Implement type inference for assignments to a static variable.

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,
@@ skipping 558 matching lines @@
 }
 
 class StaticAccessor extends Accessor {
   Member readTarget;
   Member writeTarget;
 
   StaticAccessor(
       BuilderHelper helper, this.readTarget, this.writeTarget, Token token)
       : super(helper, token);
 
-  Expression _makeRead(KernelComplexAssignment complexAssignment) =>
-      readTarget == null
-          ? makeInvalidRead()
-          : helper.makeStaticGet(readTarget, token);
+  Expression _makeRead(KernelComplexAssignment complexAssignment) {
+    if (readTarget == null) {
+      return makeInvalidRead();
+    } else {
+      var read = helper.makeStaticGet(readTarget, token);
+      complexAssignment?.read = read;
+      return read;
+    }
+  }
 
   Expression _makeWrite(Expression value, bool voidContext,
       KernelComplexAssignment complexAssignment) {
-    return writeTarget == null
-        ? makeInvalidWrite(value)
-        : new StaticSet(writeTarget, value)
-      ..fileOffset = offsetForToken(token);
+    Expression write;
+    if (writeTarget == null) {
+      write = makeInvalidWrite(value);
+    } else {
+      write = new StaticSet(writeTarget, value);
+      complexAssignment?.write = write;
+    }
+    write.fileOffset = offsetForToken(token);
+    return write;
   }
 }
 
 class ReadOnlyAccessor extends Accessor {
   Expression expression;
   VariableDeclaration value;
 
   ReadOnlyAccessor(BuilderHelper helper, this.expression, Token token)
       : super(helper, token);
 
@@ skipping 29 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);
 }