[element model] migrate type_constraint_generation_test

Change-Id: I371124dbf9e1b643f2d1d8777ac7685228ecb563
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/403701
Auto-Submit: Phil Quitslund <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

pkg/analyzer/analyzer_use_new_elements.txt

@@ -146,7 +146,6 @@ test/generated/elements_types_mixin.dart
 test/generated/non_error_resolver_test.dart
 test/generated/resolver_test_case.dart
 test/generated/type_system_test.dart
-test/id_tests/type_constraint_generation_test.dart
 test/src/dart/analysis/index_test.dart
 test/src/dart/analysis/result_printer.dart
 test/src/dart/analysis/results/get_element_declaration_test.dart

pkg/analyzer/test/id_tests/type_constraint_generation_test.dart

@@ -41,8 +41,8 @@ class _TypeConstraintGenerationDataComputer
       Map<Id, ActualData<List<GeneratedTypeConstraint>>> actualMap) {
     _TypeConstraintGenerationDataExtractor(
             testingData.uriToTypeConstraintGenerationData[
-                unit.declaredElement!.source.uri]!,
-            unit.declaredElement!.source.uri,
+                unit.declaredFragment?.source.uri]!,
+            unit.declaredFragment!.source.uri,
             actualMap)
         .run(unit);
   }