Maintain module name location in UnboundImport (again).

The change to add the `import` keyword location to AttributedImport also
removed the module name location in UnboundImport. However, we want to
keep both locations, for different diagnostic reasons, so reinstate the
module name location.

(cherry picked from commit 7552cf9)

Author: DougGregor

lib/Sema/ImportResolution.cpp

@@ -56,6 +56,9 @@ struct UnboundImport {
   /// determine the behavior expected for this import.
   AttributedImport<UnloadedImportedModule> import;
 
+  /// The source location to use when diagnosing errors for this import.
+  SourceLoc importLoc;
+
   /// If this UnboundImport directly represents an ImportDecl, contains the
   /// ImportDecl it represents. This should only be used for diagnostics and
   /// for updating the AST; if you want to read information about the import,
@@ -511,7 +514,7 @@ void ImportResolver::addImplicitImports() {
 }
 
 UnboundImport::UnboundImport(AttributedImport<UnloadedImportedModule> implicit)
-  : import(implicit),
+  : import(implicit), importLoc(),
     importOrUnderlyingModuleDecl(static_cast<ImportDecl *>(nullptr)) {}
 
 //===----------------------------------------------------------------------===//
@@ -522,7 +525,7 @@ UnboundImport::UnboundImport(AttributedImport<UnloadedImportedModule> implicit)
 UnboundImport::UnboundImport(ImportDecl *ID)
   : import(UnloadedImportedModule(ID->getImportPath(), ID->getImportKind()),
            ID->getStartLoc(), {}),
-    importOrUnderlyingModuleDecl(ID)
+    importLoc(ID->getLoc()), importOrUnderlyingModuleDecl(ID)
 {
   if (ID->isExported())
     import.options |= ImportFlags::Exported;
@@ -569,11 +572,10 @@ bool UnboundImport::checkNotTautological(const SourceFile &SF) {
 
   StringRef filename = llvm::sys::path::filename(SF.getFilename());
   if (filename.empty())
-    ctx.Diags.diagnose(import.importLoc, diag::sema_import_current_module,
+    ctx.Diags.diagnose(importLoc, diag::sema_import_current_module,
                        modulePath.front().Item);
   else
-    ctx.Diags.diagnose(import.importLoc,
-                       diag::sema_import_current_module_with_file,
+    ctx.Diags.diagnose(importLoc, diag::sema_import_current_module_with_file,
                        filename, modulePath.front().Item);
 
   return false;
@@ -583,7 +585,7 @@ bool UnboundImport::checkModuleLoaded(ModuleDecl *M, SourceFile &SF) {
   if (M)
     return true;
 
-  diagnoseNoSuchModule(SF.getParentModule(), import.importLoc,
+  diagnoseNoSuchModule(SF.getParentModule(), importLoc,
                        import.module.getModulePath(), /*nonfatalInREPL=*/true);
   return false;
 }
@@ -962,9 +964,9 @@ UnboundImport::UnboundImport(
     ASTContext &ctx, const UnboundImport &base, Identifier overlayName,
     const AttributedImport<ImportedModule> &declaringImport,
     const AttributedImport<ImportedModule> &bystandingImport)
-    : import(makeUnimportedCrossImportOverlay(
-                 ctx, overlayName, base, declaringImport),
-                 base.import.importLoc, {}),
+    : import(makeUnimportedCrossImportOverlay(ctx, overlayName, base,
+                                              declaringImport), {}),
+      importLoc(base.importLoc),
       importOrUnderlyingModuleDecl(declaringImport.module.importedModule)
 {
   // A cross-import is never private or testable, and never comes from a private
@@ -1098,16 +1100,15 @@ void ImportResolver::findCrossImports(
   // Find modules we need to import.
   SmallVector<Identifier, 4> names;
   declaringImport.module.importedModule->findDeclaredCrossImportOverlays(
-      bystandingImport.module.importedModule->getName(), names,
-      I.import.importLoc);
+      bystandingImport.module.importedModule->getName(), names, I.importLoc);
 
   // If we're diagnosing cases where we cross-import in both directions, get the
   // inverse list. Otherwise, leave the list empty.
   SmallVector<Identifier, 4> oppositeNames;
   if (shouldDiagnoseRedundantCrossImports)
     bystandingImport.module.importedModule->findDeclaredCrossImportOverlays(
         declaringImport.module.importedModule->getName(), oppositeNames,
-        I.import.importLoc);
+        I.importLoc);
 
   if (ctx.Stats && !names.empty())
     ++ctx.Stats->getFrontendCounters().NumCrossImportsFound;
@@ -1124,14 +1125,13 @@ void ImportResolver::findCrossImports(
         declaringImport, bystandingImport);
 
     if (llvm::is_contained(oppositeNames, name))
-      ctx.Diags.diagnose(I.import.importLoc,
-                         diag::cross_imported_by_both_modules,
+      ctx.Diags.diagnose(I.importLoc, diag::cross_imported_by_both_modules,
                          declaringImport.module.importedModule->getName(),
                          bystandingImport.module.importedModule->getName(),
                          name);
 
     if (ctx.LangOpts.EnableCrossImportRemarks)
-      ctx.Diags.diagnose(I.import.importLoc, diag::cross_import_added,
+      ctx.Diags.diagnose(I.importLoc, diag::cross_import_added,
                          declaringImport.module.importedModule->getName(),
                          bystandingImport.module.importedModule->getName(),
                          name);