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

pkg/analyzer/test/generated/compile_time_error_code_test.dart

Index: pkg/analyzer/test/generated/compile_time_error_code_test.dart
diff --git a/pkg/analyzer/test/generated/compile_time_error_code_test.dart b/pkg/analyzer/test/generated/compile_time_error_code_test.dart
index abea165f789d5dede42bcc438a13f4188918165c..4994f395b403c75036481505f9b89703df30bee5 100644
--- a/pkg/analyzer/test/generated/compile_time_error_code_test.dart
+++ b/pkg/analyzer/test/generated/compile_time_error_code_test.dart
@@ -4,6 +4,7 @@
 
 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';
@@ -4566,6 +4567,26 @@ part 'l2.dart';''');
     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;
@@ -4622,6 +4643,54 @@ p.A a;''');
     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);