Fixes for AST summary generation when variables are missing.

pkg/analyzer/test/src/summary/summary_common.dart

 // Copyright (c) 2015, 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 analyzer.test.src.summary.summary_common;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
@@ skipping 4731 matching lines @@
       UnlinkedVariable e = variables.singleWhere((v) => v.name == 'e');
       _assertVariableVisible(code, e, 'on int catch (', '} // 3');
       checkTypeRef(e.type, 'dart:core', 'dart:core', 'int');
     }
     {
       UnlinkedVariable st = variables.singleWhere((v) => v.name == 'st');
       _assertVariableVisible(code, st, 'on int catch (', '} // 3');
     }
   }
 
+  test_executable_localVariables_catch_noVariables() {
+    String code = r'''
+f() {
+  try {
+    throw 42;
+  } on int {}
+}
+''';
+    UnlinkedExecutable executable = serializeExecutableText(code);
+    List<UnlinkedVariable> variables = executable.localVariables;
+    expect(variables, isEmpty);
+  }
+
   test_executable_localVariables_empty() {
     UnlinkedExecutable executable = serializeExecutableText(r'''
 f() {
 }
 ''');
     expect(executable.localVariables, isEmpty);
   }
 
   test_executable_localVariables_forEachLoop() {
     String code = r'''
@@ skipping 29 matching lines @@
       _assertVariableVisible(code, i, 'for', '} // 3');
       checkTypeRef(i.type, 'dart:core', 'dart:core', 'int');
     }
     {
       UnlinkedVariable i = variables.singleWhere((v) => v.name == 'j');
       _assertVariableVisible(code, i, 'for', '} // 3');
       checkTypeRef(i.type, 'dart:core', 'dart:core', 'int');
     }
   }
 
+  test_executable_localVariables_forLoop_noVariables() {
+    String code = r'''
+f() {
+  for (; true;) {}
+}
+''';
+    UnlinkedExecutable executable = serializeExecutableText(code);
+    List<UnlinkedVariable> variables = executable.localVariables;
+    expect(variables, isEmpty);
+  }
+
   test_executable_localVariables_inConstructor() {
     String code = r'''
 class C {
   C() { // 1
     int v;
   } // 2
 }
 ''';
     UnlinkedExecutable executable =
         findExecutable('', executables: serializeClassText(code).executables);
@@ skipping 3268 matching lines @@
 class _PrefixExpectation {
   final ReferenceKind kind;
   final String name;
   final String absoluteUri;
   final String relativeUri;
   final int numTypeParameters;
 
   _PrefixExpectation(this.kind, this.name,
       {this.absoluteUri, this.relativeUri, this.numTypeParameters: 0});
 }