static param in macro crashes nim and with no error shown (nim gags internalAssert errors!)

[timotheecour]

there are multiple bugs involved here:

• crash sholdn't happen
• nim gags errors even fatal ones (errInternal) generated from internalAssert(c.config, c.prc.regInfo[dest].kind < slotSomeTemp) which calls internalErrorImpl ; the error is gagged because we're inside tryConstExpr but we not gag and crash at the same time

Example

after a painful reduction from CI failure in #18274 I obtained this:

when true: # D20210616T031729
  import macros

  # works without static
  proc `&`*(a1: static float, a2: string, a3: float) = discard

  macro fmt2*(): untyped =
    let res = genSym(nskVar, "bar")
    result = quote do:
      var `res` = "zook"
      `res`
  # this would work:
  # template fmt3(pattern: float): untyped = (var ret = "zok"; ret)
  proc main =
    var zook = fmt2() & "a2" & "a3"

Current Output

nim crashes, no error shown (even though it went through normal error handling path as shown in stacktrace, ie reached handleError):
stacktrace with in nim debug mode: https://gist.github.com/timotheecour/081237875166325b692a0fbc6af6f977

Expected Output

works

Example 2

ditto

looks like the problem happens when a static param is in same position as a var (temporary?) and sigmatch tries to match it via tryConstExpr and fails

when defined case9c:
  import macros
  proc add2(a, b: string): string =
    result = ""
    result.add a
    result.add b
  proc add2(a1: static float, a2: string, a3: float) = discard
  # proc add2(x0: float, a1: static float, a2: string, a3: float) = discard # would be no bug
  macro fmt2*(): untyped =
    let res = genSym(nskVar, "bar")
    result = quote do:
      var `res` = "zook"
      `res`
  proc main =
    var zook = add2(add2(fmt2(), "a2"), "a3")

Example 3

when defined case9e:
  proc add2(a, b: string): string = discard
  proc add2(a1: static float, a2: string, a3: float) = discard

  when defined case9e_1:
    import macros
    macro fmt2*(): untyped =
      let res = genSym(nskVar, "bar")
      result = quote do:
        var `res` = "zook"
        `res`

  when defined case9e_2:
    template fmt2(): untyped =
      var res = "zook"
      res

  proc main =
    const x = add2(fmt2(), "a2")

with case9e_1:
/Users/timothee/git_clone/nim/timn/tests/nim/all/t12411.nim(11, 1) template/generic instantiation from here
/Users/timothee/git_clone/nim/timn/tests/nim/all/t12411.nim(11, 1) template/generic instantiation from here
Error: internal error: /Users/timothee/git_clone/nim/Nim_devel/compiler/vmgen.nim(1665, 23)
=> same error but not gagged

with case9e_2:
Error: cannot evaluate at compile time: res`gensym0
var res = "zook"

Additional Information

1.5.1 e80d7ff
CI in #18274 failed because of this

after debugging, conf.m.errorOutputs is {}, which gags the errors in msgs.nim (eg styledMsgWriteln)

it has vibes of #18275 (and in fact i hit both bugs with that simpler change); both might be related

[timotheecour]

#18290 fixes the "don't gag fatal msgs part", and #18282 improves stacktraces, but the underlying bug remains