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Kavon Farvardin
19119ad88a
@_preInverseGenerics(except: <inverses>) is an extension of the existing @_preInverseGenerics attribute that provides selective control over which inverse requirements are mangled into a declaration's symbol name. While the bare @_preInverseGenerics strips all inverse constraints (~Copyable and ~Escapable) from mangling, the 'except:' form allows specific inverses to be retained. This is needed when a type like Span already had ~Copyable mangled into its ABI-stable symbols and now needs to retroactively adopt ~Escapable without changing those existing symbols. You can now express that with `@_preInverseGenerics(except: ~Copyable)` to strip-out every inverse except ~Copyable to preserve the pre-existing ~Copyable-containing symbols. It requires the new experimental feature `PreInverseGenericsExcept`. rdar://176395527
41 lines
1.9 KiB
Swift
41 lines
1.9 KiB
Swift
// RUN: %target-typecheck-verify-swift -enable-experimental-feature PreInverseGenericsExcept
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// REQUIRES: swift_feature_PreInverseGenericsExcept
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@_preInverseGenerics
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func bare<T: ~Copyable>(_ t: borrowing T) {}
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@_preInverseGenerics(except: ~Copyable)
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func exceptCopyable<T: ~Copyable & ~Escapable>(_ t: borrowing T) {}
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@_preInverseGenerics(except: ~Escapable)
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func exceptEscapable<T: ~Copyable & ~Escapable>(_ t: borrowing T) {}
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// excepting all inverses is equivalent to not using the attribute
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@_preInverseGenerics(except: ~Copyable & ~Escapable) // expected-warning {{'@_preInverseGenerics' that excepts all inverse constraints is equivalent to not using the attribute}}
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func exceptBoth<T: ~Copyable & ~Escapable>(_ t: borrowing T) {}
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// `except: Any` is confusing; reject it in favor of the bare form.
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@_preInverseGenerics(except: Any) // expected-error {{'except' argument to '@_preInverseGenerics' must consist only of inverse constraints such as '~Copyable' or '~Escapable'}}
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func exceptAny<T: ~Copyable & ~Escapable>(_ t: borrowing T) {}
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// wrong label
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@_preInverseGenerics(foo: ~Copyable) // expected-error {{expected 'except:' argument in '@_preInverseGenerics'}}
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func bad1() {}
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// non-inverse type
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@_preInverseGenerics(except: Int) // expected-error {{'except' argument to '@_preInverseGenerics' must consist only of inverse constraints such as '~Copyable' or '~Escapable'}}
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func bad2() {}
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// positive protocol (not inverted)
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@_preInverseGenerics(except: Copyable) // expected-error {{'except' argument to '@_preInverseGenerics' must consist only of inverse constraints such as '~Copyable' or '~Escapable'}}
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func bad3() {}
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// Warning: attribute on extension has no effect
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struct S<T: ~Copyable>: ~Copyable {}
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@_preInverseGenerics // expected-warning {{'@_preInverseGenerics' has no effect on an extension; place it on individual members instead}}
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extension S where T: ~Copyable {
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func extMethod() {}
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}
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