Revert "Library functions can never be constructors."

sdk/lib/_internal/compiler/implementation/ssa/builder.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 /// A synthetic local variable only used with the SSA graph.
 ///
 /// For instance used for holding return value of function or the exception of a
 /// try-catch statement.
@@ skipping 2158 matching lines @@
           localsHandler.closureData.capturingScopes[node];
       signature.orderedForEachParameter((ParameterElement parameterElement) {
         if (element.isGenerativeConstructorBody) {
           if (scopeData != null &&
               scopeData.isCapturedVariable(parameterElement)) {
             // The parameter will be a field in the box passed as the
             // last parameter. So no need to have it.
             return;
           }
         }
-        HInstruction newParameter =
-            localsHandler.directLocals[parameterElement];
-        if (!element.isConstructor ||
-            !(element as ConstructorElement).isRedirectingFactory) {
-          // Redirection factories must not check their argument types.
-          // Example:
-          //
-          //     class A {
-          //       A(String foo) = A.b;
-          //       A(int foo) { print(foo); }
-          //     }
-          //     main() {
-          //       new A(499);    // valid even in checked mode.
-          //       new A("foo");  // invalid in checked mode.
-          //
-          // Only the final target is allowed to check for the argument types.
-          newParameter =
-              potentiallyCheckType(newParameter, parameterElement.type);
-        }
+        HInstruction newParameter = potentiallyCheckType(
+            localsHandler.directLocals[parameterElement],
+            parameterElement.type);
         localsHandler.directLocals[parameterElement] = newParameter;
       });
 
       returnType = signature.type.returnType;
     } else {
       // Otherwise it is a lazy initializer which does not have parameters.
       assert(element is VariableElement);
     }
 
     insertTraceCall(element);
@@ skipping 4219 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.findHelper('DynamicRuntimeType');
     builder.push(new HDynamicType(type, new TypeMask.exact(cls)));
   }
 }