Issue 23409. Don't set 'propagatedType' in (vs. after) 'name is Type'.

pkg/analyzer/test/generated/resolver_test.dart

 // Copyright (c) 2014, 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.
 
 library engine.resolver_test;
 
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 12393 matching lines @@
   if (p is A) {
     return p;
   } else {
     return null;
   }
 }''');
     LibraryElement library = resolve(source);
     assertNoErrors(source);
     verify([source]);
     CompilationUnit unit = resolveCompilationUnit(source, library);
-    ClassDeclaration classA = unit.declarations[0] as ClassDeclaration;
-    InterfaceType typeA = classA.element.type;
+    // prepare A
+    InterfaceType typeA;
+    {
+      ClassDeclaration classA = unit.declarations[0] as ClassDeclaration;
+      typeA = classA.element.type;
+    }
+    // verify "f"
     FunctionDeclaration function = unit.declarations[1] as FunctionDeclaration;
     BlockFunctionBody body =
         function.functionExpression.body as BlockFunctionBody;
     IfStatement ifStatement = body.block.statements[0] as IfStatement;
-    ReturnStatement statement =
-        (ifStatement.thenStatement as Block).statements[0] as ReturnStatement;
-    SimpleIdentifier variableName = statement.expression as SimpleIdentifier;
-    expect(variableName.propagatedType, same(typeA));
+    // "p is A"
+    {
+      IsExpression isExpression = ifStatement.condition;
+      SimpleIdentifier variableName = isExpression.expression;
+      expect(variableName.propagatedType, isNull);
+    }
+    // "return p;"
+    {
+      ReturnStatement statement =
+          (ifStatement.thenStatement as Block).statements[0] as ReturnStatement;
+      SimpleIdentifier variableName = statement.expression as SimpleIdentifier;
+      expect(variableName.propagatedType, same(typeA));
+    }
   }
 
   void test_is_if_lessSpecific() {
     Source source = addSource(r'''
 class A {}
 A f(A p) {
   if (p is String) {
     return p;
   } else {
     return null;
@@ skipping 1363 matching lines @@
         // check propagated type
         FunctionType propagatedType = node.propagatedType as FunctionType;
         expect(propagatedType.returnType, test.typeProvider.stringType);
       } on AnalysisException catch (e, stackTrace) {
         thrownException[0] = new CaughtException(e, stackTrace);
       }
     }
     return null;
   }
 }