Generic type parameters not recoverable in macro with alias

[arnetheduck]

Description

In this snippet, I'm looking to extract E from the given instance - however, when going via an alias, there seems to be no way for a macro to recover it - the functions either return the generic type without the specialisation or the alias sym but nothing in between.

import std/[macros]

type
  Future2[T, E] = object

type Y = Future2[void, (int, )]
var v: Y

macro internalCheckComplete*[T, E](f: Future2[T, E]): untyped =
  # for v2, we can get the generic type from getTypeInst(f) - for v (with the
  # alias), this returns `nnkSym("Y")` and nesting combinations of calls all end
  # up in nnkObjectTy - there's no way to get the specialised generic parameters
  echo astGenRepr(getTypeInst(f))
  echo astGenRepr(getType(getTypeInst(f)))
  echo astGenRepr(getType(f))
  echo astGenRepr(getTypeImpl(f))

internalCheckComplete(v)

var v2: Future2[void, (int, )]
internalCheckComplete(v2)

Nim Version

1.6.16, devel

Current Output

newSymNode("Y")
nnkObjectTy.newTree(
  newEmptyNode(),
  newEmptyNode(),
  nnkRecList.newTree(
  )
)
nnkObjectTy.newTree(
  newEmptyNode(),
  newEmptyNode(),
  nnkRecList.newTree(
  )
)
nnkObjectTy.newTree(
  newEmptyNode(),
  newEmptyNode(),
  newEmptyNode()
)
nnkBracketExpr.newTree(
  newSymNode("Future2"),
  newSymNode("void"),
  nnkTupleConstr.newTree(
    newSymNode("int")
  )
)
nnkObjectTy.newTree(
  newEmptyNode(),
  newEmptyNode(),
  nnkRecList.newTree(
  )
)
nnkObjectTy.newTree(
  newEmptyNode(),
  newEmptyNode(),
  nnkRecList.newTree(
  )
)
nnkObjectTy.newTree(
  newEmptyNode(),
  newEmptyNode(),
  newEmptyNode()
)

Expected Output

No response

Possible Solution

No response

Additional Information

No response

[mratsim]

An instance of nim-lang/RFCs#44