diff --git a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
index 77c6eaa..53fa58e 100644
--- a/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/source_library_builder.dart
@@ -2149,7 +2149,18 @@
       /// 1. `_Named&S&M1`
       /// 2. `_Named&S&M1&M2`
       /// 3. `Named`.
-      String runningName = extractName(supertype.name);
+      Object nameSourceForExtraction;
+      if (supertype.name == null) {
+        assert(supertype is FunctionTypeBuilder);
+
+        // Function types don't have names, and we can supply any string that
+        // doesn't have to be unique. The actual supertype of the mixin will
+        // not be built in that case.
+        nameSourceForExtraction = "";
+      } else {
+        nameSourceForExtraction = supertype.name!;
+      }
+      String runningName = extractName(nameSourceForExtraction);
 
       /// True when we're building a named mixin application. Notice that for
       /// the `Named` example above, this is only true on the last
@@ -5245,7 +5256,9 @@
       declaration.charOffset, declaration.fileUri);
 }
 
-String extractName(name) => name is QualifiedName ? name.name : name;
+String extractName(Object name) {
+  return name is QualifiedName ? name.name : name as String;
+}
 
 class PostponedProblem {
   final Message message;
diff --git a/pkg/front_end/testcases/general/issue48919.dart b/pkg/front_end/testcases/general/issue48919.dart
new file mode 100644
index 0000000..9bec7cc
--- /dev/null
+++ b/pkg/front_end/testcases/general/issue48919.dart
@@ -0,0 +1,8 @@
+// Copyright (c) 2022, 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.
+
+mixin M {}
+class A = void Function() with M;
+
+main() {}
diff --git a/pkg/front_end/testcases/general/issue48919.dart.textual_outline.expect b/pkg/front_end/testcases/general/issue48919.dart.textual_outline.expect
new file mode 100644
index 0000000..21a461f
--- /dev/null
+++ b/pkg/front_end/testcases/general/issue48919.dart.textual_outline.expect
@@ -0,0 +1,3 @@
+mixin M {}
+class A = void Function() with M;
+main() {}
diff --git a/pkg/front_end/testcases/general/issue48919.dart.weak.expect b/pkg/front_end/testcases/general/issue48919.dart.weak.expect
new file mode 100644
index 0000000..ac31d73
--- /dev/null
+++ b/pkg/front_end/testcases/general/issue48919.dart.weak.expect
@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/general/issue48919.dart:6:16: Error: Can't use a function type as supertype.
+// class A = void Function() with M;
+//                ^
+//
+import self as self;
+import "dart:core" as core;
+
+abstract class M extends core::Object /*isMixinDeclaration*/  {
+}
+class A = core::Object with self::M /*hasConstConstructor*/  {
+  const synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/general/issue48919.dart.weak.modular.expect b/pkg/front_end/testcases/general/issue48919.dart.weak.modular.expect
new file mode 100644
index 0000000..ac31d73
--- /dev/null
+++ b/pkg/front_end/testcases/general/issue48919.dart.weak.modular.expect
@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/general/issue48919.dart:6:16: Error: Can't use a function type as supertype.
+// class A = void Function() with M;
+//                ^
+//
+import self as self;
+import "dart:core" as core;
+
+abstract class M extends core::Object /*isMixinDeclaration*/  {
+}
+class A = core::Object with self::M /*hasConstConstructor*/  {
+  const synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/general/issue48919.dart.weak.outline.expect b/pkg/front_end/testcases/general/issue48919.dart.weak.outline.expect
new file mode 100644
index 0000000..10edd8f
--- /dev/null
+++ b/pkg/front_end/testcases/general/issue48919.dart.weak.outline.expect
@@ -0,0 +1,20 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/general/issue48919.dart:6:16: Error: Can't use a function type as supertype.
+// class A = void Function() with M;
+//                ^
+//
+import self as self;
+import "dart:core" as core;
+
+abstract class M extends core::Object /*isMixinDeclaration*/  {
+}
+class A = core::Object with self::M /*hasConstConstructor*/  {
+  const synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method main() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/general/issue48919.dart.weak.transformed.expect b/pkg/front_end/testcases/general/issue48919.dart.weak.transformed.expect
new file mode 100644
index 0000000..4683e8a
--- /dev/null
+++ b/pkg/front_end/testcases/general/issue48919.dart.weak.transformed.expect
@@ -0,0 +1,19 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/general/issue48919.dart:6:16: Error: Can't use a function type as supertype.
+// class A = void Function() with M;
+//                ^
+//
+import self as self;
+import "dart:core" as core;
+
+abstract class M extends core::Object /*isMixinDeclaration*/  {
+}
+class A extends core::Object implements self::M /*isEliminatedMixin,hasConstConstructor*/  {
+  const synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method main() → dynamic {}
diff --git a/pkg/front_end/testcases/textual_outline.status b/pkg/front_end/testcases/textual_outline.status
index 259a964..7f8673a 100644
--- a/pkg/front_end/testcases/textual_outline.status
+++ b/pkg/front_end/testcases/textual_outline.status
@@ -98,6 +98,7 @@
 general/issue47922: FormatterCrash
 general/issue48487: FormatterCrash
 general/issue48487b: FormatterCrash
+general/issue48919: FormatterCrash
 general/issue_46886: FormatterCrash
 general/macro_class: FormatterCrash
 general/many_errors2: FormatterCrash
diff --git a/pkg/test_runner/lib/src/configuration.dart b/pkg/test_runner/lib/src/configuration.dart
index 92cf4a9..e6a0901 100644
--- a/pkg/test_runner/lib/src/configuration.dart
+++ b/pkg/test_runner/lib/src/configuration.dart
@@ -171,7 +171,7 @@
   String _packages;
 
   String get packages {
-    // If the .packages file path wasn't given, find it.
+    // If the package config file path wasn't given, find it.
     _packages ??=
         Repository.uri.resolve('.dart_tool/package_config.json').toFilePath();
 
diff --git a/pkg/test_runner/lib/src/options.dart b/pkg/test_runner/lib/src/options.dart
index d0a67e1..89d461b8 100644
--- a/pkg/test_runner/lib/src/options.dart
+++ b/pkg/test_runner/lib/src/options.dart
@@ -613,7 +613,10 @@
       var value = data[name];
       if (data[name] == option.defaultValue ||
           (name == 'packages' &&
-              value == Repository.uri.resolve('.packages').toFilePath())) {
+              value ==
+                  Repository.uri
+                      .resolve('.dart_tool/package_config.json')
+                      .toFilePath())) {
         continue;
       }
 
@@ -634,8 +637,9 @@
     // Only one value in the configuration map is mutable:
     if (selectors.containsKey('observatory_ui')) {
       if (selectors.length == 1) {
-        configuration['packages'] =
-            Repository.uri.resolve('.packages').toFilePath();
+        configuration['packages'] = Repository.uri
+            .resolve('.dart_tool/package_config.json')
+            .toFilePath();
       } else {
         // Make a new configuration whose selectors map only contains
         // observatory_ui, and remove observatory_ui from the original
@@ -648,8 +652,9 @@
         selectors.remove('observatory_ui');
 
         // Set the packages flag.
-        observatoryConfiguration['packages'] =
-            Repository.uri.resolve('.packages').toFilePath();
+        observatoryConfiguration['packages'] = Repository.uri
+            .resolve('.dart_tool/package_config.json')
+            .toFilePath();
 
         return [
           ..._expandConfigurations(configuration, selectors),
diff --git a/tests/language/const/map_hashcode_override_test.dart b/tests/language/const/map_hashcode_override_test.dart
index f8aa3cc..b9dd257 100644
--- a/tests/language/const/map_hashcode_override_test.dart
+++ b/tests/language/const/map_hashcode_override_test.dart
@@ -23,11 +23,14 @@
   const Nasty(this.n);
 
   int get hashCode {
-    while (true) {}
+    throw "Evil hashCode";
   }
 }
 
 main() {
+  // Test that when using an instance of a custom class as a key in a const Map,
+  // its hash code is computed as its identity hash, and even if the class
+  // overrides `hashCode`, that `hashCode` implementation is not called.
   final map = const {1: 42, 'foo': 499, 2: 'bar', Nasty(1): 'baz'};
   Expect.equals(42, map[getValueNonOptimized(1.0)]);
   Expect.equals(
diff --git a/tests/language_2/const/map_hashcode_override_test.dart b/tests/language_2/const/map_hashcode_override_test.dart
index a696d36..6558b75 100644
--- a/tests/language_2/const/map_hashcode_override_test.dart
+++ b/tests/language_2/const/map_hashcode_override_test.dart
@@ -25,11 +25,14 @@
   const Nasty(this.n);
 
   int get hashCode {
-    while (true) {}
+    throw "Evil hashCode";
   }
 }
 
 main() {
+  // Test that when using an instance of a custom class as a key in a const Map,
+  // its hash code is computed as its identity hash, and even if the class
+  // overrides `hashCode`, that `hashCode` implementation is not called.
   final map = const {1: 42, 'foo': 499, 2: 'bar', Nasty(1): 'baz'};
   Expect.equals(42, map[getValueNonOptimized(1.0)]);
   Expect.equals(
diff --git a/tools/VERSION b/tools/VERSION
index a3b581e..1d283ff 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 18
 PATCH 0
-PRERELEASE 104
+PRERELEASE 105
 PRERELEASE_PATCH 0
\ No newline at end of file
diff --git a/tools/generate_package_config.dart b/tools/generate_package_config.dart
index b147a28..150f06f 100644
--- a/tools/generate_package_config.dart
+++ b/tools/generate_package_config.dart
@@ -113,28 +113,6 @@
     },
   );
   writeIfDifferent(configFile, packageConfig.generateJson('..'));
-
-  // Also generate the repo's .packages file.
-  var packagesFile = File(join(repoRoot, '.packages'));
-  var buffer = StringBuffer('''
-# Copyright (c) 2016, 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.
-#
-# This file is generated; do not edit. To re-generate, run:
-#   'dart tools/generate_package_config.dart'.
-
-''');
-  for (var package in packages) {
-    final name = package.name;
-    final rootUri = package.rootUri;
-    final packageUri = package.packageUri;
-
-    if (packageUri != null && packageUri != '.nonexisting') {
-      buffer.writeln('$name:${posix(rootUri)}/${posix(packageUri)}');
-    }
-  }
-  writeIfDifferent(packagesFile, buffer.toString());
 }
 
 /// Writes the given [contents] string to [file] if the contents are different