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Trait methods that return an unsized type only error when implementing trait #26204

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Aatch opened this issue Jun 11, 2015 · 3 comments
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Trait methods that return an unsized type only error when implementing trait #26204

Aatch opened this issue Jun 11, 2015 · 3 comments
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T-lang Relevant to the language team, which will review and decide on the PR/issue.

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@Aatch
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Aatch commented Jun 11, 2015

This doesn't cause an error:

trait A { }
trait B { fn foo() -> A; }

despite the fact you wouldn't be able to ever implement B.

Making this an error should be fine for backwards compatiblity, since you'd not be able to implement the trait anyway. It's a bit confusing that the error is only when implementing the trait.
@Aatch Aatch added I-papercut T-lang Relevant to the language team, which will review and decide on the PR/issue. labels Jun 11, 2015
@apasel422
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Possibly related to #19182.

@arielb1
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arielb1 commented Jun 17, 2015

I think this is by-design according to @nikomatsakis

@apasel422 apasel422 mentioned this issue Jun 22, 2015
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@arielb1
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arielb1 commented Aug 14, 2015

closed as by-design.

@arielb1 arielb1 closed this as completed Aug 14, 2015
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