From 01a11800ab0c827d946129415a1813b6f7e005a3 Mon Sep 17 00:00:00 2001
From: Sergio Benitez <sb@sergio.bz>
Date: Wed, 30 Jun 2021 06:20:51 -0700
Subject: [PATCH] Support all generics in 'UriDisplay' derive.

This ports the technique used for 'FromForm' and 'Responder' to the
'UriDisplay' trait derives.
---
 core/codegen/src/derive/uri_display.rs | 46 ++++++++++++++++++--------
 1 file changed, 33 insertions(+), 13 deletions(-)

diff --git a/core/codegen/src/derive/uri_display.rs b/core/codegen/src/derive/uri_display.rs
index 87e5ca5a..eaa00792 100644
--- a/core/codegen/src/derive/uri_display.rs
+++ b/core/codegen/src/derive/uri_display.rs
@@ -3,6 +3,7 @@ use devise::{*, ext::SpanDiagnosticExt};
 
 use crate::exports::*;
 use crate::derive::form_field::{FieldExt, VariantExt};
+use crate::syn_ext::{GenericsExt as _, TypeExt as _};
 use crate::http::uri::fmt;
 
 const NO_EMPTY_FIELDS: &str = "fieldless structs are not supported";
@@ -11,11 +12,28 @@ const NO_EMPTY_ENUMS: &str = "empty enums are not supported";
 const ONLY_ONE_UNNAMED: &str = "tuple structs or variants must have exactly one field";
 const EXACTLY_ONE_FIELD: &str = "struct must have exactly one field";
 
-pub fn derive_uri_display_query(input: proc_macro::TokenStream) -> TokenStream {
-    const URI_DISPLAY: StaticTokens = quote_static!(#_fmt::UriDisplay<#_fmt::Query>);
-    const FORMATTER: StaticTokens = quote_static!(#_fmt::Formatter<#_fmt::Query>);
+const Q_URI_DISPLAY: StaticTokens = quote_static!(#_fmt::UriDisplay<#_fmt::Query>);
+const Q_FORMATTER: StaticTokens = quote_static!(#_fmt::Formatter<#_fmt::Query>);
 
-    let uri_display = DeriveGenerator::build_for(input.clone(), quote!(impl #URI_DISPLAY))
+const P_URI_DISPLAY: StaticTokens = quote_static!(#_fmt::UriDisplay<#_fmt::Path>);
+const P_FORMATTER: StaticTokens = quote_static!(#_fmt::Formatter<#_fmt::Path>);
+
+fn generic_bounds_mapper(bound: StaticTokens) -> MapperBuild {
+    MapperBuild::new()
+        .try_enum_map(|m, e| mapper::enum_null(m, e))
+        .try_fields_map(move |_, fields| {
+            let generic_idents = fields.parent.input().generics().type_idents();
+
+            let bounds = fields.iter()
+                .filter(|f| !f.ty.is_concrete(&generic_idents))
+                .map(move |ty| quote_spanned!(ty.span() => #ty: #bound));
+
+            Ok(quote!(#(#bounds,)*))
+        })
+}
+
+pub fn derive_uri_display_query(input: proc_macro::TokenStream) -> TokenStream {
+    let uri_display = DeriveGenerator::build_for(input.clone(), quote!(impl #Q_URI_DISPLAY))
         .support(Support::Struct | Support::Enum | Support::Type | Support::Lifetime)
         .validator(ValidatorBuild::new()
             .enum_validate(|_, data| {
@@ -43,10 +61,10 @@ pub fn derive_uri_display_query(input: proc_macro::TokenStream) -> TokenStream {
                 }
             })
         )
-        .type_bound(URI_DISPLAY)
+        .type_bound_mapper(generic_bounds_mapper(Q_URI_DISPLAY))
         .inner_mapper(MapperBuild::new()
             .with_output(|_, output| quote! {
-                fn fmt(&self, f: &mut #FORMATTER) -> ::std::fmt::Result {
+                fn fmt(&self, f: &mut #Q_FORMATTER) -> ::std::fmt::Result {
                     #output
                     Ok(())
                 }
@@ -93,12 +111,9 @@ pub fn derive_uri_display_query(input: proc_macro::TokenStream) -> TokenStream {
 
 #[allow(non_snake_case)]
 pub fn derive_uri_display_path(input: proc_macro::TokenStream) -> TokenStream {
-    const URI_DISPLAY: StaticTokens = quote_static!(#_fmt::UriDisplay<#_fmt::Path>);
-    const FORMATTER: StaticTokens = quote_static!(#_fmt::Formatter<#_fmt::Path>);
-
-    let uri_display = DeriveGenerator::build_for(input.clone(), quote!(impl #URI_DISPLAY))
+    let uri_display = DeriveGenerator::build_for(input.clone(), quote!(impl #P_URI_DISPLAY))
         .support(Support::TupleStruct | Support::Type | Support::Lifetime)
-        .type_bound(URI_DISPLAY)
+        .type_bound_mapper(generic_bounds_mapper(P_URI_DISPLAY))
         .validator(ValidatorBuild::new()
             .fields_validate(|_, fields| match fields.count() {
                 1 => Ok(()),
@@ -107,7 +122,7 @@ pub fn derive_uri_display_path(input: proc_macro::TokenStream) -> TokenStream {
         )
         .inner_mapper(MapperBuild::new()
             .with_output(|_, output| quote! {
-                fn fmt(&self, f: &mut #FORMATTER) -> ::std::fmt::Result {
+                fn fmt(&self, f: &mut #P_FORMATTER) -> ::std::fmt::Result {
                     #output
                     Ok(())
                 }
@@ -141,6 +156,11 @@ fn from_uri_param<P: fmt::Part>(input: proc_macro::TokenStream, ty: TokenStream)
         fmt::Kind::Query => quote!(#_fmt::Query),
     };
 
+    let display_trait = match P::KIND {
+        fmt::Kind::Path => P_URI_DISPLAY,
+        fmt::Kind::Query => Q_URI_DISPLAY,
+    };
+
     let ty: syn::Type = syn::parse2(ty).expect("valid type");
     let gen = match ty {
         syn::Type::Reference(ref r) => r.lifetime.as_ref().map(|l| quote!(<#l>)),
@@ -150,7 +170,7 @@ fn from_uri_param<P: fmt::Part>(input: proc_macro::TokenStream, ty: TokenStream)
     let param_trait = quote!(impl #gen #_fmt::FromUriParam<#part, #ty>);
     DeriveGenerator::build_for(input, param_trait)
         .support(Support::All)
-        .type_bound(quote!(#_fmt::UriDisplay<#part>))
+        .type_bound_mapper(generic_bounds_mapper(display_trait))
         .inner_mapper(MapperBuild::new()
             .with_output(move |_, _| quote! {
                 type Target = #ty;