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SumType fails to replace This[] inside Tuple!() #62
Description
Using sumtype 1.1.1:
import std.typecons : Tuple;
import sumtype;
alias A = SumType!(Tuple!(This[]));
void main() {}
fails with:
.dub/packages/sumtype-1.1.1/sumtype/src/sumtype.d(281,16): Error: template instance `AliasSeq!(ReplaceTypeUnless!(isSumTypeInstance, This, SumType!(Tuple!(This[])), Tuple!(This[])))` recursive template expansion
/dlang/dmd/linux/bin64/../../src/phobos/std/typecons.d(9037,39): Error: template instance `std.typecons.U!(SumType!(Tuple!(This[]))[])` error instantiating
.dub/packages/sumtype-1.1.1/sumtype/src/sumtype.d(282,3): instantiated from here: `ReplaceTypeUnless!(isSumTypeInstance, This, SumType!(Tuple!(This[])), Tuple!(This[]))`
onlineapp.d(7,11): instantiated from here: `SumType!(Tuple!(This[]))`
dmd failed with exit code 1.
Link to run.dlang.io: https://run.dlang.io/is/Vm8AAK
Same code but with This[] outside of Tuple!() works fine
Activity
pbackus commentedon May 1, 2021
The example compiles successfully if you replace
std.typecons.Tuplewith the following simplified version:(run.dlang.io link: https://run.dlang.io/is/avNK7w)
So, something in the implementation of
std.typecons.Tuplemust be creating a circular dependency. I'm not sure there's anythingSumTypecan do about this, but I'll investigate anyway, since there may be a way to work around it inTuple.