The error message on a reference to an unresolved symbol is not helpful

[ithinuel]

The following snippet fails to compile with:

pio_proc::pio_asm!(
    ".wrap_target"
    "jmp wrap_target"
);

error: proc macro panicked
   --> src/pio.rs:107:23
    |
xxx |           let program = pio_proc::pio_asm!(
    |  _______________________^
xxx | |             ".wrap_target"
xxx | |             "jmp wrap_target"
xxx | |         )
    | |_________^
    |
    = help: message: no entry found for key

ProgramState::resolve should handle this case with a better error message.