1// SPDX-License-Identifier: Apache-2.0 OR MIT
  2
  3use crate::helpers::{parse_generics, Generics};
  4use proc_macro::{Group, Punct, Spacing, TokenStream, TokenTree};
  5
  6pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream {
  7    // This proc-macro only does some pre-parsing and then delegates the actual parsing to
  8    // `kernel::__pin_data!`.
  9
 10    let (
 11        Generics {
 12            impl_generics,
 13            ty_generics,
 14        },
 15        rest,
 16    ) = parse_generics(input);
 17    // The struct definition might contain the `Self` type. Since `__pin_data!` will define a new
 18    // type with the same generics and bounds, this poses a problem, since `Self` will refer to the
 19    // new type as opposed to this struct definition. Therefore we have to replace `Self` with the
 20    // concrete name.
 21
 22    // Errors that occur when replacing `Self` with `struct_name`.
 23    let mut errs = TokenStream::new();
 24    // The name of the struct with ty_generics.
 25    let struct_name = rest
 26        .iter()
 27        .skip_while(|tt| !matches!(tt, TokenTree::Ident(i) if i.to_string() == "struct"))
 28        .nth(1)
 29        .and_then(|tt| match tt {
 30            TokenTree::Ident(_) => {
 31                let tt = tt.clone();
 32                let mut res = vec![tt];
 33                if !ty_generics.is_empty() {
 34                    // We add this, so it is maximally compatible with e.g. `Self::CONST` which
 35                    // will be replaced by `StructName::<$generics>::CONST`.
 36                    res.push(TokenTree::Punct(Punct::new(':', Spacing::Joint)));
 37                    res.push(TokenTree::Punct(Punct::new(':', Spacing::Alone)));
 38                    res.push(TokenTree::Punct(Punct::new('<', Spacing::Alone)));
 39                    res.extend(ty_generics.iter().cloned());
 40                    res.push(TokenTree::Punct(Punct::new('>', Spacing::Alone)));
 41                }
 42                Some(res)
 43            }
 44            _ => None,
 45        })
 46        .unwrap_or_else(|| {
 47            // If we did not find the name of the struct then we will use `Self` as the replacement
 48            // and add a compile error to ensure it does not compile.
 49            errs.extend(
 50                "::core::compile_error!(\"Could not locate type name.\");"
 51                    .parse::<TokenStream>()
 52                    .unwrap(),
 53            );
 54            "Self".parse::<TokenStream>().unwrap().into_iter().collect()
 55        });
 56    let impl_generics = impl_generics
 57        .into_iter()
 58        .flat_map(|tt| replace_self_and_deny_type_defs(&struct_name, tt, &mut errs))
 59        .collect::<Vec<_>>();
 60    let mut rest = rest
 61        .into_iter()
 62        .flat_map(|tt| {
 63            // We ignore top level `struct` tokens, since they would emit a compile error.
 64            if matches!(&tt, TokenTree::Ident(i) if i.to_string() == "struct") {
 65                vec![tt]
 66            } else {
 67                replace_self_and_deny_type_defs(&struct_name, tt, &mut errs)
 68            }
 69        })
 70        .collect::<Vec<_>>();
 71    // This should be the body of the struct `{...}`.
 72    let last = rest.pop();
 73    let mut quoted = quote!(::kernel::__pin_data! {
 74        parse_input:
 75        @args(#args),
 76        @sig(#(#rest)*),
 77        @impl_generics(#(#impl_generics)*),
 78        @ty_generics(#(#ty_generics)*),
 79        @body(#last),
 80    });
 81    quoted.extend(errs);
 82    quoted
 83}
 84
 85/// Replaces `Self` with `struct_name` and errors on `enum`, `trait`, `struct` `union` and `impl`
 86/// keywords.
 87///
 88/// The error is appended to `errs` to allow normal parsing to continue.
 89fn replace_self_and_deny_type_defs(
 90    struct_name: &Vec<TokenTree>,
 91    tt: TokenTree,
 92    errs: &mut TokenStream,
 93) -> Vec<TokenTree> {
 94    match tt {
 95        TokenTree::Ident(ref i)
 96            if i.to_string() == "enum"
 97                || i.to_string() == "trait"
 98                || i.to_string() == "struct"
 99                || i.to_string() == "union"
100                || i.to_string() == "impl" =>
101        {
102            errs.extend(
103                format!(
104                    "::core::compile_error!(\"Cannot use `{i}` inside of struct definition with \
105                        `#[pin_data]`.\");"
106                )
107                .parse::<TokenStream>()
108                .unwrap()
109                .into_iter()
110                .map(|mut tok| {
111                    tok.set_span(tt.span());
112                    tok
113                }),
114            );
115            vec![tt]
116        }
117        TokenTree::Ident(i) if i.to_string() == "Self" => struct_name.clone(),
118        TokenTree::Literal(_) | TokenTree::Punct(_) | TokenTree::Ident(_) => vec![tt],
119        TokenTree::Group(g) => vec![TokenTree::Group(Group::new(
120            g.delimiter(),
121            g.stream()
122                .into_iter()
123                .flat_map(|tt| replace_self_and_deny_type_defs(struct_name, tt, errs))
124                .collect(),
125        ))],
126    }
127}