Use the explicit string 'void' to refer to void in summaries.

pkg/analyzer/lib/src/summary/summarize_ast.dart

 // Copyright (c) 2016, 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 serialization.summarize_ast;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
@@ skipping 427 matching lines @@
       b.kind = UnlinkedExecutableKind.functionOrMethod;
     }
     b.isAbstract = body is EmptyFunctionBody;
     b.name = nameString;
     b.nameOffset = name.offset;
     b.typeParameters =
         serializeTypeParameters(typeParameters, typeParameterScope);
     if (!isTopLevel) {
       b.isStatic = isStatic;
     }
-    b.returnType = serializeTypeName(returnType, allowVoid: true);
+    b.returnType = serializeTypeName(returnType);
     b.hasImplicitReturnType = returnType == null;
     b.isExternal = isExternal;
     if (formalParameters != null) {
       b.parameters = formalParameters.parameters
           .map((FormalParameter p) => p.accept(this))
           .toList();
     }
     b.documentationComment = serializeDocumentation(documentationComment);
     scopes.removeLast();
     assert(scopes.length == oldScopesLength);
     return b;
   }
 
   /**
    * Serialize the return type and parameters of a function-typed formal
    * parameter and store them in [b].
    */
   void serializeFunctionTypedParameterDetails(UnlinkedParamBuilder b,
       TypeName returnType, FormalParameterList parameters) {
-    EntityRefBuilder serializedReturnType =
-        serializeTypeName(returnType, allowVoid: true);
+    EntityRefBuilder serializedReturnType = serializeTypeName(returnType);
     if (serializedReturnType != null) {
       b.type = serializedReturnType;
     }
     b.parameters = parameters.parameters
         .map((FormalParameter p) => p.accept(this))
         .toList();
   }
 
   /**
    * Serialize a [FieldFormalParameter], [FunctionTypedFormalParameter], or
@@ skipping 33 matching lines @@
             prefixReference: prefixIndex, name: name));
         return index;
       });
 
   /**
    * Serialize a type name (which might be defined in a nested scope, at top
    * level within this library, or at top level within an imported library) to
    * a [EntityRef].  Note that this method does the right thing if the
    * name doesn't refer to an entity other than a type (e.g. a class member).
    */
-  EntityRefBuilder serializeTypeName(TypeName node, {bool allowVoid: false}) {
+  EntityRefBuilder serializeTypeName(TypeName node) {
     EntityRefBuilder b = new EntityRefBuilder();
     if (node == null) {
       b.reference = serializeReference(null, 'dynamic');
     } else {
       Identifier identifier = node.name;
       if (identifier is SimpleIdentifier) {
         String name = identifier.name;
         int indexOffset = 0;
         for (int i = scopes.length - 1; i >= 0; i--) {
           _Scope scope = scopes[i];
           _ScopedEntity entity = scope[name];
           if (entity != null) {
             if (entity is _ScopedTypeParameter) {
               b.paramReference = indexOffset + entity.index;
               return b;
             } else {
               // None of the other things that can be declared in local scopes
               // are types, so this is an error and should be treated as a
               // reference to `dynamic`.
               b.reference = serializeReference(null, 'dynamic');
               return b;
             }
           }
           if (scope is _TypeParameterScope) {
             indexOffset += scope.length;
           }
         }
-        if (allowVoid && name == 'void') {
-          return null;
-        }
         b.reference = serializeReference(null, name);
       } else if (identifier is PrefixedIdentifier) {
         int prefixIndex = prefixIndices.putIfAbsent(identifier.prefix.name,
             () => serializeReference(null, identifier.prefix.name));
         b.reference =
             serializeReference(prefixIndex, identifier.identifier.name);
       } else {
         throw new StateError(
             'Unexpected identifier type: ${identifier.runtimeType}');
       }
@@ skipping 191 matching lines @@
   @override
   void visitFunctionTypeAlias(FunctionTypeAlias node) {
     int oldScopesLength = scopes.length;
     _TypeParameterScope typeParameterScope = new _TypeParameterScope();
     scopes.add(typeParameterScope);
     UnlinkedTypedefBuilder b = new UnlinkedTypedefBuilder();
     b.name = node.name.name;
     b.nameOffset = node.name.offset;
     b.typeParameters =
         serializeTypeParameters(node.typeParameters, typeParameterScope);
-    EntityRefBuilder serializedReturnType =
-        serializeTypeName(node.returnType, allowVoid: true);
+    EntityRefBuilder serializedReturnType = serializeTypeName(node.returnType);
     if (serializedReturnType != null) {
       b.returnType = serializedReturnType;
     }
     b.parameters = node.parameters.parameters
         .map((FormalParameter p) => p.accept(this))
         .toList();
     b.documentationComment = serializeDocumentation(node.documentationComment);
     typedefs.add(b);
     scopes.removeLast();
     assert(scopes.length == oldScopesLength);
@@ skipping 98 matching lines @@
 /**
  * A [_TypeParameterScope] is a [_Scope] which defines [_ScopedTypeParameter]s.
  */
 class _TypeParameterScope extends _Scope {
   /**
    * Get the number of [_ScopedTypeParameter]s defined in this
    * [_TypeParameterScope].
    */
   int get length => _definedNames.length;
 }