Implement type inference of getters/setters based on inheritance.

pkg/analyzer/test/src/task/strong/front_end_inference_test.dart

Index: pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
diff --git a/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart b/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
index 278050ae7e0eca761621a55c98b71596d1b9b0aa..16e115fcfb764f49c65edcb60b5094f9fda2fdd8 100644
--- a/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
+++ b/pkg/analyzer/test/src/task/strong/front_end_inference_test.dart
@@ -452,6 +452,23 @@ class _InstrumentationVisitor extends RecursiveAstVisitor<Null> {
     }
   }
 
+  @override
+  visitMethodDeclaration(MethodDeclaration node) {
+    super.visitMethodDeclaration(node);
+    if (node.element.enclosingElement is ClassElement) {
+      if (node.isGetter && node.returnType == null) {
+        _recordTopType(node.name.offset, node.element.returnType);
+      }
+      if (node.isSetter) {
+        for (var parameter in node.parameters.parameters) {
+          if (parameter.element.hasImplicitType) {

[scheglov, 2017/06/18 23:03:43]

Would "parameter.type == null" work?
It would be consistent with the returnType check.

[Paul Berry, 2017/06/18 23:34:31]

I considered that too, but it wouldn't work because FormalParameter doesn't have
a getter `type`.  The reason is because of function-typed formal parameters,
which have `returnType` and `parameters` getters rather than a `type` getter.

I suppose I could have done:

  var parameterElement = parameter.element;
  if (parameterElement is SimpleFormalParameter && parameterElement.type ==
null)

But it seemed simpler to just use `hasImplicitType`.

I've added a comment explaining this.

[Paul Berry, 2017/06/19 18:18:27]

After further experimentation it turns out that ParameterElement.hasImplicitType
has a bug where it returns `true` for a function-typed parameter without an
explicit return type.  So this code is no good either until we fix the bug.

I'll send out a bug fix and add some more test cases.

+            _recordTopType(parameter.identifier.offset, parameter.element.type);
+          }
+        }
+      }
+    }
+  }
+
   visitMethodInvocation(MethodInvocation node) {
     super.visitMethodInvocation(node);
     if (node.typeArguments == null) {