[stable][kernel] Fix record type equivalence

- Increment index to avoid infinite loop when the first named elements
  in the two record types are equivalent.
- Add some test cases for record types.

Fixes: #52817
Cherry-pick: https://dart-review.googlesource.com/c/sdk/+/311929
Change-Id: Iaa4dbf7d2659deeac1eab642cc3aefad9a08f67e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/312709
Commit-Queue: Nicholas Shahan <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>
Reviewed-by: Kevin Chisholm <[email protected]>

CHANGELOG.md

@@ -4,10 +4,13 @@ This is a patch release that:
 
 - Fixes a flow in flow analysis that causes it to sometimes ignore destructuring
   assignments (issue [#52767]).
+- Fixes an infinite loop in some web development compiles that include `is` or
+  `as` expressions involving record types with named fields (issue [#52869]).
 - Fixes a memory leak in Dart analyzer's file-watching (issue [#52791]).
 - Fixes a memory leak of file system watcher related data structures (issue [#52793]).
 
 [#52767]: https://github.com/dart-lang/sdk/issues/52767
+[#52869]: https://github.com/dart-lang/sdk/issues/52869
 [#52791]: https://github.com/dart-lang/sdk/issues/52791
 [#52793]: https://github.com/dart-lang/sdk/issues/52793
 

pkg/kernel/lib/src/dart_type_equivalence.dart

@@ -129,18 +129,19 @@ class DartTypeEquivalence implements DartTypeVisitor1<bool, DartType> {
         }
       }
 
-      // The named fields of [RecordType]s are supposed to be sorted, so we can
-      // use a linear search to compare them.
-      int nodeIndex = 0;
-      int otherIndex = 0;
-      while (result && nodeIndex < node.named.length) {
-        NamedType nodeNamedType = node.named[nodeIndex];
-        NamedType otherNamedType = other.named[otherIndex];
+      // The named fields of [RecordType]s are supposed to be sorted and we know
+      // there are the same number of named fields, so we can use a linear
+      // search to compare them.
+      int i = 0;
+      while (result && i < node.named.length) {
+        NamedType nodeNamedType = node.named[i];
+        NamedType otherNamedType = other.named[i];
         if (nodeNamedType.name != otherNamedType.name) {
           result = false;
         } else {
           result = nodeNamedType.type.accept1(this, otherNamedType.type);
         }
+        i++;
       }
 
       return result;

pkg/kernel/test/dart_type_equivalence_test.dart

@@ -162,6 +162,22 @@ void run() {
   notEqual("Typedef<Object?>?", "Typedef<dynamic>", equateTopTypes: true);
   areEqual("Typedef<Object?>?", "Typedef<dynamic>",
       equateTopTypes: true, ignoreTopLevelNullability: true);
+
+  // Record types.
+  areEqual("(int, bool)", "(int, bool)");
+  notEqual("(int, bool)", "(int?, bool)");
+  notEqual("(int, bool)", "(int, bool?)");
+  notEqual("(int, bool)", "({int i, bool b})");
+  areEqual("({int i, bool b})", "({int i, bool b})");
+  areEqual("({int i, bool b})", "({bool b ,int i})");
+  notEqual("({int i, bool b})", "({int? i, bool b})");
+  notEqual("({int i, bool b})", "({int i, bool? b})");
+  notEqual("({int i, bool b})", "({int n, bool b})");
+  notEqual("({int i, bool b})", "({int i, bool t})");
+  areEqual("(int, {bool b})", "(int, {bool b})");
+  notEqual("(int, {bool b})", "(int?, {bool b})");
+  notEqual("(int, {bool b})", "(int, {bool? b})");
+  notEqual("(int, {bool b})", "(int, {bool t})");
 }
 
 void areEqual(String type1, String type2,