LanguageFeatures/nnbd/flow-analysis/reachability_A07_t05.dart

// Copyright (c) 2020, 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.

/// @assertion If N is an expression of the form E1.m1(E2), then:
///
///  Let before(E1) = before(N)
///  Let before(E2) = after(E2)
///  Let T be the static return type of the invocation
///  If T <: Never then:
///    Let null(N) = unreachable(before(N)).
///    Let notNull(N) = unreachable(before(N)).
///  Otherwise if T <: Null then:
///    Let null(N) = before(N).
///    Let notNull(N) = unreachable(before(N)).
///  Otherwise if T is non-nullable then:
///    Let null(N) = before(N).
///    Let notNull(N) = unreachable(before(N)).
///  Otherwise:
///    Let null(N) = promote(x, Null, before(N))
///    Let notNull(N) = promoteToNonNull(x, before(N))
///
/// @description Checks reachability after method call. Test return type T <: Null
///
/// @author sgrekhov@unipro.ru
/// @issue 41985

// Requirements=nnbd-strong

class C {
  Null m1() => null;
}

main() {
  C c = new C();
  int i;
  if (c.m1() == null) {
    i = 42;   // condition is always true therefore `i` must be definitely assigned
  }
  i; // It's not an error to read local non-nullable variable if it is definitely assigned
}