Casting Char to Int fail signedness checker

[yongweiy]

final class C {
  char c;
  public int foo() {
    int x = 1;
    x = x + (int) c;
    return x;
  }
}

gives

error: [return.type.incompatible] incompatible types in return.
    return x;
           ^
  type of expression: @Unsigned int
  method return type: @Signed int

However, this is okay.

final class C {
  public int foo() {
    char c = 65535;
    int x = 1;
    x = x + (int) c;
    return x;
  }
}

I wonder if it is a false positive.

My current workaround is to trade the error for a warning.

import org.checkerframework.checker.signedness.qual.SignedPositive;

final class C {
  char c;
  public int foo() {
    int x = 1;
    x = x + (@SignedPositive int) c;
    return x;
  }
}

results in

warning: [cast.unsafe] cast from "@Unsigned char" to "@SignednessGlb int" cannot be statically verified
    x = x + (@SignedPositive int) c;
            ^

[mernst]

Thanks for your bug report. I'm sorry you are having trouble.

What version of the Checker Framework are you using?
I was unable to reproduce your problem on the latest version of the Checker Framework from its version control repository. You can see that #5257 is passing tests.

[yongweiy]

Thanks for looking into it, Michael!

You are right. I am using an old version (3.6.0) of the Checker Framework.

Sorry about the confusion. I will close the issue.