Explicitly provide type parameters. (#805)

This is an info diagnostic that will soon become a warning.

lib/src/devtool.dart

@@ -60,13 +60,13 @@ class ProviderNode {
  required this.id,
  required this.childrenNodeIds,
  required this.type,
- required _InheritedProviderScopeElement element,
+ required _InheritedProviderScopeElement<Object?> element,
  }) : _element = element;
 
  final String id;
  final String type;
  final List<String> childrenNodeIds;
- final _InheritedProviderScopeElement _element;
+ final _InheritedProviderScopeElement<Object?> _element;
 
  Object? get value => _element._delegateState.value;
 }

lib/src/listenable_provider.dart

@@ -55,7 +55,7 @@ class ListenableProvider<T extends Listenable?> extends InheritedProvider<T> {
  );
 
  static VoidCallback _startListening(
- InheritedContext e,
+ InheritedContext<Listenable?> e,
  Listenable? value,
  ) {
  value?.addListener(e.markNeedsNotifyDependents);

test/null_safe/common.dart

@@ -26,7 +26,7 @@ Type typeOf<T>() => T;
 ///
 /// For use in legacy tests: they can't instantiate a `Provider<T?>` directly
 /// because they can't write `<T?>`. But, they can pass around a `Provider<T?`>.
-Provider<T?> nullableProviderOfValue<T>(T value, Provider? child) =>
+Provider<T?> nullableProviderOfValue<T>(T value, Provider<dynamic>? child) =>
  Provider<T?>.value(
  value: value,
  child: child,
@@ -35,7 +35,7 @@ Provider<T?> nullableProviderOfValue<T>(T value, Provider? child) =>
 /// Given `T`, returns a `Provider<T>`.
 ///
 /// For legacy tests to get a `Provider<T>`.
-Provider<T> nullSafeProviderOfValue<T>(T value, Provider? child) =>
+Provider<T> nullSafeProviderOfValue<T>(T value, Provider<dynamic>? child) =>
  Provider<T>.value(
  value: value,
  child: child,