#[constant] doesn't evaluate const fns.

[sagefarrenholz]

I would like the IDL to include output from constant functions. I am guessing that it doesn't work because the preprocessor runs before constant function evaluation.

What I have:

#[constant]
const AccountSize: usize = size_of::<SomeAccount>();

The IDL looks like:

"constants": [
  {
    "name": "AccountSize",
    "type": {
      "defined": "usize"
    },
    "value": "mem_macros :: size_of ! (SomeAccount)"
  }
],

Is there an idiomatic method to use a constant function in a IDL constant declaration in Anchor?
I also tried switching the size_of::<SomeAccount>(); to a proc macro but it didn't evaluate either, just copying TokenStream into IDL.

[acheroncrypto]

Fixed in #2824.