Add fasta-based summary generation code.

pkg/analyzer/lib/src/summary/fasta/model.dart

Index: pkg/analyzer/lib/src/summary/fasta/model.dart
diff --git a/pkg/analyzer/lib/src/summary/fasta/model.dart b/pkg/analyzer/lib/src/summary/fasta/model.dart
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+// Copyright (c) 2017, 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.
+
+/// Additional data model classes used by the summary builder.
+///
+/// The summary builder uses 4 pieces of data:
+///
+///   * Unlinked**Builders: builder classes for each piece of output in the
+///     summary (see format.dart).
+///
+///   * A simplified expression syntax: model relevant pieces of initializers
+///     and constants before serializing them (see expressions.dart).
+///
+///   * Lazy references: a way to model references on the fly so we can build
+///     summaries in a single pass.
+///
+///   * Scopes: used to track the current context of the parser, used in great
+///     part to easily resolve lazy references at the end of the build process.
+library summary.src.scope;
+
+import 'package:analyzer/src/summary/format.dart';
+import 'package:analyzer/src/summary/idl.dart';
+
+export 'package:analyzer/src/summary/format.dart';
+export 'package:analyzer/src/summary/idl.dart';
+export 'package:analyzer/src/summary/api_signature.dart';
+export 'expressions.dart';
+export 'visitor.dart';
+
+/// A scope corresponding to a scope in the program like units, classes, or
+/// enums.
+///
+/// It is used to hold results that correspond to a given scope in the program
+/// and to lazily resolve name references.
+abstract class Scope {
+  Scope get parent;
+
+  TopScope get top {
+    var s = this;
+    while (s.parent != null) s = s.parent;
+    return s;
+  }
+
+  void computeReference(LazyEntityRef ref);
+}
+
+/// Top scope, where the top-level unit is built.
+class TopScope extends Scope {
+  get parent => null;
+  toString() => "<top-scope>";
+
+  /// Results of parsing the unit.
+  final UnlinkedUnitBuilder unit = new UnlinkedUnitBuilder(
+      classes: [],
+      enums: [],
+      executables: [],
+      exports: [],
+      imports: [],
+      parts: [],
+      references: [new UnlinkedReferenceBuilder()],
+      typedefs: [],
+      variables: []);
+
+  /// Stores publicly visible names exported from the unit.
+  final UnlinkedPublicNamespaceBuilder publicNamespace =
+      new UnlinkedPublicNamespaceBuilder(names: [], exports: [], parts: []);
+
+  /// Lazy references that need to be expanded after all scope information is
+  /// known.
+  List<LazyEntityRef> _toExpand = [];
+
+  void expandLazyReferences() {
+    _toExpand.forEach((r) => r.expand());
+  }
+
+  TopScope() {
+    unit.publicNamespace = publicNamespace;
+  }
+
+  final Map<int, Map<String, int>> nameToReference = <int, Map<String, int>>{};
+  int serializeReference(int prefixIndex, String name) => nameToReference
+      .putIfAbsent(prefixIndex, () => <String, int>{})
+      .putIfAbsent(name, () {
+          int index = unit.references.length;
+          unit.references.add(new UnlinkedReferenceBuilder(
+              prefixReference: prefixIndex, name: name));
+          return index;
+      });
+
+  void computeReference(LazyEntityRef ref) {
+    ref.reference = serializeReference(null, ref.name);
+  }
+}
+
+class TypeParameterScope extends Scope {
+  final Scope parent;
+  TypeParameterScope(this.parent);
+
+  List<String> typeParameters = [];
+
+  void computeReference(LazyEntityRef ref) {
+    var i = typeParameters.indexOf(ref.name);
+    if (i < 0) return parent.computeReference(ref);
+    // Note: there is no indexOffset here because we don't go into functions at
+    // all (so there is no nesting of type-parameter scopes).
+    ref.paramReference = typeParameters.length - i;
+  }
+}
+
+class ClassScope extends TypeParameterScope {
+  String className;
+  UnlinkedClassBuilder currentClass = new UnlinkedClassBuilder();
+  UnlinkedPublicNameBuilder publicName = new UnlinkedPublicNameBuilder();
+  Set<String> members = new Set<String>();
+  toString() => "<class-scope: $className>";
+
+  ClassScope(Scope parent) : super(parent);
+
+  void computeReference(LazyEntityRef ref) {
+    if (!members.contains(ref.name)) {
+      return super.computeReference(ref);
+    }
+    ref.reference = top.serializeReference(
+        top.serializeReference(null, className), ref.name);
+  }
+}
+
+class EnumScope extends Scope {
+  final Scope parent;
+  UnlinkedEnumBuilder currentEnum = new UnlinkedEnumBuilder();
+
+  EnumScope(this.parent);
+
+  void computeReference(LazyEntityRef ref) => throw "unexpected";
+}
+
+
+/// A lazily encoded reference.
+///
+/// References in summaries are encoded based on the scope where they appear.
+/// Most top-level references can be encoded eagerly, but references in the
+/// scope of a class need to check whether a name is a member of such class.
+/// Because we don't have such list of members available upfront, we create
+/// these lazy references and finalize them after we finish going through the
+/// program.
+class LazyEntityRef extends EntityRefBuilder {
+  Scope scope;
+  String name;
+  LazyEntityRef(this.name, this.scope) : super() {
+    scope.top._toExpand.add(this);
+  }
+
+
+  bool wasExpanded = false;
+  expand() {
+    if (!wasExpanded) {
+      scope.computeReference(this);
+      wasExpanded = true;
+    }
+  }
+
+  @override
+  int get reference {
+    expand();
+    return super.reference;
+  }
+
+  @override
+  int get paramReference {
+    expand();
+    return super.paramReference;
+  }
+}
+
+/// A nested lazy reference, modeling something like `a.b.c`.
+class NestedLazyEntityRef extends LazyEntityRef {
+  EntityRef prefix;
+  NestedLazyEntityRef(this.prefix, String name, Scope scope)
+      : super(name, scope.top);
+
+  @override
+  expand() {
+    if (!wasExpanded) {
+      super.reference = scope.top.serializeReference(prefix.reference, name);
+      wasExpanded = true;
+    }
+  }
+}