Enable strong mode in DDC, fix all warnings/errors

lib/src/analyzer/context.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.
 
 import 'package:args/args.dart' show ArgParser, ArgResults;
+import 'package:analyzer/src/context/context.dart' show AnalysisContextImpl;
 import 'package:analyzer/src/generated/engine.dart'
     show AnalysisContext, AnalysisEngine, AnalysisOptionsImpl;
 import 'package:analyzer/src/generated/java_io.dart' show JavaFile;
 import 'package:analyzer/src/generated/sdk_io.dart' show DirectoryBasedDartSdk;
 import 'package:analyzer/src/generated/source_io.dart'
     show
         CustomUriResolver,
         DartUriResolver,
         FileUriResolver,
         PackageUriResolver,
@@ skipping 40 matching lines @@
       {this.summaryPaths: const [],
       this.useMockSdk: false,
       String dartSdkPath,
       this.dartSdkSummaryPath,
       this.customUrlMappings: const {},
       this.packageRoot: 'packages/',
       this.packagePaths: const []})
       : dartSdkPath = dartSdkPath ?? getSdkDir().path;
 
   AnalyzerOptions.fromArguments(ArgResults args)
-      : summaryPaths = args['summary'],
+      : summaryPaths = args['summary'] as List<String>,
         useMockSdk = false,
         dartSdkPath = args['dart-sdk'] ?? getSdkDir().path,
         dartSdkSummaryPath = args['dart-sdk-summary'],
         customUrlMappings = _parseUrlMappings(args['url-mapping']),
         packageRoot = args['package-root'],
-        packagePaths = args['package-paths']?.split(',') ?? [];
+        packagePaths = (args['package-paths'] as String)?.split(',') ?? [];
 
   /// Whether to resolve 'package:' uris using the multi-package resolver.
   bool get useMultiPackage => packagePaths.isNotEmpty;
 
   static ArgParser addArguments(ArgParser parser) {
     return parser
       ..addOption('summary',
           abbr: 's', help: 'summary file(s) to include', allowMultiple: true)
       ..addOption('dart-sdk', help: 'Dart SDK Path', defaultsTo: null)
       ..addOption('dart-sdk-summary',
@@ skipping 48 matching lines @@
   context.sourceFactory = srcFactory;
   if (summaryData != null) {
     context.typeProvider = sdkResolver.dartSdk.context.typeProvider;
     context.resultProvider =
         new InputPackagesResultProvider(context, summaryData);
   }
   return context;
 }
 
 /// Creates an analysis context that contains our restricted typing rules.
-AnalysisContext createAnalysisContext() {
+AnalysisContextImpl createAnalysisContext() {
   var res = AnalysisEngine.instance.createAnalysisContext();
   res.analysisOptions = new AnalysisOptionsImpl()..strongMode = true;
   return res;
 }
 
 /// Creates a SourceFactory configured by the [options].
 ///
 /// Use [options.useMockSdk] to specify the SDK mode, or use [sdkResolver]
 /// to entirely override the DartUriResolver.
 ///
@@ skipping 38 matching lines @@
   return sdk;
 }
 
 /// Creates a [DartUriResolver] that uses the SDK at the given [sdkPath].
 DartUriResolver createSdkPathResolver(String sdkSummaryPath, String sdkPath) {
   var sdk = (sdkSummaryPath != null)
       ? new SummaryBasedDartSdk(sdkSummaryPath, true)
       : _createDirectoryBasedDartSdk(sdkPath);
   return new DartUriResolver(sdk);
 }