Analysis.getHover should return the field's documentation for field formal parameters.

pkg/analysis_server/lib/src/computer/computer_hover.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library computer.hover;
 
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     show HoverInformation;
 import 'package:analysis_server/src/computer/computer_overrides.dart';
 import 'package:analysis_server/src/utilities/documentation.dart';
@@ skipping 64 matching lines @@
         // documentation
         hover.dartdoc = _computeDocumentation(element);
       }
       // parameter
       hover.parameter = _safeToString(expression.bestParameterElement);
       // types
       {
         AstNode parent = expression.parent;
         DartType staticType = null;
         DartType propagatedType = expression.propagatedType;
-        if (element == null || element is VariableElement) {
+        if (element is ParameterElement) {
+          staticType = element.type;
+        } else if (element == null || element is VariableElement) {
           staticType = expression.staticType;
         }
         if (parent is MethodInvocation && parent.methodName == expression) {
           staticType = parent.staticInvokeType;
           propagatedType = parent.propagatedInvokeType;
           if (staticType != null && staticType.isDynamic) {
             staticType = null;
           }
           if (propagatedType != null && propagatedType.isDynamic) {
             propagatedType = null;
           }
         }
         hover.staticType = _safeToString(staticType);
         hover.propagatedType = _safeToString(propagatedType);
       }
       // done
       return hover;
     }
     // not an expression
     return null;
   }
 
   String _computeDocumentation(Element element) {
+    if (element is FieldFormalParameterElement) {
+      element = (element as FieldFormalParameterElement).field;
+    }
     if (element is ParameterElement) {
       element = element.enclosingElement;
     }
     // The documentation of the element itself.
     if (element.documentationComment != null) {
       return removeDartDocDelimiters(element.documentationComment);
     }
     // Look for documentation comments of overridden members.
     OverriddenElements overridden = findOverriddenElements(element);
     for (Element superElement in []
       ..addAll(overridden.superElements)
       ..addAll(overridden.interfaceElements)) {
       String rawDoc = superElement.documentationComment;
       if (rawDoc != null) {
         Element interfaceClass = superElement.enclosingElement;
         return removeDartDocDelimiters(rawDoc) +
             '\n\nCopied from `${interfaceClass.displayName}`.';
       }
     }
     return null;
   }
 
   static _safeToString(obj) => obj?.toString();
 }