);
     short v1 = lo16(in);
-    v0 += ((v1 << 2) + 0 ^ v1) + (salt ^ (v1 >>> 3)) + 1;
-    v1 += ((v0 << 2) + 2 ^ v0) + (salt ^ (v0 >>> 3)) + 3;
+    v0 += (short) (((v1 << 2) + 0 ^ v1) + (salt ^ (v1 >>> 3)) + 1);
+    v1 += (short) (((v0 << 2) + 2 ^ v0) + (salt ^ (v0 >>> 3)) + 3);
     return result(v0, v1);
   }
 
@@ -54,8 +54,8 @@ public class IdGenerator {
   static int unmix(int in) {
     short v0 = hi16(in);
     short v1 = lo16(in);
-    v1 -= ((v0 << 2) + 2 ^ v0) + (salt ^ (v0 >>> 3)) + 3;
-    v0 -= ((v1 << 2) + 0 ^ v1) + (salt ^ (v1 >>> 3)) + 1;
+    v1 -= (short) (((v0 << 2) + 2 ^ v0) + (salt ^ (v0 >>> 3)) + 3);
+    v0 -= (short) (((v1 << 2) + 0 ^ v1) + (salt ^ (v1 >>> 3)) + 1);
     return result(v0, v1);
   }
 

tools/BUILD

@@ -74,7 +74,7 @@ java_package_configuration(
         "-Xep:MissingFail:ERROR",
         "-Xep:MissingOverride:ERROR",
         "-Xep:MutableConstantField:ERROR",
-        #"-Xep:NarrowingCompoundAssignment:ERROR",
+        "-Xep:NarrowingCompoundAssignment:ERROR",
         "-Xep:StringEquality:ERROR",
         "-Xep:MissingCasesInEnumSwitch:ERROR",
         "-Xep:WildcardImport:ERROR",