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Introduce base builder type-alias #55

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Introduce base builder type-alias #55

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9 changes: 8 additions & 1 deletion src/struct_info.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -126,6 +126,13 @@ impl<'a> StructInfo<'a> {
quote!(#[doc(hidden)])
};

let mut b_decl_generics = b_generics.clone();
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Why is this required? b_generics is only used when declaring the builder type (and you want the default there) and when splitting it for the impl block (where defaults should not be looked at anyway). So why clone it instead of modifying the original?

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That's redundant, indeed.

for param in &mut b_decl_generics.params {
if let syn::GenericParam::Type(ref mut param) = param {
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Wouldn't this match all type parameters? The one you want to add a default to is always the first one, so you can just modify that.

Or even better - just add the default when creating b_generics.

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Yes, that would match all parameters. I guess that barely make sense.

Though unfortunately rust doesn't allow to specify defaults for non-trailing generics and the TypedBuilderFields is the first one. I'm not sure whether it's fine to set it as the last one, perhaps it might break some code.

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I'm half minded to just go with your original design as a temporary solution. Once const generics support strings I plan on doing a great refactor that'll break anything (other than regular by-the-book usage) anyway, and once that come I may remove it in favor of something else.

param.default = Some(empties_tuple.clone().into());
}
}

let (b_generics_impl, b_generics_ty, b_generics_where_extras_predicates) = b_generics.split_for_impl();
let mut b_generics_where: syn::WhereClause = syn::parse2(quote! {
where TypedBuilderFields: Clone
Expand All @@ -149,7 +156,7 @@ impl<'a> StructInfo<'a> {
#[must_use]
#builder_type_doc
#[allow(dead_code, non_camel_case_types, non_snake_case)]
#vis struct #builder_name #b_generics {
#vis struct #builder_name #b_decl_generics {
fields: #all_fields_param,
phantom: (#( #phantom_generics ),*),
}
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1 change: 1 addition & 0 deletions tests/tests.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -253,6 +253,7 @@ fn test_builder_name() {
#[derive(TypedBuilder)]
struct Foo {}

let _: FooBuilder = Foo::builder();
let _: FooBuilder<_> = Foo::builder();
}

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