diff options
Diffstat (limited to 'vendor/derive_more/src/from_str.rs')
-rw-r--r-- | vendor/derive_more/src/from_str.rs | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/vendor/derive_more/src/from_str.rs b/vendor/derive_more/src/from_str.rs new file mode 100644 index 000000000..5f26fdd18 --- /dev/null +++ b/vendor/derive_more/src/from_str.rs @@ -0,0 +1,49 @@ +use crate::utils::{SingleFieldData, State}; +use proc_macro2::TokenStream; +use quote::quote; +use syn::{parse::Result, DeriveInput}; + +/// Provides the hook to expand `#[derive(FromStr)]` into an implementation of `FromStr` +pub fn expand(input: &DeriveInput, trait_name: &'static str) -> Result<TokenStream> { + let state = State::new( + input, + trait_name, + quote!(::core::str), + trait_name.to_lowercase(), + )?; + + // We cannot set defaults for fields, once we do we can remove this check + if state.fields.len() != 1 || state.enabled_fields().len() != 1 { + panic_one_field(trait_name); + } + + let single_field_data = state.assert_single_enabled_field(); + let SingleFieldData { + input_type, + field_type, + trait_path, + casted_trait, + impl_generics, + ty_generics, + where_clause, + .. + } = single_field_data.clone(); + + let initializers = [quote!(#casted_trait::from_str(src)?)]; + let body = single_field_data.initializer(&initializers); + + Ok(quote! { + impl#impl_generics #trait_path for #input_type#ty_generics #where_clause + { + type Err = <#field_type as #trait_path>::Err; + #[inline] + fn from_str(src: &str) -> ::core::result::Result<Self, Self::Err> { + Ok(#body) + } + } + }) +} + +fn panic_one_field(trait_name: &str) -> ! { + panic!("Only structs with one field can derive({})", trait_name) +} |