8328178: javac erroneously allows widening conversion followed by box…

…ing to Short in assignment context
biboudis · Mar 18, 2024 · aea4887 · aea4887
1 parent dec68d7
commit aea4887
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Showing 5 changed files with 45 additions and 6 deletions.
diff --git a/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java b/src/jdk.compiler/share/classes/com/sun/tools/javac/code/Types.java
@@ -2368,11 +2368,13 @@ public boolean isAssignable(Type t, Type s, Warner warn) {
                     return true;
                 break;
             case CLASS:
-                switch (unboxedType(s).getTag()) {
-                case BYTE:
-                case CHAR:
-                case SHORT:
-                    return isAssignable(t, unboxedType(s), warn);
+                Type unboxedType = unboxedType(s);
+                switch (unboxedType.getTag()) {
+                    case BYTE:
+                    case CHAR:
+                    case SHORT:
+                        return !t.getTag().isStrictSubRangeOf(unboxedType(s).getTag()) &&
+                               isAssignable(t, unboxedType(s), warn);
                 }
                 break;
             }

diff --git a/test/langtools/tools/javac/boxing/T6816548.java b/test/langtools/tools/javac/boxing/T6816548.java
@@ -53,7 +53,6 @@ public static void testShort() {
     public static void testByte() {
         final byte fb = 0;
         Byte b = fb;
-        Short s = fb;
         Character c = fb;
     }
 

diff --git a/test/langtools/tools/javac/patterns/T8328178.java b/test/langtools/tools/javac/patterns/T8328178.java
@@ -0,0 +1,31 @@
+/*
+ * @test /nodynamiccopyright/
+ * @summary javac erroneously allows widening conversion followed by boxing to Short in assignment context
+ * @compile/fail/ref=T8328178.out -XDrawDiagnostics -XDshould-stop.at=FLOW T8328178.java
+ */
+public class T8328178 {
+
+    void test() {
+        Integer t = (byte) 0;       // error, no widening p.c. from byte to int and boxing
+        Short s = (byte) 0;         // error, no widening p.c. from byte to short and boxing
+
+        Byte B1 = (char)0;          // ok, narrowing p.c. from char to byte and boxing when target is Byte
+        Byte B2 = (short)0;         // ok, narrowing p.c. from short to byte and boxing when target is Byte
+        Character C1 = (short)0;    // ok, narrowing p.c. from short to char and boxing when target is Character
+        Short S1 = (int)0;          // ok, narrowing p.c. from int to char and boxing to Short
+    }
+
+    void testWithSwitches() {
+        Integer i = 42;
+        var s1 = switch (i) {
+            case (byte)0 -> true;   // error
+            default -> false;
+        };
+
+        Short s = 42;
+        var s2 = switch (s) {
+            case (byte)0 -> true;   // error
+            default -> false;
+        };
+    }
+}
diff --git a/test/langtools/tools/javac/patterns/T8328178.out b/test/langtools/tools/javac/patterns/T8328178.out
@@ -0,0 +1,5 @@
+T8328178.java:9:21: compiler.err.prob.found.req: (compiler.misc.inconvertible.types: byte, java.lang.Integer)
+T8328178.java:10:19: compiler.err.prob.found.req: (compiler.misc.inconvertible.types: byte, java.lang.Short)
+T8328178.java:21:18: compiler.err.prob.found.req: (compiler.misc.inconvertible.types: byte, java.lang.Integer)
+T8328178.java:27:18: compiler.err.prob.found.req: (compiler.misc.inconvertible.types: byte, java.lang.Short)
+4 errors
diff --git a/test/langtools/tools/javac/types/BoxingConversionTest.java b/test/langtools/tools/javac/types/BoxingConversionTest.java
@@ -146,6 +146,7 @@ Result[][] getResults(BoxingConversionTest harness) {
     Result[][] results2 = {
                 //Byte, Short, Integer, Long, Float, Double, Chararacter, Boolean
     /*byte*/    { T   , F    , F      , F   , F    , F     , F          , F },
+    /*byte1*/   { T   , F    , F      , F   , F    , F     , A          , F },
     /*short*/   { F   , T    , F      , F   , F    , F     , F          , F },
     /*short1*/  { A   , T    , F      , F   , F    , F     , A          , F },
     /*short2*/  { F   , T    , F      , F   , F    , F     , A          , F },
@@ -192,6 +193,7 @@ Result[][] getResults(BoxingConversionTest harness) {
 
         types2 = new Type[] {
             predef.byteType,
+            fac.Constant((byte)0x0001),
             predef.shortType,
             fac.Constant((short)0x0001),
             fac.Constant((short)0x0100),