Remove redundant optimization from callers of `withNullability`.

Change-Id: I9b9ccd3b5c85499ac2667e864374a86b5ff1c2f9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/102000
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Commit-Queue: Paul Berry <paulberry@google.com>
diff --git a/pkg/analyzer/lib/src/dart/element/type.dart b/pkg/analyzer/lib/src/dart/element/type.dart
index b55b9e6..ec7f129 100644
--- a/pkg/analyzer/lib/src/dart/element/type.dart
+++ b/pkg/analyzer/lib/src/dart/element/type.dart
@@ -2921,6 +2921,9 @@
 
   /**
    * Return the same type, but with the given [nullabilitySuffix].
+   *
+   * If the nullability of `this` already matches [nullabilitySuffix], `this`
+   * is returned.
    */
   TypeImpl withNullability(NullabilitySuffix nullabilitySuffix);
 
diff --git a/pkg/analyzer/lib/src/summary/link.dart b/pkg/analyzer/lib/src/summary/link.dart
index e5cf09c..47692db 100644
--- a/pkg/analyzer/lib/src/summary/link.dart
+++ b/pkg/analyzer/lib/src/summary/link.dart
@@ -1463,11 +1463,7 @@
       }
     }
     var nullabilitySuffix = decodeNullabilitySuffix(entity.nullabilitySuffix);
-    var resultAsImpl = result as TypeImpl;
-    if (resultAsImpl.nullabilitySuffix != nullabilitySuffix) {
-      result = resultAsImpl.withNullability(nullabilitySuffix);
-    }
-    return result;
+    return (result as TypeImpl).withNullability(nullabilitySuffix);
   }
 
   @override
diff --git a/pkg/analyzer/lib/src/summary/resynthesize.dart b/pkg/analyzer/lib/src/summary/resynthesize.dart
index 62665a9..840947d 100644
--- a/pkg/analyzer/lib/src/summary/resynthesize.dart
+++ b/pkg/analyzer/lib/src/summary/resynthesize.dart
@@ -1401,11 +1401,7 @@
           type.implicitFunctionTypeIndices);
     }
     var nullabilitySuffix = decodeNullabilitySuffix(type.nullabilitySuffix);
-    var resultAsImpl = result as TypeImpl;
-    if (resultAsImpl.nullabilitySuffix != nullabilitySuffix) {
-      result = resultAsImpl.withNullability(nullabilitySuffix);
-    }
-    return result;
+    return (result as TypeImpl).withNullability(nullabilitySuffix);
   }
 
   @override