diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index c67595127c2..a9f13373499 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -8347,8 +8347,37 @@ class BodyBuilder extends StackListenerImpl
     // TODO(cstefantsova): Handle the case of secondIdentifier != null
     handleIdentifier(firstIdentifier, IdentifierContext.typeReference);
     Object? resolvedIdentifier = pop();
+
     if (resolvedIdentifier is TypeUseGenerator) {
       TypeDeclarationBuilder typeDeclaration = resolvedIdentifier.declaration;
+
+      if (typeDeclaration is TypeAliasBuilder) {
+        if (typeArguments == null ||
+            typeArguments.length ==
+                typeDeclaration.typedef.typeParameters.length) {
+          TypeDeclarationBuilder? unaliasedTypeDeclaration =
+              typeDeclaration.unaliasDeclaration(typeArguments);
+          List<TypeBuilder>? unaliasedTypeArguments =
+              typeDeclaration.unaliasTypeArguments(typeArguments);
+          if (unaliasedTypeDeclaration == null) {
+            // TODO(cstefantsova): Make sure an error is reported elsewhere.
+            push(new DummyPattern(firstIdentifier.charOffset));
+            return;
+          } else {
+            typeDeclaration = unaliasedTypeDeclaration;
+            typeArguments = unaliasedTypeArguments;
+          }
+        } else {
+          addProblem(
+              fasta.templateTypeArgumentMismatch
+                  .withArguments(typeDeclaration.typedef.typeParameters.length),
+              firstIdentifier.charOffset,
+              noLength);
+          push(new DummyPattern(firstIdentifier.charOffset));
+          return;
+        }
+      }
+
       if (typeDeclaration is ClassBuilder) {
         List<DartType>? builtTypeArguments;
         if (typeArguments != null) {
@@ -8359,7 +8388,13 @@ class BodyBuilder extends StackListenerImpl
                   .add(typeBuilder.build(libraryBuilder, TypeUse.typeArgument));
             }
           } else {
-            // TODO(cstefantsova): Report an error.
+            addProblem(
+                fasta.templateTypeArgumentMismatch
+                    .withArguments(typeDeclaration.cls.typeParameters.length),
+                firstIdentifier.charOffset,
+                noLength);
+            push(new DummyPattern(firstIdentifier.charOffset));
+            return;
           }
         }
         push(new ObjectPattern(
@@ -8368,7 +8403,7 @@ class BodyBuilder extends StackListenerImpl
             builtTypeArguments,
             firstIdentifier.offset));
       } else {
-        // TODO(cstefantsova): Handle this case.
+        // TODO(cstefantsova): Handle other possibilities.
         push(new DummyPattern(firstIdentifier.charOffset));
       }
     } else {
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart b/pkg/front_end/testcases/patterns/object_pattern_errors.dart
new file mode 100644
index 00000000000..ca53cfd300c
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart
@@ -0,0 +1,14 @@
+// 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.
+
+class A {}
+
+typedef B<X> = A;
+
+test(dynamic x) {
+  if (x case A<int>()) {} // Error.
+  if (x case B()) {} // Ok: the type argument is inferred.
+  if (x case B<int>()) {} // Ok.
+  if (x case B<String, num>()) {} // Error.
+}
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.expect
new file mode 100644
index 00000000000..12565fa5ce4
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.expect
@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.transformed.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.transformed.expect
new file mode 100644
index 00000000000..12565fa5ce4
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.strong.transformed.expect
@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline.expect
new file mode 100644
index 00000000000..7570659d58f
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline.expect
@@ -0,0 +1,4 @@
+class A {}
+
+typedef B<X> = A;
+test(dynamic x) {}
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..ec8e681c68d
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.textual_outline_modelled.expect
@@ -0,0 +1,4 @@
+class A {}
+
+test(dynamic x) {}
+typedef B<X> = A;
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.expect
new file mode 100644
index 00000000000..12565fa5ce4
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.expect
@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.modular.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.modular.expect
new file mode 100644
index 00000000000..12565fa5ce4
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.modular.expect
@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.outline.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.outline.expect
new file mode 100644
index 00000000000..292f781d2e3
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.outline.expect
@@ -0,0 +1,13 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    ;
+}
+static method test(dynamic x) → dynamic
+  ;
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();
diff --git a/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.transformed.expect b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.transformed.expect
new file mode 100644
index 00000000000..12565fa5ce4
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/object_pattern_errors.dart.weak.transformed.expect
@@ -0,0 +1,35 @@
+library /*isNonNullableByDefault*/;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:10:14: Error: Expected 0 type arguments.
+//   if (x case A<int>()) {} // Error.
+//              ^
+//
+// pkg/front_end/testcases/patterns/object_pattern_errors.dart:13:14: Error: Expected 1 type arguments.
+//   if (x case B<String, num>()) {} // Error.
+//              ^
+//
+import self as self;
+import "dart:core" as core;
+
+typedef B<unrelated X extends core::Object? = dynamic> = self::A;
+class A extends core::Object {
+  synthetic constructor •() → self::A
+    : super core::Object::•()
+    ;
+}
+static method test(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final dynamic #t2 = x;
+  final dynamic #t3 = #t2;
+  if(#t3 is self::A) {
+  }
+  final dynamic #t4 = x;
+  final dynamic #t5 = #t4;
+  if(#t5 is self::A) {
+  }
+  final dynamic #t6 = x;
+}
+static method _#B#new#tearOff<unrelated X extends core::Object? = dynamic>() → self::A
+  return new self::A::•();
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart
new file mode 100644
index 00000000000..763547bed09
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart
@@ -0,0 +1,52 @@
+// 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.
+
+class A {
+  int foo;
+
+  A(this.foo);
+}
+
+typedef B = A;
+
+class C<X, Y> {
+  X x;
+  Y y;
+
+  C(this.x, this.y);
+}
+
+typedef D<X> = C<X, X>;
+
+test1(dynamic x) {
+  if (x case B(:var foo)) {
+    return foo;
+  } else {
+    return null;
+  }
+}
+
+test2(dynamic x) {
+  if (x case D<String>(:var x)) {
+    return x;
+  } else {
+    return null;
+  }
+}
+
+main() {
+  expectEquals(0, test1(new A(0)));
+  expectEquals(1, test1(new B(1)));
+  expectEquals(null, test1(null));
+
+  expectEquals("one", test2(new C("one", "two")));
+  expectEquals("one", test2(new D("one", "two")));
+  expectEquals(null, test2(null));
+}
+
+expectEquals(x, y) {
+  if (x != y) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.strong.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.strong.expect
new file mode 100644
index 00000000000..e6c5ae8d97b
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.strong.expect
@@ -0,0 +1,70 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B = self::A;
+typedef D<X extends core::Object? = dynamic> = self::C<X%, X%>;
+class A extends core::Object {
+  field core::int foo;
+  constructor •(core::int foo) → self::A
+    : self::A::foo = foo, super core::Object::•()
+    ;
+}
+class C<X extends core::Object? = dynamic, Y extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C::X% x;
+  covariant-by-class field self::C::Y% y;
+  constructor •(self::C::X% x, self::C::Y% y) → self::C<self::C::X%, self::C::Y%>
+    : self::C::x = x, self::C::y = y, super core::Object::•()
+    ;
+}
+static method test1(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final core::bool #t2 = true;
+  final dynamic #t3 = #t1;
+  if(#t3 is self::A) {
+    final core::int #t4 = #t3{self::A}.{self::A::foo}{core::int};
+    #t2 = false;
+    {
+      dynamic foo = #t4;
+      {
+        return foo;
+      }
+    }
+  }
+  if(#t2) {
+    return null;
+  }
+}
+static method test2(dynamic x) → dynamic {
+  final dynamic #t5 = x;
+  final core::bool #t6 = true;
+  final dynamic #t7 = #t5;
+  if(#t7 is self::C<core::String, core::String>) {
+    final core::String #t8 = #t7{self::C<core::String, core::String>}.{self::C::x}{core::String};
+    #t6 = false;
+    {
+      dynamic x = #t8;
+      {
+        return x;
+      }
+    }
+  }
+  if(#t6) {
+    return null;
+  }
+}
+static method main() → dynamic {
+  self::expectEquals(0, self::test1(new self::A::•(0)));
+  self::expectEquals(1, self::test1(new self::A::•(1)));
+  self::expectEquals(null, self::test1(null));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals(null, self::test2(null));
+}
+static method expectEquals(dynamic x, dynamic y) → dynamic {
+  if(!(x =={core::Object::==}{(core::Object) → core::bool} y)) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}
+static method _#D#new#tearOff<X extends core::Object? = dynamic>(self::_#D#new#tearOff::X% x, self::_#D#new#tearOff::X% y) → self::C<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>
+  return new self::C::•<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>(x, y);
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.strong.transformed.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.strong.transformed.expect
new file mode 100644
index 00000000000..e6c5ae8d97b
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.strong.transformed.expect
@@ -0,0 +1,70 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B = self::A;
+typedef D<X extends core::Object? = dynamic> = self::C<X%, X%>;
+class A extends core::Object {
+  field core::int foo;
+  constructor •(core::int foo) → self::A
+    : self::A::foo = foo, super core::Object::•()
+    ;
+}
+class C<X extends core::Object? = dynamic, Y extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C::X% x;
+  covariant-by-class field self::C::Y% y;
+  constructor •(self::C::X% x, self::C::Y% y) → self::C<self::C::X%, self::C::Y%>
+    : self::C::x = x, self::C::y = y, super core::Object::•()
+    ;
+}
+static method test1(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final core::bool #t2 = true;
+  final dynamic #t3 = #t1;
+  if(#t3 is self::A) {
+    final core::int #t4 = #t3{self::A}.{self::A::foo}{core::int};
+    #t2 = false;
+    {
+      dynamic foo = #t4;
+      {
+        return foo;
+      }
+    }
+  }
+  if(#t2) {
+    return null;
+  }
+}
+static method test2(dynamic x) → dynamic {
+  final dynamic #t5 = x;
+  final core::bool #t6 = true;
+  final dynamic #t7 = #t5;
+  if(#t7 is self::C<core::String, core::String>) {
+    final core::String #t8 = #t7{self::C<core::String, core::String>}.{self::C::x}{core::String};
+    #t6 = false;
+    {
+      dynamic x = #t8;
+      {
+        return x;
+      }
+    }
+  }
+  if(#t6) {
+    return null;
+  }
+}
+static method main() → dynamic {
+  self::expectEquals(0, self::test1(new self::A::•(0)));
+  self::expectEquals(1, self::test1(new self::A::•(1)));
+  self::expectEquals(null, self::test1(null));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals(null, self::test2(null));
+}
+static method expectEquals(dynamic x, dynamic y) → dynamic {
+  if(!(x =={core::Object::==}{(core::Object) → core::bool} y)) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}
+static method _#D#new#tearOff<X extends core::Object? = dynamic>(self::_#D#new#tearOff::X% x, self::_#D#new#tearOff::X% y) → self::C<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>
+  return new self::C::•<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>(x, y);
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.textual_outline.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.textual_outline.expect
new file mode 100644
index 00000000000..c4cc6decf62
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.textual_outline.expect
@@ -0,0 +1,18 @@
+class A {
+  int foo;
+  A(this.foo);
+}
+
+typedef B = A;
+
+class C<X, Y> {
+  X x;
+  Y y;
+  C(this.x, this.y);
+}
+
+typedef D<X> = C<X, X>;
+test1(dynamic x) {}
+test2(dynamic x) {}
+main() {}
+expectEquals(x, y) {}
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..33e21fff1e8
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.textual_outline_modelled.expect
@@ -0,0 +1,17 @@
+class A {
+  A(this.foo);
+  int foo;
+}
+
+class C<X, Y> {
+  C(this.x, this.y);
+  X x;
+  Y y;
+}
+
+expectEquals(x, y) {}
+main() {}
+test1(dynamic x) {}
+test2(dynamic x) {}
+typedef B = A;
+typedef D<X> = C<X, X>;
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.expect
new file mode 100644
index 00000000000..e6c5ae8d97b
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.expect
@@ -0,0 +1,70 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B = self::A;
+typedef D<X extends core::Object? = dynamic> = self::C<X%, X%>;
+class A extends core::Object {
+  field core::int foo;
+  constructor •(core::int foo) → self::A
+    : self::A::foo = foo, super core::Object::•()
+    ;
+}
+class C<X extends core::Object? = dynamic, Y extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C::X% x;
+  covariant-by-class field self::C::Y% y;
+  constructor •(self::C::X% x, self::C::Y% y) → self::C<self::C::X%, self::C::Y%>
+    : self::C::x = x, self::C::y = y, super core::Object::•()
+    ;
+}
+static method test1(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final core::bool #t2 = true;
+  final dynamic #t3 = #t1;
+  if(#t3 is self::A) {
+    final core::int #t4 = #t3{self::A}.{self::A::foo}{core::int};
+    #t2 = false;
+    {
+      dynamic foo = #t4;
+      {
+        return foo;
+      }
+    }
+  }
+  if(#t2) {
+    return null;
+  }
+}
+static method test2(dynamic x) → dynamic {
+  final dynamic #t5 = x;
+  final core::bool #t6 = true;
+  final dynamic #t7 = #t5;
+  if(#t7 is self::C<core::String, core::String>) {
+    final core::String #t8 = #t7{self::C<core::String, core::String>}.{self::C::x}{core::String};
+    #t6 = false;
+    {
+      dynamic x = #t8;
+      {
+        return x;
+      }
+    }
+  }
+  if(#t6) {
+    return null;
+  }
+}
+static method main() → dynamic {
+  self::expectEquals(0, self::test1(new self::A::•(0)));
+  self::expectEquals(1, self::test1(new self::A::•(1)));
+  self::expectEquals(null, self::test1(null));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals(null, self::test2(null));
+}
+static method expectEquals(dynamic x, dynamic y) → dynamic {
+  if(!(x =={core::Object::==}{(core::Object) → core::bool} y)) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}
+static method _#D#new#tearOff<X extends core::Object? = dynamic>(self::_#D#new#tearOff::X% x, self::_#D#new#tearOff::X% y) → self::C<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>
+  return new self::C::•<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>(x, y);
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.modular.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.modular.expect
new file mode 100644
index 00000000000..e6c5ae8d97b
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.modular.expect
@@ -0,0 +1,70 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B = self::A;
+typedef D<X extends core::Object? = dynamic> = self::C<X%, X%>;
+class A extends core::Object {
+  field core::int foo;
+  constructor •(core::int foo) → self::A
+    : self::A::foo = foo, super core::Object::•()
+    ;
+}
+class C<X extends core::Object? = dynamic, Y extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C::X% x;
+  covariant-by-class field self::C::Y% y;
+  constructor •(self::C::X% x, self::C::Y% y) → self::C<self::C::X%, self::C::Y%>
+    : self::C::x = x, self::C::y = y, super core::Object::•()
+    ;
+}
+static method test1(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final core::bool #t2 = true;
+  final dynamic #t3 = #t1;
+  if(#t3 is self::A) {
+    final core::int #t4 = #t3{self::A}.{self::A::foo}{core::int};
+    #t2 = false;
+    {
+      dynamic foo = #t4;
+      {
+        return foo;
+      }
+    }
+  }
+  if(#t2) {
+    return null;
+  }
+}
+static method test2(dynamic x) → dynamic {
+  final dynamic #t5 = x;
+  final core::bool #t6 = true;
+  final dynamic #t7 = #t5;
+  if(#t7 is self::C<core::String, core::String>) {
+    final core::String #t8 = #t7{self::C<core::String, core::String>}.{self::C::x}{core::String};
+    #t6 = false;
+    {
+      dynamic x = #t8;
+      {
+        return x;
+      }
+    }
+  }
+  if(#t6) {
+    return null;
+  }
+}
+static method main() → dynamic {
+  self::expectEquals(0, self::test1(new self::A::•(0)));
+  self::expectEquals(1, self::test1(new self::A::•(1)));
+  self::expectEquals(null, self::test1(null));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals(null, self::test2(null));
+}
+static method expectEquals(dynamic x, dynamic y) → dynamic {
+  if(!(x =={core::Object::==}{(core::Object) → core::bool} y)) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}
+static method _#D#new#tearOff<X extends core::Object? = dynamic>(self::_#D#new#tearOff::X% x, self::_#D#new#tearOff::X% y) → self::C<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>
+  return new self::C::•<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>(x, y);
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.outline.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.outline.expect
new file mode 100644
index 00000000000..09ecd76ef8d
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.outline.expect
@@ -0,0 +1,27 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B = self::A;
+typedef D<X extends core::Object? = dynamic> = self::C<X%, X%>;
+class A extends core::Object {
+  field core::int foo;
+  constructor •(core::int foo) → self::A
+    ;
+}
+class C<X extends core::Object? = dynamic, Y extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C::X% x;
+  covariant-by-class field self::C::Y% y;
+  constructor •(self::C::X% x, self::C::Y% y) → self::C<self::C::X%, self::C::Y%>
+    ;
+}
+static method test1(dynamic x) → dynamic
+  ;
+static method test2(dynamic x) → dynamic
+  ;
+static method main() → dynamic
+  ;
+static method expectEquals(dynamic x, dynamic y) → dynamic
+  ;
+static method _#D#new#tearOff<X extends core::Object? = dynamic>(self::_#D#new#tearOff::X% x, self::_#D#new#tearOff::X% y) → self::C<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>
+  return new self::C::•<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>(x, y);
diff --git a/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.transformed.expect b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.transformed.expect
new file mode 100644
index 00000000000..e6c5ae8d97b
--- /dev/null
+++ b/pkg/front_end/testcases/patterns/typedef_in_object_pattern.dart.weak.transformed.expect
@@ -0,0 +1,70 @@
+library /*isNonNullableByDefault*/;
+import self as self;
+import "dart:core" as core;
+
+typedef B = self::A;
+typedef D<X extends core::Object? = dynamic> = self::C<X%, X%>;
+class A extends core::Object {
+  field core::int foo;
+  constructor •(core::int foo) → self::A
+    : self::A::foo = foo, super core::Object::•()
+    ;
+}
+class C<X extends core::Object? = dynamic, Y extends core::Object? = dynamic> extends core::Object {
+  covariant-by-class field self::C::X% x;
+  covariant-by-class field self::C::Y% y;
+  constructor •(self::C::X% x, self::C::Y% y) → self::C<self::C::X%, self::C::Y%>
+    : self::C::x = x, self::C::y = y, super core::Object::•()
+    ;
+}
+static method test1(dynamic x) → dynamic {
+  final dynamic #t1 = x;
+  final core::bool #t2 = true;
+  final dynamic #t3 = #t1;
+  if(#t3 is self::A) {
+    final core::int #t4 = #t3{self::A}.{self::A::foo}{core::int};
+    #t2 = false;
+    {
+      dynamic foo = #t4;
+      {
+        return foo;
+      }
+    }
+  }
+  if(#t2) {
+    return null;
+  }
+}
+static method test2(dynamic x) → dynamic {
+  final dynamic #t5 = x;
+  final core::bool #t6 = true;
+  final dynamic #t7 = #t5;
+  if(#t7 is self::C<core::String, core::String>) {
+    final core::String #t8 = #t7{self::C<core::String, core::String>}.{self::C::x}{core::String};
+    #t6 = false;
+    {
+      dynamic x = #t8;
+      {
+        return x;
+      }
+    }
+  }
+  if(#t6) {
+    return null;
+  }
+}
+static method main() → dynamic {
+  self::expectEquals(0, self::test1(new self::A::•(0)));
+  self::expectEquals(1, self::test1(new self::A::•(1)));
+  self::expectEquals(null, self::test1(null));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals("one", self::test2(new self::C::•<core::String, core::String>("one", "two")));
+  self::expectEquals(null, self::test2(null));
+}
+static method expectEquals(dynamic x, dynamic y) → dynamic {
+  if(!(x =={core::Object::==}{(core::Object) → core::bool} y)) {
+    throw "Expected ${x} to be equal to ${y}.";
+  }
+}
+static method _#D#new#tearOff<X extends core::Object? = dynamic>(self::_#D#new#tearOff::X% x, self::_#D#new#tearOff::X% y) → self::C<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>
+  return new self::C::•<self::_#D#new#tearOff::X%, self::_#D#new#tearOff::X%>(x, y);