Compiler crash with auto return type and recursion

[metagn]

Example

proc foo(n: int): auto =
  if n < 5:
    return foo(n + 1)
  else:
    return 9

echo foo(3)

Current Output

Error: internal error: getTypeDescAux(tyUntyped)

Expected Output

Error: cannot infer type of recursive call

Additional Information

• Changing return to result = does the same thing
• The following doesn't crash but a proper error message would be preferred:

proc foo(n: int): auto =
  if n < 5:
    foo(n + 1) # Error: type mismatch: got <untyped> but expected 'int literal(9)'
  else:
    9

echo foo(3)

$ nim -v
Nim Compiler Version 1.0.6

[bung87]

workaround exchange if else branch, make first branch has concrete type