Make pub strong-mode clean.

lib/src/lock_file.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.
 
 import 'dart:collection';
 
 import 'package:path/path.dart' as p;
 import 'package:package_config/packages_file.dart' as packages_file;
 import 'package:pub_semver/pub_semver.dart';
 import 'package:source_span/source_span.dart';
@@ skipping 58 matching lines @@
   /// `null`.
   static LockFile _parse(String filePath, String contents,
       SourceRegistry sources) {
     if (contents.trim() == '') return new LockFile.empty();
 
     var sourceUrl;
     if (filePath != null) sourceUrl = p.toUri(filePath);
     var parsed = loadYamlNode(contents, sourceUrl: sourceUrl);
 
     _validate(parsed is Map, 'The lockfile must be a YAML mapping.', parsed);
+    var parsedMap = parsed as YamlMap;
 
     var dartSdkConstraint = VersionConstraint.any;
     VersionConstraint flutterSdkConstraint;
-    var sdkNode = parsed.nodes['sdk'];
+    var sdkNode = parsedMap.nodes['sdk'];
     if (sdkNode != null) {
       // Lockfiles produced by pub versions from 1.14.0 through 1.18.0 included
       // a top-level "sdk" field which encoded the unified constraint on the
       // Dart SDK. They had no way of specifying constraints on other SDKs.
       dartSdkConstraint = _parseVersionConstraint(sdkNode);
-    } else if ((parsed as Map).containsKey('sdks')) {
-      var sdksField = parsed['sdks'];
+    } else if (parsedMap.containsKey('sdks')) {
+      var sdksField = parsedMap['sdks'];
       _validate(
           sdksField is Map,
           'The "sdks" field must be a mapping.',
-          parsed.nodes['sdks']);
+          parsedMap.nodes['sdks']);
 
       dartSdkConstraint = _parseVersionConstraint(sdksField.nodes['dart']);
       flutterSdkConstraint =
           _parseVersionConstraint(sdksField.nodes['flutter']);
     }
 
-    var packages = {};
-    var packageEntries = parsed['packages'];
+    var packages = <String, PackageId>{};
+    var packageEntries = parsedMap['packages'];
     if (packageEntries != null) {
       _validate(packageEntries is Map, 'The "packages" field must be a map.',
-          parsed.nodes['packages']);
+          parsedMap.nodes['packages']);
 
       packageEntries.forEach((name, spec) {
         // Parse the version.
         _validate(spec.containsKey('version'),
             'Package $name is missing a version.', spec);
         var version = new Version.parse(spec['version']);
 
         // Parse the source.
         _validate(spec.containsKey('source'),
             'Package $name is missing a source.', spec);
@@ skipping 60 matching lines @@
     throw new SourceSpanFormatException(message, node.span);
   }
 
   /// Returns a copy of this LockFile with [id] added.
   ///
   /// If there's already an ID with the same name as [id] in the LockFile, it's
   /// overwritten.
   LockFile setPackage(PackageId id) {
     if (id.isRoot) return this;
 
-    var packages = new Map.from(this.packages);
+    var packages = new Map<String, PackageId>.from(this.packages);
     packages[id.name] = id;
     return new LockFile._(packages, dartSdkConstraint, flutterSdkConstraint);
   }
 
   /// Returns a copy of this LockFile with a package named [name] removed.
   ///
   /// Returns an identical [LockFile] if there's no package named [name].
   LockFile removePackage(String name) {
     if (!this.packages.containsKey(name)) return this;
 
-    var packages = new Map.from(this.packages);
+    var packages = new Map<String, PackageId>.from(this.packages);
     packages.remove(name);
     return new LockFile._(packages, dartSdkConstraint, flutterSdkConstraint);
   }
 
   /// Returns the contents of the `.packages` file generated from this lockfile.
   ///
   /// If [entrypoint] is passed, a relative entry is added for its "lib/"
   /// directory.
   String packagesFile(SystemCache cache, [String entrypoint]) {
     var header = "Generated by pub on ${new DateTime.now()}.";
 
-    var map = new Map.fromIterable(ordered(packages.keys), value: (name) {
+    var map = new Map<String, Uri>.fromIterable(ordered(packages.keys),
+        value: (name) {
       var id = packages[name];
       var source = cache.source(id.source);
       return p.toUri(p.join(source.getDirectory(id), "lib"));
     });
 
     if (entrypoint != null) map[entrypoint] = Uri.parse("lib/");
 
     var text = new StringBuffer();
     packages_file.write(text, map, comment: header);
     return text.toString();
@@ skipping 25 matching lines @@
     }
 
     var data = {'sdks': sdks, 'packages': packageMap};
     return """
 # Generated by pub
 # See http://pub.dartlang.org/doc/glossary.html#lockfile
 ${yamlToString(data)}
 """;
   }
 }