Regression: compile error using when/elif/else and typedesc in template

[arkanoid87]

Please help me find a better title for this issue.

The example compiles with 1.4.8 and returns error with 1.6.0.
Bisect has found 2aba116 as first bad commit

Tested with both orc and refc

https://play.nim-lang.org/#ix=3MTf

Example

type
  MyInt = object
    bitWidth: int

template toRealType*(t: MyInt): typedesc =
  when t.bitWidth == 32: int32
  elif t.bitWidth == 64: int64
  else: {.error.}

proc doFail(T: typedesc): T = default(T)

proc test =
  const myInt = MyInt(bitWidth:32)
  discard doFail(toRealType(myInt))

test()

Current Output

Error: unhandled exception: field 'sym' is not accessible for type 'TNode' using 'kind = nkIdent' [FieldDefect]

Expected Output

compilation successful

Additional Information

It's a regression:

• 1.4.8: compiles successfully
• 1.6.0 up to devel: compilation error

Bisect result

first bad commit: [2aba116] when statements branches exit early (#17143)