darling_core 0.3.1

Helper crate for proc-macro library for reading attributes into structs when implementing custom derives. Use https://crates.io/crates/darling in your code.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60

use quote::{Tokens, ToTokens};

/// Declares the local variable into which errors will be accumulated.
pub struct ErrorDeclaration {
    __hidden: ()
}

impl ErrorDeclaration {
    pub fn new() -> Self {
        ErrorDeclaration {
            __hidden: ()
        }
    }
}

impl ToTokens for ErrorDeclaration {
    fn to_tokens(&self, tokens: &mut Tokens) {
        tokens.append_all(quote! {
            let mut __errors = Vec::new();
        })
    }
}

/// Returns early if attribute or body parsing has caused any errors.
pub struct ErrorCheck<'a> {
    location: Option<&'a str>,
    __hidden: ()
}

impl<'a> ErrorCheck<'a> {
    pub fn new() -> Self {
        ErrorCheck {
            location: None,
            __hidden: ()
        }
    }

    pub fn with_location(location: &'a str) -> Self {
        ErrorCheck {
            location: Some(location),
            __hidden: (),
        }
    }
}

impl<'a> ToTokens for ErrorCheck<'a> {
    fn to_tokens(&self, tokens: &mut Tokens) {
        let at_call = if let Some(ref s) = self.location {
            quote!(.at(#s))
        } else {
            quote!()
        };

        tokens.append_all(quote! {
            if !__errors.is_empty() {
                return ::darling::export::Err(::darling::Error::multiple(__errors) #at_call);
            }
        })
    }
}