Follow ClassTypeAlias constructor redirections.

pkg/analyzer/lib/src/summary/index_unit.dart

Index: pkg/analyzer/lib/src/summary/index_unit.dart
diff --git a/pkg/analyzer/lib/src/summary/index_unit.dart b/pkg/analyzer/lib/src/summary/index_unit.dart
index 1b8f329a0a28904c7db2cde48ccfafbd9968fbc9..98258b20e57f920f30878db2990368977ec791b5 100644
--- a/pkg/analyzer/lib/src/summary/index_unit.dart
+++ b/pkg/analyzer/lib/src/summary/index_unit.dart
@@ -373,14 +373,7 @@ class _IndexContributor extends GeneralizingAstVisitor {
   @override
   visitConstructorName(ConstructorName node) {
     ConstructorElement element = node.staticElement;
-    // in 'class B = A;' actually A constructors are invoked
-    // TODO(scheglov) add support for multiple levels of redirection
-    // TODO(scheglov) test for a loop of redirection
-    if (element != null &&
-        element.isSynthetic &&
-        element.redirectedConstructor != null) {
-      element = element.redirectedConstructor;
-    }
+    element = _getActualConstructorElement(element);
     // record relation
     if (node.name != null) {
       int offset = node.period.offset;
@@ -549,6 +542,33 @@ class _IndexContributor extends GeneralizingAstVisitor {
       recordSuperType(typeName, IndexRelationKind.IS_MIXED_IN_BY);
     }
   }
+
+  /**
+   * If the given [constructor] is a synthetic constructor created for a
+   * [ClassTypeAlias], return the actual constructor of a [ClassDeclaration]
+   * which is invoked.  Return `null` if a redirection cycle is detected.
+   */
+  ConstructorElement _getActualConstructorElement(
+      ConstructorElement constructor) {
+    Set<ConstructorElement> seenConstructors;
+    // follow zero or more redirections
+    while (constructor != null &&
+        constructor.isSynthetic &&
+        constructor.redirectedConstructor != null) {
+      constructor = constructor.redirectedConstructor;
+      // fail if a cycle is detected
+      if (seenConstructors?.add(constructor) == false) {
+        return null;
+      }
+      // done if no another redirection

[Paul Berry, 2016/02/29 21:28:01]

s/no another redirection/no more redirections/

+      if (constructor.redirectedConstructor == false) {

[Brian Wilkerson, 2016/02/29 21:27:18]

"false"?

Do we need this test anyway? Isn't it going to drop out of the while and then
return the constructor at the end of the method?

[Paul Berry, 2016/02/29 21:28:01]

I think you mean `== null`, not `== false`.

But I'm concerned that this bug wasn't found by unit tests.  Is it possible to
write a unit test that would have caught this bug?  If so, we should add that
test.  If not, perhaps this "if" test is not needed at all.

[scheglov, 2016/02/29 22:11:55]

Well, yes, it is going to drop out of the while on the next cycle.
But I as trying to avoid creating a new Set when we have just one redirection.
But maybe this is a premature optimization.
So, I'm removing this code and switch to always creating a new Set.

+        return constructor;
+      }
+      // delay the Set creation until we have a potential cycle
+      seenConstructors ??= new Set<ConstructorElement>();
+    }
+    return constructor;
+  }
 }
 
 /**