RELNOTES: Changed MathRoundIntLong's behavior with longs from casting…

… to an int to using Guava's Ints.saturatedCast().

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=201705887

core/src/main/java/com/google/errorprone/bugpatterns/MathRoundIntLong.java

@@ -27,7 +27,6 @@
 import com.google.errorprone.BugPattern.ProvidesFix;
 import com.google.errorprone.VisitorState;
 import com.google.errorprone.bugpatterns.BugChecker.MethodInvocationTreeMatcher;
-import com.google.errorprone.fixes.Fix;
 import com.google.errorprone.fixes.SuggestedFix;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.matchers.Matcher;
@@ -58,23 +57,51 @@ public final class MathRoundIntLong extends BugChecker implements MethodInvocati
       allOf(
           MATH_ROUND_CALLS, argument(0, anyOf(isSameType("int"), isSameType("java.lang.Integer"))));
 
-  private static final Matcher<MethodInvocationTree> ROUND_CALLS_WITH_PRIMITIVE_LONG_ARG =
-      allOf(MATH_ROUND_CALLS, argument(0, isSameType("long")));
-
   private static final Matcher<MethodInvocationTree> ROUND_CALLS_WITH_LONG_ARG =
-      allOf(MATH_ROUND_CALLS, argument(0, isSameType("java.lang.Long")));
+      allOf(MATH_ROUND_CALLS, argument(0, anyOf(isSameType("long"), isSameType("java.lang.Long"))));
 
   private static final Matcher<MethodInvocationTree> ROUND_CALLS_WITH_INT_OR_LONG_ARG =
-      anyOf(
-          ROUND_CALLS_WITH_INT_ARG, ROUND_CALLS_WITH_PRIMITIVE_LONG_ARG, ROUND_CALLS_WITH_LONG_ARG);
+      anyOf(ROUND_CALLS_WITH_INT_ARG, ROUND_CALLS_WITH_LONG_ARG);
 
   @Override
   public Description matchMethodInvocation(MethodInvocationTree tree, VisitorState state) {
     return ROUND_CALLS_WITH_INT_OR_LONG_ARG.matches(tree, state)
-        ? describeMatch(tree, removeMathRoundCall(tree, state))
+        ? removeMathRoundCall(tree, state)
         : Description.NO_MATCH;
   }
 
+  private Description removeMathRoundCall(MethodInvocationTree tree, VisitorState state) {
+    if (ROUND_CALLS_WITH_INT_ARG.matches(tree, state)) {
+      return describeMatch(
+          tree, SuggestedFix.replace(tree, state.getSourceForNode(tree.getArguments().get(0))));
+    } else if (ROUND_CALLS_WITH_LONG_ARG.matches(tree, state)) {
+      if (state.getTypeFromString("com.google.common.primitives.Ints") != null) {
+        return describeMatch(
+            tree,
+            SuggestedFix.builder()
+                .addImport("com.google.common.primitives.Ints")
+                .prefixWith(tree, "Ints.saturatedCast(")
+                .replace(tree, state.getSourceForNode(tree.getArguments().get(0)))
+                .postfixWith(tree, ")")
+                .build());
+      } else {
+        return buildDescription(tree)
+            .setMessage(
+                "Calling Math.round() when the argument is an integer or a long can result "
+                    + "in a loss of information because it coerces the argument to a float before "
+                    + "rounding back to an int. We suggest replacing Math.round() with Guava's"
+                    + " Ints.saturatedCast(). Another suggestion is to cast to an integer but that "
+                    + " may cause other errors when dealing with large numbers.")
+            .addFix(
+                SuggestedFix.builder()
+                    .prefixWith(tree, castPrimitive(tree, state.getSourceForNode(tree)))
+                    .build())
+            .build();
+      }
+    }
+    throw new AssertionError("Unknown argument type to round call: " + tree);
+  }
+
   private static String castPrimitive(Tree tree, String sourceForNode) {
     String openingBracket;
     String closingBracket;
@@ -86,24 +113,4 @@ private static String castPrimitive(Tree tree, String sourceForNode) {
     }
     return String.format("%s%s%s", openingBracket, sourceForNode, closingBracket);
   }
-
-  private static Fix removeMathRoundCall(MethodInvocationTree tree, VisitorState state) {
-    if (ROUND_CALLS_WITH_INT_ARG.matches(tree, state)) {
-      return SuggestedFix.replace(tree, state.getSourceForNode(tree.getArguments().get(0)));
-    } else if (ROUND_CALLS_WITH_PRIMITIVE_LONG_ARG.matches(tree, state)) {
-      return SuggestedFix.builder()
-          .replace(
-              tree,
-              castPrimitive(
-                  tree.getArguments().get(0), state.getSourceForNode(tree.getArguments().get(0))))
-          .prefixWith(tree, "(int) ")
-          .build();
-    } else if (ROUND_CALLS_WITH_LONG_ARG.matches(tree, state)) {
-      return SuggestedFix.builder()
-          .replace(tree, state.getSourceForNode(tree.getArguments().get(0)))
-          .postfixWith(tree, ".intValue()")
-          .build();
-    }
-    throw new AssertionError("Unknown argument type to round call: " + tree);
-  }
 }

core/src/test/java/com/google/errorprone/bugpatterns/MathRoundIntLongTest.java

@@ -70,7 +70,7 @@ public void deleteRoundMethodIntClass() throws Exception {
   }
 
   @Test
-  public void deleteRoundMethodLong() throws Exception {
+  public void replaceRoundMethodLong() throws Exception {
     helper
         .addInputLines(
             "Test.java", //
@@ -82,17 +82,18 @@ public void deleteRoundMethodLong() throws Exception {
             "}")
         .addOutputLines(
             "Test.java", //
+            "import com.google.common.primitives.Ints;",
             "class Test {",
             "  void f() {",
             "    long l = 3L;",
-            "    int y = (int) l;",
+            "    int y = Ints.saturatedCast(l);",
             "  }",
             "}")
         .doTest();
   }
 
   @Test
-  public void deleteRoundMethodLongClass() throws Exception {
+  public void replaceRoundMethodLongClass() throws Exception {
     helper
         .addInputLines(
             "Test.java", //
@@ -104,10 +105,11 @@ public void deleteRoundMethodLongClass() throws Exception {
             "}")
         .addOutputLines(
             "Test.java", //
+            "import com.google.common.primitives.Ints;",
             "class Test {",
             "  void f() {",
             "    Long l = new Long(\"3\");",
-            "    int y = l.intValue();",
+            "    int y = Ints.saturatedCast(l);",
             "  }",
             "}")
         .doTest();
@@ -144,10 +146,11 @@ public void roundingDoubleNegative() throws Exception {
   }
 
   @Test
-  public void deleteRoundMethodAddParenthesis() throws Exception {
+  public void replaceRoundMethodAddParenthesis() throws Exception {
     helper
         .addInputLines(
             "Test.java", //
+            "import com.google.common.primitives.Ints;",
             "class Test {",
             "  void f() {",
             "    long l = 3L;",
@@ -157,11 +160,12 @@ public void deleteRoundMethodAddParenthesis() throws Exception {
             "}")
         .addOutputLines(
             "Test.java", //
+            "import com.google.common.primitives.Ints;",
             "class Test {",
             "  void f() {",
             "    long l = 3L;",
             "    long x = 6L;",
-            "    int y = (int) (l/x);",
+            "    int y = Ints.saturatedCast(l/x);",
             "  }",
             "}")
         .doTest();