[Typechecker] Missing typechecker error when redeclared properties in traits with stricter accessibility modifiers

[lexidor]

HHVM Version

HipHop VM 4.38.0-dev (rel)
Compiler: 1577504418_723705903
Repo schema: c0008085502abfa268d64b7193673709d52f0a0c
hackc-cc9cfe59f273bf16e25b5f524e7c7f044851ec5d-4.38.0-dev

Operating System and Version

Ubuntu 18.04

Standalone code, or other way to reproduce the problem

class SailPrivateUseProtected {
  use RedeclareSailProtected;
  private null $sail; // << Typing[4113] This member visibility is: private
}
class SailPrivateUsePublic {
  use RedeclareSailPublic;
  private null $sail; // << Typing[4113] This member visibility is: private
}

class SailProtectedUsePrivate {
  use RedeclareSailPrivate;
  protected null $sail; // << Only fails at runtime
}
class SailProtectedUsePublic {
  use RedeclareSailPublic;
  protected null $sail; // << Typing[4113] This member visibility is: protected
}

class SailPublicUsePrivate {
  use RedeclareSailPrivate;
  public null $sail; // << Only fails at runtime
}
class SailPublicUsePublic {
  use RedeclareSailProtected;
  public null $sail; // << Only fails at runtime
}

trait RedeclareSailPrivate {
  private null $sail;
}
trait RedeclareSailProtected {
  protected null $sail;
}
trait RedeclareSailPublic {
  public null $sail;
}

Actual result

Typing[4113] This member visibility is: private
   --> file.hack
  3 |   private null $sail; // << Typing[4113] This member visibility is: private
    |           ^^^^
 32 |   protected null $sail;
    |             ^^^^ protected was expected

Typing[4113] This member visibility is: private
   --> file.hack
  7 |   private null $sail; // << Typing[4113] This member visibility is: private
    |           ^^^^
 35 |   public null $sail;
    |          ^^^^ public was expected

Typing[4113] This member visibility is: protected
   --> file.hack
 16 |   protected null $sail; // << Typing[4113] This member visibility is: protected
    |             ^^^^
 35 |   public null $sail;
    |          ^^^^ public was expected

3 errors found.

Expected result

All of these cases should generate an error, since they all fail at runtime with an error like:

Fatal error: Uncaught Error: trait declaration of property 'sail' is incompatible with previous declaration in file.hack:line

[lexidor]

The code that generates this error message can be found here.

[Wilfred]

@francesco-zappa-nardelli this might be interesting to you.