Document that setter expressions return their right-hand side.

pkg/kernel/lib/ast.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 /// -----------------------------------------------------------------------
 ///                           ERROR HANDLING
 /// -----------------------------------------------------------------------
 ///
 /// As a rule of thumb, errors that can be detected statically are handled by
 /// the frontend, typically by translating the erroneous code into a 'throw' or
@@ skipping 1288 matching lines @@
   }
 
   transformChildren(Transformer v) {
     if (promotedType != null) {
       promotedType = v.visitDartType(promotedType);
     }
   }
 }
 
 /// Assign a local variable or function parameter.
+///
+/// Evaluates to the value of [value].
 class VariableSet extends Expression {
   VariableDeclaration variable;
   Expression value;
 
   VariableSet(this.variable, this.value) {
     value?.parent = this;
   }
 
   DartType getStaticType(TypeEnvironment types) => value.getStaticType(types);
 
@@ skipping 61 matching lines @@
     if (receiver != null) {
       receiver = receiver.accept(v);
       receiver?.parent = this;
     }
   }
 }
 
 /// Expression of form `x.field = value`.
 ///
 /// This may invoke a setter or assign a field.
+///
+/// Evaluates to the value of [value].
 class PropertySet extends Expression {
   Expression receiver;
   Name name;
   Expression value;
 
   _MemberAccessor _interfaceTargetReference;
 
   PropertySet(this.receiver, this.name, this.value, [Member interfaceTarget]) {
     receiver?.parent = this;
     value?.parent = this;
@@ skipping 54 matching lines @@
   DartType getStaticType(TypeEnvironment types) {
     Class superclass = target.enclosingClass;
     var receiverType = receiver.getStaticTypeAsInstanceOf(superclass, types);
     return Substitution
         .fromInterfaceType(receiverType)
         .substituteType(target.getterType);
   }
 }
 
 /// Directly assign a field, or call a setter.
+///
+/// Evaluates to the value of [value].
 class DirectPropertySet extends Expression {
   Expression receiver;
   Member target;
   Expression value;
 
   DirectPropertySet(this.receiver, this.target, this.value) {
     receiver?.parent = this;
     value?.parent = this;
   }
 
@@ skipping 99 matching lines @@
   visitChildren(Visitor v) {
     name?.accept(v);
   }
 
   transformChildren(Transformer v) {}
 }
 
 /// Expression of form `super.field = value`.
 ///
 /// This may invoke a setter or assign a field.
+///
+/// Evaluates to the value of [value].
 class SuperPropertySet extends Expression {
   Name name;
   Expression value;
   _MemberAccessor _interfaceTargetReference;
 
   SuperPropertySet(this.name, this.value, [Member interfaceTarget]) {
     value?.parent = this;
     _interfaceTargetReference = interfaceTarget?._setterInterface;
   }
 
@@ skipping 32 matching lines @@
   accept(ExpressionVisitor v) => v.visitStaticGet(this);
 
   visitChildren(Visitor v) {
     target?.acceptReference(v);
   }
 
   transformChildren(Transformer v) {}
 }
 
 /// Assign a static field or call a static setter.
+///
+/// Evaluates to the value of [value].
 class StaticSet extends Expression {
   /// A mutable static field or a static setter.
   Member target;
   Expression value;
 
   StaticSet(this.target, this.value) {
     value?.parent = this;
   }
 
   DartType getStaticType(TypeEnvironment types) => value.getStaticType(types);
@@ skipping 1986 matching lines @@
 
   @override
   defaultTreeNode(TreeNode node) {
     if (node == child) {
       return replacement;
     } else {
       return node;
     }
   }
 }