Implement canonical name scheme in kernel.

pkg/kernel/lib/verifier.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.
 library kernel.checks;
 
 import 'ast.dart';
 import 'transformations/flags.dart';
 
 void verifyProgram(Program program) {
   VerifyingVisitor.check(program);
@@ skipping 115 matching lines @@
     }
     visitChildren(program);
     for (var library in program.libraries) {
       library.members.forEach(undeclareMember);
       for (var class_ in library.classes) {
         class_.members.forEach(undeclareMember);
       }
     }
   }
 
+  void checkCanonicalName(CanonicalName name, LinkedNode definition) {

[kustermann, 2017/02/01 13:00:54]

You could also verify that name._children is minimal?

[asgerf, 2017/02/02 12:30:27]

Follow-up on the previous comment:

It is hard to purge unused canonical names while maintaining a nice API,
especially since we have intermediate canonical name nodes that are not bound to
anything, such as <class>::@methods.  It's not very nice that calling
getChild('@methods') makes the tree invalid if there happens to be no methods.

+    if (name == null) {
+      throw '$definition has no canonical name';
+    }
+    if (name.definition != definition) {
+      throw '$definition has name $name, but that is bound to ${name.definition}';

[kustermann, 2017/02/01 13:00:54]

maybe run dartfmt

[asgerf, 2017/02/02 12:30:27]

Done.

+    }
+  }
+
   visitField(Field node) {
+    checkCanonicalName(node.canonicalName, node);
     currentMember = node;
     var oldParent = enterParent(node);
     classTypeParametersAreInScope = !node.isStatic;
     node.initializer?.accept(this);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     exitParent(oldParent);
     currentMember = null;
   }
 
   visitProcedure(Procedure node) {
+    checkCanonicalName(node.canonicalName, node);
     currentMember = node;
     var oldParent = enterParent(node);
     classTypeParametersAreInScope = !node.isStatic;
     node.function.accept(this);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     exitParent(oldParent);
     currentMember = null;
   }
 
   visitConstructor(Constructor node) {
+    checkCanonicalName(node.canonicalName, node);
     currentMember = node;
     classTypeParametersAreInScope = true;
     // The constructor member needs special treatment due to parameters being
     // in scope in the initializer list.
     var oldParent = enterParent(node);
     int stackHeight = enterLocalScope();
     visitChildren(node.function);
     visitList(node.initializers, this);
     exitLocalScope(stackHeight);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     exitParent(oldParent);
     classTypeParametersAreInScope = false;
     currentMember = null;
   }
 
   visitClass(Class node) {
+    checkCanonicalName(node.canonicalName, node);
     currentClass = node;
     declareTypeParameters(node.typeParameters);
     var oldParent = enterParent(node);
     classTypeParametersAreInScope = false;
     visitList(node.annotations, this);
     classTypeParametersAreInScope = true;
     visitList(node.typeParameters, this);
     visitList(node.fields, this);
     visitList(node.constructors, this);
     visitList(node.procedures, this);
@@ skipping 256 matching lines @@
       throw 'Parent pointer on ${node.runtimeType} '
           'is ${node.parent.runtimeType} '
           'but should be ${parent.runtimeType}';
     }
     var oldParent = parent;
     parent = node;
     node.visitChildren(this);
     parent = oldParent;
   }
 }