1//! Functions to derive `darling`'s traits from well-formed input, without directly depending
2//! on `proc_macro`.
3
4use proc_macro2::TokenStream;
5use quote::ToTokens;
6use syn::DeriveInput;
7
8use crate::options;
9
10/// Run an expression which returns a `darling::Result`, then either return the tokenized
11/// representation of the `Ok` value, or the tokens of the compiler errors in the `Err` case.
12macro_rules! emit_impl_or_error {
13 ($e:expr) => {
14 match $e {
15 Ok(val) => val.into_token_stream(),
16 Err(err) => err.write_errors(),
17 }
18 };
19}
20
21/// Create tokens for a `darling::FromMeta` impl from a `DeriveInput`. If
22/// the input cannot produce a valid impl, the returned tokens will contain
23/// compile errors instead.
24pub fn from_meta(input: &DeriveInput) -> TokenStream {
25 emit_impl_or_error!(options::FromMetaOptions::new(input))
26}
27
28/// Create tokens for a `darling::FromAttributes` impl from a `DeriveInput`. If
29/// the input cannot produce a valid impl, the returned tokens will contain
30/// compile errors instead.
31pub fn from_attributes(input: &DeriveInput) -> TokenStream {
32 emit_impl_or_error!(options::FromAttributesOptions::new(input))
33}
34
35/// Create tokens for a `darling::FromDeriveInput` impl from a `DeriveInput`. If
36/// the input cannot produce a valid impl, the returned tokens will contain
37/// compile errors instead.
38pub fn from_derive_input(input: &DeriveInput) -> TokenStream {
39 emit_impl_or_error!(options::FdiOptions::new(input))
40}
41
42/// Create tokens for a `darling::FromField` impl from a `DeriveInput`. If
43/// the input cannot produce a valid impl, the returned tokens will contain
44/// compile errors instead.
45pub fn from_field(input: &DeriveInput) -> TokenStream {
46 emit_impl_or_error!(options::FromFieldOptions::new(input))
47}
48
49/// Create tokens for a `darling::FromTypeParam` impl from a `DeriveInput`. If
50/// the input cannot produce a valid impl, the returned tokens will contain
51/// compile errors instead.
52pub fn from_type_param(input: &DeriveInput) -> TokenStream {
53 emit_impl_or_error!(options::FromTypeParamOptions::new(input))
54}
55
56/// Create tokens for a `darling::FromVariant` impl from a `DeriveInput`. If
57/// the input cannot produce a valid impl, the returned tokens will contain
58/// compile errors instead.
59pub fn from_variant(input: &DeriveInput) -> TokenStream {
60 emit_impl_or_error!(options::FromVariantOptions::new(input))
61}
62