Fix #29130: only consider classes allocated with generative constructors as potential closures

pkg/compiler/lib/src/inferrer/inferrer_engine.dart

 // 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.
 
 import 'package:kernel/ast.dart' as ir;
 
 import '../common.dart';
 import '../common/names.dart';
 import '../compiler.dart';
 import '../constants/expressions.dart';
@@ skipping 364 matching lines @@
 
       if (info is ClosureTypeInformation) {
         Iterable<FunctionElement> elements = [info.element];
         trace(elements, new ClosureTracerVisitor(elements, info, this));
       } else if (info is CallSiteTypeInformation) {
         if (info is StaticCallSiteTypeInformation &&
             info.selector != null &&
             info.selector.isCall) {
           // This is a constructor call to a class with a call method. So we
           // need to trace the call method here.
-          assert(info.calledElement.isConstructor);
+          assert(info.calledElement.isGenerativeConstructor);
           ClassElement cls = info.calledElement.enclosingClass;
           FunctionElement callMethod = cls.lookupMember(Identifiers.call);
           assert(invariant(cls, callMethod != null));
           Iterable<FunctionElement> elements = [callMethod];
           trace(elements, new ClosureTracerVisitor(elements, info, this));
         } else {
           // We only are interested in functions here, as other targets
           // of this closure call are not a root to trace but an intermediate
           // for some other function.
           Iterable<FunctionElement> elements = new List<FunctionElement>.from(
@@ skipping 441 matching lines @@
         types.currentMember,
         node,
         caller,
         callee,
         selector,
         mask,
         arguments,
         inLoop);
     // If this class has a 'call' method then we have essentially created a
     // closure here. Register it as such so that it is traced.
-    if (selector != null && selector.isCall && callee.isConstructor) {
+    // Note: we exclude factory constructors because they don't always create an
+    // instance of the type. They are static methods that delegate to some other
+    // generative constructor to do the actual creation of the object.
+    if (selector != null && selector.isCall && callee.isGenerativeConstructor) {
       ClassElement cls = callee.enclosingClass;
       if (cls.callType != null) {
         types.allocatedClosures.add(info);
       }
     }
     info.addToGraph(this);
     types.allocatedCalls.add(info);
     updateSideEffects(sideEffects, selector, callee);
     return info;
   }
@@ skipping 195 matching lines @@
   /**
    * Records that the captured variable [local] is read.
    */
   void recordCapturedLocalRead(Local local) {}
 
   /**
    * Records that the variable [local] is being updated.
    */
   void recordLocalUpdate(Local local, TypeInformation type) {}
 }