Move ExpressibleByArrayLiteral conformance of _TinyArray to the d…

…eclaring module (#157)

Motivation

Nightly compilers start complaining about retroactive conformances.

Modifications

- move conformance to declaring module
- optimise code to not allocate

Result

no warning, optimal generated code for:

```swift
func foo1(int: Int) -> _TinyArray<Int> {
    [int]
}
```

compiles down to:
```
output.foo1(int: Swift.Int) -> output._TinyArray<Swift.Int>:
        mov     rax, rdi
        xor     edx, edx
        ret
```

https://godbolt.org/z/a91fPe6or

Sources/X509/CryptographicMessageSyntax/CMSSignature.swift

@@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 import SwiftASN1
-#if canImport(Darwin)
+#if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation

Sources/X509/OCSP/OCSPPolicy.swift

@@ -14,7 +14,7 @@
 
 import SwiftASN1
 import Crypto
-#if canImport(Darwin)
+#if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation

Sources/_CertificateInternals/_TinyArray.swift

@@ -32,6 +32,20 @@ extension _TinyArray: Equatable where Element: Equatable {}
 extension _TinyArray: Hashable where Element: Hashable {}
 extension _TinyArray: Sendable where Element: Sendable {}
 
+extension _TinyArray: ExpressibleByArrayLiteral {
+    @inlinable
+    public init(arrayLiteral elements: Element...) {
+        switch elements.count {
+        case 0:
+            self = .init()
+        case 1:
+            self = .init(CollectionOfOne(elements[0]))
+        default:
+            self = .init(elements)
+        }
+    }
+}
+
 extension _TinyArray: RandomAccessCollection {
     public typealias Element = Element
 

Tests/CertificateInternalsTests/TinyArrayTests.swift

@@ -67,6 +67,15 @@ final class TinyArrayTests: XCTestCase {
         XCTAssertEqual(Array(_TinyArray<Int>([1, 2, 3, 4, 5])), [1, 2, 3, 4, 5])
     }
 
+    func testExpressibleByArrayLiteral() {
+        XCTAssertEqual(Array([] as _TinyArray<Int>), [])
+        XCTAssertEqual(Array([1] as _TinyArray<Int>), [1])
+        XCTAssertEqual(Array([1, 2] as _TinyArray<Int>), [1, 2])
+        XCTAssertEqual(Array([1, 2, 3] as _TinyArray<Int>), [1, 2, 3])
+        XCTAssertEqual(Array([1, 2, 3, 4] as _TinyArray<Int>), [1, 2, 3, 4])
+        XCTAssertEqual(Array([1, 2, 3, 4, 5] as _TinyArray<Int>), [1, 2, 3, 4, 5])
+    }
+
     func testAppend() {
         assertEqual([1]) { array in
             array.append(1)
@@ -339,11 +348,3 @@ final class TinyArrayTests: XCTestCase {
         )
     }
 }
-
-extension _TinyArray: ExpressibleByArrayLiteral {
-    public typealias ArrayLiteralElement = Element
-
-    public init(arrayLiteral elements: Element...) {
-        self.init(elements)
-    }
-}

Tests/X509Tests/OCSPPolicyVerifierTests.swift

@@ -16,7 +16,7 @@ import XCTest
 import Crypto
 import SwiftASN1
 @testable import X509
-#if canImport(Darwin)
+#if canImport(Darwin) || swift(>=5.9.1)
 import Foundation
 #else
 @preconcurrency import Foundation