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(let final<BottomType> #t1 = 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 let self::B? #t2 = x in #t2.==(null) ?{self::A} #t2 as{TypeError,ForNonNullableByDefault} self::A : #t2{self::A});
  self::A a = let final<BottomType> #t3 = 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 let self::B? #t4 = x in #t4.==(null) ?{self::A} #t4 as{TypeError,ForNonNullableByDefault} self::A : #t4{self::A};
  <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.
         ^"];
  <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};
    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
      final self::B? #t5 = :sync-for-iterator.{core::Iterator::current};
      {
        self::A y = let final<BottomType> #t6 = 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 let self::B? #t7 = #t5 in #t7.==(null) ?{self::A} #t7 as{TypeError,ForNonNullableByDefault} self::A : #t7{self::A};
      }
    }
  }
  {
    core::Iterator<dynamic> :sync-for-iterator = (let final<BottomType> #t8 = 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 let core::List<self::B>? #t9 = l2 in #t9.==(null) ?{core::Iterable<dynamic>} #t9 as{TypeError,ForNonNullableByDefault} core::Iterable<dynamic> : #t9{core::Iterable<dynamic>}).{core::Iterable::iterator};
    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
      self::A y = :sync-for-iterator.{core::Iterator::current};
      {}
    }
  }
  #L1:
  switch(x) {
    #L2:
    case #C1:
      {
        break #L1;
      }
    #L3:
    default:
      {
        break #L1;
      }
  }
  function local() → FutureOr<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 :async_stack_trace;
    (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, dynamic :exception, dynamic :stack_trace]) → dynamic yielding 
      try {
        #L4:
        {
          if(true) {
            :return_value = let final<BottomType> #t10 = 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 let self::B? #t11 = x in #t11.==(null) ?{self::A} #t11 as{TypeError,ForNonNullableByDefault} self::A : #t11{self::A};
            break #L4;
          }
          else {
            :return_value = let final<BottomType> #t12 = 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_stack_trace = asy::_asyncStackTraceHelper(:async_op);
    :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
    :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
    :async_op.call();
    :is_sync = true;
    return :async_future;
  }
  return let final<BottomType> #t13 = 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 let self::B? #t14 = x in #t14.==(null) ?{self::A} #t14 as{TypeError,ForNonNullableByDefault} self::A : #t14{self::A};
}
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(let final<BottomType> #t15 = 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 as{TypeError,ForNonNullableByDefault} core::List<self::A>);
  core::List<self::A> y = let final<BottomType> #t16 = 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 as{TypeError,ForNonNullableByDefault} core::List<self::A>;
  <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};
    for (; :sync-for-iterator.{core::Iterator::moveNext}(); ) {
      final core::List<self::B?> #t17 = :sync-for-iterator.{core::Iterator::current};
      {
        core::List<self::A> y = let final<BottomType> #t18 = 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 #t17 as{TypeError,ForNonNullableByDefault} core::List<self::A>;
      }
    }
  }
  return let final<BottomType> #t19 = 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 as{TypeError,ForNonNullableByDefault} core::List<self::A>;
}
static method baz(self::C c) → void {
  self::bazContext(let final<BottomType> #t20 = 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 #t21 = c in #t21.==(null) ?{() → core::num?} null : #t21.{self::C::call}) as{TypeError,ForNonNullableByDefault} () → core::num);
}
static method boz(Null x) → self::A {
  self::fooContext(let final<BottomType> #t22 = 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 let Null #t23 = x in #t23.==(null) ?{self::A} #t23 as{TypeError,ForNonNullableByDefault} self::A : #t23{self::A});
  self::fooContext(let final<BottomType> #t24 = 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 let Null #t25 = null in #t25.==(null) ?{self::A} #t25 as{TypeError,ForNonNullableByDefault} self::A : #t25{self::A});
  self::A a1 = let final<BottomType> #t26 = 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 let Null #t27 = x in #t27.==(null) ?{self::A} #t27 as{TypeError,ForNonNullableByDefault} self::A : #t27{self::A};
  self::A a2 = let final<BottomType> #t28 = 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 let Null #t29 = null in #t29.==(null) ?{self::A} #t29 as{TypeError,ForNonNullableByDefault} self::A : #t29{self::A};
  if(true) {
    return let final<BottomType> #t30 = 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 let Null #t31 = x in #t31.==(null) ?{self::A} #t31 as{TypeError,ForNonNullableByDefault} self::A : #t31{self::A};
  }
  else {
    return let final<BottomType> #t32 = 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 let Null #t33 = null in #t33.==(null) ?{self::A} #t33 as{TypeError,ForNonNullableByDefault} self::A : #t33{self::A};
  }
  function local() → FutureOr<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 :async_stack_trace;
    (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, dynamic :exception, dynamic :stack_trace]) → dynamic yielding 
      try {
        #L5:
        {
          if(true) {
            :return_value = let final<BottomType> #t34 = 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 let Null #t35 = null in #t35.==(null) ?{self::A} #t35 as{TypeError,ForNonNullableByDefault} self::A : #t35{self::A};
            break #L5;
          }
          else {
            :return_value = let final<BottomType> #t36 = 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_stack_trace = asy::_asyncStackTraceHelper(:async_op);
    :async_op_then = asy::_asyncThenWrapperHelper(:async_op);
    :async_op_error = asy::_asyncErrorWrapperHelper(:async_op);
    :async_op.call();
    :is_sync = true;
    return :async_future;
  }
}
static method main() → dynamic {}

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

Extra constant evaluation status:
Evaluated: MethodInvocation @ org-dartlang-testcase:///assignability_error_messages.dart:67:14 -> BoolConstant(true)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:67:14 -> NullConstant(null)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:67:14 -> NullConstant(null)
Evaluated: MethodInvocation @ org-dartlang-testcase:///assignability_error_messages.dart:69:10 -> BoolConstant(true)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:69:10 -> NullConstant(null)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:69:10 -> NullConstant(null)
Evaluated: MethodInvocation @ org-dartlang-testcase:///assignability_error_messages.dart:73:12 -> BoolConstant(true)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:73:12 -> NullConstant(null)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:73:12 -> NullConstant(null)
Evaluated: MethodInvocation @ org-dartlang-testcase:///assignability_error_messages.dart:77:14 -> BoolConstant(true)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:77:14 -> NullConstant(null)
Evaluated: VariableGet @ org-dartlang-testcase:///assignability_error_messages.dart:77:14 -> NullConstant(null)
Extra constant evaluation: evaluated: 216, effectively constant: 12