(wip) Add support for existential uniforms.

This commit provides support for existential in `Uniform<T>`, so that
it’s possible to ask for things like `&'a [T; N]`, where `'a` comes from
call-site.

The current implementation is not perfect as it would be normally
implemented with GATs… but I don’t have GATs.

Relates to #438.

Author: hadronized

luminance-derive/src/uniform_interface.rs

@@ -120,18 +120,18 @@ pub(crate) fn generate_uniform_interface_impl(
           let #field_ident = #build_call;
         });
         field_where_clause.push(quote! {
-          S: luminance::backend::shader::Uniformable<#field_ty>
+          B: for<'a> luminance::backend::shader::Uniformable<'a, #field_ty>
         });
       }
 
       let output = quote! {
-        impl<S> luminance::shader::UniformInterface<S> for #ident
+        impl<B> luminance::shader::UniformInterface<B> for #ident
         where
-          S: ?Sized + luminance::backend::shader::Shader,
+          B: luminance::backend::shader::Shader,
           #(#field_where_clause),*,
         {
           fn uniform_interface<'a>(
-            builder: &mut luminance::shader::UniformBuilder<'a, S>,
+            builder: &mut luminance::shader::UniformBuilder<'a, B>,
             _: &mut ()
           ) -> Result<Self, luminance::shader::UniformWarning> {
             #(#field_decls)*

luminance-gl/src/gl33/pipeline.rs

@@ -20,7 +20,7 @@ use luminance::{
   tess::{Deinterleaved, DeinterleavedData, Interleaved, TessIndex, TessVertexData},
   texture::Dimensionable,
 };
-use luminance_std140::{Arr, Std140};
+use luminance_std140::{ArrElem, Std140};
 use std::{cell::RefCell, marker::PhantomData, rc::Rc};
 
 pub struct Pipeline {
@@ -187,7 +187,7 @@ where
 
 unsafe impl<T> PipelineShaderData<T> for GL33
 where
-  Self: ShaderData<T, ShaderDataRepr = Buffer<<Arr<T> as Std140>::Encoded>>,
+  Self: ShaderData<T, ShaderDataRepr = Buffer<<ArrElem<T> as Std140>::Encoded>>,
   T: Std140,
 {
   type BoundShaderDataRepr = BoundShaderData<T>;