Use explicit keys for often accessed closures (#1591)

* Use explicit keys for often accessed closures

* _HashableList: don't use UnodifiableListView

Adds unnecessary overhead in a perf-critical case
Also cache the hashCode

Author: kevmoo

lib/src/model.dart

@@ -1560,8 +1560,8 @@ abstract class GetterSetterCombo implements ModelElement {
     if (targetClass.name == target.name) {
       return original.replaceAll(constructorName, "${target.linkedName}");
     }
-    return original.replaceAll(
-        "${targetClass.name}.${target.name}", "${targetClass.linkedName}.${target.linkedName}");
+    return original.replaceAll("${targetClass.name}.${target.name}",
+        "${targetClass.linkedName}.${target.linkedName}");
   }
 
   String _constantValueBase() {
@@ -2892,7 +2892,8 @@ abstract class ModelElement extends Canonicalization
   ///
   /// For example: libraryName.className.methodName
   @override
-  String get fullyQualifiedName => _memoizer.memoized(_buildFullyQualifiedName);
+  String get fullyQualifiedName => _memoizer.memoized(_buildFullyQualifiedName,
+      altKey: 'fullyQualifiedName');
 
   String _fullyQualifiedNameWithoutLibrary() {
     // Remember, periods are legal in library names.
@@ -2904,7 +2905,8 @@ abstract class ModelElement extends Canonicalization
   // library.fullyQualifiedName seems somehow to break things.
   //String get fullyQualifiedNameWithoutLibrary => _memoizer.memoized2(fullyQualifiedName.replaceFirst, "${library.fullyQualifiedName}.", '');
   String get fullyQualifiedNameWithoutLibrary =>
-      _memoizer.memoized(_fullyQualifiedNameWithoutLibrary);
+      _memoizer.memoized(_fullyQualifiedNameWithoutLibrary,
+          altKey: 'fullyQualifiedNameWithoutLibrary');
 
   String get sourceFileName => element.source.fullName;
 

lib/src/model_utils.dart

@@ -172,15 +172,17 @@ String crossdartifySource(
 
 /// An UnmodifiableListView that computes equality and hashCode based on the
 /// equality and hashCode of its contained objects.
-class _HashableList extends UnmodifiableListView<dynamic> {
-  _HashableList(Iterable<dynamic> iterable) : super(iterable);
+class _HashableList {
+  final List _source;
+  int _hashCache;
+  _HashableList(this._source);
 
   @override
   bool operator ==(other) {
     if (other is _HashableList) {
-      if (this.length == other.length) {
-        for (var index = 0; index < length; ++index) {
-          if (this[index] != other[index]) return false;
+      if (_source.length == other._source.length) {
+        for (var index = 0; index < _source.length; ++index) {
+          if (_source[index] != other._source[index]) return false;
         }
         return true;
       }
@@ -189,7 +191,7 @@ class _HashableList extends UnmodifiableListView<dynamic> {
   }
 
   @override
-  get hashCode => hashObjects(this);
+  get hashCode => _hashCache ??= hashObjects(_source);
 }
 
 /// Like [Memoizer], except in checked mode will validate that the value of the
@@ -252,11 +254,11 @@ class ValidatingMemoizer extends Memoizer {
 /// ```
 class Memoizer {
   /// Map of a function and its positional parameters (if any), to a value.
-  Map<_HashableList, dynamic> _memoizationTable = new Map();
+  final Map<_HashableList, dynamic> _memoizationTable = new HashMap();
 
   /// Reset the memoization table, forcing calls of the underlying functions.
   void invalidateMemos() {
-    _memoizationTable = new Map();
+    _memoizationTable.clear();
   }
 
   /// A wrapper around putIfAbsent, exposed to allow overrides.
@@ -266,8 +268,9 @@ class Memoizer {
 
   /// Calls and caches the return value of [f]() if not in the cache, then
   /// returns the cached value of [f]().
-  R memoized<R>(Function f) {
-    _HashableList key = new _HashableList([f]);
+  R memoized<R>(Function f, {String altKey}) {
+    Object obj = altKey ?? f;
+    _HashableList key = new _HashableList([obj]);
     return _cacheIfAbsent(key, f);
   }