Add OriginalType<A, B>: 'pin bound to projected type
#188
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Aaron1011
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The UI test output seems to have changes on Nightly (the span is slightly different). I'm not sure how best to deal with this. |
taiki-e
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Fixes taiki-e#185 Usually, Rust will automatically add lifetime bounds of the form `T: 'lifetime` when required (e.g. when a struct contains `&'a T`). However, the compiler will not normalize associated types before performing this analysis, which can require users to manually add `T: 'lifetime` bounds themselves. When this happens with a generated projection struct, the user has no ability to add such a bound, since they cannot name the 'pin lifetime. This PR adds a bound of the form `OriginalType<A, B>: 'pin` to the `where` clause of the generated projection types. This ensures that any type parameters which need to outlive 'pin will do so, without unnecessarily constraining other type parameters. The generated bound does not need to be added to the `where` clause of any impls for the generated projection types. For more details, see https://github.com/rust-lang/rfcs/blob/d89de6a5857597cca9f6e1c7ebb70476f31a9159/text/2093-infer-outlives.md#background-outlives-requirements-today
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Looks good, Thanks! bors r+ |
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Fixes #185
Usually, Rust will automatically add lifetime bounds of the form
T: 'lifetimewhen required (e.g. when a struct contains&'a T).However, the compiler will not normalize associated types before
performing this analysis, which can require users to manually add
T: 'lifetimebounds themselves. When this happens with a generatedprojection struct, the user has no ability to add such a bound, since
they cannot name the 'pin lifetime.
This PR adds a bound of the form
OriginalType<A, B>: 'pinto thewhereclause of the generated projection types. This ensures thatany type parameters which need to outlive 'pin will do so, without
unnecessarily constraining other type parameters.