Add enums for LPC55 pin codegen

[mkeeter]

This means that invalid pin configuration parameters will fail to parse, instead of making it through codegen and then failing at (Hubris) compile time.

I don't love leaning on the derived Debug here:

let mode = format_ident!("{}", format!("{:?}", self.get_mode()));
let slew = format_ident!("{}", format!("{:?}", self.get_slew()));
let invert = format_ident!("{}", format!("{:?}", self.get_invert()));
let digimode = format_ident!("{}", format!("{:?}", self.get_digimode()));
let od = format_ident!("{}", format!("{:?}", self.get_opendrain()));
tokens.append_all(final_pin);
tokens.append_all(quote::quote! {
    AltFn::#alt_num,
    Mode::#mode,
    Slew::#slew,
    Invert::#invert,
    Digimode::#digimode,
    Opendrain::#od,
});

but my other experiments were all worse; I'm open to suggestions for how to make this cleaner!

[hawkw]

can't these just be

Suggested change

	let mode = format_ident!("{}", format!("{:?}", self.get_mode()));
	let slew = format_ident!("{}", format!("{:?}", self.get_slew()));
	let invert = format_ident!("{}", format!("{:?}", self.get_invert()));
	let digimode =
	format_ident!("{}", format!("{:?}", self.get_digimode()));
	let od = format_ident!("{}", format!("{:?}", self.get_opendrain()));
	let mode = format_ident!("{:?}", self.get_mode());
	let slew = format_ident!("{:?}", self.get_slew());
	let invert = format_ident!("{:?}", format!("{:?}", self.get_invert());
	let digimode =
	format_ident!("{:?}", self.get_digimode());
	let od = format_ident!("{:?}", self.get_opendrain());

AFAICT, we shouldn't need the second string allocation?

[hawkw]

also, it occurs to me an alternative to using the Debug impl could be implementing ToTokens for the various enums, but...that would probably just internally use syn::Ident::new or something, which would end up looking similarish. But, you could hard-code the string, which is probably either better or worse...

[mkeeter]

Unfortunately, the former suggestion doesn't work, spitting out an impressive 4 errors per line:

error[E0277]: the trait bound `Mode: IdentFragment` is not satisfied
   --> build/lpc55pins/src/lib.rs:131:20
    |
131 |         let mode = format_ident!("{:?}", self.get_mode());
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |                    |
    |                    the trait `IdentFragment` is not implemented for `Mode`
    |                    required by a bound introduced by this call
    |
    = help: the following other types implement trait `IdentFragment`:
              &T
              &mut T
              Cow<'_, T>
              bool
              char
              proc_macro2::Ident
              std::string::String
              str
            and 6 others
    = note: required for `&Mode` to implement `IdentFragment`
note: required by a bound in `IdentFragmentAdapter`
   --> /Users/mjk/.cargo/registry/src/github.com-1ecc6299db9ec823/quote-1.0.35/src/runtime.rs:494:36
    |
494 | pub struct IdentFragmentAdapter<T: IdentFragment>(pub T);
    |                                    ^^^^^^^^^^^^^ required by this bound in `IdentFragmentAdapter`
    = note: this error originates in the macro `$crate::format_ident_impl` which comes from the expansion of the macro `format_ident` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: the trait bound `Mode: IdentFragment` is not satisfied
   --> build/lpc55pins/src/lib.rs:131:20
    |
131 |         let mode = format_ident!("{:?}", self.get_mode());
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `IdentFragment` is not implemented for `Mode`
    |
    = help: the following other types implement trait `IdentFragment`:
              &T
              &mut T
              Cow<'_, T>
              bool
              char
              proc_macro2::Ident
              std::string::String
              str
            and 6 others
    = note: required for `&Mode` to implement `IdentFragment`
note: required by a bound in `IdentFragmentAdapter`
   --> /Users/mjk/.cargo/registry/src/github.com-1ecc6299db9ec823/quote-1.0.35/src/runtime.rs:494:36
    |
494 | pub struct IdentFragmentAdapter<T: IdentFragment>(pub T);
    |                                    ^^^^^^^^^^^^^ required by this bound in `IdentFragmentAdapter`
    = note: this error originates in the macro `$crate::format_ident_impl` which comes from the expansion of the macro `format_ident` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `IdentFragmentAdapter<&Mode>` doesn't implement `Debug`
   --> build/lpc55pins/src/lib.rs:131:20
    |
131 |         let mode = format_ident!("{:?}", self.get_mode());
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `IdentFragmentAdapter<&Mode>` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
    = help: the trait `Debug` is not implemented for `IdentFragmentAdapter<&Mode>`
    = note: this error originates in the macro `$crate::__export::format_args` which comes from the expansion of the macro `format_ident` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: the trait bound `Mode: IdentFragment` is not satisfied
   --> build/lpc55pins/src/lib.rs:131:20
    |
131 |         let mode = format_ident!("{:?}", self.get_mode());
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `IdentFragment` is not implemented for `Mode`
    |
    = help: the following other types implement trait `IdentFragment`:
              &T
              &mut T
              Cow<'_, T>
              bool
              char
              proc_macro2::Ident
              std::string::String
              str
            and 6 others
    = note: required for `&Mode` to implement `IdentFragment`
note: required by a bound in `IdentFragmentAdapter`
   --> /Users/mjk/.cargo/registry/src/github.com-1ecc6299db9ec823/quote-1.0.35/src/runtime.rs:494:36
    |
494 | pub struct IdentFragmentAdapter<T: IdentFragment>(pub T);
    |                                    ^^^^^^^^^^^^^ required by this bound in `IdentFragmentAdapter`
    = note: this error originates in the macro `$crate::__export::format_args` which comes from the expansion of the macro `format_ident` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0599]: the method `span` exists for struct `IdentFragmentAdapter<&Mode>`, but its trait bounds were not satisfied
   --> build/lpc55pins/src/lib.rs:131:20
    |
131 |         let mode = format_ident!("{:?}", self.get_mode());
    |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ method cannot be called on `IdentFragmentAdapter<&Mode>` due to unsatisfied trait bounds
    |
    = note: the following trait bounds were not satisfied:
            `&Mode: IdentFragment`
    = note: this error originates in the macro `$crate::format_ident_impl` which comes from the expansion of the macro `format_ident` (in Nightly builds, run with -Z macro-backtrace for more info)

(an easy way to test is running cargo xtask build --dirty app/oxide-rot-1/app.toml swd)

I experimented with implementing some of the syn traits, but am iffy about the amount of boilerplate required...

[hawkw]

Oh, huh, I was apparently wrong about how format_ident! works!

I suppose another option would just be to write

syn::Ident::new(format!("{:?}", self.get_mode()), proc_macro2::Span::call_site())

to avoid the second allocation, although this is, admittedly, uglier...

[mkeeter]

Yeah, I'm on the fence here; if all solutions are equally ugly, then might as well pick the shorter one.

[hawkw]

Yeah...the impact on build time is probably not meaningful. Carry on.

[cbiffle]

On all of these, I recommend derive(Default) on the enum with a #[default] tag on the variant you want. These become unwrap_or_default. Or, at that point, you might leave the defaulting to the caller, depending on how it's used.

[mkeeter]

Nice, that comes out slightly shorter