Cannot explicitly instantiate generic templates and macros with static parameters

[timotheecour]

• proc allows calling proc fun*[N: static int](): auto = with fun[2] but not macro or template
• case2b is fishy as N:int syntax accepts both 2 and int

import std/macros

when defined(case1):
  # Error: type expected
  macro fun*[N: static int](): untyped =
    # 1 # original bug report
    newLit 1 # EDIT

  const a = fun[2]()

when defined(case2):
  # compiles: ok
  proc fun*[N: static int](): auto =
    1
  const a = fun[2]()

when defined(case2b):
  # compiles, but this exposes an ambiguity in `N:int` syntax as it accepts both 2 and int
  proc fun*[N: int](): auto =
    1
  const a = fun[2]()
  const a2 = fun[int]()

when defined(case3):
  # Error: type expected
  template fun*[N: static int](): untyped =
    1
  const a = fun[2]()

when defined(case3b):
  # Error: type expected
  template fun*[N: int](): untyped =
    1
  const a = fun[2]()

[zah]

"regular" static params don't have this problem though, so you can work-around with:

template fun*(n: static int): auto = 1

[exelotl]

This bit me yesterday, makes it hard to use templates for a generic fixed-point arithmetic API.

var n = toFixed[int32,5](3.142)  # new fixed-point number with 5 fractional bits

[metagn]

Still an issue, now says "expected type, but got: 2".

Culprit:

Nim/compiler/semexprs.nim

Line 1068 in f1789cc

setGenericParams(c, n[0])

Somewhat related case, also caused by setGenericParams:

proc newSeq[x: static int]() = echo x

template foo =
  newSeq[123]()

foo()

This time caused by this line:

Nim/compiler/semexprs.nim

Line 3177 in f1789cc

setGenericParams(c, n[0])