Add type inference for assignments to properties.

pkg/front_end/lib/src/fasta/kernel/frontend_accessors.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.
 
 /// A library to help transform compounds and null-aware accessors into
 /// let expressions.
 
 import 'package:front_end/src/fasta/kernel/kernel_shadow_ast.dart'
     show
         KernelArguments,
         KernelComplexAssignment,
         KernelConditionalExpression,
         KernelMethodInvocation,
+        KernelPropertyAssign,
         KernelPropertyGet,
         KernelPropertySet,
         KernelThisExpression,
         KernelVariableDeclaration,
         KernelVariableGet,
         KernelVariableSet;
 
 import 'package:front_end/src/fasta/kernel/utils.dart' show offsetForToken;
 
 import 'package:front_end/src/scanner/token.dart' show Token;
@@ skipping 218 matching lines @@
 
   PropertyAccessor.internal(BuilderHelper helper, this.receiver, this.name,
       this.getter, this.setter, Token token)
       : super(helper, token);
 
   Expression _makeSimpleRead() => new KernelPropertyGet(receiver, name, getter)
     ..fileOffset = offsetForToken(token);
 
   Expression _makeSimpleWrite(Expression value, bool voidContext,
       KernelComplexAssignment complexAssignment) {
-    return new KernelPropertySet(receiver, name, value, setter)
+    var write = new KernelPropertySet(receiver, name, value, setter)
       ..fileOffset = offsetForToken(token);
+    complexAssignment?.write = write;
+    return write;
   }
 
   receiverAccess() {
     _receiverVariable ??= new VariableDeclaration.forValue(receiver);
     return new VariableGet(_receiverVariable)
       ..fileOffset = offsetForToken(token);
   }
 
-  Expression _makeRead(KernelComplexAssignment complexAssignment) =>
-      new KernelPropertyGet(receiverAccess(), name, getter)
-        ..fileOffset = offsetForToken(token);
+  Expression _makeRead(KernelComplexAssignment complexAssignment) {
+    var read = new KernelPropertyGet(receiverAccess(), name, getter)
+      ..fileOffset = offsetForToken(token);
+    complexAssignment?.read = read;
+    return read;
+  }
 
   Expression _makeWrite(Expression value, bool voidContext,
       KernelComplexAssignment complexAssignment) {
-    return new KernelPropertySet(receiverAccess(), name, value, setter)
+    var write = new KernelPropertySet(receiverAccess(), name, value, setter)
       ..fileOffset = offsetForToken(token);
+    complexAssignment?.write = write;
+    return write;
   }
 
   Expression _finish(
-          Expression body, KernelComplexAssignment complexAssignment) =>
-      makeLet(_receiverVariable, body);
+      Expression body, KernelComplexAssignment complexAssignment) {
+    body = makeLet(_receiverVariable, body);
+    if (complexAssignment != null) {
+      complexAssignment.desugared = body;
+      return complexAssignment;
+    } else {
+      return body;
+    }
+  }
 }
 
 /// Special case of [PropertyAccessor] to avoid creating an indirect access to
 /// 'this'.
 class ThisPropertyAccessor extends Accessor {
   Name name;
   Member getter, setter;
 
   ThisPropertyAccessor(
       BuilderHelper helper, this.name, this.getter, this.setter, Token token)
       : super(helper, token);
 
-  Expression _makeRead(KernelComplexAssignment complexAssignment) =>
-      new KernelPropertyGet(new KernelThisExpression(), name, getter)
-        ..fileOffset = offsetForToken(token);
+  Expression _makeRead(KernelComplexAssignment complexAssignment) {
+    var read = new KernelPropertyGet(new KernelThisExpression(), name, getter)
+      ..fileOffset = offsetForToken(token);
+    complexAssignment?.read = read;
+    return read;
+  }
 
   Expression _makeWrite(Expression value, bool voidContext,
       KernelComplexAssignment complexAssignment) {
-    return new KernelPropertySet(
-        new KernelThisExpression(), name, value, setter)
-      ..fileOffset = offsetForToken(token);
+    var write =
+        new KernelPropertySet(new KernelThisExpression(), name, value, setter)
+          ..fileOffset = offsetForToken(token);
+    complexAssignment?.write = write;
+    return write;
   }
 }
 
 class NullAwarePropertyAccessor extends Accessor {
   VariableDeclaration receiver;
+  Expression receiverExpression;
   Name name;
   Member getter, setter;
   DartType type;
 
-  NullAwarePropertyAccessor(BuilderHelper helper, Expression receiver,
+  NullAwarePropertyAccessor(BuilderHelper helper, this.receiverExpression,
       this.name, this.getter, this.setter, this.type, Token token)
-      : this.receiver = makeOrReuseVariable(receiver),
+      : this.receiver = makeOrReuseVariable(receiverExpression),
         super(helper, token);
 
   receiverAccess() => new VariableGet(receiver);
 
-  Expression _makeRead(KernelComplexAssignment complexAssignment) =>
-      new KernelPropertyGet(receiverAccess(), name, getter);
+  Expression _makeRead(KernelComplexAssignment complexAssignment) {
+    var read = new KernelPropertyGet(receiverAccess(), name, getter)
+      ..fileOffset = offsetForToken(token);
+    complexAssignment?.read = read;
+    return read;
+  }
 
   Expression _makeWrite(Expression value, bool voidContext,
       KernelComplexAssignment complexAssignment) {
-    return new KernelPropertySet(receiverAccess(), name, value, setter);
+    var write = new KernelPropertySet(receiverAccess(), name, value, setter)
+      ..fileOffset = offsetForToken(token);
+    complexAssignment?.write = write;
+    return write;
   }
 
   Expression _finish(
-          Expression body, KernelComplexAssignment complexAssignment) =>
-      makeLet(
-          receiver,
-          new KernelConditionalExpression(
-              buildIsNull(receiverAccess()), new NullLiteral(), body));
+      Expression body, KernelComplexAssignment complexAssignment) {
+    var nullAwareGuard = new KernelConditionalExpression(
+        buildIsNull(receiverAccess()), new NullLiteral(), body)
+      ..fileOffset = offsetForToken(token);
+    body = makeLet(receiver, nullAwareGuard);
+    if (complexAssignment != null) {
+      KernelPropertyAssign kernelPropertyAssign = complexAssignment;
+      kernelPropertyAssign.nullAwareGuard = nullAwareGuard;
+      kernelPropertyAssign.desugared = body;
+      return kernelPropertyAssign;
+    } else {
+      return body;
+    }
+  }
 }
 
 class SuperPropertyAccessor extends Accessor {
   Name name;
   Member getter, setter;
 
   SuperPropertyAccessor(
       BuilderHelper helper, this.name, this.getter, this.setter, Token token)
       : super(helper, token);
 
   Expression _makeRead(KernelComplexAssignment complexAssignment) {
     if (getter == null) return makeInvalidRead();
     // TODO(ahe): Use [DirectPropertyGet] when possible.
-    return new SuperPropertyGet(name, getter)
+    var read = new SuperPropertyGet(name, getter)
       ..fileOffset = offsetForToken(token);
+    complexAssignment?.read = read;
+    return read;
   }
 
   Expression _makeWrite(Expression value, bool voidContext,
       KernelComplexAssignment complexAssignment) {
     if (setter == null) return makeInvalidWrite(value);
     // TODO(ahe): Use [DirectPropertySet] when possible.
-    return new SuperPropertySet(name, value, setter)
+    var write = new SuperPropertySet(name, value, setter)
       ..fileOffset = offsetForToken(token);
+    complexAssignment?.write = write;
+    return write;
   }
 }
 
 class IndexAccessor extends Accessor {
   Expression receiver;
   Expression index;
   VariableDeclaration receiverVariable;
   VariableDeclaration indexVariable;
   Procedure getter, setter;
 
@@ skipping 282 matching lines @@
 
 Expression buildIsNull(Expression value, {int offset: TreeNode.noOffset}) {
   return makeBinary(value, equalsName, null, new NullLiteral(), offset: offset);
 }
 
 VariableDeclaration makeOrReuseVariable(Expression value) {
   // TODO: Devise a way to remember if a variable declaration was reused
   // or is fresh (hence needs a let binding).
   return new VariableDeclaration.forValue(value);
 }