@chiselName on a Module with a nested ChiselEnum results an error

[kammoh]

Type of issue: bug report

Impact: unknown

Development Phase: request

Other information

Applying @chiselName annotation on a Module with a ChiselEnum object results in compilation error.

If the current behavior is a bug, please provide the steps to reproduce the problem:

@chiselName
class MyModule extends MultiIOModule {
  object State extends ChiselEnum {
    val x, y, z = Value
  }
}

Scala compile error:
Error: Value cannot be called without assigning to an enum val x, y, z = Value
What is the current behavior?

What is the expected behavior?

Please tell us about your environment:

• version: 3.0-SNAPSHOT
• OS: macOS

What is the use case for changing the behavior?

[hngenc]

It seems the problem is that @chiselName will change val x = Value to val x = context.name(Value, x), at least judging by this line: https://github.com/freechipsproject/chisel3/blob/820e2688f0cb966d4528ff074fdbdc623ed8f940/coreMacros/src/main/scala/chisel3/internal/sourceinfo/NamingAnnotations.scala#L156

Value is a macro which tries to figure out the name of the variable that it is being assigned to, so it is searching for assignments like val x = Value, and will fail if it cannot find them. I am busy this week, but I can fix this over the weekend or early next week.

In the meantime, I think you could work around this by just rewriting your code to:

object State extends ChiselEnum {
  val x, y, z = Value
}

@chiselName
class MyModule extends MultiIOModule {
  val state = RegInit(State.x)
  // ...
}

[ducky64]

That sounds like a reasonable root-cause - the chiselName macro really mostly is a simple rewrite that adds a context.name call to anything of the form val name = expr. Blacklisting Value would be one possible solution, though it's not a selective / general one. Thoughts? Perhaps if type information is available to macros, we could whitelist only expressions that type to Data?

[hngenc]

My plan was to change the Value macro so that it also recognizes statements of the form val x = foo(x, ...). Macros can be tricky, but I think that would be possible.