[cxx-interop] Add fix-it for foreign reference types.

Author: zoecarver

lib/ClangImporter/ClangImporter.cpp

@@ -4402,12 +4402,24 @@ ClangImporter::Implementation::importDiagnosticTargetFromLookupTableEntry(
                    "MacroInfo or ModuleMacro pointer");
 }
 
+static void diagnoseForeignReferenceTypeFixit(ClangImporter::Implementation &Impl,
+                                              HeaderLoc loc, Diagnostic diag) {
+  auto importedLoc =
+    Impl.SwiftContext.getClangModuleLoader()->importSourceLocation(loc.clangLoc);
+  Impl.diagnose(loc, diag)
+    .fixItInsert(importedLoc, "SWIFT_REFERENCE_TYPE(<#retain#>, <#release#>) ");
+}
+
 bool ClangImporter::Implementation::emitDiagnosticsForTarget(
     ImportDiagnosticTarget target, clang::SourceLocation fallbackLoc) {
   for (auto it = ImportDiagnostics[target].rbegin();
        it != ImportDiagnostics[target].rend(); ++it) {
     HeaderLoc loc = HeaderLoc(it->loc.isValid() ? it->loc : fallbackLoc);
-    diagnose(loc, it->diag);
+    if (it->diag.getID() == diag::record_not_automatically_importable.ID) {
+      diagnoseForeignReferenceTypeFixit(*this, loc, it->diag);
+    } else {
+      diagnose(loc, it->diag);
+    }
   }
   return ImportDiagnostics[target].size();
 }

lib/ClangImporter/ImporterImpl.h

@@ -917,10 +917,10 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
   /// interface. Use this to diagnose issues with declarations that are not
   /// imported or that are not reflected in a generated interface.
   template<typename ...Args>
-  void diagnose(HeaderLoc loc, Args &&...args) {
+  InFlightDiagnostic diagnose(HeaderLoc loc, Args &&...args) {
     // If we're in the middle of pretty-printing, suppress diagnostics.
     if (SwiftContext.Diags.isPrettyPrintingDecl()) {
-      return;
+      return InFlightDiagnostic();
     }
 
     auto swiftLoc = loc.fallbackLoc;
@@ -932,7 +932,7 @@ class LLVM_LIBRARY_VISIBILITY ClangImporter::Implementation
                                                       loc.clangLoc);
     }
 
-    SwiftContext.Diags.diagnose(swiftLoc, std::forward<Args>(args)...);
+    return SwiftContext.Diags.diagnose(swiftLoc, std::forward<Args>(args)...);
   }
 
   void addImportDiagnostic(