Improve error output for types with type parameters

Helps with #713
google · Sep 10, 2020 · ae72259 · ae72259
1 parent d09c99f
commit ae72259
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Showing 3 changed files with 13 additions and 0 deletions.
diff --git a/json_serializable/lib/src/helper_core.dart b/json_serializable/lib/src/helper_core.dart
@@ -126,6 +126,8 @@ String typeToCode(DartType type) {
       final typeArgumentsCode = typeArguments.map(typeToCode).join(', ');
       return '${type.element.name}<$typeArgumentsCode>';
     }
+  } else if (type is TypeParameterType) {
+    return '${type.getDisplayString()} (type parameter)';
   }
   throw UnimplementedError('(${type.runtimeType}) $type');
 }
diff --git a/json_serializable/test/json_serializable_test.dart b/json_serializable/test/json_serializable_test.dart
@@ -63,6 +63,7 @@ const _expectedAnnotatedTests = [
   'InvalidChildClassFromJson3',
   'InvalidFromFunc2Args',
   'InvalidToFunc2Args',
+  'Issue713',
   'JsonConverterCtorParams',
   'JsonConverterDuplicateAnnotations',
   'JsonConverterNamedCtor',

diff --git a/json_serializable/test/src/generic_test_input.dart b/json_serializable/test/src/generic_test_input.dart
@@ -4,6 +4,16 @@
 
 part of '_json_serializable_test_input.dart';
 
+@ShouldThrow(
+  'Could not generate `fromJson` code for `result` because of type '
+  '`TResult (type parameter)`.\n'
+  'None of the provided `TypeHelper` instances support the defined type.',
+)
+@JsonSerializable()
+class Issue713<TResult> {
+  List<TResult> result;
+}
+
 @ShouldGenerate(r'''
 GenericClass<T, S> _$GenericClassFromJson<T extends num, S>(
     Map<String, dynamic> json) {