Invalid codegen with default argument invalid in generic context

[refi64]

I couldn't really think of a better title (why do I always run into the weirdest bugs), so here's an example:

Example

type
  A = object
  B = object

proc f(a: A) = discard

proc g[T](value: T, cb: (proc(a: T)) = f) =
  cb value

# This should fail because there is no f(a: B) overload available
g B()

Current Output

/usercode/nimcache/@min.nim.c: In function 'NimMainModule':
/usercode/nimcache/@min.nim.c:138:34: error: expected expression before ')' token
  g__blFRD9cre3iSc5obJINpxvg(T1_, );
                                  ^
Error: execution of an external program failed: 'gcc -c  -w  -I/playground/nim/lib -I/usercode -o /usercode/nimcache/@min.nim.c.o /usercode/nimcache/@min.nim.c'

Expected Output

A compiler error because g(a: B) does not exist.

Possible Solution

I'm honestly not sure why this occurs, but it's definitely related to the default value of cb. If I remove the default and pass f as a second argument to g at the call site, an error is properly displayed.

$ nim -v
Nim Compiler Version 1.0.6

[metagn]

Now gives

Error: type mismatch: got <proc (a: A){.noSideEffect, gcsafe.}> but expected 'proc (a: B){.closure.}'
  Calling convention mismatch: got '{.nimcall.}', but expected '{.closure.}'.

probably since #24006