fix #29028, understand promoted type parameters

pkg/dev_compiler/lib/src/compiler/type_utilities.dart

Index: pkg/dev_compiler/lib/src/compiler/type_utilities.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/type_utilities.dart b/pkg/dev_compiler/lib/src/compiler/type_utilities.dart
index 7632f08124f5eebde8a9a488025b40b4e8d656d0..1f1afa7b1513ac0b0e7f02b43e5ce7ce5198dd87 100644
--- a/pkg/dev_compiler/lib/src/compiler/type_utilities.dart
+++ b/pkg/dev_compiler/lib/src/compiler/type_utilities.dart
@@ -2,9 +2,8 @@
 // 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.
 
-import 'dart:collection' show HashMap, HashSet, LinkedHashMap;
-
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/src/dart/element/member.dart' show TypeParameterMember;
 import 'package:analyzer/dart/element/type.dart';
 
 import '../js_ast/js_ast.dart' as JS;
@@ -12,7 +11,7 @@ import '../js_ast/js_ast.dart' show js;
 import 'js_names.dart' as JS;
 
 Set<TypeParameterElement> freeTypeParameters(DartType t) {
-  var result = new HashSet<TypeParameterElement>();
+  var result = new Set<TypeParameterElement>();
   void find(DartType t) {
     if (t is TypeParameterType) {
       result.add(t.element);
@@ -37,7 +36,7 @@ class _CacheTable {
   // Use a LinkedHashMap to maintain key insertion order so the generated code
   // is stable under slight perturbation.  (If this is not good enough we could
   // sort by name to canonicalize order.)
-  final _names = new LinkedHashMap<DartType, JS.TemporaryId>();
+  final _names = <DartType, JS.TemporaryId>{};
   Iterable<DartType> get keys => _names.keys.toList();
 
   JS.Statement _dischargeType(DartType type) {
@@ -120,7 +119,7 @@ class _CacheTable {
 /// _GeneratorTable tracks types which have been
 /// named and hoisted.
 class _GeneratorTable extends _CacheTable {
-  final _defs = new HashMap<DartType, JS.Expression>();
+  final _defs = <DartType, JS.Expression>{};
 
   final JS.Identifier _runtimeModule;
 
@@ -167,8 +166,7 @@ class TypeTable {
   /// cache/generator variables discharged at the binding site for the
   /// type variable since the type definition depends on the type
   /// parameter.
-  final _scopeDependencies =
-      new HashMap<TypeParameterElement, List<DartType>>();
+  final _scopeDependencies = <TypeParameterElement, List<DartType>>{};
 
   TypeTable(JS.Identifier runtime)
       : _generators = new _GeneratorTable(runtime),
@@ -191,22 +189,22 @@ class TypeTable {
 
   /// Record the dependencies of the type on its free variables
   bool recordScopeDependencies(DartType type) {
-    var fvs = freeTypeParameters(type);
+    var freeVariables = freeTypeParameters(type);
     // TODO(leafp): This is a hack to avoid trying to hoist out of
     // generic functions and generic function types.  This often degrades
     // readability to little or no benefit.  It would be good to do this
     // when we know that we can hoist it to an outer scope, but for
     // now we just disable it.
-    if (fvs.any((i) => i.enclosingElement is FunctionTypedElement)) {
+    if (freeVariables.any((i) => i.enclosingElement is FunctionTypedElement)) {
       return true;
     }
-    void addScope(TypeParameterElement i) {
-      List<DartType> types = _scopeDependencies[i];
-      if (types == null) _scopeDependencies[i] = types = [];
-      types.add(type);
-    }
 
-    fvs.forEach(addScope);
+    for (var free in freeVariables) {
+      // If `free` is a promoted type parameter, get the original one so we can
+      // find it in our map.
+      var key = free is TypeParameterMember ? free.baseElement : free;
+      _scopeDependencies.putIfAbsent(key, () => []).add(type);
+    }
     return false;
   }