Use the entire SHA-256 hash as an exit test ID. (#1053)

This PR uses the entire 256 bits of the computed SHA-256 hash for an
exit test's ID, not just the first 128. They're there, might as well use
them.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: grynspan

Diff for: Sources/Testing/ExitTests/ExitTest.swift

@@ -48,13 +48,17 @@ public struct ExitTest: Sendable, ~Copyable {
     /// Storage for the underlying bits of the ID.
     ///
     /// - Note: On Apple platforms, we deploy to OS versions that do not include
-    ///   support for `UInt128`, so we use two `UInt64`s for storage instead.
-    private var _lo: UInt64
-    private var _hi: UInt64
-
-    init(_ uuid: (UInt64, UInt64)) {
-      self._lo = uuid.0
-      self._hi = uuid.1
+    ///   support for `UInt128`, so we use four `UInt64`s for storage instead.
+    private var _0: UInt64
+    private var _1: UInt64
+    private var _2: UInt64
+    private var _3: UInt64
+
+    init(_ uuid: (UInt64, UInt64, UInt64, UInt64)) {
+      self._0 = uuid.0
+      self._1 = uuid.1
+      self._2 = uuid.2
+      self._3 = uuid.3
     }
   }
 
@@ -270,7 +274,7 @@ extension ExitTest: DiscoverableAsTestContent {
   /// - Warning: This function is used to implement the `#expect(exitsWith:)`
   ///   macro. Do not use it directly.
   public static func __store(
-    _ id: (UInt64, UInt64),
+    _ id: (UInt64, UInt64, UInt64, UInt64),
     _ body: @escaping @Sendable () async throws -> Void,
     into outValue: UnsafeMutableRawPointer,
     asTypeAt typeAddress: UnsafeRawPointer,
@@ -344,7 +348,7 @@ extension ExitTest {
 /// `await #expect(exitsWith:) { }` invocations regardless of calling
 /// convention.
 func callExitTest(
-  identifiedBy exitTestID: (UInt64, UInt64),
+  identifiedBy exitTestID: (UInt64, UInt64, UInt64, UInt64),
   exitsWith expectedExitCondition: ExitTest.Condition,
   observing observedValues: [any PartialKeyPath<ExitTest.Result> & Sendable],
   expression: __Expression,

Diff for: Sources/Testing/Expectations/ExpectationChecking+Macro.swift

@@ -1147,7 +1147,7 @@ public func __checkClosureCall<R>(
 ///   `#require()` macros. Do not call it directly.
 @_spi(Experimental)
 public func __checkClosureCall(
-  identifiedBy exitTestID: (UInt64, UInt64),
+  identifiedBy exitTestID: (UInt64, UInt64, UInt64, UInt64),
   exitsWith expectedExitCondition: ExitTest.Condition,
   observing observedValues: [any PartialKeyPath<ExitTest.Result> & Sendable],
   performing body: @convention(thin) () -> Void,

Diff for: Sources/TestingMacros/ConditionMacro.swift

@@ -551,30 +551,35 @@ extension ExitTestConditionMacro {
     for macro: some FreestandingMacroExpansionSyntax,
     in context: some MacroExpansionContext
   ) -> ExprSyntax {
-    let exitTestID: (UInt64, UInt64)
-    if let sourceLocation = context.location(of: macro, at: .afterLeadingTrivia, filePathMode: .fileID),
-       let fileID = sourceLocation.file.as(StringLiteralExprSyntax.self)?.representedLiteralValue,
-       let line = sourceLocation.line.as(IntegerLiteralExprSyntax.self)?.representedLiteralValue,
-       let column = sourceLocation.column.as(IntegerLiteralExprSyntax.self)?.representedLiteralValue {
-      // Hash the entire source location and store as many bits as possible in
-      // the resulting ID.
-      let stringValue = "\(fileID):\(line):\(column)"
-      exitTestID = SHA256.hash(stringValue.utf8).withUnsafeBytes { sha256 in
-        sha256.loadUnaligned(as: (UInt64, UInt64).self)
+    withUnsafeTemporaryAllocation(of: UInt64.self, capacity: 4) { exitTestID in
+      if let sourceLocation = context.location(of: macro, at: .afterLeadingTrivia, filePathMode: .fileID),
+         let fileID = sourceLocation.file.as(StringLiteralExprSyntax.self)?.representedLiteralValue,
+         let line = sourceLocation.line.as(IntegerLiteralExprSyntax.self)?.representedLiteralValue,
+         let column = sourceLocation.column.as(IntegerLiteralExprSyntax.self)?.representedLiteralValue {
+        // Hash the entire source location and store the entire hash in the
+        // resulting ID.
+        let stringValue = "\(fileID):\(line):\(column)"
+        exitTestID.withMemoryRebound(to: UInt8.self) { exitTestID in
+          _ = exitTestID.initialize(from: SHA256.hash(stringValue.utf8))
+        }
+      } else {
+        // This branch is dead code in production, but is used when we expand a
+        // macro in our own unit tests because the macro expansion context does
+        // not have real source location information.
+        for i in 0 ..< exitTestID.count {
+          exitTestID[i] = .random(in: 0 ... .max)
+        }
       }
-    } else {
-      // This branch is dead code in production, but is used when we expand a
-      // macro in our own unit tests because the macro expansion context does
-      // not have real source location information.
-      exitTestID.0 = .random(in: 0 ... .max)
-      exitTestID.1 = .random(in: 0 ... .max)
-    }
 
-    // Return a tuple of integer literals (which is what the runtime __store()
-    // function is expecting.)
-    return """
-    (\(IntegerLiteralExprSyntax(exitTestID.0, radix: .hex)), \(IntegerLiteralExprSyntax(exitTestID.1, radix: .hex)))
-    """
+      // Return a tuple of integer literals (which is what the runtime __store()
+      // function is expecting.)
+      let tupleExpr = TupleExprSyntax {
+        for uint64 in exitTestID {
+          LabeledExprSyntax(expression: IntegerLiteralExprSyntax(uint64, radix: .hex))
+        }
+      }
+      return ExprSyntax(tupleExpr)
+    }
   }
 }