Fix optionality issues after revert

(cherry picked from commit 8de70d3)

# Conflicts:
#	Tests/BasicsTests/TripleTests.swift

Author: MaxDesiatov

Sources/Basics/Vendor/Triple.swift

@@ -1526,7 +1526,7 @@ extension Triple {
   /// `darwin` OS version number is not adjusted to match the equivalent
   /// `macosx` version number. It's usually better to use `version(for:)`
   /// to get Darwin versions.
-  public var osVersion: Version {
+  public var osVersion: Version? {
     var osName = self.osName[...]
 
     // Assume that the OS portion of the triple starts with the canonical name.
@@ -1623,7 +1623,7 @@ extension Triple {
   ///
   /// This accessor is semi-private; it's typically better to use `version(for:)` or
   /// `Triple.FeatureAvailability`.
-  public var _iOSVersion: Version {
+  public var _iOSVersion: Version? {
     switch os {
     case .darwin, .macosx:
       // Ignore the version from the triple.  This is only handled because the
@@ -1650,7 +1650,7 @@ extension Triple {
   ///
   /// This accessor is semi-private; it's typically better to use `version(for:)` or
   /// `Triple.FeatureAvailability`.
-  public var _watchOSVersion: Version {
+  public var _watchOSVersion: Version? {
     switch os {
     case .darwin, .macosx:
       // Ignore the version from the triple.  This is only handled because the
@@ -1659,7 +1659,7 @@ extension Triple {
       // OS X.
       return Version(2, 0, 0)
     case .watchos:
-      var version = self.osVersion
+      guard var version = self.osVersion else { return nil }
       if version.major == 0 {
         version.major = 2
       }

Tests/BasicsTests/TripleTests.swift

@@ -164,5 +164,53 @@ final class TripleTests: XCTestCase {
         XCTAssertTriple("aarch64-unknown-linux-android", matches: (.aarch64, nil, nil, .linux, .android, .elf))
         XCTAssertTriple("x86_64-unknown-windows-msvc", matches: (.x86_64, nil, nil, .win32, .msvc, .coff))
         XCTAssertTriple("wasm32-unknown-wasi", matches: (.wasm32, nil, nil, .wasi, nil, .wasm))
+    }    
+
+    func testTriple() {
+        let linux = try? Triple("x86_64-unknown-linux-gnu")
+        XCTAssertNotNil(linux)
+        XCTAssertEqual(linux!.os, .linux)
+        XCTAssertNil(linux!.osVersion)
+        XCTAssertEqual(linux!.environment, .gnu)
+
+        let macos = try? Triple("x86_64-apple-macosx10.15")
+        XCTAssertNotNil(macos!)
+        XCTAssertEqual(macos!.osVersion, .init(parse: "10.15")!)
+        let newVersion = "10.12"
+        let tripleString = macos!.tripleString(forPlatformVersion: newVersion)
+        XCTAssertEqual(tripleString, "x86_64-apple-macosx10.12")
+        let macosNoX = try? Triple("x86_64-apple-macos12.2")
+        XCTAssertNotNil(macosNoX!)
+        XCTAssertEqual(macosNoX!.os, .macosx)
+        XCTAssertEqual(macosNoX!.osVersion, .init(parse: "12.2")!)
+
+        let android = try? Triple("aarch64-unknown-linux-android24")
+        XCTAssertNotNil(android)
+        XCTAssertEqual(android!.os, .linux)
+        XCTAssertEqual(android!.environment, .android)
+
+        let linuxWithABIVersion = try? Triple("x86_64-unknown-linux-gnu42")
+        XCTAssertEqual(linuxWithABIVersion!.environment, .gnu)
+    }
+
+    func testEquality() throws {
+        let macOSTriple = try Triple("arm64-apple-macos")
+        let macOSXTriple = try Triple("arm64-apple-macosx")
+        XCTAssertEqual(macOSTriple, macOSXTriple)
+
+        let intelMacOSTriple = try Triple("x86_64-apple-macos")
+        XCTAssertNotEqual(macOSTriple, intelMacOSTriple)
+
+        let linuxWithoutGNUABI = try Triple("x86_64-unknown-linux")
+        let linuxWithGNUABI = try Triple("x86_64-unknown-linux-gnu")
+        XCTAssertNotEqual(linuxWithoutGNUABI, linuxWithGNUABI)
+    }
+
+    func testWASI() throws {
+        let wasi = try Triple("wasm32-unknown-wasi")
+
+        // WASI dynamic libraries are only experimental,
+        // but SwiftPM requires this property not to crash.
+        _ = wasi.dynamicLibraryExtension
     }
 }