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

pkg/analyzer/test/generated/compile_time_error_code_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.compile_time_error_code_test;
 
+import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:unittest/unittest.dart' as _ut;
 
 import '../reflective_tests.dart';
 import 'resolver_test.dart';
 
 main() {
   _ut.groupSep = ' | ';
@@ skipping 4542 matching lines @@
   void test_partOfNonPart() {
     Source source = addSource(r'''
 library l1;
 part 'l2.dart';''');
     addNamedSource("/l2.dart", "library l2;");
     resolve(source);
     assertErrors(source, [CompileTimeErrorCode.PART_OF_NON_PART]);
     verify([source]);
   }
 
+  void test_prefix_conditionalPropertyAccess_call() {
+    AnalysisOptionsImpl options = new AnalysisOptionsImpl();
+    options.enableNullAwareOperators = true;
+    resetWithOptions(options);
+    addNamedSource('/lib.dart', '''
+library lib;
+g() {}
+''');
+    Source source = addSource('''
+import 'lib.dart' as p;
+f() {
+  p?.g();
+}
+''');
+    resolve(source);
+    assertErrors(
+        source, [CompileTimeErrorCode.PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT]);
+    verify([source]);
+  }
+
   void test_prefixCollidesWithTopLevelMembers_functionTypeAlias() {
     addNamedSource("/lib.dart", r'''
 library lib;
 class A{}''');
     Source source = addSource(r'''
 import 'lib.dart' as p;
 typedef p();
 p.A a;''');
     resolve(source);
     assertErrors(
@@ skipping 36 matching lines @@
     Source source = addSource(r'''
 import 'lib.dart' as p;
 class p {}
 p.A a;''');
     resolve(source);
     assertErrors(
         source, [CompileTimeErrorCode.PREFIX_COLLIDES_WITH_TOP_LEVEL_MEMBER]);
     verify([source]);
   }
 
+  void test_prefixNotFollowedByDot() {
+    addNamedSource('/lib.dart', 'library lib;');
+    Source source = addSource('''
+import 'lib.dart' as p;
+f() {
+  return p;
+}
+''');
+    resolve(source);
+    assertErrors(
+        source, [CompileTimeErrorCode.PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT]);
+    verify([source]);
+  }
+
+  void test_prefixNotFollowedByDot_compoundAssignment() {
+    addNamedSource('/lib.dart', 'library lib;');
+    Source source = addSource('''
+import 'lib.dart' as p;
+f() {
+  p += 1;
+}
+''');
+    resolve(source);
+    assertErrors(
+        source, [CompileTimeErrorCode.PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT]);
+    verify([source]);
+  }
+
+  void test_prefixNotFollowedByDot_conditionalMethodInvocation() {
+    AnalysisOptionsImpl options = new AnalysisOptionsImpl();
+    options.enableNullAwareOperators = true;
+    resetWithOptions(options);
+    addNamedSource('/lib.dart', '''
+library lib;
+g() {}
+''');
+    Source source = addSource('''
+import 'lib.dart' as p;
+f() {
+  p?.g();
+}
+''');
+    resolve(source);
+    assertErrors(
+        source, [CompileTimeErrorCode.PREFIX_IDENTIFIER_NOT_FOLLOWED_BY_DOT]);
+    verify([source]);
+  }
+
   void test_privateOptionalParameter() {
     Source source = addSource("f({var _p}) {}");
     resolve(source);
     assertErrors(source, [CompileTimeErrorCode.PRIVATE_OPTIONAL_PARAMETER]);
     verify([source]);
   }
 
   void test_privateOptionalParameter_fieldFormal() {
     Source source = addSource(r'''
 class A {
@@ skipping 1105 matching lines @@
         source, [CompileTimeErrorCode.WRONG_NUMBER_OF_PARAMETERS_FOR_OPERATOR]);
     verify([source]);
     reset();
   }
 
   void _check_wrongNumberOfParametersForOperator1(String name) {
     _check_wrongNumberOfParametersForOperator(name, "");
     _check_wrongNumberOfParametersForOperator(name, "a, b");
   }
 }