8314632: Intra-case dominance check fails in the presence of a guard

Reviewed-by: vromero

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

@@ -4712,7 +4712,7 @@ public class Check {
                                          TreeInfo.unguardedCase(testCase);
                         } else if (label instanceof JCPatternCaseLabel patternCL &&
                                    testCaseLabel instanceof JCPatternCaseLabel testPatternCaseLabel &&
-                                   TreeInfo.unguardedCase(testCase)) {
+                                   (testCase.equals(c) || TreeInfo.unguardedCase(testCase))) {
                             dominated = patternDominated(testPatternCaseLabel.pat,
                                                          patternCL.pat);
                         }

test/langtools/tools/javac/patterns/T8314632.java

@@ -0,0 +1,40 @@
+/*
+ * @test /nodynamiccopyright/
+ * @bug 8314632
+ * @summary Intra-case dominance check fails in the presence of a guard
+ * @enablePreview
+ * @compile/fail/ref=T8314632.out -XDrawDiagnostics T8314632.java
+ */
+public class T8314632 {
+    void test1(Object obj) {
+        switch (obj) {
+            case Float _ -> {}
+            case Integer _, CharSequence _, String _ when obj.hashCode() > 0 -> { } // error
+            default -> throw new IllegalStateException("Unexpected value: " + obj);
+        }
+    }
+
+    void test2(Object obj) {
+        switch (obj) {
+            case Float _ -> {}
+            case Integer _, CharSequence _, String _ -> { }
+            default -> throw new IllegalStateException("Unexpected value: " + obj); // error
+        }
+    }
+
+    void test3(Object obj) {
+        switch (obj) {
+            case Float _, CharSequence _ when obj.hashCode() > 0 -> { } // OK
+            case Integer _, String _     when obj.hashCode() > 0 -> { } // OK, since the previous case is guarded
+            default -> throw new IllegalStateException("Unexpected value: " + obj);
+        }
+    }
+
+    void test4(Object obj) {
+        switch (obj) {
+            case Float _, CharSequence _ -> { } // OK
+            case Integer _, String _     when obj.hashCode() > 0 -> { } // error, since the previous case is unguarded
+            default -> throw new IllegalStateException("Unexpected value: " + obj);
+        }
+    }
+}

test/langtools/tools/javac/patterns/T8314632.out

@@ -0,0 +1,6 @@
+T8314632.java:12:45: compiler.err.pattern.dominated
+T8314632.java:20:45: compiler.err.pattern.dominated
+T8314632.java:36:29: compiler.err.pattern.dominated
+- compiler.note.preview.filename: T8314632.java, DEFAULT
+- compiler.note.preview.recompile
+3 errors