library /*isNonNullableByDefault*/;
//
// Problems in library:
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:27:14: Error: The argument type 'B?' can't be assigned to the parameter type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   fooContext(x); // Error.
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:28:9: Error: A value of type 'B?' can't be assigned to a variable of type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   A a = x; // Error.
//         ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:29:10: Error: Can't assign spread elements of type 'B?' to collection elements of type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   <A>[...l]; // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:30:10: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
//   <A>[...l2]; // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:31:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   <A, A>{...m}; // Error.
//             ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:31:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   <A, A>{...m}; // Error.
//             ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:32:13: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
//   <A, A>{...m2}; // Error.
//             ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:10: Error: A value of type 'B?' can't be assigned to a variable of type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
// Try changing the type of the variable.
//   for (A y in l) {} // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:34:15: Error: The type 'List<B>?' used in the 'for' loop must implement 'Iterable<dynamic>' because 'List<B>?' is nullable and 'Iterable<dynamic>' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'Iterable' is from 'dart:core'.
//   for (A y in l2) {} // Error.
//               ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:36:16: Error: Type 'A' of the case expression is not a subtype of type 'B?' of this switch expression.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//     case const A():
//                ^
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:35:11: Context: The switch expression is here.
//   switch (x) /*  Error. */ {
//           ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:43:14: Error: A value of type 'B?' can't be returned from an async function with return type 'FutureOr<A>' because 'B?' is nullable and 'FutureOr<A>' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//       return x; // Error.
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:45:18: Error: A value of type 'Future<B?>' can't be returned from an async function with return type 'FutureOr<A>'.
//  - 'Future' is from 'dart:async'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//       return new Future<B?>.value(x); // Error.
//                  ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:49:10: Error: A value of type 'B?' can't be returned from a function with return type 'A' because 'B?' is nullable and 'A' isn't.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   return x; // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:53:14: Error: The argument type 'List<B?>' can't be assigned to the parameter type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   barContext(x); // Error.
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:54:15: Error: A value of type 'List<B?>' can't be assigned to a variable of type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   List<A> y = x; // Error.
//               ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:55:16: Error: Can't assign spread elements of type 'List<B?>' to collection elements of type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   <List<A>>[...l]; // Error.
//                ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:56:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   <List<A>, List<A>>{...m}; // Error.
//                         ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:56:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   <List<A>, List<A>>{...m}; // Error.
//                         ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:57:16: Error: A value of type 'List<B?>' can't be assigned to a variable of type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
// Try changing the type of the variable.
//   for (List<A> y in l) {} // Error.
//                ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:10: Error: A value of type 'List<B?>' can't be returned from a function with return type 'List<A>' because 'B?' is nullable and 'A' isn't.
//  - 'List' is from 'dart:core'.
//  - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   return x; // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:62:14: Error: The argument type 'num? Function()' can't be assigned to the parameter type 'num Function()' because 'num?' is nullable and 'num' isn't.
//   bazContext(c);
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:66:14: Error: The argument type 'Null' can't be assigned to the parameter type 'A' because 'A' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   fooContext(x); // Error.
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:67:14: Error: The value 'null' can't be assigned to the parameter type 'A' because 'A' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   fooContext(null); // Error.
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:68:10: Error: A value of type 'Null' can't be assigned to a variable of type 'A' because 'A' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   A a1 = x; // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:69:10: Error: The value 'null' can't be assigned to a variable of type 'A' because 'A' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//   A a2 = null; // Error.
//          ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:71:12: Error: A value of type 'Null' can't be returned from a function with return type 'A' because 'A' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//     return x; // Error.
//            ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:73:12: Error: The value 'null' can't be returned from a function with return type 'A' because 'A' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//     return null; // Error.
//            ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:77:14: Error: The value 'null' can't be returned from an async function with return type 'FutureOr<A>' because 'FutureOr<A>' is not nullable.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//       return null; // Error.
//              ^
//
// pkg/front_end/testcases/nnbd/assignability_error_messages.dart:79:18: Error: A value of type 'Future<Null>' can't be returned from an async function with return type 'FutureOr<A>'.
//  - 'Future' is from 'dart:async'.
//  - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
//       return new Future<Null>.value(null); // Error.
//                  ^
//
import self as self;
import "dart:core" as core;
import "dart:async" as asy;

import "dart:async";

class A extends core::Object /*hasConstConstructor*/  {
  const constructor •() → self::A
    : super core::Object::•()
    ;
}
class B extends self::A {
  synthetic constructor •() → self::B
    : super self::A::•()
    ;
}
class C extends core::Object {
  synthetic constructor •() → self::C
    : super core::Object::•()
    ;
  method call() → core::num? {}
}
static method fooContext(self::A x) → void {}
static method barContext(core::List<self::A> x) → void {}
static method bazContext(() → core::num f) → void {}
static method foo(self::B? x, core::List<self::B?> l, core::Map<self::B?, self::B?> m, core::List<self::B>? l2, core::Map<self::B, self::B>? m2) → self::A {
  self::fooContext(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:27:14: Error: The argument type 'B?' can't be assigned to the parameter type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  fooContext(x); // Error.
             ^" in x);
  self::A a = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:28:9: Error: A value of type 'B?' can't be assigned to a variable of type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  A a = x; // Error.
        ^" in x;
  core::_GrowableList::_literal1<self::A>(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:29:10: Error: Can't assign spread elements of type 'B?' to collection elements of type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  <A>[...l]; // Error.
         ^");
  core::_GrowableList::_literal1<self::A>(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:30:10: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
  <A>[...l2]; // Error.
         ^");
  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:31:13: Error: Can't assign spread entry keys of type 'B?' to map entry keys of type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  <A, A>{...m}; // Error.
            ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:31:13: Error: Can't assign spread entry values of type 'B?' to map entry values of type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  <A, A>{...m}; // Error.
            ^"};
  <self::A, self::A>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:32:13: Error: An expression whose value can be 'null' must be null-checked before it can be dereferenced.
  <A, A>{...m2}; // Error.
            ^": null};
  {
    core::Iterator<self::B?> :sync-for-iterator = l.{core::Iterable::iterator}{core::Iterator<self::B?>};
    for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
      final self::B? #t1 = :sync-for-iterator.{core::Iterator::current}{self::B?};
      {
        self::A y = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:33:10: Error: A value of type 'B?' can't be assigned to a variable of type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
Try changing the type of the variable.
  for (A y in l) {} // Error.
         ^" in #t1;
      }
    }
  }
  {
    core::Iterator<Never> :sync-for-iterator = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:34:15: Error: The type 'List<B>?' used in the 'for' loop must implement 'Iterable<dynamic>' because 'List<B>?' is nullable and 'Iterable<dynamic>' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'Iterable' is from 'dart:core'.
  for (A y in l2) {} // Error.
              ^" in l2.{core::Iterable::iterator}{core::Iterator<Never>};
    for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
      self::A y = :sync-for-iterator.{core::Iterator::current}{Never};
      {}
    }
  }
  #L1:
  switch(x) {
    #L2:
    case #C1:
      {
        break #L1;
      }
    #L3:
    default:
      {
        break #L1;
      }
  }
  function local() → FutureOr<self::A> /* futureValueType= self::A */ /* originally async */ {
    final asy::_Future<self::A> :async_future = new asy::_Future::•<self::A>();
    core::bool* :is_sync = false;
    FutureOr<self::A>? :return_value;
    (dynamic) → dynamic :async_op_then;
    (core::Object, core::StackTrace) → dynamic :async_op_error;
    core::int :await_jump_var = 0;
    dynamic :await_ctx_var;
    function :async_op(dynamic :result_or_exception, dynamic :stack_trace) → dynamic yielding 
      try {
        #L4:
        {
          if(true) {
            :return_value = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:43:14: Error: A value of type 'B?' can't be returned from an async function with return type 'FutureOr<A>' because 'B?' is nullable and 'FutureOr<A>' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
      return x; // Error.
             ^" in x;
            break #L4;
          }
          else {
            :return_value = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:45:18: Error: A value of type 'Future<B?>' can't be returned from an async function with return type 'FutureOr<A>'.
 - 'Future' is from 'dart:async'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
      return new Future<B?>.value(x); // Error.
                 ^" in asy::Future::value<self::B?>(x) as{TypeError,ForNonNullableByDefault} self::A;
            break #L4;
          }
        }
        asy::_completeOnAsyncReturn(:async_future, :return_value, :is_sync);
        return;
      }
      on dynamic catch(dynamic exception, core::StackTrace stack_trace) {
        asy::_completeOnAsyncError(:async_future, exception, stack_trace, :is_sync);
      }
    :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
    :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
    :async_op(null, null){() → dynamic};
    :is_sync = true;
    return :async_future;
  }
  return invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:49:10: Error: A value of type 'B?' can't be returned from a function with return type 'A' because 'B?' is nullable and 'A' isn't.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  return x; // Error.
         ^" in x;
}
static method bar(core::List<self::B?> x, core::List<core::List<self::B?>> l, core::Map<core::List<self::B?>, core::List<self::B?>> m) → core::List<self::A> {
  self::barContext(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:53:14: Error: The argument type 'List<B?>' can't be assigned to the parameter type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  barContext(x); // Error.
             ^" in x);
  core::List<self::A> y = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:54:15: Error: A value of type 'List<B?>' can't be assigned to a variable of type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  List<A> y = x; // Error.
              ^" in x;
  core::_GrowableList::_literal1<core::List<self::A>>(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:55:16: Error: Can't assign spread elements of type 'List<B?>' to collection elements of type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  <List<A>>[...l]; // Error.
               ^");
  <core::List<self::A>, core::List<self::A>>{invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:56:25: Error: Can't assign spread entry keys of type 'List<B?>' to map entry keys of type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  <List<A>, List<A>>{...m}; // Error.
                        ^": invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:56:25: Error: Can't assign spread entry values of type 'List<B?>' to map entry values of type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  <List<A>, List<A>>{...m}; // Error.
                        ^"};
  {
    core::Iterator<core::List<self::B?>> :sync-for-iterator = l.{core::Iterable::iterator}{core::Iterator<core::List<self::B?>>};
    for (; :sync-for-iterator.{core::Iterator::moveNext}(){() → core::bool}; ) {
      final core::List<self::B?> #t2 = :sync-for-iterator.{core::Iterator::current}{core::List<self::B?>};
      {
        core::List<self::A> y = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:57:16: Error: A value of type 'List<B?>' can't be assigned to a variable of type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
Try changing the type of the variable.
  for (List<A> y in l) {} // Error.
               ^" in #t2;
      }
    }
  }
  return invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:58:10: Error: A value of type 'List<B?>' can't be returned from a function with return type 'List<A>' because 'B?' is nullable and 'A' isn't.
 - 'List' is from 'dart:core'.
 - 'B' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  return x; // Error.
         ^" in x;
}
static method baz(self::C c) → void {
  self::bazContext(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:62:14: Error: The argument type 'num? Function()' can't be assigned to the parameter type 'num Function()' because 'num?' is nullable and 'num' isn't.
  bazContext(c);
             ^" in let final self::C #t3 = c in #t3 == null ?{() → core::num?} null : #t3.{self::C::call}{() → core::num?});
}
static method boz(Null x) → self::A {
  self::fooContext(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:66:14: Error: The argument type 'Null' can't be assigned to the parameter type 'A' because 'A' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  fooContext(x); // Error.
             ^" in x);
  self::fooContext(invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:67:14: Error: The value 'null' can't be assigned to the parameter type 'A' because 'A' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  fooContext(null); // Error.
             ^" in null);
  self::A a1 = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:68:10: Error: A value of type 'Null' can't be assigned to a variable of type 'A' because 'A' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  A a1 = x; // Error.
         ^" in x;
  self::A a2 = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:69:10: Error: The value 'null' can't be assigned to a variable of type 'A' because 'A' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
  A a2 = null; // Error.
         ^" in null;
  if(true) {
    return invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:71:12: Error: A value of type 'Null' can't be returned from a function with return type 'A' because 'A' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
    return x; // Error.
           ^" in x;
  }
  else {
    return invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:73:12: Error: The value 'null' can't be returned from a function with return type 'A' because 'A' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
    return null; // Error.
           ^" in null;
  }
  function local() → FutureOr<self::A> /* futureValueType= self::A */ /* originally async */ {
    final asy::_Future<self::A> :async_future = new asy::_Future::•<self::A>();
    core::bool* :is_sync = false;
    FutureOr<self::A>? :return_value;
    (dynamic) → dynamic :async_op_then;
    (core::Object, core::StackTrace) → dynamic :async_op_error;
    core::int :await_jump_var = 0;
    dynamic :await_ctx_var;
    function :async_op(dynamic :result_or_exception, dynamic :stack_trace) → dynamic yielding 
      try {
        #L5:
        {
          if(true) {
            :return_value = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:77:14: Error: The value 'null' can't be returned from an async function with return type 'FutureOr<A>' because 'FutureOr<A>' is not nullable.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
      return null; // Error.
             ^" in null;
            break #L5;
          }
          else {
            :return_value = invalid-expression "pkg/front_end/testcases/nnbd/assignability_error_messages.dart:79:18: Error: A value of type 'Future<Null>' can't be returned from an async function with return type 'FutureOr<A>'.
 - 'Future' is from 'dart:async'.
 - 'A' is from 'pkg/front_end/testcases/nnbd/assignability_error_messages.dart'.
      return new Future<Null>.value(null); // Error.
                 ^" in asy::Future::value<Null>(null) as{TypeError,ForNonNullableByDefault} self::A;
            break #L5;
          }
        }
        asy::_completeOnAsyncReturn(:async_future, :return_value, :is_sync);
        return;
      }
      on dynamic catch(dynamic exception, core::StackTrace stack_trace) {
        asy::_completeOnAsyncError(:async_future, exception, stack_trace, :is_sync);
      }
    :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
    :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
    :async_op(null, null){() → dynamic};
    :is_sync = true;
    return :async_future;
  }
}
static method main() → dynamic {}

constants  {
  #C1 = self::A {}
}


Constructor coverage from constants:
org-dartlang-testcase:///assignability_error_messages.dart:
- A. (from org-dartlang-testcase:///assignability_error_messages.dart:11:9)
- Object. (from org-dartlang-sdk:///sdk/lib/core/object.dart:25:9)