8270006: Switches with 'case null:' should be exhaustive

Reviewed-by: vromero
openjdk · Jul 8, 2021 · 4f70759 · 4f70759 · openjdk-notifier · Jul 8, 2021
1 parent 8f798b8
commit 4f70759
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Showing 3 changed files with 13 additions and 3 deletions.
diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java b/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Flow.java
@@ -664,7 +664,11 @@ public void visitSwitch(JCSwitch tree) {
             ListBuffer<PendingExit> prevPendingExits = pendingExits;
             pendingExits = new ListBuffer<>();
             scan(tree.selector);
-            Set<Symbol> constants = tree.patternSwitch ? new HashSet<>() : null;
+            boolean exhaustiveSwitch = tree.patternSwitch ||
+                                       tree.cases.stream()
+                                                 .flatMap(c -> c.labels.stream())
+                                                 .anyMatch(l -> TreeInfo.isNull(l));
+            Set<Symbol> constants = exhaustiveSwitch ? new HashSet<>() : null;
             for (List<JCCase> l = tree.cases; l.nonEmpty(); l = l.tail) {
                 alive = Liveness.ALIVE;
                 JCCase c = l.head;
@@ -686,7 +690,7 @@ public void visitSwitch(JCSwitch tree) {
                                 l.tail.head.pos(),
                                 Warnings.PossibleFallThroughIntoCase);
             }
-            if (!tree.hasTotalPattern && tree.patternSwitch &&
+            if (!tree.hasTotalPattern && exhaustiveSwitch &&
                 !TreeInfo.isErrorEnumSwitch(tree.selector, tree.cases) &&
                 (constants == null || !isExhaustive(tree.selector.type, constants))) {
                 log.error(tree, Errors.NotExhaustiveStatement);

diff --git a/test/langtools/tools/javac/patterns/SwitchErrors.java b/test/langtools/tools/javac/patterns/SwitchErrors.java
@@ -185,4 +185,9 @@ Object guardWithMatchingExpression(Object o1, Object o2) {
             default -> null;
         };
     }
+    void exhaustiveAndNull(String s) {
+        switch (s) {
+            case null: break;
+        }
+    }
 }
diff --git a/test/langtools/tools/javac/patterns/SwitchErrors.out b/test/langtools/tools/javac/patterns/SwitchErrors.out
@@ -42,6 +42,7 @@ SwitchErrors.java:91:9: compiler.err.not.exhaustive.statement
 SwitchErrors.java:97:9: compiler.err.not.exhaustive.statement
 SwitchErrors.java:104:9: compiler.err.not.exhaustive.statement
 SwitchErrors.java:164:9: compiler.err.not.exhaustive.statement
+SwitchErrors.java:189:9: compiler.err.not.exhaustive.statement
 - compiler.note.preview.filename: SwitchErrors.java, DEFAULT
 - compiler.note.preview.recompile
-44 errors
+45 errors