8138914: javac, method visitTypeVar() at visitor Types.hashCode generates the...

8138914: javac, method visitTypeVar() at visitor Types.hashCode generates the same hash code for different type variables
Reviewed-by: mcimadamore

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

@@ -3781,11 +3781,24 @@ public class Types {
      * Compute a hash code on a type.
      */
     public int hashCode(Type t) {
-        return hashCode.visit(t);
+        return hashCode(t, false);
+    }
+
+    public int hashCode(Type t, boolean strict) {
+        return strict ?
+                hashCodeStrictVisitor.visit(t) :
+                hashCodeVisitor.visit(t);
     }
     // where
-        private static final UnaryVisitor<Integer> hashCode = new UnaryVisitor<Integer>() {
+        private static final HashCodeVisitor hashCodeVisitor = new HashCodeVisitor();
+        private static final HashCodeVisitor hashCodeStrictVisitor = new HashCodeVisitor() {
+            @Override
+            public Integer visitTypeVar(TypeVar t, Void ignored) {
+                return System.identityHashCode(t);
+            }
+        };
 
+        private static class HashCodeVisitor extends UnaryVisitor<Integer> {
             public Integer visitType(Type t, Void ignored) {
                 return t.getTag().ordinal();
             }
@@ -3841,7 +3854,7 @@ public class Types {
             public Integer visitErrorType(ErrorType t, Void ignored) {
                 return 0;
             }
-        };
+        }
     // </editor-fold>
 
     // <editor-fold defaultstate="collapsed" desc="Return-Type-Substitutable">

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

@@ -1254,9 +1254,9 @@ public class Infer {
         public int hashCode() {
             int result = opKind.hashCode();
             result *= 127;
-            result += types.hashCode(op1);
+            result += types.hashCode(op1, true);
             result *= 127;
-            result += types.hashCode(op2);
+            result += types.hashCode(op2, true);
             return result;
         }