Fix for parsing named factory constructors with Fasta.

pkg/analyzer/lib/src/fasta/ast_builder.dart

Index: pkg/analyzer/lib/src/fasta/ast_builder.dart
diff --git a/pkg/analyzer/lib/src/fasta/ast_builder.dart b/pkg/analyzer/lib/src/fasta/ast_builder.dart
index 0a3a9b05a7cec6304088911a6bbce171c1d686f2..96efce12a2138203b500fda7cba27febc9bbc66b 100644
--- a/pkg/analyzer/lib/src/fasta/ast_builder.dart
+++ b/pkg/analyzer/lib/src/fasta/ast_builder.dart
@@ -1548,15 +1548,31 @@ class AstBuilder extends ScopeListener {
     _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,