return error for unused #[convert]s

1 files changed, 12 insertions, 4 deletions

diff --git a/src/transform.rs b/src/transform.rs
index ae345c8..c56bec1 100644
--- a/src/transform.rs
+++ b/src/transform.rs
@@ -1,4 +1,7 @@
-use std::{collections::HashMap, rc::Rc};
+use std::{
+    collections::{HashMap, HashSet},
+    rc::Rc,
+};
 
 use proc_macro2::Span;
 use quote::quote;
@@ -20,6 +23,7 @@ pub struct TypeConverter {
     pub collections: HashMap<Ident, usize>,
     pub trait_ident: Ident,
     pub type_conversions: HashMap<Type, Rc<Convert>>,
+    pub used_conversions: HashSet<Type>,
 }
 
 #[derive(Debug)]
@@ -60,8 +64,12 @@ impl TypeConverter {
         None
     }
 
-    pub fn convert_type(&self, type_: &mut Type) -> Result<TypeTransform, (Span, TransformError)> {
+    pub fn convert_type(
+        &mut self,
+        type_: &mut Type,
+    ) -> Result<TypeTransform, (Span, TransformError)> {
         if let Some(conv) = self.type_conversions.get(type_) {
+            self.used_conversions.insert(conv.original_type.clone());
             *type_ = conv.dest_type.clone();
             return Ok(TypeTransform::Verbatim(conv.clone()));
         }
@@ -223,7 +231,7 @@ impl TypeConverter {
 
 pub fn dynamize_function_bounds(
     generics: &mut Generics,
-    type_converter: &TypeConverter,
+    type_converter: &mut TypeConverter,
 ) -> Result<HashMap<Ident, Vec<TypeTransform>>, (Span, MethodError)> {
     let mut type_param_transforms = HashMap::new();
 
@@ -285,7 +293,7 @@ pub fn dynamize_function_bounds(
 
 fn dynamize_trait_bound(
     bound: &mut TraitBound,
-    type_converter: &TypeConverter,
+    type_converter: &mut TypeConverter,
     type_ident: &Ident,
     type_param_transforms: &mut HashMap<Ident, Vec<TypeTransform>>,
 ) -> Result<(), (Span, MethodError)> {