Add documentation for a few more lints

Change-Id: Ia6db16cee152856b277b01812b8019eb2afca5a2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/373727
Reviewed-by: Marya Belanger <[email protected]>
Reviewed-by: Phil Quitslund <[email protected]>
Commit-Queue: Brian Wilkerson <[email protected]>

Author: bwilkerson

pkg/analyzer/lib/src/test_utilities/mock_sdk.dart

@@ -380,12 +380,15 @@ abstract final class double extends num {
 }
 
 class Duration implements Comparable<Duration> {
+  static const Duration zero = Duration(seconds: 0);
+
   const Duration({int days = 0,
       int hours = 0,
       int minutes = 0,
       int seconds = 0,
       int milliseconds = 0,
       int microseconds = 0});
+
   int compareTo(Duration other) => 0;
 }
 
@@ -685,6 +688,12 @@ abstract final class String implements Comparable<String>, Pattern {
   String toUpperCase();
 }
 
+class StringBuffer implements StringSink {
+  external void write(Object? object);
+}
+
+abstract interface class StringSink {}
+
 class Symbol {
   const factory Symbol(String name) = internal.Symbol;
 }

pkg/analyzer/test/src/dart/element/name_union_test.dart

@@ -55,9 +55,14 @@ class _ElementVisitor extends GeneralizingElementVisitor<void> {
         element is PropertyAccessorElement) {
       var name = element.name;
       if (name != null) {
-        expect(union.contains(name), isTrue, reason: name);
-        // Might fail, but probably we don't have such names.
-        expect(union.contains('Z$name'), isFalse, reason: name);
+        expect(union.contains(name), isTrue, reason: 'Expected to find $name');
+        // This might fail, but the probability is low. If this does fail, try
+        // adding another `z` to the prefix.
+        expect(
+          union.contains('zz$name'),
+          isFalse,
+          reason: 'Expected to not find $name',
+        );
       }
     }
 

pkg/analyzer/test/verify_diagnostics_test.dart

@@ -124,6 +124,11 @@ class DocumentationValidator {
     'LintCode.secure_pubspec_urls',
     // The test framework doesn't yet support lints in non-dart files.
     'LintCode.sort_pub_dependencies',
+    // Doesn't produce a lint for the first example, even though the analyzer
+    // does when the example is pasted into a file.
+    'LintCode.unnecessary_lambdas',
+    // Produces an unused_field warning.
+    'LintCode.use_setters_to_change_properties',
     // Extra warning.
     'LintCode.recursive_getters',