8223914: specification of j.l.c.MethodTypeDesc::of should document better the exceptions thrown

Reviewed-by: rriggs

src/java.base/share/classes/java/lang/constant/MethodTypeDesc.java

@@ -65,7 +65,9 @@ public interface MethodTypeDesc
      * @param returnDesc a {@linkplain ClassDesc} describing the return type
      * @param paramDescs {@linkplain ClassDesc}s describing the argument types
      * @return a {@linkplain MethodTypeDesc} describing the desired method type
-     * @throws NullPointerException if any argument is {@code null}
+     * @throws NullPointerException if any argument or its contents are {@code null}
+     * @throws IllegalArgumentException if any element of {@code paramDescs} is a
+     * {@link ClassDesc} for {@code void}
      */
     static MethodTypeDesc of(ClassDesc returnDesc, ClassDesc... paramDescs) {
         return new MethodTypeDescImpl(returnDesc, paramDescs);

test/jdk/java/lang/constant/MethodTypeDescTest.java

@@ -286,5 +286,23 @@ public class MethodTypeDescTest extends SymbolicDescTest {
         catch (IllegalArgumentException e) {
             // good
         }
+
+        try {
+            MethodTypeDesc r = MethodTypeDesc.of(CD_int, null);
+            fail("ClassDesc array should not be null");
+        }
+        catch (NullPointerException e) {
+            // good
+        }
+
+        try {
+            ClassDesc[] paramDescs = new ClassDesc[1];
+            paramDescs[0] = null;
+            MethodTypeDesc r = MethodTypeDesc.of(CD_int, paramDescs);
+            fail("ClassDesc should not be null");
+        }
+        catch (NullPointerException e) {
+            // good
+        }
     }
 }