Use the new Dart 2.3.0 literal syntax (#684)

lib/src/ast/css/media_query.dart

@@ -54,8 +54,8 @@ class CssMediaQuery {
     var theirType = other.type?.toLowerCase();
 
     if (ourType == null && theirType == null) {
-      return MediaQuerySuccessfulMergeResult._(CssMediaQuery.condition(
-          this.features.toList()..addAll(other.features)));
+      return MediaQuerySuccessfulMergeResult._(
+          CssMediaQuery.condition([...this.features, ...other.features]));
     }
 
     String modifier;
@@ -120,17 +120,17 @@ class CssMediaQuery {
       // Omit the type if either input query did, since that indicates that they
       // aren't targeting a browser that requires "all and".
       type = (other.matchesAllTypes && ourType == null) ? null : theirType;
-      features = this.features.toList()..addAll(other.features);
+      features = [...this.features, ...other.features];
     } else if (other.matchesAllTypes) {
       modifier = ourModifier;
       type = ourType;
-      features = this.features.toList()..addAll(other.features);
+      features = [...this.features, ...other.features];
     } else if (ourType != theirType) {
       return MediaQueryMergeResult.empty;
     } else {
       modifier = ourModifier ?? theirModifier;
       type = ourType;
-      features = this.features.toList()..addAll(other.features);
+      features = [...this.features, ...other.features];
     }
 
     return MediaQuerySuccessfulMergeResult._(CssMediaQuery(

lib/src/ast/sass/argument_declaration.dart

@@ -100,9 +100,8 @@ class ArgumentDeclaration implements SassNode {
     return true;
   }
 
-  String toString() {
-    var components = List.of(arguments.map((arg) => arg.toString()));
-    if (restArgument != null) components.add('$restArgument...');
-    return components.join(', ');
-  }
+  String toString() => [
+        for (var arg in arguments) arg.toString(),
+        if (restArgument != null) '$restArgument...'
+      ].join(', ');
 }

lib/src/ast/sass/argument_invocation.dart

@@ -42,10 +42,12 @@ class ArgumentInvocation implements SassNode {
         keywordRest = null;
 
   String toString() {
-    var components = List<Object>.from(positional)
-      ..addAll(named.keys.map((name) => "$name: ${named[name]}"));
-    if (rest != null) components.add("$rest...");
-    if (keywordRest != null) components.add("$keywordRest...");
+    var components = [
+      ...positional,
+      for (var name in named.keys) "$name: ${named[name]}",
+      if (rest != null) "$rest...",
+      if (keywordRest != null) "$keywordRest..."
+    ];
     return "(${components.join(', ')})";
   }
 }

lib/src/ast/selector/list.dart

@@ -103,7 +103,7 @@ class SelectorList extends Selector {
       if (!_complexContainsParentSelector(complex)) {
         if (!implicitParent) return [complex];
         return parent.components.map((parentComplex) => ComplexSelector(
-            parentComplex.components.toList()..addAll(complex.components),
+            [...parentComplex.components, ...complex.components],
             lineBreak: complex.lineBreak || parentComplex.lineBreak));
       }
 
@@ -127,8 +127,7 @@ class SelectorList extends Selector {
           for (var newComplex in previousComplexes) {
             var lineBreak = previousLineBreaks[i++];
             for (var resolvedComplex in resolved) {
-              newComplexes
-                  .add(newComplex.toList()..addAll(resolvedComplex.components));
+              newComplexes.add([...newComplex, ...resolvedComplex.components]);
               lineBreaks.add(lineBreak || resolvedComplex.lineBreak);
             }
           }
@@ -204,18 +203,18 @@ class SelectorList extends Selector {
       var last = lastComponent as CompoundSelector;
       var suffix = (compound.components.first as ParentSelector).suffix;
       if (suffix != null) {
-        last = CompoundSelector(
-            last.components.take(last.components.length - 1).toList()
-              ..add(last.components.last.addSuffix(suffix))
-              ..addAll(resolvedMembers.skip(1)));
+        last = CompoundSelector([
+          ...last.components.take(last.components.length - 1),
+          last.components.last.addSuffix(suffix),
+          ...resolvedMembers.skip(1)
+        ]);
       } else {
-        last = CompoundSelector(
-            last.components.toList()..addAll(resolvedMembers.skip(1)));
+        last =
+            CompoundSelector([...last.components, ...resolvedMembers.skip(1)]);
       }
 
       return ComplexSelector(
-          complex.components.take(complex.components.length - 1).toList()
-            ..add(last),
+          [...complex.components.take(complex.components.length - 1), last],
           lineBreak: complex.lineBreak);
     });
   }

lib/src/ast/selector/type.dart

@@ -25,9 +25,9 @@ class TypeSelector extends SimpleSelector {
     if (compound.first is UniversalSelector || compound.first is TypeSelector) {
       var unified = unifyUniversalAndElement(this, compound.first);
       if (unified == null) return null;
-      return [unified]..addAll(compound.skip(1));
+      return [unified, ...compound.skip(1)];
     } else {
-      return <SimpleSelector>[this]..addAll(compound);
+      return [this, ...compound];
     }
   }
 

lib/src/ast/selector/universal.dart

@@ -27,12 +27,10 @@ class UniversalSelector extends SimpleSelector {
     if (compound.first is UniversalSelector || compound.first is TypeSelector) {
       var unified = unifyUniversalAndElement(this, compound.first);
       if (unified == null) return null;
-      return [unified]..addAll(compound.skip(1));
+      return [unified, ...compound.skip(1)];
     }
 
-    if (namespace != null && namespace != "*") {
-      return <SimpleSelector>[this]..addAll(compound);
-    }
+    if (namespace != null && namespace != "*") return [this, ...compound];
     if (compound.isNotEmpty) return compound;
     return [this];
   }

lib/src/async_import_cache.dart

@@ -77,24 +77,16 @@ class AsyncImportCache {
   /// options into a single list of importers.
   static List<AsyncImporter> _toImporters(Iterable<AsyncImporter> importers,
       Iterable<String> loadPaths, SyncPackageResolver packageResolver) {
-    var list = importers?.toList() ?? [];
-
-    if (loadPaths != null) {
-      list.addAll(loadPaths.map((path) => FilesystemImporter(path)));
-    }
-
     var sassPath = getEnvironmentVariable('SASS_PATH');
-    if (sassPath != null) {
-      list.addAll(sassPath
-          .split(isWindows ? ';' : ':')
-          .map((path) => FilesystemImporter(path)));
-    }
-
-    if (packageResolver != null) {
-      list.add(PackageImporter(packageResolver));
-    }
-
-    return list;
+    return [
+      ...?importers,
+      if (loadPaths != null)
+        for (var path in loadPaths) FilesystemImporter(path),
+      if (sassPath != null)
+        for (var path in sassPath.split(isWindows ? ';' : ':'))
+          FilesystemImporter(path),
+      if (packageResolver != null) PackageImporter(packageResolver)
+    ];
   }
 
   /// Creates a cache that contains no importers.

lib/src/executable/options.dart

@@ -371,18 +371,19 @@ class ExecutableOptions {
   /// Returns the sub-map of [sourcesToDestinations] for the given [source] and
   /// [destination] directories.
   Map<String, String> _listSourceDirectory(String source, String destination) {
-    var map = <String, String>{};
-    for (var path in listDir(source, recursive: true)) {
-      var basename = p.basename(path);
-      if (basename.startsWith("_")) continue;
+    return {
+      for (var path in listDir(source, recursive: true))
+        if (_isEntrypoint(path))
+          path: p.join(destination,
+              p.setExtension(p.relative(path, from: source), '.css'))
+    };
+  }
 
-      var extension = p.extension(path);
-      if (extension != ".scss" && extension != ".sass") continue;
-
-      map[path] = p.join(
-          destination, p.setExtension(p.relative(path, from: source), '.css'));
-    }
-    return map;
+  /// Returns whether [path] is a Sass entrypoint (that is, not a partial).
+  bool _isEntrypoint(String path) {
+    if (p.basename(path).startsWith("_")) return false;
+    var extension = p.extension(path);
+    return extension == ".scss" || extension == ".sass";
   }
 
   /// Whether to emit a source map file.

lib/src/executable/watch.dart

@@ -20,10 +20,11 @@ import 'options.dart';
 
 /// Watches all the files in [graph] for changes and updates them as necessary.
 Future watch(ExecutableOptions options, StylesheetGraph graph) async {
-  var directoriesToWatch = <String>[]
-    ..addAll(options.sourceDirectoriesToDestinations.keys)
-    ..addAll(options.sourcesToDestinations.keys.map(p.dirname))
-    ..addAll(options.loadPaths);
+  var directoriesToWatch = [
+    ...options.sourceDirectoriesToDestinations.keys,
+    ...options.sourcesToDestinations.keys.map(p.dirname),
+    ...options.loadPaths
+  ];
 
   var dirWatcher = MultiDirWatcher(poll: options.poll);
   await Future.wait(directoriesToWatch.map((dir) {

lib/src/extend/extender.dart

@@ -96,11 +96,10 @@ class Extender {
         throw SassScriptException("Can't extend complex selector $complex.");
       }
 
-      var extensions = <SimpleSelector, Map<ComplexSelector, Extension>>{};
       var compound = complex.components.first as CompoundSelector;
-      for (var simple in compound.components) {
-        extensions[simple] = extenders;
-      }
+      var extensions = {
+        for (var simple in compound.components) simple: extenders
+      };
 
       var extender = Extender._mode(mode);
       if (!selector.isInvisible) {
@@ -702,10 +701,7 @@ class Extender {
       targetsUsed?.add(simple);
       if (_mode == ExtendMode.replace) return extenders.values.toList();
 
-      var extenderList = List<Extension>(extenders.length + 1);
-      extenderList[0] = _extensionForSimple(simple);
-      extenderList.setRange(1, extenderList.length, extenders.values);
-      return extenderList;
+      return [_extensionForSimple(simple), ...extenders.values];
     }
 
     if (simple is PseudoSelector && simple.selector != null) {

lib/src/extend/functions.dart

@@ -21,8 +21,7 @@ import '../utils.dart';
 /// subselectors of their arguments.
 ///
 /// For example, `.foo` is a superselector of `:matches(.foo)`.
-final _subselectorPseudos =
-    Set.of(['matches', 'any', 'nth-child', 'nth-last-child']);
+final _subselectorPseudos = {'matches', 'any', 'nth-child', 'nth-last-child'};
 
 /// Returns the contents of a [SelectorList] that matches only elements that are
 /// matched by both [complex1] and [complex2].
@@ -381,18 +380,16 @@ List<List<List<ComplexSelectorComponent>>> _mergeFinalCombinators(
           [nextSiblingSelector, Combinator.nextSibling]
         ]);
       } else {
-        var choices = [
+        var unified = unifyCompound(compound1.components, compound2.components);
+        result.addFirst([
           [
             followingSiblingSelector,
             Combinator.followingSibling,
             nextSiblingSelector,
             Combinator.nextSibling
-          ]
-        ];
-
-        var unified = unifyCompound(compound1.components, compound2.components);
-        if (unified != null) choices.add([unified, Combinator.nextSibling]);
-        result.addFirst(choices);
+          ],
+          if (unified != null) [unified, Combinator.nextSibling]
+        ]);
       }
     } else if (combinator1 == Combinator.child &&
         (combinator2 == Combinator.nextSibling ||
@@ -451,12 +448,11 @@ List<List<List<ComplexSelectorComponent>>> _mergeFinalCombinators(
 /// selector, such as an ID.
 bool _mustUnify(List<ComplexSelectorComponent> complex1,
     List<ComplexSelectorComponent> complex2) {
-  var uniqueSelectors = Set<SimpleSelector>();
-  for (var component in complex1) {
-    if (component is CompoundSelector) {
-      uniqueSelectors.addAll(component.components.where(_isUnique));
-    }
-  }
+  var uniqueSelectors = {
+    for (var component in complex1)
+      if (component is CompoundSelector)
+        ...component.components.where(_isUnique)
+  };
   if (uniqueSelectors.isEmpty) return false;
 
   return complex2.any((component) =>
@@ -496,7 +492,10 @@ List<List<T>> _chunks<T>(
   if (chunk1.isEmpty && chunk2.isEmpty) return [];
   if (chunk1.isEmpty) return [chunk2];
   if (chunk2.isEmpty) return [chunk1];
-  return [chunk1.toList()..addAll(chunk2), chunk2..addAll(chunk1)];
+  return [
+    [...chunk1, ...chunk2],
+    [...chunk2, ...chunk1]
+  ];
 }
 
 /// Returns a list of all possible paths through the given lists.
@@ -512,7 +511,7 @@ List<List<T>> _chunks<T>(
 List<List<T>> paths<T>(Iterable<List<T>> choices) => choices.fold(
     [[]],
     (paths, choice) => choice
-        .expand((option) => paths.map((path) => path.toList()..add(option)))
+        .expand((option) => paths.map((path) => [...path, option]))
         .toList());
 
 /// Returns [complex], grouped into sub-lists such that no sub-list contains two
@@ -566,8 +565,7 @@ bool complexIsParentSuperselector(List<ComplexSelectorComponent> complex1,
   // TODO(nweiz): There's got to be a way to do this without a bunch of extra
   // allocations...
   var base = CompoundSelector([PlaceholderSelector('<temp>')]);
-  return complexIsSuperselector(
-      complex1.toList()..add(base), complex2.toList()..add(base));
+  return complexIsSuperselector([...complex1, base], [...complex2, base]);
 }
 
 /// Returns whether [complex1] is a superselector of [complex2].
@@ -732,11 +730,8 @@ bool _selectorPseudoIsSuperselector(
       return pseudos.any((pseudo2) {
             return pseudo1.selector.isSuperselector(pseudo2.selector);
           }) ||
-          pseudo1.selector.components.any((complex1) {
-            var complex2 = (parents?.toList() ?? <ComplexSelectorComponent>[])
-              ..add(compound2);
-            return complexIsSuperselector(complex1.components, complex2);
-          });
+          pseudo1.selector.components.any((complex1) => complexIsSuperselector(
+              complex1.components, [...?parents, compound2]));
 
     case 'has':
     case 'host':

lib/src/functions.dart

@@ -21,13 +21,13 @@ import 'value.dart';
 final _microsoftFilterStart = RegExp(r'^[a-zA-Z]+\s*=');
 
 /// Feature names supported by Dart sass.
-final _features = Set.of([
+final _features = {
   "global-variable-shadowing",
   "extend-selector-pseudoclass",
   "units-level-3",
   "at-error",
   "custom-property"
-]);
+};
 
 /// A random number generator.
 final _random = math.Random();
@@ -627,7 +627,7 @@ final List<BuiltInCallable> coreFunctions = UnmodifiableListView([
             ? list1.hasBrackets
             : bracketedParam.isTruthy;
 
-    var newList = list1.asList.toList()..addAll(list2.asList);
+    var newList = [...list1.asList, ...list2.asList];
     return SassList(newList, separator, brackets: bracketed);
   }),
 
@@ -650,7 +650,7 @@ final List<BuiltInCallable> coreFunctions = UnmodifiableListView([
           '\$$separator: Must be "space", "comma", or "auto".');
     }
 
-    var newList = list.asList.toList()..add(value);
+    var newList = [...list.asList, value];
     return list.changeListContents(newList, separator: separator);
   }),
 
@@ -694,7 +694,7 @@ final List<BuiltInCallable> coreFunctions = UnmodifiableListView([
   BuiltInCallable("map-merge", r"$map1, $map2", (arguments) {
     var map1 = arguments[0].assertMap("map1");
     var map2 = arguments[1].assertMap("map2");
-    return SassMap(Map.of(map1.contents)..addAll(map2.contents));
+    return SassMap({...map1.contents, ...map2.contents});
   }),
 
   BuiltInCallable("map-remove", r"$map, $keys...", (arguments) {
@@ -769,8 +769,7 @@ final List<BuiltInCallable> coreFunctions = UnmodifiableListView([
             throw SassScriptException("Can't append $complex to $parent.");
           }
 
-          return ComplexSelector(<ComplexSelectorComponent>[newCompound]
-            ..addAll(complex.components.skip(1)));
+          return ComplexSelector([newCompound, ...complex.components.skip(1)]);
         } else {
           throw SassScriptException("Can't append $complex to $parent.");
         }
@@ -1139,12 +1138,12 @@ CompoundSelector _prependParent(CompoundSelector compound) {
   if (first is UniversalSelector) return null;
   if (first is TypeSelector) {
     if (first.name.namespace != null) return null;
-    return CompoundSelector(<SimpleSelector>[
-      ParentSelector(suffix: first.name.name)
-    ]..addAll(compound.components.skip(1)));
+    return CompoundSelector([
+      ParentSelector(suffix: first.name.name),
+      ...compound.components.skip(1)
+    ]);
   } else {
-    return CompoundSelector(
-        <SimpleSelector>[ParentSelector()]..addAll(compound.components));
+    return CompoundSelector([ParentSelector(), ...compound.components]);
   }
 }
 

lib/src/import_cache.dart

@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_import_cache.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: 291afac7e0d5edc6610685b28741786f667f83e8
+// Checksum: 1e51fceaa60c0a65fa9c447cfe25eda5109a819f
 //
 // ignore_for_file: unused_import
 
@@ -82,24 +82,16 @@ class ImportCache {
   /// options into a single list of importers.
   static List<Importer> _toImporters(Iterable<Importer> importers,
       Iterable<String> loadPaths, SyncPackageResolver packageResolver) {
-    var list = importers?.toList() ?? [];
-
-    if (loadPaths != null) {
-      list.addAll(loadPaths.map((path) => FilesystemImporter(path)));
-    }
-
     var sassPath = getEnvironmentVariable('SASS_PATH');
-    if (sassPath != null) {
-      list.addAll(sassPath
-          .split(isWindows ? ';' : ':')
-          .map((path) => FilesystemImporter(path)));
-    }
-
-    if (packageResolver != null) {
-      list.add(PackageImporter(packageResolver));
-    }
-
-    return list;
+    return [
+      ...?importers,
+      if (loadPaths != null)
+        for (var path in loadPaths) FilesystemImporter(path),
+      if (sassPath != null)
+        for (var path in sassPath.split(isWindows ? ';' : ':'))
+          FilesystemImporter(path),
+      if (packageResolver != null) PackageImporter(packageResolver)
+    ];
   }
 
   /// Creates a cache that contains no importers.

lib/src/importer/utils.dart

@@ -68,11 +68,8 @@ List<String> _tryPathWithExtensions(String path) {
 ///
 /// If neither exists, returns an empty list.
 List<String> _tryPath(String path) {
-  var paths = <String>[];
   var partial = p.join(p.dirname(path), "_${p.basename(path)}");
-  if (fileExists(partial)) paths.add(partial);
-  if (fileExists(path)) paths.add(path);
-  return paths;
+  return [if (fileExists(partial)) partial, if (fileExists(path)) path];
 }
 
 /// Returns the resolved index file for [path] if [path] is a directory and the

lib/src/interpolation_buffer.dart

@@ -70,9 +70,8 @@ class InterpolationBuffer implements StringSink {
   /// Creates an [Interpolation] with the given [span] from the contents of this
   /// buffer.
   Interpolation interpolation(FileSpan span) {
-    var contents = _contents.toList();
-    if (_text.isNotEmpty) contents.add(_text.toString());
-    return Interpolation(contents, span);
+    return Interpolation(
+        [..._contents, if (_text.isNotEmpty) _text.toString()], span);
   }
 
   String toString() {

lib/src/node.dart

@@ -204,12 +204,14 @@ List<AsyncCallable> _parseFunctions(RenderOptions options,
     if (options.fiber != null) {
       result.add(BuiltInCallable.parsed(tuple.item1, tuple.item2, (arguments) {
         var fiber = options.fiber.current;
-        var jsArguments = arguments.map(wrapValue).toList()
-          ..add(allowInterop(([result]) {
+        var jsArguments = [
+          ...arguments.map(wrapValue),
+          allowInterop(([result]) {
             // Schedule a microtask so we don't try to resume the running fiber
             // if [importer] calls `done()` synchronously.
             scheduleMicrotask(() => fiber.run(result));
-          }));
+          })
+        ];
         var result = Function.apply(callback as Function, jsArguments);
         return unwrapValue(
             isUndefined(result) ? options.fiber.yield() : result);
@@ -224,8 +226,10 @@ List<AsyncCallable> _parseFunctions(RenderOptions options,
       result.add(AsyncBuiltInCallable.parsed(tuple.item1, tuple.item2,
           (arguments) async {
         var completer = Completer();
-        var jsArguments = arguments.map(wrapValue).toList()
-          ..add(allowInterop(([result]) => completer.complete(result)));
+        var jsArguments = [
+          ...arguments.map(wrapValue),
+          allowInterop(([result]) => completer.complete(result))
+        ];
         var result = Function.apply(callback as Function, jsArguments);
         return unwrapValue(
             isUndefined(result) ? await completer.future : result);
@@ -256,7 +260,7 @@ NodeImporter _parseImporter(RenderOptions options, DateTime start) {
             file: options.file,
             data: options.data,
             includePaths:
-                ([p.current]..addAll(includePaths)).join(isWindows ? ';' : ':'),
+                ([p.current, ...includePaths]).join(isWindows ? ';' : ':'),
             precision: SassNumber.precision,
             style: 1,
             indentType: options.indentType == 'tab' ? 1 : 0,

lib/src/node/value/map.dart

@@ -55,10 +55,8 @@ final Function mapConstructor =
   },
   'setValue': (_NodeSassMap thisArg, int index, value) {
     var key = thisArg.dartValue.contents.keys.elementAt(index);
-
-    var mutable = Map.of(thisArg.dartValue.contents);
-    mutable[key] = unwrapValue(value);
-    thisArg.dartValue = SassMap(mutable);
+    thisArg.dartValue =
+        SassMap({...thisArg.dartValue.contents, key: unwrapValue(value)});
   },
   'toString': (_NodeSassMap thisArg) => thisArg.dartValue.toString()
 });

lib/src/parse/selector.dart

@@ -11,11 +11,18 @@ import '../utils.dart';
 import 'parser.dart';
 
 /// Pseudo-class selectors that take unadorned selectors as arguments.
-final _selectorPseudoClasses =
-    Set.of(["not", "matches", "current", "any", "has", "host", "host-context"]);
+final _selectorPseudoClasses = {
+  "not",
+  "matches",
+  "current",
+  "any",
+  "has",
+  "host",
+  "host-context"
+};
 
 /// Pseudo-element selectors that take unadorned selectors as arguments.
-final _selectorPseudoElements = Set.of(["slotted"]);
+final _selectorPseudoElements = {"slotted"};
 
 /// A parser for selectors.
 class SelectorParser extends Parser {

lib/src/stylesheet_graph.dart

@@ -94,13 +94,13 @@ class StylesheetGraph {
   /// appears within [baseUrl] imported by [baseImporter].
   Map<Uri, StylesheetNode> _upstreamNodes(
       Stylesheet stylesheet, Importer baseImporter, Uri baseUrl) {
-    var active = Set.of([baseUrl]);
-    var upstream = <Uri, StylesheetNode>{};
-    for (var import in findImports(stylesheet)) {
-      var url = Uri.parse(import.url);
-      upstream[url] = _nodeFor(url, baseImporter, baseUrl, active);
-    }
-    return upstream;
+    var active = {baseUrl};
+    var upstreamUrls =
+        findImports(stylesheet).map((import) => Uri.parse(import.url));
+    return {
+      for (var url in upstreamUrls)
+        url: _nodeFor(url, baseImporter, baseUrl, active)
+    };
   }
 
   /// Re-parses the stylesheet at [canonicalUrl] and updates the dependency graph

lib/src/utils.dart

@@ -406,13 +406,8 @@ void rotateSlice(List list, int start, int end) {
 
 /// Like [Iterable.map] but for an asynchronous [callback].
 Future<Iterable<F>> mapAsync<E, F>(
-    Iterable<E> iterable, Future<F> callback(E value)) async {
-  var result = <F>[];
-  for (var element in iterable) {
-    result.add(await callback(element));
-  }
-  return result;
-}
+        Iterable<E> iterable, Future<F> callback(E value)) async =>
+    [for (var element in iterable) await callback(element)];
 
 /// Like [Map.putIfAbsent], but for an asynchronous [ifAbsent].
 ///

lib/src/visitor/async_evaluate.dart

@@ -1072,8 +1072,7 @@ class _EvaluateVisitor
         throw "Can't find stylesheet to import.";
       }
     } on SassException catch (error) {
-      var frames = error.trace.frames.toList()
-        ..addAll(_stackTrace(span).frames);
+      var frames = [...error.trace.frames, ..._stackTrace(span).frames];
       throw SassRuntimeException(error.message, error.span, Trace(frames));
     } catch (error) {
       String message;
@@ -2416,10 +2415,10 @@ class _EvaluateVisitor
   ///
   /// [span] is the current location, used for the bottom-most stack frame.
   Trace _stackTrace(FileSpan span) {
-    var frames = _stack
-        .map((tuple) => _stackFrame(tuple.item1, tuple.item2.span))
-        .toList()
-          ..add(_stackFrame(_member, span));
+    var frames = [
+      ..._stack.map((tuple) => _stackFrame(tuple.item1, tuple.item2.span)),
+      _stackFrame(_member, span)
+    ];
     return Trace(frames.reversed);
   }
 

lib/src/visitor/evaluate.dart

@@ -5,7 +5,7 @@
 // DO NOT EDIT. This file was generated from async_evaluate.dart.
 // See tool/grind/synchronize.dart for details.
 //
-// Checksum: c41c933bbae5af96a77e39cea8c4d7a4c86cb564
+// Checksum: 71e3dfeef2683bd246e21ddfd25b21df408cf18e
 //
 // ignore_for_file: unused_import
 
@@ -1074,8 +1074,7 @@ class _EvaluateVisitor
         throw "Can't find stylesheet to import.";
       }
     } on SassException catch (error) {
-      var frames = error.trace.frames.toList()
-        ..addAll(_stackTrace(span).frames);
+      var frames = [...error.trace.frames, ..._stackTrace(span).frames];
       throw SassRuntimeException(error.message, error.span, Trace(frames));
     } catch (error) {
       String message;
@@ -2393,10 +2392,10 @@ class _EvaluateVisitor
   ///
   /// [span] is the current location, used for the bottom-most stack frame.
   Trace _stackTrace(FileSpan span) {
-    var frames = _stack
-        .map((tuple) => _stackFrame(tuple.item1, tuple.item2.span))
-        .toList()
-          ..add(_stackFrame(_member, span));
+    var frames = [
+      ..._stack.map((tuple) => _stackFrame(tuple.item1, tuple.item2.span)),
+      _stackFrame(_member, span)
+    ];
     return Trace(frames.reversed);
   }
 

test/cli/dart_test.dart

@@ -50,16 +50,17 @@ Future<TestProcess> runSass(Iterable<String> arguments,
   var executable = _snapshotPaths.firstWhere((path) => File(path).existsSync(),
       orElse: () => p.absolute("bin/sass.dart"));
 
-  var args = ["--enable-asserts"];
-
-  // Work around dart-lang/sdk#33622.
-  if (Platform.isWindows) args.add("--packages=${p.absolute('.packages')}");
-
   return TestProcess.start(
       Platform.executable,
-      args
-        ..add(executable)
-        ..addAll(arguments),
+      [
+        "--enable-asserts",
+        // Work around dart-lang/sdk#33622.
+        if (Platform.isWindows)
+          "--packages=${p.absolute('.packages')}",
+
+        executable,
+        ...arguments
+      ],
       workingDirectory: d.sandbox,
       environment: environment,
       description: "sass");

test/cli/node_test.dart

@@ -32,8 +32,7 @@ void main() {
 
 Future<TestProcess> runSass(Iterable<String> arguments,
         {Map<String, String> environment}) =>
-    TestProcess.start(
-        "node", [p.absolute("build/npm/sass.js")]..addAll(arguments),
+    TestProcess.start("node", [p.absolute("build/npm/sass.js"), ...arguments],
         workingDirectory: d.sandbox,
         environment: environment,
         description: "sass");

test/cli/shared.dart

@@ -19,8 +19,7 @@ void sharedTests(
   /// the contents of the output file match [expected].
   Future expectCompiles(List<String> arguments, expected,
       {Map<String, String> environment}) async {
-    var sass = await runSass(
-        arguments.toList()..add("out.css")..add("--no-source-map"),
+    var sass = await runSass([...arguments, "out.css", "--no-source-map"],
         environment: environment);
     await sass.shouldExit(0);
     await d.file("out.css", expected).validate();

test/cli/shared/update.dart

@@ -13,7 +13,7 @@ import '../../utils.dart';
 /// Defines test that are shared between the Dart and Node.js CLI test suites.
 void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
   Future<TestProcess> update(Iterable<String> arguments) =>
-      runSass(["--no-source-map", "--update"]..addAll(arguments));
+      runSass(["--no-source-map", "--update", ...arguments]);
 
   group("updates CSS", () {
     test("that doesn't exist yet", () async {

test/cli/shared/watch.dart

@@ -23,11 +23,8 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
   });
 
   for (var poll in [true, false]) {
-    Future<TestProcess> watch(Iterable<String> arguments) {
-      var allArguments = ["--no-source-map", "--watch"]..addAll(arguments);
-      if (poll) allArguments.add("--poll");
-      return runSass(allArguments);
-    }
+    Future<TestProcess> watch(Iterable<String> arguments) => runSass(
+        ["--no-source-map", "--watch", ...arguments, if (poll) "--poll"]);
 
     /// Returns a future that completes after a delay if [poll] is `true`.
     ///

test/io.dart

@@ -18,20 +18,21 @@ void ensureUpToDate(String path, String commandToRun) {
     throw "$path does not exist. Run $commandToRun.";
   }
 
+  var entriesToCheck = [
+    ...Directory("lib").listSync(recursive: true),
+
+    // If we have a dependency override, "pub run" will touch the lockfile to
+    // mark it as newer than the pubspec, which makes it unsuitable to use for
+    // freshness checking.
+    if (File("pubspec.yaml")
+        .readAsStringSync()
+        .contains("dependency_overrides"))
+      File("pubspec.yaml")
+    else
+      File("pubspec.lock")
+  ];
+
   var lastModified = File(path).lastModifiedSync();
-  var entriesToCheck = Directory("lib").listSync(recursive: true).toList();
-
-  // If we have a dependency override, "pub run" will touch the lockfile to mark
-  // it as newer than the pubspec, which makes it unsuitable to use for
-  // freshness checking.
-  if (File("pubspec.yaml")
-      .readAsStringSync()
-      .contains("dependency_overrides")) {
-    entriesToCheck.add(File("pubspec.yaml"));
-  } else {
-    entriesToCheck.add(File("pubspec.lock"));
-  }
-
   for (var entry in entriesToCheck) {
     if (entry is File) {
       var entryLastModified = entry.lastModifiedSync();

test/source_map_test.dart

@@ -795,7 +795,7 @@ void _expectMapMatches(
     Map<String, SourceLocation> sourceLocations,
     List<Tuple2<String, SourceLocation>> targetLocations) {
   expect(sourceLocations.keys,
-      equals(Set.of(targetLocations.map((tuple) => tuple.item1))));
+      equals({for (var tuple in targetLocations) tuple.item1}));
 
   String actualMap() =>
       "\nActual map:\n\n" + _mapToString(map, sourceText, targetText) + "\n";

tool/grind.dart

@@ -26,10 +26,11 @@ all() {}
 
 @Task('Run the Dart formatter.')
 format() {
-  Pub.run('dart_style',
-      script: 'format',
-      arguments: ['--overwrite', '--fix']
-        ..addAll(existingSourceDirs.map((dir) => dir.path)));
+  Pub.run('dart_style', script: 'format', arguments: [
+    '--overwrite',
+    '--fix',
+    for (var dir in existingSourceDirs) dir.path
+  ]);
 }
 
 @Task('Installs dependencies from npm.')

tool/grind/npm.dart

@@ -29,23 +29,19 @@ void _js({@required bool release}) {
   ensureBuild();
   var destination = File('build/sass.dart.js');
 
-  var args = [
+  Dart2js.compile(File('bin/sass.dart'), outFile: destination, extraArgs: [
     '--categories=Server',
     '-Dnode=true',
     '-Dversion=$version',
     '-Ddart-version=$dartVersion',
-  ];
-  if (release) {
     // We use O4 because:
     //
     // * We don't care about the string representation of types.
     // * We expect our test coverage to ensure that nothing throws subtypes of
     //   Error.
     // * We thoroughly test edge cases in user input.
-    args..add("-O4")..add("--fast-startup");
-  }
-
-  Dart2js.compile(File('bin/sass.dart'), outFile: destination, extraArgs: args);
+    if (release) ...["-O4", "--fast-startup"]
+  ]);
   var text = destination.readAsStringSync();
 
   if (release) {
@@ -71,13 +67,15 @@ npmReleasePackage() => _npm(release: true);
 /// --trust-type-annotations. Otherwise, it compiles unminified with pessimistic
 /// type checks.
 void _npm({@required bool release}) {
-  var json = jsonDecode(File('package/package.json').readAsStringSync())
-      as Map<String, dynamic>;
-  json['version'] = version;
+  var json = {
+    ...(jsonDecode(File('package/package.json').readAsStringSync())
+        as Map<String, dynamic>),
+    "version": version
+  };
 
   _writeNpmPackage('build/npm', json);
   if (release) {
-    _writeNpmPackage('build/npm-old', json..addAll({"name": "dart-sass"}));
+    _writeNpmPackage('build/npm-old', {...json, "name": "dart-sass"});
   }
 }