Macro with typed param can't be used as a pragma attached to a type

[liquidev]

Example

macro entity(entityType: typed) =
  discard

type
  RootEntity = ref object of RootObj
  Player {.entity.} = ref object of RootEntity
    x, y: int

Current Output

/tmp/issue.nim(6, 21) Error: invalid expression: Player {..} = ref object of RootEntity
  x, y: int

Expected Output

Successful compilation. Expected behavior would be similar to procs. You cannot re-emit a procedure's AST after it's been sem-checked, but you are still able to read it with all the idents resolved (which is what I'm trying to do):

import std/macros

# this compiles
macro readAst(p: typed) =
  echo p.treeRepr

proc testRead {.readAst.} =
  echo 1

# this doesn't
macro modifyAst(p: typed): untyped =
  echo p.treeRepr
  result = p

proc testModify {.modifyAst.} =
  echo 1
# /usercode/in.nim(13, 1) Error: redefinition of 'testModify'; previous declaration here: /usercode/in.nim(13, 6)

Additional Information

• This might be difficult to implement because of recursive types. I'm not sure about the details of the compiler though; it probably does some first pass on the type section to figure out which types may recur, but that's just a guess.

$ nim -v
Nim Compiler Version 1.3.5 [Linux: amd64]
Compiled at 2020-09-15
Copyright (c) 2006-2020 by Andreas Rumpf

git hash: c38487aa225674f67659c28ce171fd93e2231ad1
active boot switches: -d:release

[timotheecour]

this would be fixed by https://github.com/nim-lang/Nim/issues/13830 as many other things:

• https://forum.nim-lang.org/t/6907#43251
• https://forum.nim-lang.org/t/6907#43253
• see enummaps syntax limitation mentioned in https://github.com/nim-lang/Nim/pull/14008

note: @liquid600pgm please always reduce your example; here's a reduced one:

when true:
  # macro entity(entityType: untyped) = discard
  macro entity(entityType: typed) = discard
  type Player {.entity.} = object
    x: int

gives:

Error: invalid expression: Player {..} = object

with macro entity(entityType: untyped) = discard it also doesn't work with a different error:

Error: illformed AST:

[metagn]

Related: #18864, workaround outlined in https://github.com/nim-lang/Nim/issues/18864#issuecomment-1695215373