[WIP] Rethink how we capture expectation conditions and their subexpressions.

Package.swift

@@ -178,6 +178,13 @@ let package = Package(
       path: "Tests/_MemorySafeTestingTests",
       swiftSettings: .packageSettings(isTestTarget: true) + [.strictMemorySafety()]
     ),
+    .testTarget(
+      name: "SubexpressionShowcase",
+      dependencies: [
+        "Testing",
+      ],
+      swiftSettings: .packageSettings(isTestTarget: true)
+    ),
 
     .macro(
       name: "TestingMacros",

Sources/Testing/CMakeLists.txt

@@ -53,6 +53,7 @@ add_library(Testing
   Expectations/Expectation.swift
   Expectations/Expectation+Macro.swift
   Expectations/ExpectationChecking+Macro.swift
+  Expectations/ExpectationContext.swift
   Issues/Confirmation.swift
   Issues/ErrorSnapshot.swift
   Issues/Issue.swift
@@ -76,7 +77,7 @@ add_library(Testing
   SourceAttribution/CustomTestReflectable.swift
   SourceAttribution/CustomTestStringConvertible.swift
   SourceAttribution/Expression.swift
-  SourceAttribution/Expression+Macro.swift
+  SourceAttribution/ExpressionID.swift
   SourceAttribution/SourceBounds.swift
   SourceAttribution/SourceContext.swift
   SourceAttribution/SourceLocation.swift

Sources/Testing/Events/Recorder/Event.ConsoleOutputRecorder.swift

@@ -185,7 +185,7 @@ extension Event.Symbol {
       case .attachment:
         return "\(_ansiEscapeCodePrefix)94m\(symbolCharacter)\(_resetANSIEscapeCode)"
       case .details:
-        return symbolCharacter
+        return "\(symbolCharacter)"
       }
     }
     return symbolCharacter

Sources/Testing/ExitTests/ExitTest.swift

@@ -464,17 +464,16 @@ extension ExitTest {
 /// This function contains the common implementation for all
 /// `await #expect(processExitsWith:) { }` invocations regardless of calling
 /// convention.
-func callExitTest(
+nonisolated(nonsending) func callExitTest(
   identifiedBy exitTestID: (UInt64, UInt64, UInt64, UInt64),
   encodingCapturedValues capturedValues: [ExitTest.CapturedValue],
   processExitsWith expectedExitCondition: ExitTest.Condition,
   observing observedValues: [any PartialKeyPath<ExitTest.Result> & Sendable],
-  expression: __Expression,
+  sourceCode: @escaping @autoclosure @Sendable () -> KeyValuePairs<__ExpressionID, String>,
   comments: @autoclosure () -> [Comment],
   isRequired: Bool,
-  isolation: isolated (any Actor)? = #isolation,
   sourceLocation: SourceLocation
-) async -> Result<ExitTest.Result?, any Error> {
+) async -> Result<ExitTest.Result?, ExpectationFailedError> {
   guard let configuration = Configuration.current ?? Configuration.all.first else {
     preconditionFailure("A test must be running on the current task to use #expect(processExitsWith:).")
   }
@@ -527,27 +526,14 @@ func callExitTest(
   }
 
   // Plumb the exit test's result through the general expectation machinery.
-  func expressionWithCapturedRuntimeValues() -> __Expression {
-    var expression = expression.capturingRuntimeValues(result.exitStatus)
-
-    expression.subexpressions = [expectedExitCondition.exitStatus, result.exitStatus]
-      .compactMap { exitStatus in
-        guard let exitStatus, let exitStatusName = exitStatus.name else {
-          return nil
-        }
-        return __Expression(
-          exitStatusName,
-          runtimeValue: __Expression.Value(describing: exitStatus.code)
-        )
-      }
-
-    return expression
-  }
-  return __checkValue(
+  let expectationContext = __ExpectationContext<Bool>(
+    sourceCode: [.root: String(describingForTest: expectedExitCondition)],
+    runtimeValues: [.root: { Expression.Value(reflecting: result.exitStatus) }]
+  )
+  return check(
     expectedExitCondition.isApproximatelyEqual(to: result.exitStatus),
-    expression: expression,
-    expressionWithCapturedRuntimeValues: expressionWithCapturedRuntimeValues(),
-    mismatchedExitConditionDescription: #"expected exit status "\#(expectedExitCondition)", but "\#(result.exitStatus)" was reported instead"#,
+    expectationContext: expectationContext,
+    mismatchedErrorDescription: nil,
     comments: comments(),
     isRequired: isRequired,
     sourceLocation: sourceLocation

Sources/Testing/Expectations/Expectation+Macro.swift

@@ -66,10 +66,10 @@
 /// running in the current task and an instance of ``ExpectationFailedError`` is
 /// thrown.
 @freestanding(expression) public macro require<T>(
-  _ optionalValue: T?,
+  _ optionalValue: consuming T?,
   _ comment: @autoclosure () -> Comment? = nil,
   sourceLocation: SourceLocation = #_sourceLocation
-) -> T = #externalMacro(module: "TestingMacros", type: "RequireMacro")
+) -> T = #externalMacro(module: "TestingMacros", type: "UnwrapMacro") where T: ~Copyable
 
 /// Unwrap an optional boolean value or, if it is `nil`, fail and throw an
 /// error.
@@ -89,7 +89,7 @@
 /// running in the current task and an instance of ``ExpectationFailedError`` is
 /// thrown.
 ///
-/// This overload of ``require(_:_:sourceLocation:)-6w9oo`` checks if
+/// This overload of ``require(_:_:sourceLocation:)-5l63q`` checks if
 /// `optionalValue` may be ambiguous (i.e. it is unclear if the developer
 /// intended to check for a boolean value or unwrap an optional boolean value)
 /// and provides additional compile-time diagnostics when it is.
@@ -118,16 +118,16 @@ public macro require(
 /// running in the current task and an instance of ``ExpectationFailedError`` is
 /// thrown.
 ///
-/// This overload of ``require(_:_:sourceLocation:)-6w9oo`` is used when a
+/// This overload of ``require(_:_:sourceLocation:)-5l63q`` is used when a
 /// non-optional, non-`Bool` value is passed to `#require()`. It emits a warning
 /// diagnostic indicating that the expectation is redundant.
 @freestanding(expression)
 @_documentation(visibility: private)
 public macro require<T>(
-  _ optionalValue: T,
+  _ optionalValue: consuming T,
   _ comment: @autoclosure () -> Comment? = nil,
   sourceLocation: SourceLocation = #_sourceLocation
-) -> T = #externalMacro(module: "TestingMacros", type: "NonOptionalRequireMacro")
+) -> T = #externalMacro(module: "TestingMacros", type: "NonOptionalRequireMacro") where T: ~Copyable
 
 // MARK: - Matching errors by type
 

Sources/Testing/Expectations/Expectation.swift

@@ -12,14 +12,14 @@
 public struct Expectation: Sendable {
   /// The expression evaluated by this expectation.
   @_spi(ForToolsIntegrationOnly)
-  public var evaluatedExpression: Expression
+  public internal(set) var evaluatedExpression: Expression
 
   /// A description of the error mismatch that occurred, if any.
   ///
   /// If this expectation passed, the value of this property is `nil` because no
   /// error mismatch occurred.
   @_spi(Experimental) @_spi(ForToolsIntegrationOnly)
-  public var mismatchedErrorDescription: String?
+  public internal(set) var mismatchedErrorDescription: String?
 
   /// A description of the difference between the operands in the expression
   /// evaluated by this expectation, if the difference could be determined.
@@ -28,14 +28,9 @@ public struct Expectation: Sendable {
   /// the difference is only computed when necessary to assist with diagnosing
   /// test failures.
   @_spi(Experimental) @_spi(ForToolsIntegrationOnly)
-  public var differenceDescription: String?
-
-  /// A description of the exit condition that was expected to be matched.
-  ///
-  /// If this expectation passed, the value of this property is `nil` because no
-  /// exit test failed.
-  @_spi(Experimental) @_spi(ForToolsIntegrationOnly)
-  public var mismatchedExitConditionDescription: String?
+  public var differenceDescription: String? {
+    evaluatedExpression.differenceDescription
+  }
 
   /// Whether the expectation passed or failed.
   ///
@@ -100,7 +95,7 @@ extension Expectation {
     /// - Parameter expectation: The real expectation.
     public init(snapshotting expectation: borrowing Expectation) {
       self.evaluatedExpression = expectation.evaluatedExpression
-      self.mismatchedErrorDescription = expectation.mismatchedErrorDescription ?? expectation.mismatchedExitConditionDescription
+      self.mismatchedErrorDescription = expectation.mismatchedErrorDescription
       self.differenceDescription = expectation.differenceDescription
       self.isPassing = expectation.isPassing
       self.isRequired = expectation.isRequired