diff options
Diffstat (limited to 'third_party/rust/derive_more-impl/src/from_str.rs')
-rw-r--r-- | third_party/rust/derive_more-impl/src/from_str.rs | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/third_party/rust/derive_more-impl/src/from_str.rs b/third_party/rust/derive_more-impl/src/from_str.rs new file mode 100644 index 0000000000..bc0ec5413a --- /dev/null +++ b/third_party/rust/derive_more-impl/src/from_str.rs @@ -0,0 +1,112 @@ +use crate::utils::{DeriveType, HashMap}; +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, trait_name.to_lowercase())?; + + if state.derive_type == DeriveType::Enum { + Ok(enum_from(input, state, trait_name)) + } else { + Ok(struct_from(&state, trait_name)) + } +} + +pub fn struct_from(state: &State, trait_name: &'static str) -> TokenStream { + // 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); + + quote! { + #[automatically_derived] + 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 enum_from( + input: &DeriveInput, + state: State, + trait_name: &'static str, +) -> TokenStream { + let mut variants_caseinsensitive = HashMap::default(); + for variant_state in state.enabled_variant_data().variant_states { + let variant = variant_state.variant.unwrap(); + if !variant.fields.is_empty() { + panic!("Only enums with no fields can derive({trait_name})") + } + + variants_caseinsensitive + .entry(variant.ident.to_string().to_lowercase()) + .or_insert_with(Vec::new) + .push(variant.ident.clone()); + } + + let input_type = &input.ident; + let input_type_name = input_type.to_string(); + + let mut cases = vec![]; + + // if a case insensitive match is unique match do that + // otherwise do a case sensitive match + for (ref canonical, ref variants) in variants_caseinsensitive { + if variants.len() == 1 { + let variant = &variants[0]; + cases.push(quote! { + #canonical => #input_type::#variant, + }) + } else { + for variant in variants { + let variant_str = variant.to_string(); + cases.push(quote! { + #canonical if(src == #variant_str) => #input_type::#variant, + }) + } + } + } + + let trait_path = state.trait_path; + + quote! { + impl #trait_path for #input_type { + type Err = ::derive_more::FromStrError; + + #[inline] + fn from_str(src: &str) -> ::core::result::Result<Self, Self::Err> { + Ok(match src.to_lowercase().as_str() { + #(#cases)* + _ => return Err(::derive_more::FromStrError::new(#input_type_name)), + }) + } + } + } +} + +fn panic_one_field(trait_name: &str) -> ! { + panic!("Only structs with one field can derive({trait_name})") +} |