Consider writing GUIDs as strings in attribute macros

[chris-morgan]

#[com_interface(EFF8970E-C50F-45E0-9284-291CE5A6F771)]
pub trait IAnimal: IUnknown { … }

This makes me uncomfortable. I’m half-expecting a formatter to reformat the GUID as EFF8970E - C50F -45E0 -9284 -291CE5A6F771 or similar (rustfmt won’t now but could conceivably in the future), and some syntax highlighters will highlight parts of it differently, e.g. “9284” as a number but the rest not. Also, if lower-case hex is used (no idea whether it’s supported in theory or not), then some GUIDs will fail to tokenise, e.g. segments 0bd5 and 1ef3 won’t compile (invalid binary literal and invalid exponent, respectively).

I would prefer the GUID to be a string:

#[com_interface("EFF8970E-C50F-45E0-9284-291CE5A6F771")]
pub trait IAnimal: IUnknown { … }

#[com_interface = "…"] would also work.

[m-hilgendorf]

Also, if lower-case hex is used (no idea whether it’s supported in theory or not), then some GUIDs will fail to tokenise, e.g. segments 0bd5 and 1ef3 won’t compile (invalid binary literal and invalid exponent, respectively).

Ran into this problem. It's not lower case hex either, e.g

use com::com_interface;
use com::interfaces::iunknown::IUnknown;

#[com_interface(000000EA-0000-0000-0000-000000000000)]
pub trait Broken: IUnknown {}

will fail with error: expected at least one digit in exponent. What's interesting is that the macro actually expands correctly.

A quick and dirty fix for this is to change macros/support/src/com_interface/iids to the following

  pub fn generate(macro_attr: &TokenStream, interface_ident: &Ident) -> HelperTokenStream {
--      let iid_value = macro_attr.to_string().replace(' ', "");
++    let mut iid_value = macro_attr.to_string().replace(' ', "");
++    if iid_value.starts_with('\"') && iid_value.ends_with('\"') {
++        iid_value = iid_value[1..iid_value.len()-1].to_string();
++    }

[rylev]

These are definitely fair points. I think we can move to using string literals instead. Thanks for reporting!