Handle type-inference on fields, consts, and inferable overrides

lib/src/options.dart

 // Copyright (c) 2014, 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.
 
 /// Set of flags and options passed to the compiler
 library dev_compiler.src.options;
 
 import 'dart:io';
 
 import 'package:args/args.dart';
 import 'package:cli_util/cli_util.dart' show getSdkDir;
 import 'package:dev_compiler/config.dart';
 import 'package:logging/logging.dart' show Level;
 
 /// Options used by our TypeResolver.
 class ResolverOptions {
   /// Whether to resolve 'package:' uris using the multi-package resolver.
   final bool useMultiPackage;
 
   /// Package root when resolving 'package:' urls the standard way.
   final String packageRoot;
 
   /// List of paths used for the multi-package resolver.
   final List<String> packagePaths;
 
   /// Whether to infer return types and field types from overriden members.
   final bool inferFromOverrides;
   static const inferFromOverridesDefault = false;
 
-  /// Whether to infer types for consts and static fields by looking at
-  /// identifiers on the RHS. For example, in a constant declaration like:
+  /// Whether to infer types for consts and fields by looking at initializers on
+  /// the RHS. For example, in a constant declaration like:
   ///
   ///      const A = B;
   ///
   /// We can infer the type of `A` based on the type of `B`. The current
-  /// implementation of this inference is limited and will only work if `B` is
-  /// defined in a different library than `A`. Because this might be surprising
-  /// to users, this is turned off by default.
+  /// implementation of this inference is limited to ensure the answer is
+  /// deterministic when applying inference on library cycles. In the example
+  /// above, `A` is inferred to have `B`'s declared type if they are both in the
+  /// same library cycle. However, if `B`'s definition is not in the same
+  /// connected component as `A`, we use `B`'s inferred type instead.
+  ///
+  /// Because this might be surprising to users, this is turned off by default.
+  /// In the future, inference might track dependencies between variables in
+  /// more detail so that, in the example above, we can use `B`'s inferred type
+  /// always.
   final bool inferStaticsFromIdentifiers;
   static const inferStaticsFromIdentifiersDefault = false;
 
-  /// Whether to ignore ordering issues and do a best effort in inference. When
-  /// false, inference of top-levels and statics is limited to only consider
-  /// expressions in the RHS for which the type is known precisely without
-  /// regard of the ordering in which we apply inference. Turning this flag on
-  /// will consider more expressions, including expressions where the RHS is
-  /// another identifier (which [inferStaticsFromIdentifiers]).
-  ///
-  /// Note: this option is experimental will be removed once we have a proper
-  /// implementation of inference in the future, which should handle all
-  /// ordering concerns.
-  final bool inferInNonStableOrder;
-  static const inferInNonStableOrderDefault = false;
-
   /// Restrict inference of fields and top-levels to those that are final and
   /// const.
   final bool onlyInferConstsAndFinalFields;
   static const onlyInferConstAndFinalFieldsDefault = false;
 
   ResolverOptions({this.useMultiPackage: false, this.packageRoot: 'packages/',
       this.packagePaths: const <String>[],
       this.inferFromOverrides: inferFromOverridesDefault,
       this.inferStaticsFromIdentifiers: inferStaticsFromIdentifiersDefault,
-      this.inferInNonStableOrder: inferInNonStableOrderDefault,
       this.onlyInferConstsAndFinalFields: onlyInferConstAndFinalFieldsDefault});
 }
 
 // TODO(vsm): Merge RulesOptions and TypeOptions
 /// Options used by our RestrictedRules.
 class RulesOptions extends TypeOptions {
   /// Whether to allow casts in constant contexts.
   final bool allowConstCasts;
 
   /// Whether to use covariant generics
@@ skipping 99 matching lines @@
 
   /// Whether to infer return types and field types from overriden members.
   @override
   final bool inferFromOverrides;
 
   /// Whether to infer types for consts and static fields by looking at
   /// identifiers on the RHS.
   @override
   final bool inferStaticsFromIdentifiers;
 
-  /// Whether to ignore ordering issue, and do a best effort in inference.
-  @override
-  final bool inferInNonStableOrder;
-
   /// Restrict inference of fields and top-levels to those that are final and
   /// const.
   @override
   final bool onlyInferConstsAndFinalFields;
 
   /// List of non-nullable types.
   @override
   final List<String> nonnullableTypes;
 
   /// Whether to use static types for code generation.
   @override
   final bool ignoreTypes;
 
   /// Whether to emit the source map files.
   @override
   final bool emitSourceMaps;
 
   CompilerOptions({this.allowConstCasts: true, this.checkSdk: false,
       this.dumpInfo: false, this.dumpInfoFile, this.dumpSrcDir,
       this.forceCompile: false, this.formatOutput: false,
       this.cheapTestFormat: false, this.ignoreTypes: false, this.outputDir,
       this.outputDart: false, this.useColors: true,
       this.covariantGenerics: true, this.relaxedCasts: true,
       this.useMultiPackage: false, this.packageRoot: 'packages/',
       this.packagePaths: const <String>[],
       this.inferFromOverrides: ResolverOptions.inferFromOverridesDefault,
       this.inferStaticsFromIdentifiers: ResolverOptions.inferStaticsFromIdentifiersDefault,
-      this.inferInNonStableOrder: ResolverOptions.inferInNonStableOrderDefault,
       this.onlyInferConstsAndFinalFields: ResolverOptions.onlyInferConstAndFinalFieldsDefault,
       this.nonnullableTypes: TypeOptions.NONNULLABLE_TYPES, this.help: false,
       this.useMockSdk: false, this.dartSdkPath, this.logLevel: Level.SEVERE,
       this.emitSourceMaps: true, this.entryPointFile: null,
       this.serverMode: false, this.port: 8080});
 }
 
 /// Parses options from the command-line
 CompilerOptions parseOptions(List<String> argv) {
   ArgResults args = argParser.parse(argv);
@@ skipping 15 matching lines @@
       outputDart: args['dart-gen'],
       outputDir: args['out'],
       covariantGenerics: args['covariant-generics'],
       relaxedCasts: args['relaxed-casts'],
       useColors: useColors,
       useMultiPackage: args['use-multi-package'],
       packageRoot: args['package-root'],
       packagePaths: args['package-paths'].split(','),
       inferFromOverrides: args['infer-from-overrides'],
       inferStaticsFromIdentifiers: args['infer-transitively'],
-      inferInNonStableOrder: args['infer-eagerly'],
       onlyInferConstsAndFinalFields: args['infer-only-finals'],
       nonnullableTypes: optionsToList(args['nonnullable'],
           defaultValue: TypeOptions.NONNULLABLE_TYPES),
       help: args['help'],
       useMockSdk: args['mock-sdk'],
       dartSdkPath: sdkPath,
       logLevel: Level.LEVELS.firstWhere((Level l) => l.name == levelName,
           orElse: () => Level.SEVERE),
       emitSourceMaps: args['source-maps'],
       entryPointFile: args.rest.length == 0 ? null : args.rest.first,
@@ skipping 22 matching lines @@
   ..addFlag('infer-from-overrides',
       help: 'Infer unspecified types of fields and return types from '
       'definitions in supertypes',
       defaultsTo: ResolverOptions.inferFromOverridesDefault)
   ..addFlag('infer-transitively',
       help: 'Infer consts/fields from definitions in other libraries',
       defaultsTo: ResolverOptions.inferStaticsFromIdentifiersDefault)
   ..addFlag('infer-only-finals',
       help: 'Do not infer non-const or non-final fields',
       defaultsTo: ResolverOptions.onlyInferConstAndFinalFieldsDefault)
-  ..addFlag('infer-eagerly',
-      help: 'experimental: allows a non-stable order of transitive inference on'
-      ' consts and fields. This is used to test for possible inference with a '
-      'proper implementation in the future.',
-      defaultsTo: ResolverOptions.inferInNonStableOrderDefault)
 
   // input/output options
   ..addOption('out', abbr: 'o', help: 'Output directory', defaultsTo: null)
   ..addOption('dart-sdk', help: 'Dart SDK Path', defaultsTo: null)
   ..addFlag('dart-gen',
       abbr: 'd', help: 'Generate dart output', defaultsTo: false)
   ..addFlag('dart-gen-fmt',
       help: 'Generate readable dart output', defaultsTo: true)
   ..addOption('dump-src-to', help: 'Dump dart src code', defaultsTo: null)
   ..addOption('package-root',
@@ skipping 16 matching lines @@
       defaultsTo: '8080')
   ..addFlag('force-compile',
       help: 'Compile code with static errors', defaultsTo: false)
   ..addOption('log', abbr: 'l', help: 'Logging level', defaultsTo: 'severe')
   ..addFlag('dump-info',
       abbr: 'i', help: 'Dump summary information', defaultsTo: false)
   ..addOption('dump-info-file',
       abbr: 'f',
       help: 'Dump info json file (requires dump-info)',
       defaultsTo: null);