Handle invalid version syntax in pubspecs.

sdk/lib/_internal/pub/test/pubspec_test.dart

 // Copyright (c) 2012, 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 pubspec_test;
 
 import 'package:unittest/unittest.dart';
 
 import '../lib/src/pubspec.dart';
 import '../lib/src/source.dart';
@@ skipping 93 matching lines @@
     });
 
     test("throws if the description isn't valid", () {
       expectFormatError('''
 dependencies:
   foo:
     mock: bad
 ''');
     });
 
+    test("throws if dependency version is not a string", () {
+      expectFormatError('''
+dependencies:
+  foo:
+    mock: ok
+    version: 1.2
+''');
+    });
+
+    test("throws if version is not a version constraint", () {
+      expectFormatError('''
+dependencies:
+  foo:
+    mock: ok
+    version: not constraint
+''');
+    });
+
     test("throws if 'name' is not a string", () {
       expectFormatError('name: [not, a, string]');
     });
 
+    test("throws if version is not a string", () {
+      expectFormatError('''
+version: 1.0
+''');
+    });
+
+    test("throws if version is not a version", () {
+      expectFormatError('''
+version: not version
+''');
+    });
+
     test("throws if 'homepage' is not a string", () {
       expectFormatError('homepage:');
       expectFormatError('homepage: [not, a, string]');
     });
 
     test("throws if 'homepage' doesn't have an HTTP scheme", () {
       new Pubspec.parse(null, 'homepage: http://ok.com', sources);
       new Pubspec.parse(null, 'homepage: https://also-ok.com', sources);
 
       expectFormatError('homepage: ftp://badscheme.com');
@@ skipping 77 matching lines @@
             equals(new VersionConstraint.parse(">=1.2.3 <2.3.4")));
       });
 
       test("throws if the sdk isn't a string", () {
         expectFormatError('''
 environment:
   sdk: []
 ''');
       });
 
+    test("throws if the sdk is not a string", () {
+      expectFormatError('''
+environment:
+  sdk: 1.0
+''');
+    });
+
       test("throws if the sdk isn't a valid version constraint", () {
         expectFormatError('''
 environment:
   sdk: "oopies"
 ''');
       });
     });
   });
 }