Fix for parsing named factory constructors with Fasta.

pkg/analyzer/lib/src/fasta/ast_builder.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 fasta.analyzer.ast_builder;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
 import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
 import 'package:analyzer/dart/ast/token.dart' as analyzer show Token;
@@ skipping 1530 matching lines @@
       body = ast.emptyFunctionBody(toAnalyzerToken(semicolon));
     } else {
       internalError('Unexpected body object: ${bodyObject.runtimeType}');
     }
 
     FormalParameterList parameters = pop();
     ConstructorName constructorName = pop();
     _Modifiers modifiers = pop();
     List<Annotation> metadata = pop();
     Comment comment = pop();
+
+    // Decompose the preliminary ConstructorName into the type name and
+    // the actual constructor name.
+    SimpleIdentifier returnType;
+    analyzer.Token period;
+    SimpleIdentifier name;
+    Identifier typeName = constructorName.type.name;
+    if (typeName is SimpleIdentifier) {
+      returnType = typeName;
+    } else if (typeName is PrefixedIdentifier) {
+      returnType = typeName.prefix;
+      period = typeName.period;
+      name =
+          ast.simpleIdentifier(typeName.identifier.token, isDeclaration: true);
+    }
+
     push(ast.constructorDeclaration(
         comment,
         metadata,
         toAnalyzerToken(modifiers?.externalKeyword),
         toAnalyzerToken(modifiers?.finalConstOrVarKeyword),
-        toAnalyzerToken(factoryKeyword),
-        constructorName.type.name,
-        constructorName.period,
-        constructorName.name,
+        factoryKeyword,

[Paul Berry, 2017/04/06 20:36:51]

Analyzer and Fasta token types have been partially merged but not completely. 
So I don't think we should drop the call to toAnalyzerToken() yet (even though
it may not trigger any test failures right now).

[scheglov, 2017/04/06 21:11:38]

Done.

+        ast.simpleIdentifier(returnType.token),
+        period,
+        name,
         parameters,
         toAnalyzerToken(separator),
         null,
         redirectedConstructor,
         body));
   }
 
   void endFieldInitializer(Token assignment) {
     debugEvent("FieldInitializer");
     Expression initializer = pop();
@@ skipping 395 matching lines @@
       } else if (identical('static', s)) {
         staticKeyword = token;
       } else if (identical('var', s)) {
         finalConstOrVarKeyword = token;
       } else {
         internalError('Unhandled modifier: $s');
       }
     }
   }
 }