Make private fields final where possible

Change-Id: I16ee52f1b23e8d708e40cb482c5150f1e04d2417
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/128524
Commit-Queue: Samuel Rawlins <srawlins@google.com>
Reviewed-by: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analyzer/analysis_options.yaml

@@ -7,13 +7,24 @@ analyzer:
   errors:
     # Increase the severity of the unused_import hint.
     unused_import: warning
+    # There are currently 140 violations in lib/.
+    always_declare_return_types: ignore
+    # There are currently 230 violations in lib/.
+    annotate_overrides: ignore
+    # There are currently 5500 violations in lib/. This just does not fit well
+    # with the analyzer team's style.
+    omit_local_variable_types: ignore
+    # There are currently 3360 violations in lib/.
+    prefer_single_quotes: ignore
     # Ignoring "style" lint rules from pedantic for now. There are pre-existing
     # violations that need to be cleaned up. Each one can be cleaned up and
     # enabled according to the value provided.
     # TODO(srawlins): At the time of writing, 2600 violations in lib/. The fix
     # is mechanical, via `dartfmt --fix-doc-comments`, but not worth the churn
     # today.
     slash_for_doc_comments: ignore
+    # There are currently 1980 violations in lib/.
+    unnecessary_this: ignore
 
 linter:
   rules:

pkg/analyzer/lib/dart/analysis/declared_variables.dart

@@ -12,7 +12,7 @@ import 'package:analyzer/src/generated/resolver.dart' show TypeProvider;
 /// Clients may not extend, implement or mix-in this class.
 class DeclaredVariables {
   /// A table mapping the names of declared variables to their values.
-  Map<String, String> _declaredVariables = <String, String>{};
+  final Map<String, String> _declaredVariables = <String, String>{};
 
   /// Initialize a newly created set of declared variables in which there are no
   /// variables.

pkg/analyzer/lib/dart/ast/visitor.dart

@@ -49,7 +49,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 class BreadthFirstVisitor<R> extends GeneralizingAstVisitor<R> {
   /// A queue holding the nodes that have not yet been visited in the order in
   /// which they ought to be visited.
-  Queue<AstNode> _queue = Queue<AstNode>();
+  final Queue<AstNode> _queue = Queue<AstNode>();
 
   /// A visitor, used to visit the children of the current node, that will add
   /// the nodes it visits to the [_queue].

pkg/analyzer/lib/instrumentation/log_adapter.dart

@@ -25,7 +25,7 @@ class InstrumentationLogAdapter implements InstrumentationService {
   static const String TAG_WATCH_EVENT = 'Watch';
 
   /// A logger used to log instrumentation in string format.
-  InstrumentationLogger _instrumentationLogger;
+  final InstrumentationLogger _instrumentationLogger;
 
   /// Initialize a newly created instrumentation service to communicate with the
   /// given [_instrumentationLogger].

pkg/analyzer/lib/src/dart/analysis/dependency/reference_collector.dart

@@ -29,7 +29,7 @@ class ReferenceCollector {
   /// The list of names that are referenced using an import prefix.
   ///
   /// It is filled by [addImportPrefix] and shared across all nodes.
-  List<_ReferencedImportPrefixedNames> _importPrefixedReferences = [];
+  final List<_ReferencedImportPrefixedNames> _importPrefixedReferences = [];
 
   /// The list of names that are referenced with `super`.
   _NameSet _superReferences = _NameSet();

pkg/analyzer/lib/src/dart/analysis/library_context.dart

@@ -50,7 +50,7 @@ class LibraryContext {
   /// The size of the linked data that is loaded by this context.
   /// When it reaches [_maxLinkedDataInBytes] the whole context is thrown away.
   /// We use it as an approximation for the heap size of elements.
-  int _linkedDataInBytes = 0;
+  final int _linkedDataInBytes = 0;
 
   AnalysisContextImpl analysisContext;
   LinkedElementFactory elementFactory;

pkg/analyzer/lib/src/dart/ast/ast.dart

@@ -1386,7 +1386,7 @@ class ChildEntities
     with IterableMixin<SyntacticEntity>
     implements Iterable<SyntacticEntity> {
   /// The list of child entities to be iterated over.
-  List<SyntacticEntity> _entities = [];
+  final List<SyntacticEntity> _entities = [];
 
   @override
   Iterator<SyntacticEntity> get iterator => _entities.iterator;
@@ -10133,7 +10133,7 @@ abstract class UriBasedDirectiveImpl extends DirectiveImpl
     implements UriBasedDirective {
   /// The prefix of a URI using the `dart-ext` scheme to reference a native code
   /// library.
-  static String _DART_EXT_SCHEME = "dart-ext:";
+  static const String _DART_EXT_SCHEME = "dart-ext:";
 
   /// The URI referenced by this directive.
   StringLiteralImpl _uri;

pkg/analyzer/lib/src/dart/ast/utilities.dart

@@ -2498,12 +2498,12 @@ class NodeLocator extends UnifyingAstVisitor<void> {
   /**
    * The start offset of the range used to identify the node.
    */
-  int _startOffset = 0;
+  final int _startOffset;
 
   /**
    * The end offset of the range used to identify the node.
    */
-  int _endOffset = 0;
+  final int _endOffset;
 
   /**
    * The element that was found that corresponds to the given source range, or
@@ -2601,15 +2601,11 @@ class NodeLocator extends UnifyingAstVisitor<void> {
  * encompasses the specified range.
  */
 class NodeLocator2 extends UnifyingAstVisitor<void> {
-  /**
-   * The inclusive start offset of the range used to identify the node.
-   */
-  int _startOffset = 0;
+  /// The inclusive start offset of the range used to identify the node.
+  final int _startOffset;
 
-  /**
-   * The inclusive end offset of the range used to identify the node.
-   */
-  int _endOffset = 0;
+  /// The inclusive end offset of the range used to identify the node.
+  final int _endOffset;
 
   /**
    * The found node or `null` if there is no such node.
@@ -5633,7 +5629,8 @@ class ScopedNameFinder extends GeneralizingAstVisitor<void> {
 
   AstNode _immediateChild;
 
-  Map<String, SimpleIdentifier> _locals = HashMap<String, SimpleIdentifier>();
+  final Map<String, SimpleIdentifier> _locals =
+      HashMap<String, SimpleIdentifier>();
 
   final int _position;
 

pkg/analyzer/lib/src/dart/constant/evaluation.dart

@@ -34,29 +34,29 @@ import 'package:analyzer/src/task/api/model.dart';
 /// constant instance creation expressions.
 class ConstantEvaluationEngine {
   /// Parameter to "fromEnvironment" methods that denotes the default value.
-  static String _DEFAULT_VALUE_PARAM = "defaultValue";
+  static const String _DEFAULT_VALUE_PARAM = "defaultValue";
 
   /// Source of RegExp matching declarable operator names.
   /// From sdk/lib/internal/symbol.dart.
-  static String _OPERATOR_RE =
+  static const String _OPERATOR_RE =
       "(?:[\\-+*/%&|^]|\\[\\]=?|==|~/?|<[<=]?|>[>=]?|unary-)";
 
   /// Source of RegExp matching Dart reserved words.
   /// From sdk/lib/internal/symbol.dart.
-  static String _RESERVED_WORD_RE =
+  static const String _RESERVED_WORD_RE =
       "(?:assert|break|c(?:a(?:se|tch)|lass|on(?:st|tinue))|"
       "d(?:efault|o)|e(?:lse|num|xtends)|f(?:alse|inal(?:ly)?|or)|"
       "i[fns]|n(?:ew|ull)|ret(?:hrow|urn)|s(?:uper|witch)|t(?:h(?:is|row)|"
       "r(?:ue|y))|v(?:ar|oid)|w(?:hile|ith))";
 
   /// Source of RegExp matching any public identifier.
   /// From sdk/lib/internal/symbol.dart.
-  static String _PUBLIC_IDENTIFIER_RE =
+  static const String _PUBLIC_IDENTIFIER_RE =
       "(?!$_RESERVED_WORD_RE\\b(?!\\\$))[a-zA-Z\$][\\w\$]*";
 
   /// RegExp that validates a non-empty non-private symbol.
   /// From sdk/lib/internal/symbol.dart.
-  static RegExp _PUBLIC_SYMBOL_PATTERN = RegExp(
+  static final RegExp _PUBLIC_SYMBOL_PATTERN = RegExp(
       "^(?:$_OPERATOR_RE\$|$_PUBLIC_IDENTIFIER_RE(?:=?\$|[.](?!\$)))+?\$");
 
   /// The type provider used to access the known types.

pkg/analyzer/lib/src/dart/element/element.dart

@@ -2353,88 +2353,89 @@ class DynamicElementImpl extends ElementImpl implements TypeDefiningElement {
 class ElementAnnotationImpl implements ElementAnnotation {
   /// The name of the top-level variable used to mark that a function always
   /// throws, for dead code purposes.
-  static String _ALWAYS_THROWS_VARIABLE_NAME = "alwaysThrows";
+  static const String _ALWAYS_THROWS_VARIABLE_NAME = "alwaysThrows";
 
   /// The name of the class used to mark an element as being deprecated.
-  static String _DEPRECATED_CLASS_NAME = "Deprecated";
+  static const String _DEPRECATED_CLASS_NAME = "Deprecated";
 
   /// The name of the top-level variable used to mark an element as being
   /// deprecated.
-  static String _DEPRECATED_VARIABLE_NAME = "deprecated";
+  static const String _DEPRECATED_VARIABLE_NAME = "deprecated";
 
   /// The name of the top-level variable used to mark a method as being a
   /// factory.
-  static String _FACTORY_VARIABLE_NAME = "factory";
+  static const String _FACTORY_VARIABLE_NAME = "factory";
 
   /// The name of the top-level variable used to mark a class and its subclasses
   /// as being immutable.
-  static String _IMMUTABLE_VARIABLE_NAME = "immutable";
+  static const String _IMMUTABLE_VARIABLE_NAME = "immutable";
 
   /// The name of the top-level variable used to mark a constructor as being
   /// literal.
-  static String _LITERAL_VARIABLE_NAME = "literal";
+  static const String _LITERAL_VARIABLE_NAME = "literal";
 
   /// The name of the top-level variable used to mark a type as having
   /// "optional" type arguments.
-  static String _OPTIONAL_TYPE_ARGS_VARIABLE_NAME = "optionalTypeArgs";
+  static const String _OPTIONAL_TYPE_ARGS_VARIABLE_NAME = "optionalTypeArgs";
 
   /// The name of the top-level variable used to mark a function as running
   /// a single test.
-  static String _IS_TEST_VARIABLE_NAME = "isTest";
+  static const String _IS_TEST_VARIABLE_NAME = "isTest";
 
   /// The name of the top-level variable used to mark a function as running
   /// a test group.
-  static String _IS_TEST_GROUP_VARIABLE_NAME = "isTestGroup";
+  static const String _IS_TEST_GROUP_VARIABLE_NAME = "isTestGroup";
 
   /// The name of the class used to JS annotate an element.
-  static String _JS_CLASS_NAME = "JS";
+  static const String _JS_CLASS_NAME = "JS";
 
   /// The name of `js` library, used to define JS annotations.
-  static String _JS_LIB_NAME = "js";
+  static const String _JS_LIB_NAME = "js";
 
   /// The name of `meta` library, used to define analysis annotations.
-  static String _META_LIB_NAME = "meta";
+  static const String _META_LIB_NAME = "meta";
 
   /// The name of the top-level variable used to mark a method as requiring
   /// overriders to call super.
-  static String _MUST_CALL_SUPER_VARIABLE_NAME = "mustCallSuper";
+  static const String _MUST_CALL_SUPER_VARIABLE_NAME = "mustCallSuper";
 
   /// The name of `angular.meta` library, used to define angular analysis
   /// annotations.
-  static String _NG_META_LIB_NAME = "angular.meta";
+  static const String _NG_META_LIB_NAME = "angular.meta";
 
   /// The name of the top-level variable used to mark a member as being nonVirtual.
-  static String _NON_VIRTUAL_VARIABLE_NAME = "nonVirtual";
+  static const String _NON_VIRTUAL_VARIABLE_NAME = "nonVirtual";
 
   /// The name of the top-level variable used to mark a method as being expected
   /// to override an inherited method.
-  static String _OVERRIDE_VARIABLE_NAME = "override";
+  static const String _OVERRIDE_VARIABLE_NAME = "override";
 
   /// The name of the top-level variable used to mark a method as being
   /// protected.
-  static String _PROTECTED_VARIABLE_NAME = "protected";
+  static const String _PROTECTED_VARIABLE_NAME = "protected";
 
   /// The name of the top-level variable used to mark a class as implementing a
   /// proxy object.
-  static String PROXY_VARIABLE_NAME = "proxy";
+  static const String PROXY_VARIABLE_NAME = "proxy";
 
   /// The name of the class used to mark a parameter as being required.
-  static String _REQUIRED_CLASS_NAME = "Required";
+  static const String _REQUIRED_CLASS_NAME = "Required";
 
   /// The name of the top-level variable used to mark a parameter as being
   /// required.
-  static String _REQUIRED_VARIABLE_NAME = "required";
+  static const String _REQUIRED_VARIABLE_NAME = "required";
 
   /// The name of the top-level variable used to mark a class as being sealed.
-  static String _SEALED_VARIABLE_NAME = "sealed";
+  static const String _SEALED_VARIABLE_NAME = "sealed";
 
   /// The name of the top-level variable used to mark a method as being
   /// visible for templates.
-  static String _VISIBLE_FOR_TEMPLATE_VARIABLE_NAME = "visibleForTemplate";
+  static const String _VISIBLE_FOR_TEMPLATE_VARIABLE_NAME =
+      "visibleForTemplate";
 
   /// The name of the top-level variable used to mark a method as being
   /// visible for testing.
-  static String _VISIBLE_FOR_TESTING_VARIABLE_NAME = "visibleForTesting";
+  static const String _VISIBLE_FOR_TESTING_VARIABLE_NAME = "visibleForTesting";
 
   /// The element representing the field, variable, or constructor being used as
   /// an annotation.
@@ -3196,7 +3197,7 @@ abstract class ElementImpl implements Element {
 /// A concrete implementation of an [ElementLocation].
 class ElementLocationImpl implements ElementLocation {
   /// The character used to separate components in the encoded form.
-  static int _SEPARATOR_CHAR = 0x3B;
+  static const int _SEPARATOR_CHAR = 0x3B;
 
   /// The path to the element whose location is represented by this object.
   List<String> _components;

pkg/analyzer/lib/src/dart/resolver/exit_detector.dart

@@ -21,7 +21,7 @@ class ExitDetector extends GeneralizingAstVisitor<bool> {
   bool _enclosingBlockContainsContinue = false;
 
   /// Add node when a labelled `break` is encountered.
-  Set<AstNode> _enclosingBlockBreaksLabel = <AstNode>{};
+  final Set<AstNode> _enclosingBlockBreaksLabel = <AstNode>{};
 
   @override
   bool visitArgumentList(ArgumentList node) =>

pkg/analyzer/lib/src/dart/resolver/legacy_type_asserter.dart

@@ -22,7 +22,7 @@ import 'package:analyzer/src/dart/element/type.dart';
 /// nodes, have legacy types, and asserts that the legacy types are deep legacy
 /// types.
 class LegacyTypeAsserter extends GeneralizingAstVisitor {
-  Set<DartType> _visitedTypes = {};
+  final Set<DartType> _visitedTypes = {};
 
   LegacyTypeAsserter({bool requireIsDebug = true}) {
     if (requireIsDebug) {

pkg/analyzer/lib/src/dart/resolver/scope.dart

@@ -609,7 +609,7 @@ class LibraryImportScope extends Scope {
  * A scope containing all of the names defined in a given library.
  */
 class LibraryScope extends EnclosedScope {
-  List<ExtensionElement> _extensions = <ExtensionElement>[];
+  final List<ExtensionElement> _extensions = <ExtensionElement>[];
 
   /**
    * Initialize a newly created scope representing the names defined in the