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extern crate proc_macro; extern crate syn; #[macro_use] extern crate quote; use proc_macro::TokenStream; #[proc_macro_derive(EnumError)] pub fn enum_error(input: TokenStream) -> TokenStream { let ast = into_ast(input); let name = &ast.ident; let variants = get_enum_variants(&ast); let froms = impl_into_enum(&name, &variants); let display = impl_display(&name, &variants); let error = impl_error(&name, &variants); let tokens = quote!{ #froms #display #error }; tokens.parse().unwrap() } #[proc_macro_derive(IntoEnum)] pub fn into_enum(input: TokenStream) -> TokenStream { let ast = into_ast(input); let name = &ast.ident; let variants = get_enum_variants(&ast); impl_into_enum(&name, &variants).parse().unwrap() } #[proc_macro_derive(NewType)] pub fn newtype(input: TokenStream) -> TokenStream { let ast = into_ast(input); let name = &ast.ident; let field = get_basetype(&ast); let from = impl_newtype_from(&name, &field); let deref = impl_newtype_deref(&name, &field); let tokens = quote!{ #from #deref }; tokens.parse().unwrap() } fn into_ast(input: TokenStream) -> syn::DeriveInput { let s = input.to_string(); syn::parse_macro_input(&s).unwrap() } fn get_enum_variants(ast: &syn::MacroInput) -> &Vec<syn::Variant> { match ast.body { syn::Body::Enum(ref variants) => variants, syn::Body::Struct(_) => unreachable!("Struct is not supported"), } } fn get_basetype(ast: &syn::MacroInput) -> &syn::Field { match ast.body { syn::Body::Enum(_) => unreachable!("Enum is not supported"), syn::Body::Struct(ref vd) => { match *vd { syn::VariantData::Struct(_) => unreachable!("Must be tuple"), syn::VariantData::Tuple(ref t) => { if t.len() > 1 { unreachable!("Must be one type"); } &t[0] } syn::VariantData::Unit => unreachable!("Must be tuple"), } } } } fn impl_into_enum(name: &syn::Ident, variants: &Vec<syn::Variant>) -> quote::Tokens { let impls = variants.iter().map(|var| { let v = &var.ident; let cont = match var.data { syn::VariantData::Tuple(ref c) => c, _ => unreachable!(), }; assert!(cont.len() == 1, "Single Tuple is required"); let ctype = &cont[0].ty; quote!{ impl From<#ctype> for #name { fn from(val: #ctype) -> Self { #name::#v(val) } } } }); quote!{ #(#impls)* } } fn impl_newtype_from(name: &syn::Ident, field: &syn::Field) -> quote::Tokens { let base = &field.ty; quote!{ impl From<#base> for #name { fn from(val: #base) -> Self { #name(val) } } } } fn impl_newtype_deref(name: &syn::Ident, field: &syn::Field) -> quote::Tokens { let base = &field.ty; quote!{ impl ::std::ops::Deref for #name { type Target = #base; fn deref(&self) -> &Self::Target { &self.0 } } impl ::std::ops::DerefMut for #name { fn deref_mut(&mut self) -> &mut Self::Target { &mut self.0 } } } } fn impl_error(name: &syn::Ident, variants: &Vec<syn::Variant>) -> quote::Tokens { let snips = variants.iter().map(|var| { let v = &var.ident; quote!{ #name::#v(ref err) => err.description() } }); quote!{ impl ::std::error::Error for #name { fn description(&self) -> &str { match *self { #(#snips), * } } } } } fn impl_display(name: &syn::Ident, variants: &Vec<syn::Variant>) -> quote::Tokens { let snips = variants.iter().map(|var| { let v = &var.ident; quote!{ #name::#v(ref err) => err.fmt(f) } }); quote!{ impl ::std::fmt::Display for #name { fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result { match *self { #(#snips), * } } } } }