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Merged
siku2 merged 2 commits into from
Jul 31, 2021
Merged

Support const generics in #[derive(Properties)] #1978

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328d31c
Support const generics in #[derive(Properties)]
maciejhirsz Jul 31, 2021
689354b
Test and tweak comment
maciejhirsz Jul 31, 2021
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11 changes: 6 additions & 5 deletions packages/yew-macro/src/derive_props/generics.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,10 +8,11 @@ use syn::{
/// Alias for a comma-separated list of `GenericArgument`
pub type GenericArguments = Punctuated<GenericArgument, Token![,]>;

/// Finds the index of the first generic param with a default value.
fn first_default_param_position(generics: &Generics) -> Option<usize> {
/// Finds the index of the first generic param with a default value or a const generic.
fn first_default_or_const_param_position(generics: &Generics) -> Option<usize> {
generics.params.iter().position(|param| match param {
GenericParam::Type(param) => param.default.is_some(),
GenericParam::Const(_) => true,
_ => false,
})
}
Expand All @@ -25,11 +26,11 @@ pub fn to_arguments(generics: &Generics, type_ident: Ident) -> GenericArguments
GenericParam::Lifetime(lifetime_param) => {
GenericArgument::Lifetime(lifetime_param.lifetime.clone())
}
_ => unimplemented!("const params are not supported in the derive macro"),
GenericParam::Const(const_param) => new_generic_type_arg(const_param.ident.clone()),
}));

let new_arg = new_generic_type_arg(type_ident);
if let Some(index) = first_default_param_position(generics) {
if let Some(index) = first_default_or_const_param_position(generics) {
args.insert(index, new_arg);
} else {
args.push(new_arg);
Expand All @@ -44,7 +45,7 @@ pub fn with_param_bounds(generics: &Generics, param_ident: Ident, param_bounds:
let mut new_generics = generics.clone();
let params = &mut new_generics.params;
let new_param = new_param_bounds(param_ident, param_bounds);
if let Some(index) = first_default_param_position(generics) {
if let Some(index) = first_default_or_const_param_position(generics) {
params.insert(index, new_param);
} else {
params.push(new_param);
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14 changes: 14 additions & 0 deletions packages/yew-macro/tests/derive_props/pass.rs
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Expand Up @@ -188,6 +188,20 @@ mod t10 {
mod t11 {
use super::*;

// this test makes sure that Yew handles generic params with const generics properly.

#[derive(Clone, Properties)]
pub struct Foo<T, const N: usize>
where
T: Clone,
{
bar: [T; N],
}
}

mod t12 {
use super::*;

#[derive(Clone, Properties)]
pub struct Props<T: Clone> {
value: Option<T>,
Expand Down