"can't use an undefined variable in an expression" error message oddity around "always true" conditionals that defined the variable

[pmetras]

This seems related to issue #2784.

Following code (Playground)

actor Main
  var _x: U8
  new create(env: Env) =>
    while true do
      _x = 5
      break
    end
    let y = _x + 2
    env.out.print("y = " + y .string())

does not compile with error

0.52.2-f7d01e80 [release]
Compiled with: LLVM 14.0.3 -- Clang-13.0.1-x86_64
Defaults: pic=true
Error:
main.pony:8:13: can't use an undefined variable in an expression
    let y = _x + 2
            ^