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https://github.com/apple/swift.git
synced 2026-10-12 14:50:47 +02:00
Artem Chikin
d327f3401b
Although a `@usableFromInline` variable cannot be named directly by a client, its value can still reach a client binary: an `@inlinable` function may fold the variable into an integer generic argument, and that folded value is then serialized into the function body that the client inlines.
e.g.
```swift
@usableFromInline let x = 8, y = 8, z = 8
@usableFromInline func bar(_ zs: [z of Int]) {}
@inlinable public func foo() {
let xs: [x of Int] = [1, 2, 3, 4, 5, 6, 7, 8]
let ys: [y of Int] = xs
bar(ys)
}
```
A subsequent change to the folded value would leave already-compiled clients inconsistent with the evolved module, so the variable's value is, in effect, part of the ABI.
51 lines
2.7 KiB
Swift
51 lines
2.7 KiB
Swift
// Literal expressions may not reference `let` bindings that are part of the
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// module's ABI surface: publicly visible bindings, or `@usableFromInline` ones.
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// REQUIRES: swift_feature_LiteralExpressions
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// RUN: %target-swift-frontend -typecheck %s -verify \
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// RUN: -package-name myPkg \
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// RUN: -disable-availability-checking \
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// RUN: -enable-experimental-feature LiteralExpressions
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public let publicPageSize = 4096
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package let packagePageSize = 4096
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internal let internalPageSize = 4096
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@usableFromInline internal let usableFromInlinePageSize = 4096
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fileprivate let filePrivatePageSize = 4096
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private let privatePageSize = 4096
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// =============================================================================
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// @section initializer position: public and package bindings are rejected.
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// `open` is not exercised here because it cannot apply to a top-level `let`;
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// the diagnostic's `%select` branch for `open` is preserved for completeness.
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// =============================================================================
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@section("mysection") let a = 2 * publicPageSize
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// expected-error@-1 {{reference to a public 'let' binding is not permitted in a literal expression}}
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@section("mysection") let b = 2 * packagePageSize
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// expected-error@-1 {{reference to a package 'let' binding is not permitted in a literal expression}}
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@section("mysection") let bUFI = 2 * usableFromInlinePageSize
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// expected-error@-1 {{reference to a '@usableFromInline' 'let' binding is not permitted in a literal expression}}
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// Internal, fileprivate, and private bindings are allowed.
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@section("mysection") let c = 2 * internalPageSize
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@section("mysection") let d = 2 * filePrivatePageSize
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@section("mysection") let e = 2 * privatePageSize
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// =============================================================================
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// Integer generic argument position: same restriction applies.
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// =============================================================================
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let f: InlineArray<(2 * publicPageSize), UInt8> = .init(repeating: 0)
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// expected-error@-1 {{reference to a public 'let' binding is not permitted in a literal expression}}
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// expected-error@-2 {{generic value must be an integer literal expression}}
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let g: InlineArray<(2 * packagePageSize), UInt8> = .init(repeating: 0)
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// expected-error@-1 {{reference to a package 'let' binding is not permitted in a literal expression}}
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// expected-error@-2 {{generic value must be an integer literal expression}}
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let gUFI: InlineArray<(2 * usableFromInlinePageSize), UInt8> = .init(repeating: 0)
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// expected-error@-1 {{reference to a '@usableFromInline' 'let' binding is not permitted in a literal expression}}
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// expected-error@-2 {{generic value must be an integer literal expression}}
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