Handle null library in _NameTypeChecker. (#791)

* Handle null library in _NameTypeChecker.

* Add a test.

Author: davidmorgan

source_gen/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 4.0.2-wip
+
+- Bug fix: fix possible null pointer exception in `TypeChecker.typeNamed` on
+  invalid code.
+
 ## 4.0.1
 
 - Require `analyzer: '>=8.1.1 <9.0.0'`.

source_gen/lib/src/type_checker.dart

@@ -257,7 +257,9 @@ class _NameTypeChecker extends TypeChecker {
 
   @override
   bool isExactly(Element element) {
-    final uri = element.library!.uri;
+    final library = element.library;
+    if (library == null) return false;
+    final uri = library.uri;
     return element.name == _typeName &&
         (_inPackage == null ||
             (((uri.scheme == 'dart') == _inSdk) &&

source_gen/pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_gen
-version: 4.0.1
+version: 4.0.2-wip
 description: >-
   Source code generation builders and utilities for the Dart build system
 repository: https://github.com/dart-lang/source_gen/tree/master/source_gen

source_gen/test/type_checker_test.dart

@@ -208,6 +208,14 @@ void main() {
       );
     });
 
+    group('isExactly', () {
+      test('should not crash with null library', () {
+        final element = core.typeProvider.dynamicType.element!;
+        expect(element.library, isNull);
+        expect(checkMapMixin().isExactly(element), isFalse);
+      });
+    });
+
     group('isExactlyType', () {
       test('should not crash with null element', () {
         final voidType = core.typeProvider.voidType;