Intellij java editor: could not show interface parameter names

Question

Intellij java editor: could not show interface parameter names in a lib jar. e.g.,

public interface Foo {
    public Bar getBar(String name, int type);

    public default Bar getBar(String name) {
         return getBar(name, 1);
    }

}

In java editor:

Foo foo = getFoo();
foo.
    getBar(String s, int i)
    getBar(String name)

When typing dot after foo, two methods show up. The first method shows parameter names as "s" and "i", could not show the original parameter names (name, type).

The second method is "default" method and its parameter names show up correctly.

Is there way for the editor to show the interface method parameter names ?

The lib jar source code is not available.

UPDATE:

1. attaching javadoc directory to the lib jar did not help.
2. compile with -parameters option, did not help. Seen from javap, class file contains all interface method parameters. So Intellij should be able to get them.

No#1(attaching javadoc) is the preferred solution. Option -parameters will make class file size bigger and may have performance overhead.

Answer 1

The class file doesn't store parameter names for non-default methods. So if you don't have the source code of that code, after the decompilation, the IDEA has no idea about the actual parameter names before.

If you use javap -verbose Foo.class to check it, you can see the bytecode contains the parameter name for the default method but not for the normal method:

Constant pool:
   #1 = InterfaceMethodref #2.#3          // Foo.getBar:(Ljava/lang/String;I)LBar;
   #2 = Class              #4             // Foo
   #3 = NameAndType        #5:#6          // getBar:(Ljava/lang/String;I)LBar;
   #4 = Utf8               Foo
   #5 = Utf8               getBar
   #6 = Utf8               (Ljava/lang/String;I)LBar;
   #7 = Class              #8             // java/lang/Object
   #8 = Utf8               java/lang/Object
   #9 = Utf8               (Ljava/lang/String;)LBar;
  #10 = Utf8               Code
  #11 = Utf8               LineNumberTable
  #12 = Utf8               LocalVariableTable
  #13 = Utf8               this
  #14 = Utf8               LFoo;
  #15 = Utf8               name
  #16 = Utf8               Ljava/lang/String;
  #17 = Utf8               SourceFile
  #18 = Utf8               Foo.java
{
  public abstract Bar getBar(java.lang.String, int);
    descriptor: (Ljava/lang/String;I)LBar;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT

  public default Bar getBar(java.lang.String);
    descriptor: (Ljava/lang/String;)LBar;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=2, args_size=2
         0: aload_0
         1: aload_1
         2: iconst_1
         3: invokeinterface #1,  3            // InterfaceMethod getBar:(Ljava/lang/String;I)LBar;
         8: areturn
      LineNumberTable:
        line 5: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       9     0  this   LFoo;
            0       9     1  name   Ljava/lang/String;
}