Use Array.Fill in Enumerable.Repeat.ToArray #16122
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| @@ -79,10 +79,7 @@ public TResult[] ToArray() | |||
| TResult[] array = new TResult[_count]; | |||
| if (_current != null) | |||
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@jkotas, is there any efficient and built-in mechanism for checking whether a value is default(TResult)? This check will handle reference types; I'm wondering if there's something that would more generally help with any type.
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System.Runtime.CompilerServices.RuntimeHelpers.Equals(_current, default(TResult)) is identity-equality for reference types, internal representation equality for value types, ignoring all Equals and == overrides.
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But unless there's special recognition of it by the JIT (?), it'll box both value type arguments. Hence the "efficient" part of my question.
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@JonHanna That is not particularly efficient though because structs will be boxed and a call will be made. By contrast _current != null has non-existent overhead for value types because it's eliminated by the JIT. (edit: beaten by @stephentoub)
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Yeah, it'll box. And now I think about it, I wrote that skip on null, and that's precisely why I didn't test for default generally. I'd certainly love to learn of a non-boxing mechanism.
* Use Array.Fill in Enumerable.Repeat.ToArray Commit migrated from dotnet/corefx@28ffdd6
As the title says. Currently the implementation is the same (using a for-loop) and there's no difference, but in the future it could possibly be optimized by e.g. implementing it natively for reference types to avoid the checks to account for covariant arrays on every store.
/cc @JonHanna @stephentoub @VSadov