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Allow deriving Dummy with generic types #155

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Oct 25, 2023
Merged

Allow deriving Dummy with generic types #155

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26 changes: 20 additions & 6 deletions dummy_derive/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ extern crate quote;
#[macro_use]
extern crate darling;

use syn::{Ident, Type};
use syn::{parse_quote, GenericParam, Generics, Ident, Type};

use darling::{ast, FromDeriveInput};
use proc_macro::TokenStream;
Expand Down Expand Up @@ -44,6 +44,7 @@ struct DummyField {
#[darling(attributes(dummy), supports(struct_any, enum_any))]
struct Dummy {
ident: Ident,
generics: Generics,
data: ast::Data<DummyVariant, DummyField>,
}

Expand All @@ -52,6 +53,8 @@ pub fn derive_dummy(input: TokenStream) -> TokenStream {
let parsed = syn::parse(input).expect("syn::parse ok");
let receiver = Dummy::from_derive_input(&parsed).expect("Dummy::from_derive_input ok");

let generics = add_trait_bounds(receiver.generics);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let receiver_name = &receiver.ident;
let expanded = match receiver.data {
darling::ast::Data::Struct(darling::ast::Fields {
Expand All @@ -61,7 +64,7 @@ pub fn derive_dummy(input: TokenStream) -> TokenStream {
}) => match style {
ast::Style::Unit => {
let impl_dummy = quote! {
impl ::fake::Dummy<::fake::Faker> for #receiver_name {
impl #impl_generics ::fake::Dummy<::fake::Faker> for #receiver_name #ty_generics #where_clause {
fn dummy_with_rng<R: ::fake::Rng + ?Sized>(_: &::fake::Faker, rng: &mut R) -> Self {
#receiver_name
}
Expand All @@ -73,7 +76,7 @@ pub fn derive_dummy(input: TokenStream) -> TokenStream {
let tuple_fields: Vec<_> = fields.iter().map(expose_field).collect();

let impl_dummy = quote! {
impl ::fake::Dummy<::fake::Faker> for #receiver_name {
impl #impl_generics ::fake::Dummy<::fake::Faker> for #receiver_name #ty_generics #where_clause {
fn dummy_with_rng<R: ::fake::Rng + ?Sized>(_: &::fake::Faker, rng: &mut R) -> Self {
#receiver_name(#(#tuple_fields),*)
}
Expand All @@ -98,7 +101,7 @@ pub fn derive_dummy(input: TokenStream) -> TokenStream {
.collect();

let impl_dummy = quote! {
impl ::fake::Dummy<::fake::Faker> for #receiver_name {
impl #impl_generics ::fake::Dummy<::fake::Faker> for #receiver_name #ty_generics #where_clause {
fn dummy_with_rng<R: ::fake::Rng + ?Sized>(_: &::fake::Faker, rng: &mut R) -> Self {
#(#let_statements)*
#receiver_name {
Expand Down Expand Up @@ -170,7 +173,7 @@ pub fn derive_dummy(input: TokenStream) -> TokenStream {
.collect();

let impl_dummy = quote! {
impl ::fake::Dummy<::fake::Faker> for #receiver_name {
impl #impl_generics ::fake::Dummy<::fake::Faker> for #receiver_name #ty_generics #where_clause {
fn dummy_with_rng<R: ::fake::Rng + ?Sized>(_: &::fake::Faker, rng: &mut R) -> Self {
match rng.gen_range(0..#variant_count) {
#(#match_statements)*
Expand All @@ -185,7 +188,7 @@ pub fn derive_dummy(input: TokenStream) -> TokenStream {
impl_dummy
} else {
let impl_dummy = quote! {
impl ::fake::Dummy<::fake::Faker> for #receiver_name {
impl #impl_generics ::fake::Dummy<::fake::Faker> for #receiver_name #ty_generics #where_clause {
fn dummy_with_rng<R: ::fake::Rng + ?Sized>(_: &::fake::Faker, rng: &mut R) -> Self {
panic!("can not create an empty enum")
}
Expand Down Expand Up @@ -231,3 +234,14 @@ fn expose_field(f: &DummyField) -> proc_macro2::TokenStream {
}
}
}

fn add_trait_bounds(mut generics: Generics) -> Generics {
for param in &mut generics.params {
if let GenericParam::Type(ref mut type_param) = *param {
type_param
.bounds
.push(parse_quote!(::fake::Dummy<::fake::Faker>));
}
}
generics
}
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