Avoid std::move when constructing results; allow diplomat_result to be constructed from trivially copyable lvalues #336
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Manishearth
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Manishearth
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r? either @sffc or @robertbastian , whoever feels more comfortable staring at SFINAE |
Manishearth
commented
Jun 7, 2023
| @@ -56,6 +55,10 @@ template<> struct WriteableTrait<std::string> { | |||
| template<class T> struct Ok { | |||
| T inner; | |||
| Ok(T&& i): inner(std::move(i)) {} | |||
| // We don't want to expose an lvalue-capable constructor in general | |||
| // however there is no problem doing this for trivially copyable types | |||
| template<typename X = T, typename = typename std::enable_if<std::is_trivially_copyable<X>::value>::type> | |||
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the X=T is necessary here because enable_if needs to depend on parameters of the ctor not of the class (unfortunately)
I don't think it's possible to "override" the default value for X but I'm not sure.
sffc
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Jun 8, 2023
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Fixes #335
There's a small snag in that
diplomat::Ok(result.ok)starts erroring. We only use that path for primitives, and it seems fine to add a non-moving constructor for trivially copyable types. I added some SFINAE for it; which seems to work.My hunch was right that this affects cpp2 as well (which already avoids the
std::move()), and thediplomat_runtimefix works for both.