8268333: javac crashes when pattern matching switch contains default case which is not last

Reviewed-by: vromero

Author: lahodaj

src/jdk.compiler/share/classes/com/sun/tools/javac/comp/TransPatterns.java

@@ -431,6 +431,7 @@ private void handleSwitch(JCTree tree,
 
             int i = 0;
             boolean previousCompletesNormally = false;
+            boolean hasDefault = false;
 
             for (var c : cases) {
                 List<JCCaseLabel> clearedPatterns = c.labels;
@@ -477,7 +478,9 @@ private void handleSwitch(JCTree tree,
                     for (var p : c.labels) {
                         if (p.hasTag(Tag.DEFAULTCASELABEL)) {
                             translatedLabels.add(p);
-                        } else if (hasTotalPattern && c == lastCase && p.isPattern()) {
+                            hasDefault = true;
+                        } else if (hasTotalPattern && !hasDefault &&
+                                   c == lastCase && p.isPattern()) {
                             //If the switch has total pattern, the last case will contain it.
                             //Convert the total pattern to default:
                             translatedLabels.add(make.DefaultCaseLabel());

test/langtools/tools/javac/patterns/Switches.java

@@ -27,7 +27,7 @@
 
 /*
  * @test
- * @bug 8262891
+ * @bug 8262891 8268333
  * @summary Check behavior of pattern switches.
  * @compile --enable-preview -source ${jdk.version} Switches.java
  * @run main/othervm --enable-preview Switches
@@ -46,6 +46,8 @@ void run() {
         assertTrue(testNullSwitch(""));
         runArrayTypeTest(this::testArrayTypeStatement);
         runArrayTypeTest(this::testArrayTypeExpression);
+        runDefaultTest(this::testDefaultDoesNotDominateStatement);
+        runDefaultTest(this::testDefaultDoesNotDominateExpression);
         runEnumTest(this::testEnumExpression1);
         runEnumTest(this::testEnumExpression2);
         runEnumTest(this::testEnumWithGuards1);
@@ -81,6 +83,13 @@ void runArrayTypeTest(Function<Object, String> mapper) {
         assertEquals("", mapper.apply(1.0));
     }
 
+    void runDefaultTest(Function<Object, String> mapper) {
+        assertEquals("default", mapper.apply(new int[0]));
+        assertEquals("str6", mapper.apply("string"));
+        assertEquals("default", mapper.apply(1));
+        assertEquals("default", mapper.apply(1.0));
+    }
+
     void runEnumTest(Function<E, String> mapper) {
         assertEquals("a", mapper.apply(E.A));
         assertEquals("b", mapper.apply(E.B));
@@ -172,6 +181,22 @@ String testArrayTypeExpression(Object o) {
         };
     }
 
+    String testDefaultDoesNotDominateStatement(Object o) {
+        String res;
+        switch (o) {
+            default -> res = "default";
+            case String str -> res = "str" + str.length();
+        }
+        return res;
+    }
+
+    String testDefaultDoesNotDominateExpression(Object o) {
+        return switch (o) {
+            case default -> "default";
+            case String str -> "str" + str.length();
+        };
+    }
+
     int testStringWithConstant(String str) {
         switch (str) {
             case "A": return 1;