fix no backend error

drift_dev/lib/src/analysis/backend.dart

@@ -19,6 +19,8 @@ abstract class DriftBackend {
     return element.source!.uri;
   }
 
+  bool get canReadDart;
+
   /// Resolves a Dart library by its uri.
   ///
   /// This should also be able to resolve SDK libraries.

drift_dev/lib/src/analysis/driver/driver.dart

@@ -63,13 +63,15 @@ class DriftAnalysisDriver {
 
   AnalysisResultCacheReader? cacheReader;
 
-  final KnownDriftTypes knownTypes;
+  final KnownDriftTypes? _knownTypes;
+
+  KnownDriftTypes get knownTypes => _knownTypes!;
 
   @visibleForTesting
   DriftAnalysisDriver(
     this.backend,
     this.options,
-    this.knownTypes, {
+    this._knownTypes, {
     bool isTesting = false,
   }) : _isTesting = isTesting;
 

drift_dev/lib/src/analysis/resolver/dart/helper.dart

@@ -102,10 +102,14 @@ class KnownDriftTypes {
     return type?.asInstanceOf(converter);
   }
 
-  static Future<KnownDriftTypes> resolve(DriftBackend backend) async {
-    final library = await backend.readDart(uri);
+  static Future<KnownDriftTypes?> resolve(DriftBackend backend) async {
+    if (backend.canReadDart) {
+      final library = await backend.readDart(uri);
 
-    return KnownDriftTypes._fromLibrary(library);
+      return KnownDriftTypes._fromLibrary(library);
+    }
+
+    return null;
   }
 
   static final Uri uri = Uri.parse('package:drift/src/drift_dev_helper.dart');

drift_dev/lib/src/backends/analyzer_context_backend.dart

@@ -96,6 +96,9 @@ class AnalysisContextBackend extends DriftBackend {
     return Future.value(resourceProvider.getFile(path).readAsStringSync());
   }
 
+  @override
+  bool get canReadDart => true;
+
   @override
   Future<LibraryElement> readDart(Uri uri) async {
     final result = await context.currentSession.getLibraryByUri(uri.toString());

drift_dev/lib/src/backends/build/backend.dart

@@ -38,6 +38,9 @@ class DriftBuildBackend extends DriftBackend {
     return id.uri;
   }
 
+  @override
+  bool get canReadDart => true;
+
   @override
   Future<LibraryElement> readDart(Uri uri) async {
     if (uri.scheme == 'dart') {

drift_dev/lib/src/services/schema/sqlite_to_drift.dart

@@ -91,6 +91,9 @@ class _SingleFileNoAnalyzerBackend extends DriftBackend {
     return Future.value(contents);
   }
 
+  @override
+  bool get canReadDart => false;
+
   @override
   Future<LibraryElement> readDart(Uri uri) async {
     _noAnalyzer();

drift_dev/test/analysis/test_utils.dart

@@ -237,6 +237,9 @@ class TestBackend extends DriftBackend {
     return null;
   }
 
+  @override
+  bool get canReadDart => true;
+
   @override
   Future<LibraryElement> readDart(Uri uri) async {
     await ensureHasDartAnalyzer();