Type tyAnything can't be matched to proc argument of typedesc type

[mratsim]

Building on #13095 and its fix #13181, supportsCopyMem in a type section doesn't work with implicit generic parameters.
The error message in particular mentions type any which makes it hard to debug as there is no type any in the codebase.

Test case

import typetraits

type
  CpuStorage[T] {.shallow.} = ref object
    when supportsCopyMem(T):
      raw_buffer*: ptr UncheckedArray[T] # 8 bytes
      memalloc*: pointer                 # 8 bytes
      isMemOwner*: bool                  # 1 byte
    else: # Tensors of strings, other ref types or non-trivial destructors
      raw_buffer*: seq[T]                # 8 bytes (16 for seq v2 backed by destructors?)

  Tensor*[T] = object
    storage*: CpuStorage[T]

proc foo(t: Tensor): bool =
  # This breaks
  return false

proc bar[T](t: Tensor[T]): bool =
  return false

Error

Error: type mismatch: got <type any>
but expected one of: 
proc supportsCopyMem(t: typedesc): bool
  first type mismatch at position: 1
  required type for t: type T
  but expression 'T' is of type: type any

expression: supportsCopyMem(T)

[cooldome]

Test case is not complete, it doesn't reproduce the issue

[mratsim]

It does for me on commit bc14453

[cooldome]

Apologies, I managed to replicate this issue. I had a look, issue is not type trait specific. Generally type tyAnything can't be matches against type tyTypeDesc. Simplified example that fails with the same error

proc mycheck(t: typedesc): bool =
  true

type
  CpuStorage[T] {.shallow.} = ref object
    when mycheck(T):
      raw_buffer*: ptr UncheckedArray[T] # 8 bytes
      memalloc*: pointer                 # 8 bytes
      isMemOwner*: bool                  # 1 byte
    else: # Tensors of strings, other ref types or non-trivial destructors
      raw_buffer*: seq[T]                # 8 bytes (16 for seq v2 backed by destructors?)

proc foo(t: CpuStorage): bool =
  # This breaks
  return false

[Clyybber]

The underlying issue here is that in Generic[T], T defaults to any instead of type as it IMO should. (I think @timotheecour also discovered that in some PR)

Both examples compile after replacing CpuStorage[T] with CpuStorage[T: type]

[mratsim]

For posterity, from our IRC discussion back in April

From IRC: https://irclogs.nim-lang.org/21-04-2020.html#14:46:18

[metagn]

Both examples above seem to work now? Probably because of #22029