Add typedef AST node boilerplate.

pkg/kernel/lib/type_algebra.dart

Index: pkg/kernel/lib/type_algebra.dart
diff --git a/pkg/kernel/lib/type_algebra.dart b/pkg/kernel/lib/type_algebra.dart
index c86f4d21f80ec258cf0fa3dc8eb9806cad3c2852..47fbf05c3c241bdd1a56b6c80ef9d89a8269a8d7 100644
--- a/pkg/kernel/lib/type_algebra.dart
+++ b/pkg/kernel/lib/type_algebra.dart
@@ -173,6 +173,14 @@ abstract class Substitution {
         type.classNode.typeParameters, type.typeArguments));
   }
 
+  /// Substitutes the type parameters on the typedef of [type] with the
+  /// type arguments provided in [type].
+  static Substitution fromTypedefType(TypedefType type) {
+    if (type.typeArguments.isEmpty) return _NullSubstitution.instance;
+    return fromMap(new Map<TypeParameter, DartType>.fromIterables(
+        type.typedefNode.typeParameters, type.typeArguments));
+  }
+
   /// Substitutes the Nth parameter in [parameters] with the Nth type in
   /// [types].
   static Substitution fromPairs(
@@ -375,6 +383,14 @@ abstract class _TypeSubstitutor extends DartTypeVisitor<DartType> {
     return new InterfaceType(node.classNode, typeArguments);
   }
 
+  DartType visitTypedefType(TypedefType node) {
+    if (node.typeArguments.isEmpty) return node;
+    int before = useCounter;
+    var typeArguments = node.typeArguments.map(visit).toList();
+    if (useCounter == before) return node;
+    return new TypedefType(node.typedefNode, typeArguments);
+  }
+
   List<TypeParameter> freshTypeParameters(List<TypeParameter> parameters) {
     if (parameters.isEmpty) return const <TypeParameter>[];
     return parameters.map(freshTypeParameter).toList();
@@ -655,6 +671,10 @@ class _OccurrenceVisitor extends DartTypeVisitor<bool> {
     return node.typeArguments.any(visit);
   }
 
+  bool visitTypedefType(TypedefType node) {
+    return node.typeArguments.any(visit);
+  }
+
   bool visitFunctionType(FunctionType node) {
     return node.typeParameters.any(handleTypeParameter) ||
         node.positionalParameters.any(visit) ||