proc_macro_error_attr2/
lib.rs

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1//! This is `#[proc_macro_error]` attribute to be used with
2//! [`proc-macro-error`](https://docs.rs/proc-macro-error2/). There you go.
3
4use crate::parse::parse_input;
5use crate::parse::Attribute;
6use proc_macro::TokenStream;
7use proc_macro2::{Literal, Span, TokenStream as TokenStream2, TokenTree};
8use quote::{quote, quote_spanned};
9
10use crate::settings::{
11    parse_settings,
12    Setting::{AllowNotMacro, AssertUnwindSafe, ProcMacroHack},
13    Settings,
14};
15
16mod parse;
17mod settings;
18
19type Result<T> = std::result::Result<T, Error>;
20
21struct Error {
22    span: Span,
23    message: String,
24}
25
26impl Error {
27    fn new(span: Span, message: String) -> Self {
28        Error { span, message }
29    }
30
31    fn into_compile_error(self) -> TokenStream2 {
32        let mut message = Literal::string(&self.message);
33        message.set_span(self.span);
34        quote_spanned!(self.span=> compile_error!{#message})
35    }
36}
37
38#[proc_macro_attribute]
39pub fn proc_macro_error(attr: TokenStream, input: TokenStream) -> TokenStream {
40    match impl_proc_macro_error(attr.into(), input.clone().into()) {
41        Ok(ts) => ts,
42        Err(e) => {
43            let error = e.into_compile_error();
44            let input = TokenStream2::from(input);
45
46            quote!(#input #error).into()
47        }
48    }
49}
50
51fn impl_proc_macro_error(attr: TokenStream2, input: TokenStream2) -> Result<TokenStream> {
52    let (attrs, signature, body) = parse_input(input)?;
53    let mut settings = parse_settings(attr)?;
54
55    let is_proc_macro = is_proc_macro(&attrs);
56    if is_proc_macro {
57        settings.set(AssertUnwindSafe);
58    }
59
60    if detect_proc_macro_hack(&attrs) {
61        settings.set(ProcMacroHack);
62    }
63
64    if settings.is_set(ProcMacroHack) {
65        settings.set(AllowNotMacro);
66    }
67
68    if !(settings.is_set(AllowNotMacro) || is_proc_macro) {
69        return Err(Error::new(
70            Span::call_site(),
71            "#[proc_macro_error] attribute can be used only with procedural macros\n\n  \
72            = hint: if you are really sure that #[proc_macro_error] should be applied \
73            to this exact function, use #[proc_macro_error(allow_not_macro)]\n"
74                .into(),
75        ));
76    }
77
78    let body = gen_body(&body, &settings);
79
80    let res = quote! {
81        #(#attrs)*
82        #(#signature)*
83        { #body }
84    };
85    Ok(res.into())
86}
87
88fn gen_body(block: &TokenTree, settings: &Settings) -> proc_macro2::TokenStream {
89    let is_proc_macro_hack = settings.is_set(ProcMacroHack);
90    let closure = if settings.is_set(AssertUnwindSafe) {
91        quote!(::std::panic::AssertUnwindSafe(|| #block ))
92    } else {
93        quote!(|| #block)
94    };
95
96    quote!( ::proc_macro_error2::entry_point(#closure, #is_proc_macro_hack) )
97}
98
99fn detect_proc_macro_hack(attrs: &[Attribute]) -> bool {
100    attrs
101        .iter()
102        .any(|attr| attr.path_is_ident("proc_macro_hack"))
103}
104
105fn is_proc_macro(attrs: &[Attribute]) -> bool {
106    attrs.iter().any(|attr| {
107        attr.path_is_ident("proc_macro")
108            || attr.path_is_ident("proc_macro_derive")
109            || attr.path_is_ident("proc_macro_attribute")
110    })
111}
proc_macro_error_attr2/lib.rs

proc_macro_error_attr2/
lib.rs
