Build top-level variables and property accessors lazily.

pkg/analyzer/lib/src/dart/element/element.dart

Index: pkg/analyzer/lib/src/dart/element/element.dart
diff --git a/pkg/analyzer/lib/src/dart/element/element.dart b/pkg/analyzer/lib/src/dart/element/element.dart
index ddcad2b56b95a91ea758a0ac9d5815a293f76a9c..e3306e997ccfdae97f548ae180b12e414c976583 100644
--- a/pkg/analyzer/lib/src/dart/element/element.dart
+++ b/pkg/analyzer/lib/src/dart/element/element.dart
@@ -1085,7 +1085,7 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
    * A list containing all of the top-level accessors (getters and setters)
    * contained in this compilation unit.
    */
-  List<PropertyAccessorElement> _accessors = PropertyAccessorElement.EMPTY_LIST;
+  List<PropertyAccessorElement> _accessors;
 
   /**
    * A list containing all of the enums contained in this compilation unit.
@@ -1113,7 +1113,7 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
   /**
    * A list containing all of the variables contained in this compilation unit.
    */
-  List<TopLevelVariableElement> _variables = TopLevelVariableElement.EMPTY_LIST;
+  List<TopLevelVariableElement> _variables;
 
   /**
    * A map from offsets to elements of this unit at these offsets.
@@ -1121,6 +1121,24 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
   final Map<int, Element> _offsetToElementMap = new HashMap<int, Element>();
 
   /**
+   * Resynthesized explicit top-level property accessors.
+   */
+  UnitExplicitTopLevelAccessors _explicitTopLevelAccessors;
+
+  /**
+   * Resynthesized explicit top-level variables.
+   */
+  UnitExplicitTopLevelVariables _explicitTopLevelVariables;
+
+  /**
+   * Description of top-level variable replacements that should be applied
+   * to implicit top-level variables because of re-linking top-level property
+   * accessors between different unit of the same library.
+   */
+  Map<TopLevelVariableElement, TopLevelVariableElement>
+      _topLevelVariableReplaceMap;
+
+  /**
    * Initialize a newly created compilation unit element to have the given
    * [name].
    */
@@ -1146,7 +1164,30 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
   }
 
   @override
-  List<PropertyAccessorElement> get accessors => _accessors;
+  List<PropertyAccessorElement> get accessors {
+    if (_unlinkedUnit != null) {
+      if (_accessors == null) {
+        _explicitTopLevelAccessors ??=
+            resynthesizerContext.buildTopLevelAccessors();
+        _explicitTopLevelVariables ??=
+            resynthesizerContext.buildTopLevelVariables();
+        List<PropertyAccessorElementImpl> accessors =
+            <PropertyAccessorElementImpl>[];
+        accessors.addAll(_explicitTopLevelAccessors.accessors);
+        for (TopLevelVariableElementImpl implicitVariable
+            in _explicitTopLevelAccessors.implicitVariables) {
+          implicitVariable.enclosingElement = this;
+        }
+        for (PropertyAccessorElementImpl implicitAccessors
+            in _explicitTopLevelVariables.implicitAccessors) {
+          implicitAccessors.enclosingElement = this;
+          accessors.add(implicitAccessors);
+        }
+        _accessors = accessors;
+      }
+    }
+    return _accessors ?? PropertyAccessorElement.EMPTY_LIST;
+  }
 
   /**
    * Set the top-level accessors (getters and setters) contained in this
@@ -1229,7 +1270,6 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
 
   @override
   String get identifier => source.encoding;
-

[Paul Berry, 2016/05/19 11:27:29]

Nit: restore this blank line.

   @override
   ElementKind get kind => ElementKind.COMPILATION_UNIT;
 
@@ -1246,13 +1286,45 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
   }
 
   @override
-  List<TopLevelVariableElement> get topLevelVariables => _variables;
+  List<TopLevelVariableElement> get topLevelVariables {
+    if (_unlinkedUnit != null) {
+      if (_variables == null) {
+        _explicitTopLevelAccessors ??=
+            resynthesizerContext.buildTopLevelAccessors();
+        _explicitTopLevelVariables ??=
+            resynthesizerContext.buildTopLevelVariables();
+        List<TopLevelVariableElementImpl> variables =
+            <TopLevelVariableElementImpl>[];
+        variables.addAll(_explicitTopLevelVariables.variables);
+        for (PropertyAccessorElementImpl implicitAccessor
+            in _explicitTopLevelVariables.implicitAccessors) {
+          implicitAccessor.enclosingElement = this;

[Paul Berry, 2016/05/19 11:27:30]

If `.accessors` is called and then `.topLevelVariables` is called, this code
will get unnecessarily executed twice.  Same goes for
`implicitVariable.enclosingElement = this;` on line 1305.

How about if instead we pass `this` to
`resynthesizerContext.buildTopLevelAccessors()` and
`resynthesizerContext.buildTopLevelVariables()`, so that they can set the
enclosing element properly when they create the elements?

[scheglov, 2016/05/19 16:54:57]

Done.

+        }
+        for (TopLevelVariableElementImpl implicitVariable
+            in _explicitTopLevelAccessors.implicitVariables) {
+          implicitVariable.enclosingElement = this;
+          variables.add(implicitVariable);
+        }
+        _variables = variables;
+      }
+      (enclosingElement as LibraryElementImpl)
+          .resynthesizerContext
+          .patchTopLevelAccessors();
+      _topLevelVariableReplaceMap?.forEach((from, to) {
+        int index = _variables.indexOf(from);
+        _variables[index] = to;
+      });
+      _topLevelVariableReplaceMap = null;
+    }
+    return _variables ?? TopLevelVariableElement.EMPTY_LIST;
+  }
 
   /**
    * Set the top-level variables contained in this compilation unit to the given
    * [variables].
    */
   void set topLevelVariables(List<TopLevelVariableElement> variables) {
+    assert(!isResynthesized);
     for (TopLevelVariableElement field in variables) {
       (field as TopLevelVariableElementImpl).enclosingElement = this;
     }
@@ -1334,13 +1406,13 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
     // thrown a CCE if any of the elements in the arrays were not of the
     // expected types.
     //
-    for (PropertyAccessorElement accessor in _accessors) {
+    for (PropertyAccessorElement accessor in accessors) {
       PropertyAccessorElementImpl accessorImpl = accessor;
       if (accessorImpl.identifier == identifier) {
         return accessorImpl;
       }
     }
-    for (TopLevelVariableElement variable in _variables) {
+    for (TopLevelVariableElement variable in topLevelVariables) {
       TopLevelVariableElementImpl variableImpl = variable;
       if (variableImpl.identifier == identifier) {
         return variableImpl;
@@ -1360,10 +1432,58 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
     }
     for (ClassElement type in _types) {
       ClassElementImpl typeImpl = type;
+      if (typeImpl.name == identifier) {
+        return typeImpl;
+      }
+    }
+    for (ClassElement type in _enums) {
+      ClassElementImpl typeImpl = type;
       if (typeImpl.identifier == identifier) {
         return typeImpl;
       }
     }
+    return null;
+  }
+
+  /**
+   * TODO(scheglov) When `_DeferredClassElement` is replaced with

[Paul Berry, 2016/05/19 11:27:30]

In addition to the TODO, I would appreciate a longer documentation comment
explaining how this method differs from "getChild" and why one would want to
call one instead of the other (I had to do some digging before the reason was
clear to me).

Perhaps something like: "Equivalent to [getChild], but does not make the
assumption that the child implements [ElementImpl].  Intended as a temporary
measure while element model resynthesis is being made lazy."

[scheglov, 2016/05/19 16:54:57]

Done.

+   * [ClassElementImpl] remove this method.
+   */
+  Element getChildNotImpl(String identifier) {
+    //
+    // The casts in this method are safe because the set methods would have
+    // thrown a CCE if any of the elements in the arrays were not of the
+    // expected types.
+    //
+    for (PropertyAccessorElement accessor in accessors) {
+      PropertyAccessorElementImpl accessorImpl = accessor;
+      if (accessorImpl.identifier == identifier) {
+        return accessorImpl;
+      }
+    }
+    for (TopLevelVariableElement variable in topLevelVariables) {
+      TopLevelVariableElementImpl variableImpl = variable;
+      if (variableImpl.identifier == identifier) {
+        return variableImpl;
+      }
+    }
+    for (FunctionElement function in _functions) {
+      FunctionElementImpl functionImpl = function;
+      if (functionImpl.identifier == identifier) {
+        return functionImpl;
+      }
+    }
+    for (FunctionTypeAliasElement typeAlias in _typeAliases) {
+      FunctionTypeAliasElementImpl typeAliasImpl = typeAlias;
+      if (typeAliasImpl.identifier == identifier) {
+        return typeAliasImpl;
+      }
+    }
+    for (ClassElement type in _types) {
+      if (type.name == identifier) {
+        return type;
+      }
+    }
     for (ClassElement type in _enums) {
       ClassElementImpl typeImpl = type;
       if (typeImpl.identifier == identifier) {
@@ -1406,8 +1526,14 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
    */
   void replaceTopLevelVariable(
       TopLevelVariableElement from, TopLevelVariableElement to) {
-    int index = _variables.indexOf(from);
-    _variables[index] = to;
+    if (_unlinkedUnit != null) {
+      _topLevelVariableReplaceMap ??=

[Paul Berry, 2016/05/19 11:27:29]

This will only have the desired effect if the `topLevelVariables` getter hasn't
been called yet.  Please add a comment to this effect and the assertion:

assert(_variables == null);

[scheglov, 2016/05/19 16:54:57]

Done.

+          <TopLevelVariableElement, TopLevelVariableElement>{};
+      _topLevelVariableReplaceMap[from] = to;
+    } else {
+      int index = _variables.indexOf(from);
+      _variables[index] = to;
+    }
   }
 
   /**
@@ -1422,12 +1548,12 @@ class CompilationUnitElementImpl extends UriReferencedElementImpl
   @override
   void visitChildren(ElementVisitor visitor) {
     super.visitChildren(visitor);
-    safelyVisitChildren(_accessors, visitor);
+    safelyVisitChildren(accessors, visitor);
     safelyVisitChildren(_enums, visitor);
     safelyVisitChildren(_functions, visitor);
     safelyVisitChildren(_typeAliases, visitor);
     safelyVisitChildren(_types, visitor);
-    safelyVisitChildren(_variables, visitor);
+    safelyVisitChildren(topLevelVariables, visitor);
   }
 }
 
@@ -1639,6 +1765,13 @@ class ConstTopLevelVariableElementImpl extends TopLevelVariableElementImpl
    */
   ConstTopLevelVariableElementImpl.forNode(Identifier name)
       : super.forNode(name);
+
+  /**
+   * Initialize using the given serialized information.
+   */
+  ConstTopLevelVariableElementImpl.forSerialized(
+      UnlinkedVariable unlinkedVariable, ElementImpl enclosingElement)
+      : super.forSerialized(unlinkedVariable, enclosingElement);
 }
 
 /**
@@ -3644,6 +3777,10 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
    */
   final AnalysisContext context;
 
+  final LibraryResynthesizerContext resynthesizerContext;
+
+  final UnlinkedUnit _unlinkedDefiningUnit;
+
   /**
    * The compilation unit that defines this library.
    */
@@ -3653,7 +3790,7 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
    * The entry point for this library, or `null` if this library does not have
    * an entry point.
    */
-  FunctionElement entryPoint;
+  FunctionElement _entryPoint;
 
   /**
    * A list containing specifications of all of the imports defined in this
@@ -3695,22 +3832,22 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
    * The export [Namespace] of this library, `null` if it has not been
    * computed yet.
    */
-  @override
-  Namespace exportNamespace;
+  Namespace _exportNamespace;
 
   /**
    * The public [Namespace] of this library, `null` if it has not been
    * computed yet.
    */
-  @override
-  Namespace publicNamespace;
+  Namespace _publicNamespace;
 
   /**
    * Initialize a newly created library element in the given [context] to have
    * the given [name] and [offset].
    */
   LibraryElementImpl(this.context, String name, int offset, this.nameLength)
-      : super(name, offset);
+      : resynthesizerContext = null,
+        _unlinkedDefiningUnit = null,
+        super(name, offset);
 
   /**
    * Initialize a newly created library element in the given [context] to have
@@ -3718,8 +3855,20 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
    */
   LibraryElementImpl.forNode(this.context, LibraryIdentifier name)
       : nameLength = name != null ? name.length : 0,
+        resynthesizerContext = null,
+        _unlinkedDefiningUnit = null,
         super.forNode(name);
 
+  /**
+   * Initialize using the given serialized information.
+   */
+  LibraryElementImpl.forSerialized(this.context, String name, int offset,
+      this.nameLength, this.resynthesizerContext, this._unlinkedDefiningUnit)
+      : super.forSerialized(null) {
+    _name = name;
+    _nameOffset = offset;
+  }
+
   @override
   int get codeLength {
     CompilationUnitElement unit = _definingCompilationUnit;
@@ -3753,6 +3902,37 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
   }
 
   @override
+  SourceRange get docRange {
+    if (_unlinkedDefiningUnit != null) {
+      UnlinkedDocumentationComment comment =
+          _unlinkedDefiningUnit.libraryDocumentationComment;
+      return comment != null
+          ? new SourceRange(comment.offset, comment.length)
+          : null;
+    }
+    return super.docRange;
+  }
+
+  @override
+  String get documentationComment {
+    if (_unlinkedDefiningUnit != null) {
+      return _unlinkedDefiningUnit?.libraryDocumentationComment?.text;
+    }
+    return super.documentationComment;
+  }
+
+  FunctionElement get entryPoint {
+    if (resynthesizerContext != null) {
+      _entryPoint ??= resynthesizerContext.findEntryPoint();
+    }
+    return _entryPoint;
+  }
+
+  void set entryPoint(FunctionElement entryPoint) {
+    _entryPoint = entryPoint;
+  }
+
+  @override
   List<LibraryElement> get exportedLibraries {
     HashSet<LibraryElement> libraries = new HashSet<LibraryElement>();
     for (ExportElement element in _exports) {
@@ -3765,6 +3945,18 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
   }
 
   @override
+  Namespace get exportNamespace {
+    if (resynthesizerContext != null) {
+      _exportNamespace ??= resynthesizerContext.buildExportNamespace();
+    }
+    return _exportNamespace;
+  }
+
+  void set exportNamespace(Namespace exportNamespace) {
+    _exportNamespace = exportNamespace;
+  }
+
+  @override
   List<ExportElement> get exports => _exports;
 
   /**
@@ -3878,9 +4070,7 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
 
   @override
   bool get isResynthesized {
-    CompilationUnitElement definingUnit = _definingCompilationUnit;
-    return definingUnit is CompilationUnitElementImpl &&
-        definingUnit.resynthesizerContext != null;
+    return resynthesizerContext != null;
   }
 
   @override
@@ -3973,6 +4163,21 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
   }
 
   @override
+  List<ElementAnnotation> get metadata {
+    if (_unlinkedDefiningUnit != null) {
+      if (_metadata == null) {
+        CompilationUnitElementImpl definingUnit =
+            _definingCompilationUnit as CompilationUnitElementImpl;
+        _metadata ??= _unlinkedDefiningUnit.libraryAnnotations
+            .map(definingUnit.resynthesizerContext.buildAnnotation)
+            .toList();
+      }
+      return _metadata;
+    }
+    return super.metadata;
+  }
+
+  @override
   List<CompilationUnitElement> get parts => _parts;
 
   /**
@@ -4001,6 +4206,18 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
   }
 
   @override
+  Namespace get publicNamespace {
+    if (resynthesizerContext != null) {
+      _publicNamespace ??= resynthesizerContext.buildPublicNamespace();
+    }
+    return _publicNamespace;
+  }
+
+  void set publicNamespace(Namespace publicNamespace) {
+    _publicNamespace = publicNamespace;
+  }
+
+  @override
   Source get source {
     if (_definingCompilationUnit == null) {
       return null;
@@ -4233,6 +4450,16 @@ class LibraryElementImpl extends ElementImpl implements LibraryElement {
 }
 
 /**
+ * TODO(scheglov) document

[Paul Berry, 2016/05/19 11:27:29]

Did you intend to address this before sending out for review?

[scheglov, 2016/05/19 16:54:57]

Done.

+ */
+abstract class LibraryResynthesizerContext {
+  Namespace buildExportNamespace();
+  Namespace buildPublicNamespace();
+  FunctionElement findEntryPoint();
+  void patchTopLevelAccessors();
+}
+
+/**
  * A concrete implementation of a [LocalVariableElement].
  */
 class LocalVariableElementImpl extends NonParameterVariableElementImpl
@@ -4856,6 +5083,26 @@ abstract class NonParameterVariableElementImpl extends VariableElementImpl {
   }
 
   @override
+  SourceRange get docRange {
+    if (_unlinkedVariable != null) {
+      UnlinkedDocumentationComment comment =
+          _unlinkedVariable.documentationComment;
+      return comment != null
+          ? new SourceRange(comment.offset, comment.length)
+          : null;
+    }
+    return super.docRange;
+  }
+
+  @override
+  String get documentationComment {
+    if (_unlinkedVariable != null) {
+      return _unlinkedVariable?.documentationComment?.text;
+    }
+    return super.documentationComment;
+  }
+
+  @override
   void set final2(bool isFinal) {
     assert(_unlinkedVariable == null);
     super.final2 = isFinal;
@@ -5490,6 +5737,13 @@ abstract class PropertyInducingElementImpl
    * Initialize a newly created element to have the given [name].
    */
   PropertyInducingElementImpl.forNode(Identifier name) : super.forNode(name);
+
+  /**
+   * Initialize using the given serialized information.
+   */
+  PropertyInducingElementImpl.forSerialized(
+      UnlinkedVariable unlinkedVariable, ElementImpl enclosingElement)
+      : super.forSerialized(unlinkedVariable, enclosingElement);
 }
 
 /**
@@ -5507,6 +5761,16 @@ abstract class ResynthesizerContext {
   Expression buildExpression(UnlinkedConst uc);
 
   /**
+   * Build explicit top-level property accessors.
+   */
+  UnitExplicitTopLevelAccessors buildTopLevelAccessors();
+
+  /**
+   * Build explicit top-level variables.
+   */
+  UnitExplicitTopLevelVariables buildTopLevelVariables();
+
+  /**
    * Resolve an [EntityRef] into a type.  If the reference is
    * unresolved, return [DynamicTypeImpl.instance].
    *
@@ -5571,6 +5835,13 @@ class TopLevelVariableElementImpl extends PropertyInducingElementImpl
    */
   TopLevelVariableElementImpl.forNode(Identifier name) : super.forNode(name);
 
+  /**
+   * Initialize using the given serialized information.
+   */
+  TopLevelVariableElementImpl.forSerialized(
+      UnlinkedVariable unlinkedVariable, ElementImpl enclosingElement)
+      : super.forSerialized(unlinkedVariable, enclosingElement);
+
   @override
   bool get isStatic => true;
 
@@ -5851,6 +6122,28 @@ abstract class TypeParameterizedElementMixin
 }
 
 /**
+ * Container with information about explicit top-level property accessors and
+ * corresponding implicit top-level variables.
+ */
+class UnitExplicitTopLevelAccessors {
+  final List<PropertyAccessorElementImpl> accessors =
+      <PropertyAccessorElementImpl>[];
+  final List<TopLevelVariableElementImpl> implicitVariables =
+      <TopLevelVariableElementImpl>[];
+}
+
+/**
+ * Container with information about explicit top-level variables and
+ * corresponding implicit top-level property accessors.
+ */
+class UnitExplicitTopLevelVariables {
+  final List<TopLevelVariableElementImpl> variables =
+      <TopLevelVariableElementImpl>[];
+  final List<PropertyAccessorElementImpl> implicitAccessors =
+      <PropertyAccessorElementImpl>[];
+}
+
+/**
  * A concrete implementation of a [UriReferencedElement].
  */
 abstract class UriReferencedElementImpl extends ElementImpl