Remove // fall out comments, which are sometimes used to document an empty default: statement group

PiperOrigin-RevId: 658827224

Author: cushon

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

@@ -94,7 +94,7 @@ public final class StatementSwitchToExpressionSwitch extends BugChecker
       ImmutableSet.of(THROW, EXPRESSION_STATEMENT);
   private static final ImmutableSet<Kind> KINDS_RETURN_OR_THROW = ImmutableSet.of(THROW, RETURN);
   private static final Pattern FALL_THROUGH_PATTERN =
-      Pattern.compile("\\bfalls?.?through\\b", Pattern.CASE_INSENSITIVE);
+      Pattern.compile("\\bfalls?.?(through|out)\\b", Pattern.CASE_INSENSITIVE);
   // Default (negative) result for assignment switch conversion analysis. Note that the value is
   // immutable.
   private static final AssignmentSwitchAnalysisResult DEFAULT_ASSIGNMENT_SWITCH_ANALYSIS_RESULT =

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

@@ -3657,4 +3657,36 @@ public void unnecessaryBreaks() {
         .setArgs("-XepOpt:StatementSwitchToExpressionSwitch:EnableDirectConversion=true")
         .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
   }
+
+  @Test
+  public void fallOutComment() {
+    assumeTrue(RuntimeVersion.isAtLeast14());
+    refactoringHelper
+        .addInputLines(
+            "Test.java",
+            "public class Test {",
+            "  void f(int x) {",
+            "    switch (x) {",
+            "      case 0:",
+            "        System.err.println(\"ZERO\");",
+            "        break;",
+            "      default:",
+            "        // fall out",
+            "    }",
+            "  }",
+            "}")
+        .addOutputLines(
+            "Test.java",
+            "public class Test {",
+            "  void f(int x) {",
+            "    switch (x) {",
+            "      case 0 -> System.err.println(\"ZERO\");",
+            "      default -> {}",
+            "    }",
+            "  }",
+            "}")
+        .setArgs(
+            ImmutableList.of("-XepOpt:StatementSwitchToExpressionSwitch:EnableDirectConversion"))
+        .doTest(BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH);
+  }
 }