Issue 52409. Reading a Never typed getter makes the flow unreachable.

Bug: https://github.com/dart-lang/sdk/issues/52409
Change-Id: I675ed8f8cfa0d2e5327c2c6bc0fb1bda7bde038c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/303840
Reviewed-by: Paul Berry <paulberry@google.com>
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>

pkg/_fe_analyzer_shared/lib/src/type_inference/type_analyzer.dart

@@ -1293,6 +1293,9 @@ mixin TypeAnalyzer<
             receiverType: requiredType,
             field: field,
           );
+      if (operations.isNever(propertyType)) {
+        flow.handleExit();
+      }
       flow.pushSubpattern(propertyType);
       dispatchPattern(
         context.withUnnecessaryWildcardKind(null),

pkg/_fe_analyzer_shared/test/flow_analysis/flow_analysis_test.dart

@@ -8072,6 +8072,22 @@ main() {
           ]);
         });
       });
+
+      test('Read of Never typed getter makes unreachable', () {
+        h.addDownwardInfer(name: 'A', context: 'Object', result: 'A');
+        h.addMember('A', 'foo', 'Never');
+        h.run([
+          ifCase(
+            expr('Object'),
+            objectPattern(requiredType: 'A', fields: [
+              Var('foo').pattern().recordField('foo'),
+            ]),
+            [
+              checkReachable(false),
+            ],
+          ),
+        ]);
+      });
     });
 
     group('Pattern assignment:', () {

pkg/analyzer/test/src/diagnostics/dead_code_test.dart

@@ -137,6 +137,20 @@ void f(int a) {
       error(WarningCode.DEAD_CODE, 30, 7),
     ]);
   }
+
+  test_objectPattern_neverTypedGetter() async {
+    await assertErrorsInCode(r'''
+class A {
+  Never get foo => throw 0;
+}
+
+void f(Object x) {
+  if (x case A(foo: _)) {}
+}
+''', [
+      error(WarningCode.DEAD_CODE, 84, 2),
+    ]);
+  }
 }
 
 @reflectiveTest

tests/language/patterns/issue52409_test.dart

@@ -0,0 +1,28 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Regression test for https://github.com/dart-lang/sdk/issues/52409.
+
+import 'package:expect/expect.dart';
+
+import "../static_type_helper.dart";
+
+class A {
+  Never get getterThatReturnsNever => throw 0;
+}
+
+void f(Object? x) {
+  int? y = 0; // implicitly promotes to `int`
+  switch (x) {
+    case A(getterThatReturnsNever: _):
+      y = null;
+    default:
+  }
+  // `y = null` was unreachable, so `y` should still be promoted to `int`
+  y.expectStaticType<Exactly<int>>();
+}
+
+void main() {
+  f(0);
+}