clean up to warnings related code

Author: Vicente Romero

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

@@ -613,7 +613,11 @@ public boolean isConvertible(Type t, Type s, Warner warn) {
         boolean sValue = s.isPrimitiveClass();
         if (allowUniversalTVars && ((s.hasTag(TYPEVAR)) && ((TypeVar)s).isValueProjection() &&
                 (t.hasTag(BOT) || t.hasTag(TYPEVAR) && !((TypeVar)t).isValueProjection()))) {
-            warn.warn(LintCategory.UNIVERSAL);
+            if (t.hasTag(BOT)) {
+                chk.warnUniversalTVar(warn.pos(), Warnings.UniversalVariableCannotBeAssignedNull);
+            } else {
+                chk.warnUniversalTVar(warn.pos(), Warnings.UniversalVariableCannotBeAssignedNull2);
+            }
             return true;
         }
 
@@ -627,7 +631,7 @@ public boolean isConvertible(Type t, Type s, Warner warn) {
             if (result && (allowUniversalTVars && !t.hasTag(BOT) &&
                     s.isPrimitiveClass() && !t.isPrimitiveClass() &&
                     s.referenceProjectionOrSelf().tsym == t.tsym)) {
-                chk.warnValueConversion(warn.pos(), Warnings.PrimitiveValueConversion);
+                chk.warnUniversalTVar(warn.pos(), Warnings.PrimitiveValueConversion);
             }
             return result;
         }

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

@@ -300,11 +300,6 @@ public void warnUniversalTVar(DiagnosticPosition pos, Warning warnKey) {
             log.warning(LintCategory.UNIVERSAL, pos, warnKey);
     }
 
-    public void warnValueConversion(DiagnosticPosition pos, Warning warnKey) {
-        if (lint.isEnabled(LintCategory.UNIVERSAL))
-            log.warning(LintCategory.UNIVERSAL, pos, warnKey);
-    }
-
     /** Warn about unsafe vararg method decl.
      *  @param pos        Position to be used for error reporting.
      */

src/jdk.compiler/share/classes/com/sun/tools/javac/resources/compiler.properties

@@ -4028,7 +4028,10 @@ compiler.err.var.not.initialized.in.default.constructor=\
     variable {0} not initialized in the default constructor
 
 compiler.warn.universal.variable.cannot.be.assigned.null=\
-    variables of type universal type variable cannot be assigned null
+    universal type variables cannot be assigned null
+
+compiler.warn.universal.variable.cannot.be.assigned.null.2=\
+    probable null assigment to a universal type variable
 
 compiler.warn.primitive.value.conversion=\
     primitive value conversion

test/langtools/tools/javac/diags/examples/UniversalCantBeAssignedNull2.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2022, 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.
+ */
+
+// key: compiler.warn.universal.variable.cannot.be.assigned.null.2
+// options: -Xlint:universal
+
+import java.util.function.*;
+
+class UniversalCantBeAssignedNull2<__universal K, __universal V> {
+    K getKey(K k) { return k; }
+    V getValue(V v) { return v; }
+
+    void m(BiFunction<? super K, ? super V, ? extends V> f, K k1, V v1) {
+        K k = getKey(k1);
+        V v = getValue(v1);
+        v = f.apply(k, v);
+    }
+}
+

test/langtools/tools/javac/valhalla/lworld-values/universal-type-variables/UniversalTVarsCompilationTests.java

@@ -93,6 +93,23 @@ class Box<__universal T> {
                 """
         );
 
+        assertOKWithWarning("compiler.warn.universal.variable.cannot.be.assigned.null.2",
+                """
+                import java.util.function.*;
+
+                class MyMap<__universal K, __universal V> {
+                    K getKey(K k) { return k; }
+                    V getValue(V v) { return v; }
+
+                    void m(BiFunction<? super K, ? super V, ? extends V> f, K k1, V v1) {
+                        K k = getKey(k1);
+                        V v = getValue(v1);
+                        v = f.apply(k, v);
+                    }
+                }
+                """
+        );
+
         setCompileOptions(EMPTY_OPTIONS);
         assertOK(
                 """