javac pretty printer probable bugs

[Rémi Forax]

On 01/29/2012 01:40 PM, Crazy Java wrote:
> Hi,
> as part of the javac AST Visualizer project, I have some difficulties 
> with javac's pretty printer. The problem is the fact, that I am doing 
> double compilation (after first compilation I get the textual 
> representation of produced AST and that is in fact used for 
> visualization purposes). Double compilation is needed because I want 
> to visualize all the compiler sugar (default constructor, effectively 
> final variables in ARM, code generated for enum, ...).
> The problem is that javac's pretty printer (I guess it is pretty 
> printer) after calling CompilationUnitTree.toString() produces in some 
> specific situations code that is not able to compile:
> 1.) it transforms
> public class FullClassUsage {
>     {
>         new <Object> ArrayList<String>(10) {
>             {
>                 add("123");
>             }
>         };
>     }
> }
> into
> public class FullClassUsage {
>
>     public FullClassUsage() {
>         super();
>     }
>     {
>         new <Object>ArrayList<String>(10){
>
>             (int x0) {
>                 super(x0);
>             }
>             {
>                 add("123");
>             }
>         };
>     }
> }
> the (int x0) is the problem.
> 2.) when using together with enum types it transforms:
> public enum SimpleEnum {
>     ENUM_CONSTANT_1,
>     ENUM_CONSTANT_2
> }
> into
> public enum SimpleEnum {
>     /*public static final*/ ENUM_CONSTANT_1 /* = new SimpleEnum() */,
>     /*public static final*/ ENUM_CONSTANT_2 /* = new SimpleEnum() */;
>
>     private SimpleEnum() {
>         super();
>     }
> }
> that is really weird. Not only it generates comments ??? but also a 
> super call causing the code not to compile. I would also assume that 
> it will generate all the enum type code (constructors with n+2 
> arguments, valueOf() factory method, extending java.lang.Enum, ...).
> Is there any reason why it produces that weird code?

Java language != bytecode,
at the end javac will generate bytecodes and there are a lot of things 
that are allowed
in bytecode that are not allowed in Java.

The pretty printer is something used to debug and not something that 
will generate fully compatible Java code
because some de-sugared code are only valid in bytecode but not in Java.

> Is there any better way to get the Textual representation of 
> CompilationUnitTree (using pretty printer) that will compile in both 
> of these examples ?

write your own :)

> //Martin

Rémi