final inference fixes

Author: kevmoo

analysis_options.yaml

@@ -1,5 +1,6 @@
 analyzer:
-  strong-mode: true
+  strong-mode:
+    implicit-casts: false
   errors:
     unused_element: error
     unused_import: error

lib/src/json_serializable_generator.dart

@@ -357,7 +357,7 @@ class JsonSerializableGenerator
 
       // If `itemSubVal` is the same, then we don't need to do anything fancy
       if (itemVal == itemSubVal) {
-        return varExpression;
+        return '$varExpression as List';
       }
 
       var output = "($varExpression as List)?.map(($itemVal) => $itemSubVal)";

test/json_serializable_test.dart

@@ -159,7 +159,7 @@ void main() {
           await _getClassForCodeString('ParentObjectWithDynamicChildren');
       var output = await _generator.generate(element, null);
 
-      expect(output, contains('children = json[\'children\'];'));
+      expect(output, contains('children = json[\'children\'] as List;'));
     });
 
     test('class with list of int is cast for strong mode', () async {