Lint to prefer x.isNotEmpty vs. !x.isEmpty (#143).

lib/src/linter.dart

Index: lib/src/linter.dart
diff --git a/lib/src/linter.dart b/lib/src/linter.dart
index 68b40f767840fd2afbb570b4ce8d4fcb2f354b0b..a7c0a57d2f33d129e3773e1084b1fcae083d0d82 100644
--- a/lib/src/linter.dart
+++ b/lib/src/linter.dart
@@ -98,7 +98,7 @@ class DartLinter implements AnalysisErrorListener {
           } on Exception catch (e) {
             reporter.exception(new LinterException(e.toString()));
           }
-          if (rule._locationInfo != null && !rule._locationInfo.isEmpty) {
+          if (rule._locationInfo != null && rule._locationInfo.isNotEmpty) {
             results.addAll(rule._locationInfo);
             rule._locationInfo.clear();
           }
@@ -399,7 +399,7 @@ class SourceLinter implements DartLinter, AnalysisErrorListener {
           } on Exception catch (e) {
             reporter.exception(new LinterException(e.toString()));
           }
-          if (rule._locationInfo != null && !rule._locationInfo.isEmpty) {
+          if (rule._locationInfo != null && rule._locationInfo.isNotEmpty) {
             results.addAll(rule._locationInfo);
             rule._locationInfo.clear();
           }