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8772 :: Look up proc signature from an ident

• Nycto (orginal) [2022-01-04T23:20:39+01:00] view original

  If I've got a macro where I pass an ident as an argument, is it possible to read the signature of the proc? Here is an example of what I'm trying to do:

  import macros
  
  macro examine(ident: untyped) =
      ident.expectKind(nnkIdent)
      
      # My goal is to read the list of arguments right here, but
      # the following line fails with the error: "node is not a symbol"
      echo ident.getImpl
  
  # ----
  
  proc someProc[T](arg: T) =
      discard
  
  examine(someProc)
  Run

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• ElegantBeef (orginal) [2022-01-04T23:27:14+01:00] view original

  import std/macros
  
  macro examine(ident: typed{sym}) =
      # My goal is to read the list of arguments right here, but
      # the following line fails with the error: "node is not a symbol"
      echo ident.getImpl.treeRepr
  
  # ----
  
  proc someProc[T](arg: T) =
      discard
  
  examine(someProc)
  Run

  If you want to look up a symbol you need to have typed ast, as ident s are just fancy strings labels. As it's easier I used the Nim constraints so it'll only take {sym} s.

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• Nycto (orginal) [2022-01-04T23:39:05+01:00] view original

  Awesome! Thank you

  I might be pressing my luck, but is it possible to do this with concepts, too?

  import macros
  
  macro examine(ident: typed) =
      echo ident.getImpl.repr
  
  # ----
  
  type Foo = concept f
  
  proc someProc(arg: Foo) =
      discard
  
  examine(someProc)
  Run

  Fails with:

  
  tests/t_example.nim(13, 9) Error: 'someProc' doesn't have a concrete type, due to unspecified generic parameters.
  Run

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• ElegantBeef (orginal) [2022-01-05T00:18:01+01:00] view original

  Odd it works on explicit generics but not implicit, here is how you'd do it

  import std/macros
  
  
  macro examine(ident: typed) =
    echo ident.getImpl.treeRepr
  
  
  # ----
  
  type Foo = concept f
  
  proc someProc[T: Foo](arg: T) =
      discard
  
  examine(someProc)
  Run

---