depend on newer Dart version and new interface

permission_handler/pubspec.yaml

@@ -16,12 +16,14 @@ dependencies:
   flutter:
   flutter:
     sdk: flutter
     sdk: flutter
   meta: ^1.1.6
   meta: ^1.1.6
-  permission_handler_platform_interface: ^1.0.0
+  # permission_handler_platform_interface: ^1.0.0
+  permission_handler_platform_interface:
+    path: ../permission_handler_platform_interface
 
 
 dev_dependencies:
 dev_dependencies:
   effective_dart: ^1.2.1
   effective_dart: ^1.2.1
   plugin_platform_interface: ^1.0.1
   plugin_platform_interface: ^1.0.1
 
 
 environment:
 environment:
-  sdk: ">=2.1.0 <3.0.0"
-  flutter: ">=1.12.8 <2.0.0"
+  sdk: ">=2.7.0 <3.0.0"
+  flutter: ">=1.12.8 <2.0.0"
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