Doug Gregor 5bdd4e5772 Improve @_implements for associated type witnesses ...

Allow `@_implements` to be expressed in an extension of the protocol in
which the associated type is defined. Use this to uncomment an
intended use of `@_implements` in `Sequence` that could be used to
replace a longstanding hack for associated type inference.

Since this change means that the standard library module interface
won't be accepted by older compilers, introduce a suppressible feature
ssociatedTypeImplements` that covers the use of `@_implements` on type
declarations. This will hide the `@_implements` attribute from older
compilers.

2024-03-11 14:28:20 -07:00

2.8 KiB

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