[IDEA-204272] Fix varargs params losing generic info

Regression introduced in commit 82a2939271
"java-decompiler: cleanups and fixes"

src/org/jetbrains/java/decompiler/struct/gen/generics/GenericType.java

@@ -1,4 +1,4 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package org.jetbrains.java.decompiler.struct.gen.generics;
 
 import org.jetbrains.java.decompiler.code.CodeConstants;
@@ -28,6 +28,17 @@ public class GenericType {
     this.value = value;
   }
 
+  public GenericType(GenericType other, int arrayDim) {
+    this.type = other.type;
+    this.value = other.value;
+
+    this.enclosingClasses.addAll(other.enclosingClasses);
+    this.arguments.addAll(other.arguments);
+    this.wildcards.addAll(other.wildcards);
+
+    this.arrayDim = arrayDim;
+  }
+
   public GenericType(String signature) {
     int type = 0;
     int arrayDim = 0;
@@ -197,7 +208,7 @@ public class GenericType {
 
   public GenericType decreaseArrayDim() {
     assert arrayDim > 0 : this;
-    return new GenericType(type, arrayDim - 1, value);
+    return new GenericType(this, arrayDim - 1);
   }
 
   public List<GenericType> getArguments() {