Implement canonical name scheme in kernel.

pkg/kernel/lib/canonical_name.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.canonical_name;
+
+import 'ast.dart';
+
+/// A string sequence that identifies a library, class, or member.
+///
+/// Canonical names are organized in a prefix tree.  Each node knows its
+/// parent, children, and the AST node it is currently bound to.
+///
+/// The following schema specifies how the canonical name of a given object
+/// is defined:
+///
+///      Library:
+///         URI of library
+///
+///      Class:
+///         URI of enclosing library

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

Isn't this the canonical name of the enclosing library?

  236   void addClass(Class class_) {
  237     if (class_.canonicalName == null) {
  238      
getCanonicalNameOfLibrary(this).getChild(class_.name).linkTo(class_);
  239     }

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

They are the same thing. I thought it would be clearer to write it like this.

[kustermann, 2017/02/03 11:48:20]

Up to you, but for all the other things, like Field, you describe it as
"Canonical name of enclosing ... or library", so I'd do it here as well.  
 
i.e it's not an URI but a canonical name of the library.

[asgerf, 2017/02/03 12:47:38]

Done.

+///         Name of class
+///
+///      Constructor:
+///         Canonical name of enclosing class or library
+///         "@constructors"
+///         Qualified name
+///
+///      Field:
+///         Canonical name of enclosing class or library
+///         "@fields"
+///         Qualified name
+///
+///      Procedure that is not an accessor:
+///         Canonical name of enclosing class or library
+///         "@methods"
+///         Qualified name
+///
+///      Procedure that is a getter:
+///         Canonical name of enclosing class or library
+///         "@getters"
+///         Qualified name
+///
+///      Procedure that is a setter:
+///         Canonical name of enclosing class or library
+///         "@setters"
+///         Qualified name
+///
+///      Qualified name:
+///         if private: URI of library
+///         Name text
+///
+/// The "qualified name" allows a member to have a name that is private to
+/// a library other than the one containing that member.
+class CanonicalName {
+  final CanonicalName parent;
+  final String name;
+
+  Map<String, CanonicalName> _children;
+
+  /// The library, class, or member bound to this name.
+  LinkedNode definition;
+
+  /// Temporary index used during serialization.
+  int index = -1;
+
+  CanonicalName._(this.parent, this.name) {
+    assert(name != null);
+  }
+
+  CanonicalName.root()
+      : parent = null,
+        name = '';
+
+  /// Used as temporary measure to get the dart2js-kernel adaptor working.
+  ///
+  /// This canonical name cannot be used in serialization but can hold in-memory
+  /// references.
+  CanonicalName.dummy()
+      : parent = null,
+        name = 'dummy';
+
+  bool get isRoot => parent == null;
+
+  Iterable<CanonicalName> get children =>
+      _children?.values ?? const <CanonicalName>[];
+
+  CanonicalName getChild(String name) {
+    var map = _children ??= <String, CanonicalName>{};
+    return map[name] ??= new CanonicalName._(this, name);
+  }
+
+  CanonicalName getChildFromUri(Uri uri) {
+    // Note that the Uri class caches its string representation, and all library
+    // URIs will be stringified for serialization anyway, so there is no
+    // significant cost for converting the Uri to a string here.
+    return getChild('$uri');
+  }
+
+  CanonicalName getChildFromQualifiedName(Name name) {
+    return name.isPrivate
+        ? getChild(name.libraryName.name).getChild(name.name)
+        : getChild(name.name);
+  }
+
+  CanonicalName getChildFromMember(Member member) {
+    return getChild(getMemberQualifier(member))
+        .getChildFromQualifiedName(member.name);
+  }
+
+  void linkTo(LinkedNode target) {

[ahe, 2017/01/30 17:16:16]

Call this bind?

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

Changed to bindTo

+    if (definition == target) return;
+    if (definition != null) {
+      throw '$this is already bound';
+    }
+    if (target.canonicalName != null) {
+      throw 'Cannot bind $this to $target, target is already bound';
+    }
+    target.canonicalName = this;
+    this.definition = target;
+  }
+
+  void unlink() {
+    if (definition == null) return;
+    assert(definition.canonicalName == this);
+    definition.canonicalName = null;
+    definition = null;

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

Should this unlink() not also update the _children map?

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

'unlink' is not meant to "destroy" the name. It should just remove the two-way
binding.

It's not that simple to garbage collect unused canonical names from the tree, as
they might be intended to be used again. For example, it was designed so this
should work (not that we're actually using it):

  canonicalName..unlink()..linkTo(newDefinition)

+  }
+
+  String toString() => parent == null ? 'root' : '$parent::$name';
+
+  Library get asLibrary {
+    if (definition == null) throw '$this is not bound';
+    return definition as Library;
+  }
+
+  Class get asClass {
+    if (definition == null) throw '$this is not bound';
+    return definition as Class;
+  }
+
+  Member get asMember {
+    if (definition == null) throw '$this is not bound';
+    return definition as Member;
+  }
+
+  Constructor get asConstructor {
+    if (definition == null) throw '$this is not bound';
+    return definition as Constructor;
+  }
+
+  Procedure get asProcedure {
+    if (definition == null) throw '$this is not bound';
+    return definition as Procedure;
+  }
+
+  Field get asField {
+    if (definition == null) throw '$this is not bound';
+    return definition as Field;
+  }
+
+  static String getMemberQualifier(Member member) {
+    if (member is Procedure) {
+      if (member.isGetter) return '@getters';
+      if (member.isSetter) return '@setters';
+      return '@methods';
+    }
+    if (member is Field) {
+      return '@fields';
+    }
+    if (member is Constructor) {
+      return '@constructors';
+    }
+    throw 'Unexpected member: $member';
+  }
+}