cannot instantiate T, even when matching overload that doesn't require T exists

[arnetheduck]

Description

type
  R[T, E] = object
  A = object
  B = object

# Remove this overload to make it work
func err[T](_: type R[T, void]): R[T, void] = discard

func err(_: type R): R[A, B] = discard

echo R.err()

Nim Version

2.0, 2.2

Current Output

testit.nim(11, 7) template/generic instantiation of `err` from here
testit.nim(6, 10) Error: cannot instantiate: 'T'

Expected Output

Known Workarounds

No response

Additional Information

No response

[metagn]

Shouldn't give this error with just the first overload either, it should fail to match

Edit: Indeed the overload wrongly matches

Should be noted this is in opposition to #5632

[arnetheduck]

Should be noted this is in opposition

maybe can have both using a better-match resolution?

[arnetheduck]

Should be noted this is in opposition to #5632

also, in this example, A is actually bound to a type unlike here where the binding fails .. anorther mechanism would be like SFINAE in C++, ie ignore generic resolutions that fail if some work

[metagn]

maybe can have both using a better-match resolution?

The existing mechanism is that the compiler thinks a better match is one with a more specific type, which in this case is the first overload. Not sure how to work backwards on this.

[arnetheduck]

The existing mechanism is that the compiler thinks a better match is one with a more specific type

sure, I meant among the "working" overloads, so it would pick the 5632 resolution in case both "could work" (indeed for being more specific)