[lldb][ClangASTImporter][NFC] Create helper for CanImport

Upstreams a `CanImport` helper for `clang::Decl`s.

Author: Michael137

lldb/source/Plugins/ExpressionParser/Clang/ClangASTImporter.cpp

@@ -371,6 +371,16 @@ clang::Decl *ClangASTImporter::DeportDecl(clang::ASTContext *dst_ctx,
   return result;
 }
 
+bool ClangASTImporter::CanImport(const Decl *d) {
+  if (!d)
+    return false;
+  if (isa<TagDecl>(d))
+    return GetDeclOrigin(d).Valid();
+  if (isa<ObjCInterfaceDecl>(d))
+    return GetDeclOrigin(d).Valid();
+  return false;
+}
+
 bool ClangASTImporter::CanImport(const CompilerType &type) {
   if (!ClangUtil::IsClangType(type))
     return false;
@@ -380,23 +390,10 @@ bool ClangASTImporter::CanImport(const CompilerType &type) {
 
   const clang::Type::TypeClass type_class = qual_type->getTypeClass();
   switch (type_class) {
-  case clang::Type::Record: {
-    const clang::CXXRecordDecl *cxx_record_decl =
-        qual_type->getAsCXXRecordDecl();
-    if (cxx_record_decl) {
-      if (GetDeclOrigin(cxx_record_decl).Valid())
-        return true;
-    }
-  } break;
-
-  case clang::Type::Enum: {
-    auto *enum_decl = llvm::cast<clang::EnumType>(qual_type)->getOriginalDecl();
-    if (enum_decl) {
-      if (GetDeclOrigin(enum_decl).Valid())
-        return true;
-    }
-  } break;
-
+  case clang::Type::Record:
+    return CanImport(qual_type->getAsCXXRecordDecl());
+  case clang::Type::Enum:
+    return CanImport(llvm::cast<clang::EnumType>(qual_type)->getOriginalDecl());
   case clang::Type::ObjCObject:
   case clang::Type::ObjCInterface: {
     const clang::ObjCObjectType *objc_class_type =
@@ -406,10 +403,7 @@ bool ClangASTImporter::CanImport(const CompilerType &type) {
           objc_class_type->getInterface();
       // We currently can't complete objective C types through the newly added
       // ASTContext because it only supports TagDecl objects right now...
-      if (class_interface_decl) {
-        if (GetDeclOrigin(class_interface_decl).Valid())
-          return true;
-      }
+      return CanImport(class_interface_decl);
     }
   } break;
 

lldb/source/Plugins/ExpressionParser/Clang/ClangASTImporter.h

@@ -157,6 +157,8 @@ class ClangASTImporter {
   /// \see ClangASTImporter::Import
   bool CanImport(const CompilerType &type);
 
+  bool CanImport(const clang::Decl *d);
+
   /// If the given type was copied from another TypeSystemClang then copy over
   /// all missing information (e.g., the definition of a 'class' type).
   ///