rust: Switch to a neater module based step function derive

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

1 files changed, 10 insertions, 12 deletions

diff --git a/subplotlib-derive/src/lib.rs b/subplotlib-derive/src/lib.rs
index 6570750..a92ab1c 100644
--- a/subplotlib-derive/src/lib.rs
+++ b/subplotlib-derive/src/lib.rs
@@ -184,11 +184,6 @@ fn process_step(input: ItemFn) -> proc_macro2::TokenStream {
         })
         .collect::<Result<Vec<_>, _>>()?;
 
-    // The builder's name is simply the step function's name with BUILDER_
-    // prepended to it.  We give that name the span of the step function name
-    // in case it gets referred to in an error
-    let buildername = Ident::new(&format!("BUILDER_{}", stepname), stepname.span());
-
     let structdef = {
         let structfields: Vec<_> = fields
             .iter()
@@ -207,7 +202,7 @@ fn process_step(input: ItemFn) -> proc_macro2::TokenStream {
             #[allow(non_camel_case_types)]
             #[allow(unused)]
             #[derive(Default)]
-            #vis struct #buildername {
+            pub(crate) struct Builder {
                 #(#structfields),*
             }
         }
@@ -263,7 +258,7 @@ fn process_step(input: ItemFn) -> proc_macro2::TokenStream {
         };
 
         quote! {
-            impl #buildername {
+            impl Builder {
                 #(#fieldfns)*
 
                 pub fn build(self) -> ScenarioStep<#contexttype> {
@@ -275,12 +270,15 @@ fn process_step(input: ItemFn) -> proc_macro2::TokenStream {
     };
 
     let ret = quote! {
-        #structdef
-        #structimpl
+        #vis mod #stepname {
+            use super::*;
+            #structdef
+            #structimpl
 
-        #[throws(StepError)]
-        #[allow(unused)] // It's okay for step functions to not be used
-        #input
+            #[throws(StepError)]
+            #[allow(unused)] // It's okay for step functions to not be used
+            #input
+        }
     };
 
     ret