Protocols with associated types and opaque types
WHAT IT TESTS: generics and type erasure. OUTLINE: a PAT leaves a placeholder type unresolved, so it has no single concrete shape and historically could not be used as a bare existential; opaque types with some let you return one fixed underlying conforming…
WHAT IT TESTS: understanding why associated types break existentials and what tools address it. ANSWER OUTLINE: a PAT declares an associatedtype placeholder resolved per conforming type, so the protocol lacks a single concrete signature; that historically barred using it as a bare type like [MyProtocol] because the compiler cannot fix the associated types. Opaque types with some return one specific hidden conforming type, preserving type identity for the caller. RED FLAG: claiming some lets you store mixed PAT conformers in one array.
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- #swift
- #protocols
- #associated-types
- #opaque-types
- #generics
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