Exit test __capturedValue tweak

Author: grynspan

Sources/Testing/Expectations/Expectation+Macro.swift

@@ -588,7 +588,7 @@ public macro require(
 ///   macro. Do not use it directly.
 @freestanding(expression)
 public macro __capturedValue<T>(
-  _ value: T,
+  _ value: borrowing T,
   _ name: String,
   _ expectedType: T.Type
 ) -> T = #externalMacro(module: "TestingMacros", type: "ExitTestCapturedValueMacro") where T: Sendable & Codable
@@ -611,7 +611,7 @@ public macro __capturedValue<T>(
   _ value: borrowing T,
   _ name: String,
   _ expectedType: T.Type
-) -> Never = #externalMacro(module: "TestingMacros", type: "ExitTestBadCapturedValueMacro") where T: ~Copyable & ~Escapable
+) -> T = #externalMacro(module: "TestingMacros", type: "ExitTestBadCapturedValueMacro") where T: ~Copyable & ~Escapable
 
 /// Emit a compile-time diagnostic when a value is captured by an exit test but
 /// we inferred the wrong type.

Sources/TestingMacros/ExitTestCapturedValueMacro.swift

@@ -50,6 +50,9 @@ public struct ExitTestBadCapturedValueMacro: ExpressionMacro, Sendable {
     // Diagnose that the type of 'expr' is invalid.
     context.diagnose(.capturedValueMustBeSendableAndCodable(expr, name: nameExpr))
 
+    if let typeExpr = arguments[2].expression.as(MemberAccessExprSyntax.self)?.base?.as(TupleExprSyntax.self)?.elements.first?.expression {
+      return "(\(ExprSyntax.unreachable) as! \(typeExpr.trimmed))"
+    }
     return .unreachable
   }
 }