feat: Removing implicit map dereference in expressions

Closes dart-archive#915

1) Now "a.b" return a.b and "a['b']" return a['b']

Before this change a.b would have match either a.b or a['b']. The reason
is that the context was a Map (before dart-archive#914) and we don't want to write
ctrl['foo'] but ctrl.foo. It was also not possible to access Map
properties, ie map.length would have returned map['length'].

2) Accessing probes

The probes are no more accessible directly in the rootScope context but
in a $probes map on the rootScope context.

Before:

    <p probe="prb"></p>

    var probe = rootScope.context['prb'];

After:

    <p probe="prb"></p>

    var probe = rootScope.context.$probes['prb'];

3) Forms

As a side effect of this change, the forms are now available in the
context field named after the form:

    @component(
        selector: 'my-component',
        template: '''
          <form name="myForm">
            <input type="text" ng-model="model">
          </form>
        '''
    )
    class Component {
      // myForm is automatically initialized to the NgForm instance
      NgForm myForm;
    }

When the field named after the form is not present, an exception is
thrown.

Author: vicb

benchmark/watch_group_perf.dart

@@ -27,7 +27,6 @@ var _dynamicFieldGetterFactory = new DynamicFieldGetterFactory();
 main() {
   _fieldRead();
   _fieldReadGetter();
-  _mapRead();
   _methodInvoke0();
   _methodInvoke1();
   _function2();
@@ -107,39 +106,6 @@ _fieldReadGetter() {
   time('fieldReadGetter', () => watchGrp.detectChanges());
 }
 
-_mapRead() {
-  var map = {
-      'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4,
-      'f': 0, 'g': 1, 'h': 2, 'i': 3, 'j': 4,
-      'k': 0, 'l': 1, 'm': 2, 'n': 3, 'o': 4,
-      'p': 0, 'q': 1, 'r': 2, 's': 3, 't': 4};
-  var watchGrp = new RootWatchGroup(_dynamicFieldGetterFactory,
-      new DirtyCheckingChangeDetector(_dynamicFieldGetterFactory), map)
-          ..watch(_parse('a'), _reactionFn)
-          ..watch(_parse('b'), _reactionFn)
-          ..watch(_parse('c'), _reactionFn)
-          ..watch(_parse('d'), _reactionFn)
-          ..watch(_parse('e'), _reactionFn)
-          ..watch(_parse('f'), _reactionFn)
-          ..watch(_parse('g'), _reactionFn)
-          ..watch(_parse('h'), _reactionFn)
-          ..watch(_parse('i'), _reactionFn)
-          ..watch(_parse('j'), _reactionFn)
-          ..watch(_parse('k'), _reactionFn)
-          ..watch(_parse('l'), _reactionFn)
-          ..watch(_parse('m'), _reactionFn)
-          ..watch(_parse('n'), _reactionFn)
-          ..watch(_parse('o'), _reactionFn)
-          ..watch(_parse('p'), _reactionFn)
-          ..watch(_parse('q'), _reactionFn)
-          ..watch(_parse('r'), _reactionFn)
-          ..watch(_parse('s'), _reactionFn)
-          ..watch(_parse('t'), _reactionFn);
-
-  print('Watch: ${watchGrp.fieldCost}; eval: ${watchGrp.evalCost}');
-  time('mapRead', () => watchGrp.detectChanges());
-}
-
 _methodInvoke0() {
   var context = new _Obj();
   context.a = new _Obj();

lib/change_detection/dirty_checking_change_detector.dart

@@ -467,22 +467,17 @@ class DirtyCheckingRecord<H> implements WatchRecord<H> {
       return;
     }
 
-    if (object is Map) {
-      _mode =  _MODE_MAP_FIELD_;
-      _getter = null;
-    } else {
-      while (object is ContextLocals) {
-        var ctx = object as ContextLocals;
-        if (ctx.hasProperty(field)) {
-          _mode =  _MODE_MAP_FIELD_;
-          _getter = null;
-          return;
-        }
-        object = ctx.parentContext;
+    while (object is ContextLocals) {
+      var ctx = object as ContextLocals;
+      if (ctx.hasProperty(field)) {
+        _mode =  _MODE_MAP_FIELD_;
+        _getter = null;
+        return;
       }
-      _mode = _MODE_GETTER_OR_METHOD_CLOSURE_;
-      _getter = _fieldGetterFactory.getter(object, field);
+      object = ctx.parentContext;
     }
+    _mode = _MODE_GETTER_OR_METHOD_CLOSURE_;
+    _getter = _fieldGetterFactory.getter(object, field);
   }
 
   bool check() {

lib/core/parser/eval_access.dart

@@ -38,16 +38,13 @@ class AccessKeyed extends syntax.AccessKeyed {
  * where we have a pair of pre-compiled getter and setter functions that we
  * use to do the access the field.
  */
-// todo(vicb) - parser should not depend on ContextLocals
-// todo(vicb) - Map should not be a special case so that we can access the props
 abstract class AccessFast {
   String get name;
   Getter get getter;
   Setter get setter;
 
   dynamic _eval(holder) {
     if (holder == null) return null;
-    if (holder is Map) return holder[name];
     return getter(holder);
   }
 
@@ -56,7 +53,6 @@ abstract class AccessFast {
       _assignToNonExisting(scope, value);
       return value;
     } else {
-      if (holder is Map) return holder[name] = value;
       return setter(holder, value);
     }
   }

lib/core/parser/parser_dynamic.dart

@@ -8,24 +8,14 @@ class DynamicClosureMap implements ClosureMap {
   final Map<String, Symbol> symbols = {};
   Getter lookupGetter(String name) {
     var symbol = new Symbol(name);
-    return (o) {
-      if (o is Map) {
-        return o[name];
-      } else {
-        return reflect(o).getField(symbol).reflectee;
-      }
-    };
+    return (o) => reflect(o).getField(symbol).reflectee;
   }
 
   Setter lookupSetter(String name) {
     var symbol = new Symbol(name);
     return (o, value) {
-      if (o is Map) {
-        return o[name] = value;
-      } else {
-        reflect(o).setField(symbol, value);
-        return value;
-      }
+      reflect(o).setField(symbol, value);
+      return value;
     };
   }
 
@@ -37,16 +27,7 @@ class DynamicClosureMap implements ClosureMap {
         var symbol = symbols.putIfAbsent(name, () => new Symbol(name));
         sNamedArgs[symbol] = value;
       });
-      if (o is Map) {
-        var fn = o[name];
-        if (fn is Function) {
-          return Function.apply(fn, posArgs, sNamedArgs);
-        } else {
-          throw "Property '$name' is not of type function.";
-        }
-      } else {
-        return reflect(o).invoke(symbol, posArgs, sNamedArgs).reflectee;
-      }
+      return reflect(o).invoke(symbol, posArgs, sNamedArgs).reflectee;
     };
   }
 

lib/core/parser/parser_static.dart

@@ -27,16 +27,7 @@ class StaticClosureMap extends ClosureMap {
     return (o, posArgs, namedArgs) {
       var sNamedArgs = {};
       namedArgs.forEach((name, value) => sNamedArgs[symbols[name]] = value);
-      if (o is Map) {
-        var fn = o[name];
-        if (fn is Function) {
-          return Function.apply(fn, posArgs, sNamedArgs);
-        } else {
-          throw "Property '$name' is not of type function.";
-        }
-      } else {
-        return Function.apply(fn(o), posArgs, sNamedArgs);
-      }
+      return Function.apply(fn(o), posArgs, sNamedArgs);
     };
   }
 

lib/core/scope.dart

@@ -81,7 +81,7 @@ class ScopeDigestTTL {
  * a `scope` setter:
  *
  *     @Component(...)
- *     class MyComponent {
+ *     class MyComponent implements ScopeAware {
  *       Watch watch;
  *
  *       MyComponent(Dependency myDep) {
@@ -96,7 +96,7 @@ class ScopeDigestTTL {
  *     }
  */
 abstract class ScopeAware {
-  void set context(ctx);
+  void set scope(Scope scope);
 }
 
 /**
@@ -110,7 +110,7 @@ class Scope {
   int _childScopeNextId = 0;
 
   /// The default execution context for [watch]es [observe]ers, and [eval]uation.
-  final Object context;
+  final context;
 
   /// The [RootScope] of the application.
   final RootScope rootScope;
@@ -140,20 +140,20 @@ class Scope {
   // TODO(misko): WatchGroup should be private.
   // Instead we should expose performance stats about the watches
   // such as # of watches, checks/1ms, field checks, function checks, etc
-  WatchGroup _readWriteGroup;
-  WatchGroup _readOnlyGroup;
+  final WatchGroup _readWriteGroup;
+  final WatchGroup _readOnlyGroup;
 
   Scope _childHead, _childTail, _next, _prev;
   _Streams _streams;
 
   /// Do not use. Exposes internal state for testing.
   bool get hasOwnStreams => _streams != null  && _streams._scope == this;
 
-  Scope(this.context, this.rootScope, this._parentScope,
+  Scope(Object this.context, this.rootScope, this._parentScope,
         this._readWriteGroup, this._readOnlyGroup, this.id,
         this._stats)
   {
-    if (context is ScopeAware) context.scope = this;
+    if (context is ScopeAware) (context as ScopeAware).scope = this;
   }
 
   /**
@@ -651,7 +651,7 @@ class RootScope extends Scope {
     _zone.onTurnDone = apply;
     _zone.onError = (e, s, ls) => _exceptionHandler(e, s);
     _zone.onScheduleMicrotask = runAsync;
-  cacheRegister.registerCache("ScopeWatchASTs", astCache);
+    cacheRegister.registerCache("ScopeWatchASTs", astCache);
   }
 
   RootScope get rootScope => this;

lib/directive/ng_class.dart

@@ -173,8 +173,7 @@ abstract class _NgClassBase {
     nodeAttrs.observe('class', (String cls) {
       if (prevCls != cls) {
         prevCls = cls;
-        var index = _hasLocal(_scope, r'$index') ? _getLocal(_scope, r'$index') : null;
-        _applyChanges(index);
+        _applyChanges(_getLocal(_scope, r'$index', null));
       }
     });
   }
@@ -183,8 +182,7 @@ abstract class _NgClassBase {
     if (_watchExpression != null) _watchExpression.remove();
     _watchExpression = _scope.watch(expression, (v, _) {
         _computeChanges(v);
-        var index = _hasLocal(_scope, r'$index') ? _getLocal(_scope, r'$index') : null;
-        _applyChanges(index);
+        _applyChanges(_getLocal(_scope, r'$index', null));
       },
       canChangeModel: false,
       collection: true);
@@ -281,20 +279,13 @@ abstract class _NgClassBase {
   }
 }
 
-bool _hasLocal(context, name) {
-  var ctx = context;
-  while (ctx is ContextLocals) {
-    if (ctx.hasProperty(name)) return true;
-    ctx = ctx.parentScope;
-  }
-  return false;
-}
-
-dynamic _getLocal(context, name) {
-  var ctx = context;
+/// Returns a value from the [scope] context.
+/// Walks up the [ContextLocals] tree and returns the [defaultValue] when the value is not found.
+dynamic _getLocal(Scope scope, String name, defaultValue) {
+  var ctx = scope.context;
   while (ctx is ContextLocals) {
     if (ctx.hasProperty(name)) return ctx[name];
     ctx = ctx.parentScope;
   }
-  return null;
+  return defaultValue;
 }

lib/directive/ng_control.dart

@@ -3,9 +3,9 @@ part of angular.directive;
 /**
  * Contains info and error states used during form and input validation.
  *
- * NgControl is a common superclass for forms and input controls that handles info and error states, as well as
- * status flags. NgControl is used with the form and fieldset as well as all other directives that are used for
- * user input with NgModel.
+ * [NgControl] is a common superclass for forms and input controls that handles info and error
+ * states, as well as status flags. NgControl is used with the form and fieldset as well as all
+ * other directives that are used for user input with NgModel.
  */
 abstract class NgControl implements AttachAware, DetachAware {
   static const NG_VALID          = "ng-valid";