enable lints (#1822)

analysis_options.yaml

@@ -33,6 +33,7 @@ linter:
 #    - avoid_private_typedef_functions # under review (see #1068)
 #    - avoid_renaming_method_parameters # under review (see #1068)
     - avoid_returning_null
+    - avoid_returning_null_for_future
     - avoid_returning_this
     - avoid_setters_without_getters
 #    - avoid_single_cascade_in_expression_statements # under review (see #1068)
@@ -110,8 +111,8 @@ linter:
 #    - unnecessary_new (included in pedantic)
     - unnecessary_null_aware_assignments
     - unnecessary_overrides
-#    - unnecessary_parenthesis # under review (see #1068)
-#    - unnecessary_statements # under review (see #1068)
+    - unnecessary_parenthesis
+    - unnecessary_statements
     - unnecessary_this
     - use_setters_to_change_properties
     - use_string_buffers

lib/src/rules/avoid_unused_constructor_parameters.dart

@@ -55,7 +55,7 @@ class _ConstructorVisitor extends RecursiveAstVisitor {
 
   _ConstructorVisitor(this.rule, this.element)
       : unusedParameters = element.parameters.parameters
-            .where((p) => (p.declaredElement is! FieldFormalParameterElement))
+            .where((p) => p.declaredElement is! FieldFormalParameterElement)
             .toSet();
 
   @override

lib/src/util/leak_detector_visitor.dart

@@ -149,12 +149,12 @@ bool _isInvocationThroughCascadeExpression(
 
 bool _isSimpleIdentifierElementEqualToVariable(
         AstNode n, VariableDeclaration variable) =>
-    (n is SimpleIdentifier &&
-        // Assignment to VariableDeclaration as variable.
-        (n.staticElement == variable.name.staticElement ||
-            (n.staticElement is PropertyAccessorElement &&
-                (n.staticElement as PropertyAccessorElement).variable ==
-                    variable.name.staticElement)));
+    n is SimpleIdentifier &&
+    // Assignment to VariableDeclaration as variable.
+    (n.staticElement == variable.name.staticElement ||
+        (n.staticElement is PropertyAccessorElement &&
+            (n.staticElement as PropertyAccessorElement).variable ==
+                variable.name.staticElement));
 
 typedef bool DartTypePredicate(DartType type);
 

test/mocks.dart

@@ -59,7 +59,7 @@ class MockIOSink implements IOSink {
   Encoding encoding;
 
   @override
-  Future get done => null;
+  Future get done => Future.value(null);
 
   @override
   void add(List<int> data) {}
@@ -68,13 +68,13 @@ class MockIOSink implements IOSink {
   void addError(Object error, [StackTrace stackTrace]) {}
 
   @override
-  Future addStream(Stream<List<int>> stream) => null;
+  Future addStream(Stream<List<int>> stream) => Future.value(null);
 
   @override
-  Future close() => null;
+  Future close() => Future.value(null);
 
   @override
-  Future flush() => null;
+  Future flush() => Future.value(null);
 
   @override
   void write(Object obj) {}