clauser_macros 0.1.0

Macros used by the `clauser` crate.
Documentation 
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use proc_macro2::{LexError, Span, TokenStream};
use quote::{quote, ToTokens, TokenStreamExt};

#[derive(Debug)]
pub enum MacroError {
    Message(&'static str, Span),
    LexerError(String, Span),
}

impl From<LexError> for MacroError {
    fn from(value: LexError) -> Self {
        MacroError::LexerError(
            format!("LexError encountered while building macro: {}", value),
            value.span(),
        )
    }
}

fn str_to_tokens(str: &impl ToString) -> TokenStream {
    let owned = str.to_string();
    quote! { compile_error!(#owned); }
}

fn str_and_loc_to_tokens<T: ToString + ?Sized>(str: &T, span: &Span) -> TokenStream {
    let msg = format!("error at callsite {:?}: {}", span, str.to_string());
    str_to_tokens(&msg)
}

impl ToTokens for MacroError {
    #[track_caller]
    fn to_tokens(&self, tokens: &mut proc_macro2::TokenStream) {
        let new_tokens = match self {
            Self::Message(str, loc) => str_and_loc_to_tokens(str, loc),
            Self::LexerError(str, loc) => str_and_loc_to_tokens(str, loc),
        };

        tokens.append_all(new_tokens)
    }
}