Linter de-linting.

A pass through with the linter shakes out a few offenders.

Nothing like a little dogfood! ;)

BUG=
R=brianwilkerson@google.com

Review URL: https://codereview.chromium.org//1988933002 .

.analysis_options

@@ -1,9 +1,8 @@
 analyzer:
   strong-mode: true
   exclude:
-    - test/_data/p4/lib/lib1.dart
-    - test/_data/p5/p5.dart
+    - test/_data/**
+    - test/rules/**
 linter:
   rules:
     - annotate_overrides
-

lib/src/analysis.dart

@@ -236,7 +236,7 @@ class DriverOptions {
 
   /// If non-null, the function to use to run pub list.  This is used to mock
   /// out executions of pub list when testing the linter.
-  RunPubList runPubList = null;
+  RunPubList runPubList;
 
   /// Whether to show SDK warnings.
   bool showSdkWarnings = false;

lib/src/pub.dart

@@ -10,7 +10,7 @@ import 'package:source_span/source_span.dart';
 import 'package:yaml/yaml.dart';
 
 PSEntry _findEntry(YamlMap map, String key) {
-  PSEntry entry = null;
+  PSEntry entry;
   map.nodes.forEach((k, v) {
     if (k is YamlScalar && key == k.toString()) {
       entry = _processScalar(k, v);

lib/src/rules/prefer_is_not_empty.dart

@@ -59,8 +59,8 @@ class Visitor extends SimpleAstVisitor {
 
   @override
   visitSimpleIdentifier(SimpleIdentifier identifier) {
-    AstNode isEmptyAccess = null;
-    SimpleIdentifier isEmptyIdentifier = null;
+    AstNode isEmptyAccess;
+    SimpleIdentifier isEmptyIdentifier;
 
     AstNode parent = identifier.parent;
     if (parent is PropertyAccess) {

lib/src/sdk.dart

@@ -205,9 +205,7 @@ class HtmlElement {}
   final resource.MemoryResourceProvider provider =
       new resource.MemoryResourceProvider();
 
-  /**
-   * The [AnalysisContextImpl] which is used for all of the sources.
-   */
+  /// The [AnalysisContextImpl] which is used for all of the sources.
   AnalysisContextImpl _analysisContext;
 
   MockSdk() {
@@ -274,7 +272,7 @@ class HtmlElement {}
       }
       if (filePath.startsWith("$libraryPath/")) {
         String pathInLibrary = filePath.substring(libraryPath.length + 1);
-        String path = '${library.shortName}/${pathInLibrary}';
+        String path = '${library.shortName}/$pathInLibrary';
         try {
           resource.File file = provider.getResource(uri.path);
           Uri dartUri = new Uri(scheme: 'dart', path: path);
@@ -362,9 +360,7 @@ class _MockSdkLibrary implements SdkLibrary {
   UnimplementedError get unimplemented => new UnimplementedError();
 }
 
-/**
- * An [AnalysisContextImpl] that only contains sources for a Dart SDK.
- */
+/// An [AnalysisContextImpl] that only contains sources for a Dart SDK.
 class _SdkAnalysisContext extends AnalysisContextImpl {
   final DartSdk sdk;
 

lib/src/util.dart

@@ -114,7 +114,7 @@ class _ErrorListener implements AnalysisErrorListener {
   }
 
   void throwIfErrors() {
-    if (!errors.isEmpty) {
+    if (errors.isNotEmpty) {
       throw new Exception(errors);
     }
   }

test/rule_test.dart

@@ -333,7 +333,7 @@ Annotation extractAnnotation(String line) {
     if (msgIndex < 1) {
       msgIndex = annotation.indexOf('T') + 1;
     }
-    String msg = null;
+    String msg;
     if (msgIndex < line.length) {
       msg = line.substring(index + msgIndex).trim();
       if (msg.isEmpty) {