Handle qualified enum elements in MissingCasesInEnumSwitch.

PiperOrigin-RevId: 697598061

Author: graememorgan

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

@@ -18,6 +18,7 @@
 
 import static com.google.common.collect.ImmutableSet.toImmutableSet;
 import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
+import static com.google.errorprone.util.ASTHelpers.getSymbol;
 import static com.google.errorprone.util.ASTHelpers.isSwitchDefault;
 
 import com.google.common.collect.ImmutableSet;
@@ -27,9 +28,11 @@
 import com.google.errorprone.bugpatterns.BugChecker.SwitchTreeMatcher;
 import com.google.errorprone.matchers.Description;
 import com.google.errorprone.util.ASTHelpers;
-import com.sun.source.tree.IdentifierTree;
+import com.sun.source.tree.CaseTree;
+import com.sun.source.tree.ExpressionTree;
 import com.sun.source.tree.SwitchTree;
 import com.sun.tools.javac.code.Type;
+import java.util.List;
 import java.util.Set;
 import java.util.stream.Collectors;
 import javax.lang.model.element.ElementKind;
@@ -44,25 +47,26 @@ public class MissingCasesInEnumSwitch extends BugChecker implements SwitchTreeMa
 
   @Override
   public Description matchSwitch(SwitchTree tree, VisitorState state) {
-    Type switchType = ASTHelpers.getType(tree.getExpression());
+    ExpressionTree expression = tree.getExpression();
+    List<? extends CaseTree> cases = tree.getCases();
+    Type switchType = ASTHelpers.getType(expression);
     if (switchType.asElement().getKind() != ElementKind.ENUM) {
       return Description.NO_MATCH;
     }
     // default case is present
-    if (tree.getCases().stream().anyMatch(c -> isSwitchDefault(c))) {
+    if (cases.stream().anyMatch(c -> isSwitchDefault(c))) {
       return Description.NO_MATCH;
     }
     ImmutableSet<String> handled =
-        tree.getCases().stream()
+        cases.stream()
             .flatMap(c -> c.getExpressions().stream())
-            .filter(IdentifierTree.class::isInstance)
-            .map(e -> ((IdentifierTree) e).getName().toString())
+            .map(e -> getSymbol(e).getSimpleName().toString())
             .collect(toImmutableSet());
     Set<String> unhandled = Sets.difference(ASTHelpers.enumValues(switchType.asElement()), handled);
     if (unhandled.isEmpty()) {
       return Description.NO_MATCH;
     }
-    return buildDescription(tree).setMessage(buildMessage(unhandled)).build();
+    return buildDescription(expression).setMessage(buildMessage(unhandled)).build();
   }
 
   /**

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

@@ -56,9 +56,36 @@ void m(Case c) {
         .doTest();
   }
 
+  @Test
+  public void exhaustive_allowsQualifying() {
+    assume().that(Runtime.version().feature()).isAtLeast(21);
+    compilationHelper
+        .addSourceLines(
+            "Test.java",
+            """
+            class Test {
+              enum Case {
+                ONE,
+                TWO,
+                THREE
+              }
+
+              void m(Case c) {
+                switch (c) {
+                  case Case.ONE:
+                  case Case.TWO:
+                  case Case.THREE:
+                    System.err.println("found it!");
+                    break;
+                }
+              }
+            }
+            """)
+        .doTest();
+  }
+
   @Test
   public void exhaustive_multipleCaseExpressions() {
-    assume().that(Runtime.version().feature()).isAtLeast(14);
     compilationHelper
         .addSourceLines(
             "Test.java",
@@ -209,7 +236,6 @@ void m(Case e) {
 
   @Test
   public void nonExhaustive_arrowStatement() {
-    assume().that(Runtime.version().feature()).isAtLeast(14);
     compilationHelper
         .addSourceLines(
             "Test.java",
@@ -235,7 +261,6 @@ void m(Case c) {
 
   @Test
   public void nonExhaustive_multi() {
-    assume().that(Runtime.version().feature()).isAtLeast(14);
     compilationHelper
         .addSourceLines(
             "Test.java",
@@ -261,7 +286,6 @@ void m(Case c) {
 
   @Test
   public void nonExhaustive_multiArrow() {
-    assume().that(Runtime.version().feature()).isAtLeast(14);
     compilationHelper
         .addSourceLines(
             "Test.java",