Don't crash for CaseKind.RULE in UnnecessaryDefaultInEnumSwitch

Fixes #2029

PiperOrigin-RevId: 351247217

Author: sumitbhagwani

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

@@ -108,6 +108,10 @@ public Description matchSwitch(SwitchTree switchTree, VisitorState state) {
   private Description fixDefault(
       SwitchTree switchTree, CaseTree caseBeforeDefault, CaseTree defaultCase, VisitorState state) {
     List<? extends StatementTree> defaultStatements = defaultCase.getStatements();
+    if (defaultStatements == null) {
+      // TODO(b/177258673): provide fixes for `case -> ...`
+      return buildDescription(defaultCase).setMessage(DESCRIPTION_REMOVED_DEFAULT).build();
+    }
     if (trivialDefault(defaultStatements)) {
       // deleting `default:` or `default: break;` is a no-op
       return buildDescription(defaultCase)
@@ -184,6 +188,10 @@ private Description fixUnrecognized(
     List<? extends StatementTree> defaultStatements = defaultCase.getStatements();
     Description.Builder unrecognizedDescription =
         buildDescription(defaultCase).setMessage(DESCRIPTION_UNRECOGNIZED);
+    if (defaultStatements == null) {
+      // TODO(b/177258673): provide fixes for `case -> ...`
+      return unrecognizedDescription.build();
+    }
     if (trivialDefault(defaultStatements)) {
       // the default case is empty or contains only `break` -- replace it with `case UNRECOGNIZED:`
       // with fall out.

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

@@ -17,9 +17,11 @@
 package com.google.errorprone.bugpatterns;
 
 import static com.google.errorprone.BugCheckerRefactoringTestHelper.TestMode.TEXT_MATCH;
+import static org.junit.Assume.assumeTrue;
 
 import com.google.errorprone.BugCheckerRefactoringTestHelper;
 import com.google.errorprone.CompilationTestHelper;
+import com.google.errorprone.util.RuntimeVersion;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -779,4 +781,44 @@ public void messages() {
             "}")
         .doTest();
   }
+
+  @Test
+  public void defaultCaseKindRule() {
+    assumeTrue(RuntimeVersion.isAtLeast14());
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            "class Test {",
+            "  enum Case { ONE, TWO }",
+            "  void m(Case c) {",
+            "    switch (c) {",
+            "      case ONE -> {}",
+            "      case TWO -> {}",
+            "      // BUG: Diagnostic contains: UnnecessaryDefaultInEnumSwitch",
+            "      default -> {}",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
+
+  @Test
+  public void unrecognizedCaseKindRule() {
+    assumeTrue(RuntimeVersion.isAtLeast14());
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            "class Test {",
+            "  enum Case { ONE, TWO, UNRECOGNIZED }",
+            "  void m(Case c) {",
+            "    switch (c) {",
+            "      case ONE -> {}",
+            "      case TWO -> {}",
+            "      // BUG: Diagnostic contains: UnnecessaryDefaultInEnumSwitch",
+            "      default -> {}",
+            "    }",
+            "  }",
+            "}")
+        .doTest();
+  }
 }