Add Element.aliasedType to the protocol.

R=brianwilkerson@google.com

Change-Id: I95fb2c9d50096f90913c4d6670ce0841095fe6a0
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/181443
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/doc/api.html

@@ -3764,6 +3764,12 @@ a:focus, a:hover {
           The type parameter list for the element. If the element doesn't have
           type parameters, this field will not be defined.
         </p>
+      </dd><dt class="field"><b>aliasedType: String<span style="color:#999999"> (optional)</span></b></dt><dd>
+        
+        <p>
+          If the element is a type alias, this field is the aliased type.
+          Otherwise this field will not be defined.
+        </p>
       </dd></dl></dd><dt class="typeDefinition"><a name="type_ElementDeclaration">ElementDeclaration: object</a></dt><dd>
     <p>
       A declaration - top-level (class, field, etc) or a class member (method,

pkg/analysis_server/lib/plugin/protocol/protocol_dart.dart

@@ -10,25 +10,29 @@ import 'package:path/path.dart' as pathos;
 
 /// Return a protocol [Element] corresponding to the given [engine.Element].
 Element convertElement(engine.Element element) {
+  var kind = convertElementToElementKind(element);
   var name = getElementDisplayName(element);
   var elementTypeParameters = _getTypeParametersString(element);
+  var aliasedType = getAliasedTypeString(element);
   var elementParameters = _getParametersString(element);
   var elementReturnType = getReturnTypeString(element);
-  var kind = convertElementToElementKind(element);
   return Element(
-      kind,
-      name,
-      Element.makeFlags(
-          isPrivate: element.isPrivate,
-          isDeprecated: element.hasDeprecated,
-          isAbstract: _isAbstract(element),
-          isConst: _isConst(element),
-          isFinal: _isFinal(element),
-          isStatic: _isStatic(element)),
-      location: newLocation_fromElement(element),
-      typeParameters: elementTypeParameters,
-      parameters: elementParameters,
-      returnType: elementReturnType);
+    kind,
+    name,
+    Element.makeFlags(
+      isPrivate: element.isPrivate,
+      isDeprecated: element.hasDeprecated,
+      isAbstract: _isAbstract(element),
+      isConst: _isConst(element),
+      isFinal: _isFinal(element),
+      isStatic: _isStatic(element),
+    ),
+    location: newLocation_fromElement(element),
+    typeParameters: elementTypeParameters,
+    aliasedType: aliasedType,
+    parameters: elementParameters,
+    returnType: elementReturnType,
+  );
 }
 
 /// Return a protocol [ElementKind] corresponding to the given
@@ -229,7 +233,15 @@ bool _isStatic(engine.Element element) {
 /// Sort required named parameters before optional ones.
 int _preferRequiredParams(
     engine.ParameterElement e1, engine.ParameterElement e2) {
-  var rank1 = (e1.isRequiredNamed || e1.hasRequired) ? 0 : !e1.isNamed ? -1 : 1;
-  var rank2 = (e2.isRequiredNamed || e2.hasRequired) ? 0 : !e2.isNamed ? -1 : 1;
+  var rank1 = (e1.isRequiredNamed || e1.hasRequired)
+      ? 0
+      : !e1.isNamed
+          ? -1
+          : 1;
+  var rank2 = (e2.isRequiredNamed || e2.hasRequired)
+      ? 0
+      : !e2.isNamed
+          ? -1
+          : 1;
   return rank1 - rank2;
 }

pkg/analysis_server/lib/src/protocol_server.dart

@@ -46,6 +46,14 @@ void doSourceChange_addSourceEdit(
   change.addEdit(file, isNewFile ? -1 : 0, edit);
 }
 
+String getAliasedTypeString(engine.Element element) {
+  if (element is engine.TypeAliasElement) {
+    var aliasedType = element.aliasedType;
+    return aliasedType.getDisplayString(withNullability: false);
+  }
+  return null;
+}
+
 String getReturnTypeString(engine.Element element) {
   if (element is engine.ExecutableElement) {
     if (element.kind == engine.ElementKind.SETTER) {
@@ -63,12 +71,9 @@ String getReturnTypeString(engine.Element element) {
     if (aliasedType is FunctionType) {
       var returnType = aliasedType.returnType;
       return returnType.getDisplayString(withNullability: false);
-    } else {
-      return aliasedType.getDisplayString(withNullability: false);
     }
-  } else {
-    return null;
   }
+  return null;
 }
 
 /// Translates engine errors through the ErrorProcessor.

pkg/analysis_server/test/integration/support/protocol_matchers.dart

@@ -379,6 +379,7 @@ final Matcher isDiagnosticMessage = LazyMatcher(() => MatchesJsonObject(
 ///   "parameters": optional String
 ///   "returnType": optional String
 ///   "typeParameters": optional String
+///   "aliasedType": optional String
 /// }
 final Matcher isElement = LazyMatcher(() => MatchesJsonObject('Element', {
       'kind': isElementKind,
@@ -388,7 +389,8 @@ final Matcher isElement = LazyMatcher(() => MatchesJsonObject('Element', {
       'location': isLocation,
       'parameters': isString,
       'returnType': isString,
-      'typeParameters': isString
+      'typeParameters': isString,
+      'aliasedType': isString
     }));
 
 /// ElementDeclaration

pkg/analysis_server/test/plugin/protocol_dart_test.dart

@@ -381,8 +381,9 @@ typedef F<T> = Map<int, T>;
       expect(location.startLine, 1);
       expect(location.startColumn, 9);
     }
+    expect(element.aliasedType, 'Map<int, T>');
     expect(element.parameters, isNull);
-    expect(element.returnType, 'Map<int, T>');
+    expect(element.returnType, isNull);
     expect(element.flags, 0);
   }
 

pkg/analysis_server/test/services/completion/dart/combinator_contributor_test.dart

@@ -107,8 +107,10 @@ class CombinatorContributorTest extends DartCompletionContributorTest {
     assertSuggestFunction('F1', 'PB',
         kind: CompletionSuggestionKind.IDENTIFIER);
     assertSuggestClass('Clz', kind: CompletionSuggestionKind.IDENTIFIER);
-    assertSuggestTypeAlias('F2', null,
-        kind: CompletionSuggestionKind.IDENTIFIER);
+    assertSuggestTypeAlias('F2',
+        kind: CompletionSuggestionKind.IDENTIFIER,
+        aliasedType: 'dynamic Function(int)',
+        returnType: 'dynamic');
     assertNotSuggested('C');
     assertNotSuggested('D');
     assertNotSuggested('X');

pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart

@@ -501,14 +501,17 @@ abstract class _BaseDartCompletionContributorTest extends AbstractContextTest
   }
 
   CompletionSuggestion assertSuggestTypeAlias(
-    String name,
-    String returnType, {
+    String name, {
+    String aliasedType,
+    String returnType,
     bool isDeprecated = false,
     CompletionSuggestionKind kind = CompletionSuggestionKind.INVOCATION,
   }) {
     var cs = assertSuggest(name, csKind: kind, isDeprecated: isDeprecated);
     if (returnType != null) {
       expect(cs.returnType, returnType);
+    } else if (aliasedType != null) {
+      // Just to don't fall into the next 'if'.
     } else if (isNullExpectedReturnTypeConsideredDynamic) {
       expect(cs.returnType, 'dynamic');
     } else {
@@ -524,7 +527,8 @@ abstract class _BaseDartCompletionContributorTest extends AbstractContextTest
     //    expect(param, isNotNull);
     //    expect(param[0], equals('('));
     //    expect(param[param.length - 1], equals(')'));
-    expect(element.returnType, equals(returnType ?? 'dynamic'));
+    expect(element.aliasedType, aliasedType);
+    expect(element.returnType, returnType);
     // TODO (danrubel) Determine why param info is missing
     //    assertHasParameterInfo(cs);
     return cs;

pkg/analysis_server/test/services/completion/dart/imported_reference_contributor_test.dart

@@ -2400,7 +2400,8 @@ class B extends A {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -2430,7 +2431,8 @@ class B extends A {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -2461,7 +2463,8 @@ class B extends A {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -2498,7 +2501,8 @@ main() {
 }
 ''');
     await computeSuggestions();
-    assertSuggestTypeAlias('F', 'void');
+    assertSuggestTypeAlias('F',
+        aliasedType: 'void Function()', returnType: 'void');
   }
 
   Future<void> test_functionTypeAlias_old() async {
@@ -2513,7 +2517,8 @@ main() {
 }
 ''');
     await computeSuggestions();
-    assertSuggestTypeAlias('F', 'void');
+    assertSuggestTypeAlias('F',
+        aliasedType: 'void Function()', returnType: 'void');
   }
 
   Future<void> test_IfStatement() async {
@@ -2914,7 +2919,8 @@ main() {
     // in which case suggestions will have null (unresolved) returnType
     assertSuggestTopLevelVar('T1', null);
     assertSuggestFunction('F1', null);
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -3178,7 +3184,8 @@ main() {
     // to be resolved.
     assertSuggestTopLevelVar('T1', /* null */ 'int');
     assertSuggestFunction('F1', /* null */ 'dynamic');
-    assertSuggestTypeAlias('D1', /* null */ 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -3477,7 +3484,8 @@ class B {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -3506,7 +3514,8 @@ class B {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -3535,7 +3544,8 @@ class B {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -3566,7 +3576,8 @@ class B {
     assertSuggestClass('Object');
     assertNotSuggested('T1');
     assertNotSuggested('F1');
-    assertSuggestTypeAlias('D1', 'dynamic');
+    assertSuggestTypeAlias('D1',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
@@ -4611,7 +4622,8 @@ typedef void F(^);
     expect(replacementLength, 0);
     assertSuggestClass('Object');
     assertSuggestClass('C1');
-    assertSuggestTypeAlias('T1', 'String');
+    assertSuggestTypeAlias('T1',
+        aliasedType: 'String Function(int)', returnType: 'String');
     assertNotSuggested('C2');
     assertNotSuggested('T2');
     assertNotSuggested('F1');

pkg/analysis_server/test/services/completion/dart/library_member_contributor_test.dart

@@ -238,9 +238,11 @@ main() {
     expect(replacementLength, 0);
     assertSuggestClass('X');
     assertSuggestClass('Y');
-    assertSuggestTypeAlias('TypeAliasLegacy', 'void');
-    assertSuggestTypeAlias('TypeAliasFunctionType', 'void');
-    assertSuggestTypeAlias('TypeAliasInterfaceType', 'List<int>');
+    assertSuggestTypeAlias('TypeAliasLegacy',
+        aliasedType: 'void Function()', returnType: 'void');
+    assertSuggestTypeAlias('TypeAliasFunctionType',
+        aliasedType: 'void Function()', returnType: 'void');
+    assertSuggestTypeAlias('TypeAliasInterfaceType', aliasedType: 'List<int>');
     assertNotSuggested('T1');
     assertNotSuggested('T2');
     assertNotSuggested('Object');

pkg/analysis_server/test/services/completion/dart/local_library_contributor_test.dart

@@ -229,9 +229,11 @@ void f() {^}
     }
     assertSuggestFunction('af', 'int');
     assertSuggestTopLevelVar('m', null);
-    assertSuggestTypeAlias('t1', null);
-    assertSuggestTypeAlias('t2', 'void');
-    assertSuggestTypeAlias('t3', 'List<int>');
+    assertSuggestTypeAlias('t1',
+        aliasedType: 'dynamic Function(int)', returnType: 'dynamic');
+    assertSuggestTypeAlias('t2',
+        aliasedType: 'void Function(int)', returnType: 'void');
+    assertSuggestTypeAlias('t3', aliasedType: 'List<int>');
     assertNotSuggested('a1');
     assertNotSuggested('a2');
     // Suggested by LocalConstructorContributor
@@ -274,7 +276,8 @@ void f() {^}
     }
     assertSuggestFunction('bf', 'int');
     assertSuggestTopLevelVar('n', null);
-    assertSuggestTypeAlias('t1', null);
+    assertSuggestTypeAlias('t1',
+        aliasedType: 'dynamic Function(int)', returnType: 'dynamic');
     assertNotSuggested('b1');
     assertNotSuggested('b2');
     // Suggested by ConstructorContributor

pkg/analysis_server/test/services/completion/dart/local_reference_contributor_test.dart

@@ -2588,7 +2588,8 @@ class C {foo(){^} void bar() {}}''');
     assertSuggestClass('C');
     assertSuggestMethod('foo', 'C', null);
     assertSuggestMethod('bar', 'C', 'void');
-    assertSuggestTypeAlias('F2', 'int');
+    assertSuggestTypeAlias('F2',
+        aliasedType: 'int Function(int)', returnType: 'int');
     assertSuggestClass('Clz');
     assertSuggestClass('C');
     assertNotSuggested('x');
@@ -3242,7 +3243,8 @@ class C2 { }
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -3272,7 +3274,8 @@ class C2 { }
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -3303,7 +3306,8 @@ class C2 { }
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -3870,7 +3874,8 @@ main() {String name; print("hello \${^}");}''');
     assertNotSuggested('C1');
     assertSuggestTopLevelVar('T2', 'int');
     assertSuggestFunction('F2', null);
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertSuggestLocalVariable('name', 'String');
   }
@@ -4218,7 +4223,8 @@ foo = {^''');
     assertNotSuggested('C1');
     assertSuggestTopLevelVar('T2', 'int');
     assertSuggestFunction('F2', null);
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
   }
 
@@ -4767,7 +4773,8 @@ class C2 {^ zoo(z) { } String name; }''');
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -4796,7 +4803,8 @@ class C2 {/* */ ^ zoo(z) { } String name; }''');
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -4825,7 +4833,8 @@ class C2 {/** */ ^ zoo(z) { } String name; }''');
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -4856,7 +4865,8 @@ class C2 {
     assertNotSuggested('C1');
     assertNotSuggested('T2');
     assertNotSuggested('F2');
-    assertSuggestTypeAlias('D2', 'dynamic');
+    assertSuggestTypeAlias('D2',
+        aliasedType: 'dynamic Function()', returnType: 'dynamic');
     assertSuggestClass('C2');
     assertNotSuggested('name');
   }
@@ -6035,7 +6045,8 @@ main() {
 }
 ''');
     await computeSuggestions();
-    assertSuggestTypeAlias('F', 'void');
+    assertSuggestTypeAlias('F',
+        aliasedType: 'void Function()', returnType: 'void');
   }
 
   Future<void> test_typeAlias_interfaceType() async {
@@ -6046,7 +6057,7 @@ main() {
 }
 ''');
     await computeSuggestions();
-    assertSuggestTypeAlias('F', 'List<int>');
+    assertSuggestTypeAlias('F', aliasedType: 'List<int>');
   }
 
   Future<void> test_typeAlias_legacy() async {
@@ -6057,7 +6068,8 @@ main() {
 }
 ''');
     await computeSuggestions();
-    assertSuggestTypeAlias('F', 'void');
+    assertSuggestTypeAlias('F',
+        aliasedType: 'void Function()', returnType: 'void');
   }
 
   Future<void> test_TypeArgumentList() async {
@@ -6081,7 +6093,8 @@ main() { C<^> c; }''');
     assertNotSuggested('C1');
     assertNotSuggested('T1');
     assertSuggestClass('C2');
-    assertSuggestTypeAlias('T2', 'int');
+    assertSuggestTypeAlias('T2',
+        aliasedType: 'int Function(int)', returnType: 'int');
     assertNotSuggested('F1');
     assertNotSuggested('F2');
   }

pkg/analysis_server/tool/spec/generated/java/types/Element.java

@@ -94,10 +94,16 @@ public class Element {
    */
   private final String typeParameters;
 
+  /**
+   * If the element is a type alias, this field is the aliased type. Otherwise this field will not be
+   * defined.
+   */
+  private final String aliasedType;
+
   /**
    * Constructor for {@link Element}.
    */
-  public Element(String kind, String name, Location location, int flags, String parameters, String returnType, String typeParameters) {
+  public Element(String kind, String name, Location location, int flags, String parameters, String returnType, String typeParameters, String aliasedType) {
     this.kind = kind;
     this.name = name;
     this.location = location;
@@ -105,6 +111,7 @@ public class Element {
     this.parameters = parameters;
     this.returnType = returnType;
     this.typeParameters = typeParameters;
+    this.aliasedType = aliasedType;
   }
 
   @Override
@@ -118,7 +125,8 @@ public class Element {
         other.flags == flags &&
         ObjectUtilities.equals(other.parameters, parameters) &&
         ObjectUtilities.equals(other.returnType, returnType) &&
-        ObjectUtilities.equals(other.typeParameters, typeParameters);
+        ObjectUtilities.equals(other.typeParameters, typeParameters) &&
+        ObjectUtilities.equals(other.aliasedType, aliasedType);
     }
     return false;
   }
@@ -131,7 +139,8 @@ public class Element {
     String parameters = jsonObject.get("parameters") == null ? null : jsonObject.get("parameters").getAsString();
     String returnType = jsonObject.get("returnType") == null ? null : jsonObject.get("returnType").getAsString();
     String typeParameters = jsonObject.get("typeParameters") == null ? null : jsonObject.get("typeParameters").getAsString();
-    return new Element(kind, name, location, flags, parameters, returnType, typeParameters);
+    String aliasedType = jsonObject.get("aliasedType") == null ? null : jsonObject.get("aliasedType").getAsString();
+    return new Element(kind, name, location, flags, parameters, returnType, typeParameters, aliasedType);
   }
 
   public static List<Element> fromJsonArray(JsonArray jsonArray) {
@@ -146,6 +155,14 @@ public class Element {
     return list;
   }
 
+  /**
+   * If the element is a type alias, this field is the aliased type. Otherwise this field will not be
+   * defined.
+   */
+  public String getAliasedType() {
+    return aliasedType;
+  }
+
   /**
    * A bit-map containing the following flags:
    *
@@ -217,6 +234,7 @@ public class Element {
     builder.append(parameters);
     builder.append(returnType);
     builder.append(typeParameters);
+    builder.append(aliasedType);
     return builder.toHashCode();
   }
 
@@ -261,6 +279,9 @@ public class Element {
     if (typeParameters != null) {
       jsonObject.addProperty("typeParameters", typeParameters);
     }
+    if (aliasedType != null) {
+      jsonObject.addProperty("aliasedType", aliasedType);
+    }
     return jsonObject;
   }
 
@@ -281,7 +302,9 @@ public class Element {
     builder.append("returnType=");
     builder.append(returnType + ", ");
     builder.append("typeParameters=");
-    builder.append(typeParameters);
+    builder.append(typeParameters + ", ");
+    builder.append("aliasedType=");
+    builder.append(aliasedType);
     builder.append("]");
     return builder.toString();
   }

pkg/analysis_server_client/lib/src/protocol/protocol_common.dart

@@ -1435,6 +1435,7 @@ class DiagnosticMessage implements HasToJson {
 ///   "parameters": optional String
 ///   "returnType": optional String
 ///   "typeParameters": optional String
+///   "aliasedType": optional String
 /// }
 ///
 /// Clients may not extend, implement or mix-in this class.
@@ -1477,6 +1478,8 @@ class Element implements HasToJson {
 
   String _typeParameters;
 
+  String _aliasedType;
+
   /// The kind of the element.
   ElementKind get kind => _kind;
 
@@ -1566,11 +1569,22 @@ class Element implements HasToJson {
     _typeParameters = value;
   }
 
+  /// If the element is a type alias, this field is the aliased type. Otherwise
+  /// this field will not be defined.
+  String get aliasedType => _aliasedType;
+
+  /// If the element is a type alias, this field is the aliased type. Otherwise
+  /// this field will not be defined.
+  set aliasedType(String value) {
+    _aliasedType = value;
+  }
+
   Element(ElementKind kind, String name, int flags,
       {Location location,
       String parameters,
       String returnType,
-      String typeParameters}) {
+      String typeParameters,
+      String aliasedType}) {
     this.kind = kind;
     this.name = name;
     this.location = location;
@@ -1578,6 +1592,7 @@ class Element implements HasToJson {
     this.parameters = parameters;
     this.returnType = returnType;
     this.typeParameters = typeParameters;
+    this.aliasedType = aliasedType;
   }
 
   factory Element.fromJson(
@@ -1623,11 +1638,17 @@ class Element implements HasToJson {
         typeParameters = jsonDecoder.decodeString(
             jsonPath + '.typeParameters', json['typeParameters']);
       }
+      String aliasedType;
+      if (json.containsKey('aliasedType')) {
+        aliasedType = jsonDecoder.decodeString(
+            jsonPath + '.aliasedType', json['aliasedType']);
+      }
       return Element(kind, name, flags,
           location: location,
           parameters: parameters,
           returnType: returnType,
-          typeParameters: typeParameters);
+          typeParameters: typeParameters,
+          aliasedType: aliasedType);
     } else {
       throw jsonDecoder.mismatch(jsonPath, 'Element', json);
     }
@@ -1658,6 +1679,9 @@ class Element implements HasToJson {
     if (typeParameters != null) {
       result['typeParameters'] = typeParameters;
     }
+    if (aliasedType != null) {
+      result['aliasedType'] = aliasedType;
+    }
     return result;
   }
 
@@ -1673,7 +1697,8 @@ class Element implements HasToJson {
           flags == other.flags &&
           parameters == other.parameters &&
           returnType == other.returnType &&
-          typeParameters == other.typeParameters;
+          typeParameters == other.typeParameters &&
+          aliasedType == other.aliasedType;
     }
     return false;
   }
@@ -1688,6 +1713,7 @@ class Element implements HasToJson {
     hash = JenkinsSmiHash.combine(hash, parameters.hashCode);
     hash = JenkinsSmiHash.combine(hash, returnType.hashCode);
     hash = JenkinsSmiHash.combine(hash, typeParameters.hashCode);
+    hash = JenkinsSmiHash.combine(hash, aliasedType.hashCode);
     return JenkinsSmiHash.finish(hash);
   }
 }

pkg/analyzer_plugin/doc/api.html

@@ -1289,6 +1289,12 @@ a:focus, a:hover {
           The type parameter list for the element. If the element doesn't have
           type parameters, this field will not be defined.
         </p>
+      </dd><dt class="field"><b>aliasedType: String<span style="color:#999999"> (optional)</span></b></dt><dd>
+        
+        <p>
+          If the element is a type alias, this field is the aliased type.
+          Otherwise this field will not be defined.
+        </p>
       </dd></dl></dd><dt class="typeDefinition"><a name="type_ElementKind">ElementKind: String</a></dt><dd>
     <p>
       An enumeration of the kinds of elements.

pkg/analyzer_plugin/lib/protocol/protocol_common.dart

@@ -1435,6 +1435,7 @@ class DiagnosticMessage implements HasToJson {
 ///   "parameters": optional String
 ///   "returnType": optional String
 ///   "typeParameters": optional String
+///   "aliasedType": optional String
 /// }
 ///
 /// Clients may not extend, implement or mix-in this class.
@@ -1477,6 +1478,8 @@ class Element implements HasToJson {
 
   String _typeParameters;
 
+  String _aliasedType;
+
   /// The kind of the element.
   ElementKind get kind => _kind;
 
@@ -1566,11 +1569,22 @@ class Element implements HasToJson {
     _typeParameters = value;
   }
 
+  /// If the element is a type alias, this field is the aliased type. Otherwise
+  /// this field will not be defined.
+  String get aliasedType => _aliasedType;
+
+  /// If the element is a type alias, this field is the aliased type. Otherwise
+  /// this field will not be defined.
+  set aliasedType(String value) {
+    _aliasedType = value;
+  }
+
   Element(ElementKind kind, String name, int flags,
       {Location location,
       String parameters,
       String returnType,
-      String typeParameters}) {
+      String typeParameters,
+      String aliasedType}) {
     this.kind = kind;
     this.name = name;
     this.location = location;
@@ -1578,6 +1592,7 @@ class Element implements HasToJson {
     this.parameters = parameters;
     this.returnType = returnType;
     this.typeParameters = typeParameters;
+    this.aliasedType = aliasedType;
   }
 
   factory Element.fromJson(
@@ -1623,11 +1638,17 @@ class Element implements HasToJson {
         typeParameters = jsonDecoder.decodeString(
             jsonPath + '.typeParameters', json['typeParameters']);
       }
+      String aliasedType;
+      if (json.containsKey('aliasedType')) {
+        aliasedType = jsonDecoder.decodeString(
+            jsonPath + '.aliasedType', json['aliasedType']);
+      }
       return Element(kind, name, flags,
           location: location,
           parameters: parameters,
           returnType: returnType,
-          typeParameters: typeParameters);
+          typeParameters: typeParameters,
+          aliasedType: aliasedType);
     } else {
       throw jsonDecoder.mismatch(jsonPath, 'Element', json);
     }
@@ -1658,6 +1679,9 @@ class Element implements HasToJson {
     if (typeParameters != null) {
       result['typeParameters'] = typeParameters;
     }
+    if (aliasedType != null) {
+      result['aliasedType'] = aliasedType;
+    }
     return result;
   }
 
@@ -1673,7 +1697,8 @@ class Element implements HasToJson {
           flags == other.flags &&
           parameters == other.parameters &&
           returnType == other.returnType &&
-          typeParameters == other.typeParameters;
+          typeParameters == other.typeParameters &&
+          aliasedType == other.aliasedType;
     }
     return false;
   }
@@ -1688,6 +1713,7 @@ class Element implements HasToJson {
     hash = JenkinsSmiHash.combine(hash, parameters.hashCode);
     hash = JenkinsSmiHash.combine(hash, returnType.hashCode);
     hash = JenkinsSmiHash.combine(hash, typeParameters.hashCode);
+    hash = JenkinsSmiHash.combine(hash, aliasedType.hashCode);
     return JenkinsSmiHash.finish(hash);
   }
 }

pkg/analyzer_plugin/lib/utilities/analyzer_converter.dart

@@ -111,19 +111,22 @@ class AnalyzerConverter {
   plugin.Element convertElement(analyzer.Element element) {
     var kind = _convertElementToElementKind(element);
     return plugin.Element(
-        kind,
-        element.displayName,
-        plugin.Element.makeFlags(
-            isPrivate: element.isPrivate,
-            isDeprecated: element.hasDeprecated,
-            isAbstract: _isAbstract(element),
-            isConst: _isConst(element),
-            isFinal: _isFinal(element),
-            isStatic: _isStatic(element)),
-        location: locationFromElement(element),
-        typeParameters: _getTypeParametersString(element),
-        parameters: _getParametersString(element),
-        returnType: _getReturnTypeString(element));
+      kind,
+      element.displayName,
+      plugin.Element.makeFlags(
+        isPrivate: element.isPrivate,
+        isDeprecated: element.hasDeprecated,
+        isAbstract: _isAbstract(element),
+        isConst: _isConst(element),
+        isFinal: _isFinal(element),
+        isStatic: _isStatic(element),
+      ),
+      location: locationFromElement(element),
+      typeParameters: _getTypeParametersString(element),
+      aliasedType: _getAliasedTypeString(element),
+      parameters: _getParametersString(element),
+      returnType: _getReturnTypeString(element),
+    );
   }
 
   /// Convert the element [kind] from the 'analyzer' package to an element kind
@@ -224,6 +227,14 @@ class AnalyzerConverter {
     return convertElementKind(element.kind);
   }
 
+  String _getAliasedTypeString(analyzer.Element element) {
+    if (element is analyzer.TypeAliasElement) {
+      var aliasedType = element.aliasedType;
+      return aliasedType.getDisplayString(withNullability: false);
+    }
+    return null;
+  }
+
   /// Return a textual representation of the parameters of the given [element],
   /// or `null` if the element does not have any parameters.
   String _getParametersString(analyzer.Element element) {
@@ -288,8 +299,6 @@ class AnalyzerConverter {
       if (aliasedType is FunctionType) {
         var returnType = aliasedType.returnType;
         return returnType.getDisplayString(withNullability: false);
-      } else {
-        return aliasedType.getDisplayString(withNullability: false);
       }
     }
     return null;

pkg/analyzer_plugin/test/integration/support/protocol_matchers.dart

@@ -221,6 +221,7 @@ final Matcher isDiagnosticMessage = LazyMatcher(() => MatchesJsonObject(
 ///   "parameters": optional String
 ///   "returnType": optional String
 ///   "typeParameters": optional String
+///   "aliasedType": optional String
 /// }
 final Matcher isElement = LazyMatcher(() => MatchesJsonObject('Element', {
       'kind': isElementKind,
@@ -230,7 +231,8 @@ final Matcher isElement = LazyMatcher(() => MatchesJsonObject('Element', {
       'location': isLocation,
       'parameters': isString,
       'returnType': isString,
-      'typeParameters': isString
+      'typeParameters': isString,
+      'aliasedType': isString
     }));
 
 /// ElementKind

pkg/analyzer_plugin/test/utilities/analyzer_converter_test.dart

@@ -604,8 +604,9 @@ typedef A<T> = Map<int, T>;
       expect(location.startLine, 1);
       expect(location.startColumn, 9);
     }
+    expect(element.aliasedType, 'Map<int, T>');
     expect(element.parameters, isNull);
-    expect(element.returnType, 'Map<int, T>');
+    expect(element.returnType, isNull);
     expect(element.flags, 0);
   }
 

pkg/analyzer_plugin/tool/spec/common_types_spec.html

@@ -520,6 +520,13 @@
           type parameters, this field will not be defined.
         </p>
       </field>
+      <field name="aliasedType" optional="true">
+        <ref>String</ref>
+        <p>
+          If the element is a type alias, this field is the aliased type.
+          Otherwise this field will not be defined.
+        </p>
+      </field>
     </object>
   </type>
   <type name="ElementKind">