Revert "Library functions can never be constructors."

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

Index: sdk/lib/_internal/compiler/implementation/ssa/builder.dart
diff --git a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
index 9e2a04429aebd8a4a2a7ee9b068345a592b9d46f..5ab75da704e05bf9e84f2a2372503a048539ceee 100644
--- a/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
+++ b/sdk/lib/_internal/compiler/implementation/ssa/builder.dart
@@ -2176,25 +2176,9 @@ class SsaBuilder extends ResolvedVisitor {
             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;
       });