Remove dependence on 'decl_macro' in codegen.

The generated 'uri' helper macros are now re-exports of 'macro_rules'
macros, made possible by the stable 'uniform_paths' feature.

core/codegen/src/attribute/route.rs

@@ -1,3 +1,6 @@
+use std::collections::hash_map::DefaultHasher;
+use std::hash::{Hash, Hasher};
+
 use proc_macro::{TokenStream, Span};
 use crate::proc_macro2::TokenStream as TokenStream2;
 use devise::{syn, Spanned, SpanWrapped, Result, FromMeta, ext::TypeExt};
@@ -325,15 +328,31 @@ fn generate_internal_uri_macro(route: &Route) -> TokenStream2 {
         .map(|name| route.inputs.iter().find(|(ident, ..)| ident == name).unwrap())
         .map(|(ident, _, ty)| quote!(#ident: #ty));
 
-    let generated_macro_name = route.function.ident.prepend(URI_MACRO_PREFIX);
+    let mut hasher = DefaultHasher::new();
+    let route_span = route.function.span();
+    route_span.source_file().path().hash(&mut hasher);
+    let line_column = route_span.start();
+    line_column.line.hash(&mut hasher);
+    line_column.column.hash(&mut hasher);
+
+    let mut generated_macro_name = route.function.ident.prepend(URI_MACRO_PREFIX);
+    generated_macro_name.set_span(Span::call_site().into());
+    let inner_generated_macro_name = generated_macro_name.append(&hasher.finish().to_string());
     let route_uri = route.attribute.path.origin.0.to_string();
 
     quote! {
-        pub macro #generated_macro_name($($token:tt)*) {{
-            extern crate std;
-            extern crate rocket;
-            rocket::rocket_internal_uri!(#route_uri, (#(#dynamic_args),*), $($token)*)
-        }}
+        #[doc(hidden)]
+        #[macro_export]
+        macro_rules! #inner_generated_macro_name {
+            ($($token:tt)*) => {{
+                extern crate std;
+                extern crate rocket;
+                rocket::rocket_internal_uri!(#route_uri, (#(#dynamic_args),*), $($token)*)
+            }};
+        }
+
+        #[doc(hidden)]
+        pub use #inner_generated_macro_name as #generated_macro_name;
     }
 }
 

core/codegen/src/syn_ext.rs

@@ -9,12 +9,17 @@ pub fn syn_to_diag(error: syn::parse::Error) -> Diagnostic {
 
 pub trait IdentExt {
     fn prepend(&self, string: &str) -> syn::Ident;
+    fn append(&self, string: &str) -> syn::Ident;
 }
 
 impl IdentExt for syn::Ident {
     fn prepend(&self, string: &str) -> syn::Ident {
         syn::Ident::new(&format!("{}{}", string, self), self.span())
     }
+
+    fn append(&self, string: &str) -> syn::Ident {
+        syn::Ident::new(&format!("{}{}", self, string), self.span())
+    }
 }
 
 pub trait ReturnTypeExt {