From bbb7ce5137cd3e8365552b42610e19b7ebe43ba1 Mon Sep 17 00:00:00 2001
From: Jan Lahoda <jlahoda@openjdk.org>
Date: Fri, 14 Jul 2023 08:21:48 +0000
Subject: [PATCH] 8311038: Incorrect exhaustivity computation

Reviewed-by: vromero
---
 .../com/sun/tools/javac/comp/Flow.java        |  8 ++++++-
 .../tools/javac/patterns/Exhaustiveness.java  | 22 ++++++++++++++++++-
 2 files changed, 28 insertions(+), 2 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
index ff77c9cdf18..0d94e4bd351 100644
--- 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
@@ -844,6 +844,8 @@ public class Flow {
                     for (Type sup : types.directSupertypes(bpOne.type)) {
                         ClassSymbol clazz = (ClassSymbol) sup.tsym;
 
+                        clazz.complete();
+
                         if (clazz.isSealed() && clazz.isAbstract() &&
                             //if a binding pattern for clazz already exists, no need to analyze it again:
                             !existingBindings.contains(clazz)) {
@@ -891,7 +893,9 @@ public class Flow {
                                     }
 
                                     if (reduces) {
-                                        bindings.append(pdOther);
+                                        if (!types.isSubtype(types.erasure(clazz.type), types.erasure(bpOther.type))) {
+                                            bindings.append(pdOther);
+                                        }
                                     }
                                 }
                             }
@@ -926,6 +930,8 @@ public class Flow {
 
                 permittedSubtypesClosure = permittedSubtypesClosure.tail;
 
+                current.complete();
+
                 if (current.isSealed() && current.isAbstract()) {
                     for (Symbol sym : current.permitted) {
                         ClassSymbol csym = (ClassSymbol) sym;
diff --git a/test/langtools/tools/javac/patterns/Exhaustiveness.java b/test/langtools/tools/javac/patterns/Exhaustiveness.java
index dca5864e1a9..88c897e6edc 100644
--- a/test/langtools/tools/javac/patterns/Exhaustiveness.java
+++ b/test/langtools/tools/javac/patterns/Exhaustiveness.java
@@ -23,7 +23,7 @@
 
 /**
  * @test
- * @bug 8262891 8268871 8274363 8281100 8294670
+ * @bug 8262891 8268871 8274363 8281100 8294670 8311038
  * @summary Check exhaustiveness of switches over sealed types.
  * @library /tools/lib
  * @modules jdk.compiler/com.sun.tools.javac.api
@@ -1948,6 +1948,26 @@ public class Exhaustiveness extends TestRunner {
                """);
     }
 
+    @Test //JDK-8311038
+    public void testReducesTooMuch(Path base) throws Exception {
+        doTest(base,
+               new String[0],
+               """
+               package test;
+               public class Test {
+                   void test(Rec r) {
+                       switch (r) {
+                           case Rec(String s) ->
+                               System.out.println("I2" + s.toString());
+                           case Rec(Object o) ->
+                               System.out.println("I2");
+                       }
+                   }
+                   record Rec(Object o) {}
+               }
+               """);
+    }
+
     private void doTest(Path base, String[] libraryCode, String testCode, String... expectedErrors) throws IOException {
         doTest(base, libraryCode, testCode, false, expectedErrors);
     }