Instead of linking libswiftAST into SwiftBasicTests, define ActorIsolation::dumpForDiagnostics out of line.

Author: gottesmm

include/swift/AST/ActorIsolation.h

@@ -291,10 +291,10 @@ class ActorIsolation {
     llvm::dbgs() << '\n';
   }
 
-  SWIFT_DEBUG_DUMPER(dumpForDiagnostics()) {
-    printForDiagnostics(llvm::dbgs());
-    llvm::dbgs() << '\n';
-  }
+  // Defined out of line to prevent linker errors since libswiftBasic would
+  // include this header exascerbating a layering violation where libswiftBasic
+  // depends on libswiftAST.
+  SWIFT_DEBUG_DUMPER(dumpForDiagnostics());
 };
 
 /// Determine how the given value declaration is isolated.

lib/AST/TypeCheckRequests.cpp

@@ -1716,6 +1716,11 @@ void ActorIsolation::printForDiagnostics(llvm::raw_ostream &os,
   }
 }
 
+void ActorIsolation::dumpForDiagnostics() const {
+  printForDiagnostics(llvm::dbgs());
+  llvm::dbgs() << '\n';
+}
+
 void swift::simple_display(
     llvm::raw_ostream &out, const ActorIsolation &state) {
   if (state.preconcurrency())