Compiler stackoverflow with generics/options

[jwollen]

The following causes a stackoverflow in replaceTypeVarsN/S.
Apologies for the unconcreteness. I didn't investigate further :P

import options
type Bar = object
proc foo*[T](self: T; x: Option[Bar] = Bar.none) = discard
foo(1)

[LemonBoy]

I believe this is the same problem reported in another ticket whose number I can't find right now.
Does changing Bar.none into none(Bar) help?

[jwollen]

Nope, same result.

[stefanos82]

I have tried your code and as soon as I attempt to compile it, it hangs at typetraits processing.

[LemonBoy]

The instantiation of the generic calls the replaceTypeVars* on the default argument value. What happens next is that Bar points to the type Bar = object declaration that in turn points to Bar that points to type Bar = object ... and so on.

[krux02]

There is a comment about this bug in the source code. It seems to be a tough problem.

Nim/compiler/semtypinst.nim

Line 224 in 3cf3c2d

# XXX: Bound symbols in default parameter expressions may reach here.

[ghost]

Works on latest devel, need to add a test-case?

[timotheecour]

Yes, always :)

[timotheecour]

closed by #14795