Fix analyzer's handling of import prefixes not followed by '.'.

pkg/analyzer/test/generated/non_error_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.non_error_resolver_test;
 
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
@@ skipping 253 matching lines @@
 F f;
 main() {
   F f2 = (() => f());
 }
 ''');
     resolve(source);
     assertNoErrors(source);
     verify([source]);
   }
 
+  void test_assignment_to_field_with_same_name_as_prefix() {
+    // If p is an import prefix, then within a method body, p = expr should be
+    // considered equivalent to this.p = expr.
+    addNamedSource("/lib.dart", r'''
+library lib;
+''');
+    Source source = addSource(r'''
+import 'lib.dart' as p;
+class Base {
+  var p;
+}
+class Derived extends Base {
+  f() {
+    p = 0;
+  }
+}
+''');
+    resolve(source);
+    assertErrors(source, [HintCode.UNUSED_IMPORT]);
+    verify([source]);
+  }
+
   void test_assignmentToFinal_prefixNegate() {
     Source source = addSource(r'''
 f() {
   final x = 0;
   -x;
 }''');
     resolve(source);
     assertNoErrors(source);
     verify([source]);
   }
@@ skipping 4866 matching lines @@
 class B extends A {
   f() {
     super.m();
   }
 }''');
     resolve(source);
     assertNoErrors(source);
     verify([source]);
   }
 
+  void test_unqualified_invocation_of_method_with_same_name_as_prefix() {
+    // If p is an import prefix, then within a method body, p() should be
+    // considered equivalent to this.p().
+    addNamedSource("/lib.dart", r'''
+library lib;
+''');
+    Source source = addSource(r'''
+import 'lib.dart' as p;
+class Base {
+  p() {}
+}
+class Derived extends Base {
+  f() {
+    p();
+  }
+}
+''');
+    resolve(source);
+    assertErrors(source, [HintCode.UNUSED_IMPORT]);
+    verify([source]);
+  }
+
   void test_unqualifiedReferenceToNonLocalStaticMember_fromComment_new() {
     Source source = addSource(r'''
 class A {
   A() {}
   A.named() {}
 }
 /// [new A] or [new A.named]
 main() {
 }''');
     resolve(source);
@@ skipping 333 matching lines @@
     resolve(source);
     assertNoErrors(source);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "a");
   }
 }