Error: overloaded 'X' leads to ambiguous calls

[zevv]

Discussing the snippet below on #nim it was suggested this was worth filing an issue.

My expectation was that it would be fine to do this:

import strutils

proc parse[T: int](s: string): T = parseInt(s)
proc parse[T: float](s: string): T = parseFloat(s)
proc parse[T: bool](s: string): T = parseBool(s)

as long as the caller is explicitly matching one of the signatures like so:

let a parse[int]("42")

However, compilation fails with:

# /tmp/t.nim(4, 6) Error: overloaded 'parse' leads to ambiguous calls

Are my expectations wrong, and if so, which part of the manual did I not read well enough?

The suggestion "Don't do that; it's stupid" also has come up, which I would also take for an answer.

[Araq]

It's just a compiler bug, nothing wrong with the code.

[timotheecour]

• reduced:

when true:
  proc fn[T: int](): T = discard
  proc fn[T: bool](): T = discard

=> Error: overloaded 'fn' leads to ambiguous calls

• works if generic can be deduced from params:

when true:
  proc fn[T: int](a: T): T = discard
  proc fn[T: bool](a: T): T = discard

• works if using typedesc:

when true:
  proc fn(T: typedesc[int]): T = discard
  proc fn(T: typedesc[bool]): T = discard

refs nim-lang/RFCs#40

[metagn]

The problem is in searchForProc, it thinks it's redefining the other parse procs because it doesn't check if the generic params are different