8010101: Intersection type cast issues redundant unchecked warning

Summary: Code for checking intersection type cast is incorrectly swapping operands, leading to spurious warnings
Reviewed-by: jjg

src/share/classes/com/sun/tools/javac/code/Types.java

@@ -1418,23 +1418,10 @@ public class Types {
                     }
                 }
 
-                if (t.isCompound()) {
-                    Warner oldWarner = warnStack.head;
-                    warnStack.head = noWarnings;
-                    if (!visit(supertype(t), s))
-                        return false;
-                    for (Type intf : interfaces(t)) {
-                        if (!visit(intf, s))
-                            return false;
-                    }
-                    if (warnStack.head.hasLint(LintCategory.UNCHECKED))
-                        oldWarner.warn(LintCategory.UNCHECKED);
-                    return true;
-                }
-
-                if (s.isCompound()) {
-                    // call recursively to reuse the above code
-                    return visitClassType((ClassType)s, t);
+                if (t.isCompound() || s.isCompound()) {
+                    return !t.isCompound() ?
+                            visitIntersectionType((IntersectionClassType)s, t, true) :
+                            visitIntersectionType((IntersectionClassType)t, s, false);
                 }
 
                 if (s.tag == CLASS || s.tag == ARRAY) {
@@ -1512,6 +1499,18 @@ public class Types {
                 return false;
             }
 
+            boolean visitIntersectionType(IntersectionClassType ict, Type s, boolean reverse) {
+                Warner warn = noWarnings;
+                for (Type c : ict.getComponents()) {
+                    warn.clear();
+                    if (reverse ? !isCastable(s, c, warn) : !isCastable(c, s, warn))
+                        return false;
+                }
+                if (warn.hasLint(LintCategory.UNCHECKED))
+                    warnStack.head.warn(LintCategory.UNCHECKED);
+                return true;
+            }
+
             @Override
             public Boolean visitArrayType(ArrayType t, Type s) {
                 switch (s.tag) {
@@ -3889,11 +3888,18 @@ public class Types {
     }
 
     private boolean giveWarning(Type from, Type to) {
-        Type subFrom = asSub(from, to.tsym);
-        return to.isParameterized() &&
-                (!(isUnbounded(to) ||
-                isSubtype(from, to) ||
-                ((subFrom != null) && containsType(to.allparams(), subFrom.allparams()))));
+        List<Type> bounds = to.isCompound() ?
+                ((IntersectionClassType)to).getComponents() : List.of(to);
+        for (Type b : bounds) {
+            Type subFrom = asSub(from, b.tsym);
+            if (b.isParameterized() &&
+                    (!(isUnbounded(b) ||
+                    isSubtype(from, b) ||
+                    ((subFrom != null) && containsType(b.allparams(), subFrom.allparams()))))) {
+                return true;
+            }
+        }
+        return false;
     }
 
     private List<Type> superClosure(Type t, Type s) {

test/tools/javac/lambda/Intersection02.java

+/*
+ * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8010101
+ * @summary Intersection type cast issues redundant unchecked warning
+ * @compile/fail/ref=Intersection02.out -Werror -Xlint:unchecked -XDrawDiagnostics Intersection02.java
+ */
+import java.io.Serializable;
+import java.util.List;
+
+class Intersection02 {
+
+    interface P<X> { }
+
+    void test(List<String> ls) {
+        Object o1 = (List<String> & Serializable)ls;
+        Object o2 = (List<String> & Serializable & P<String>)ls;
+    }
+}

test/tools/javac/lambda/Intersection02.out

+Intersection02.java:39:62: compiler.warn.prob.found.req: (compiler.misc.unchecked.cast.to.type), java.util.List<java.lang.String>, java.lang.Object&java.util.List<java.lang.String>&java.io.Serializable&Intersection02.P<java.lang.String>
+- compiler.err.warnings.and.werror
+1 error
+1 warning