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core/codegen/src/derive/from_param.rs

@@ -19,11 +19,11 @@ pub fn derive_from_param(input: proc_macro::TokenStream) -> TokenStream {
         )
         .inner_mapper(MapperBuild::new()
                       .enum_map(|_, data| {
-                          let mut matches = quote!();
+                          let mut matches = vec![];
 
                           for field in data.variants() {
                               let field_name = &field;
-                              matches.extend(quote!(
+                              matches.push(quote!(
                                   stringify!(#field_name) => Ok(Self::#field_name),
                               ))
                           }
@@ -32,7 +32,7 @@ pub fn derive_from_param(input: proc_macro::TokenStream) -> TokenStream {
                               type Error = &'a str;
                               fn from_param(param: &'a str) -> Result<Self, Self::Error> {
                                   match param {
-                                      #matches
+                                      #(#matches)*
                                       _ => Err("Failed to find enum")
                                   }
                               }

core/codegen/src/lib.rs

@@ -782,14 +782,17 @@ pub fn derive_from_form(input: TokenStream) -> TokenStream {
 /// ```rust
 /// # #[macro_use] extern crate rocket;
 /// #
+/// use rocket::request::FromParam;
+///
 /// #[derive(FromParam)]
 /// enum MyParam {
 ///     A,
 ///     B,
 /// }
 /// ```
 ///
-/// Now `MyParam` can be used in an endpoint and will accept either 'A' or 'B'.
+/// Now `MyParam` can be used in an endpoint and will accept either `A` or `B`.
+/// [`FromParam`]: ../rocket/request/trait.FromParam.html
 ///
 #[proc_macro_derive(FromParam)]
 pub fn derive_from_param(input: TokenStream) -> TokenStream {

core/codegen/tests/from_param.rs

@@ -6,13 +6,14 @@ enum Test {
     Test2
 }
 
-
-
 #[test]
 fn derive_from_param() {
     let test1 = Test::from_param("Test1").expect("Should be valid");
     assert_eq!(test1, Test::Test1);
 
     let test2 = Test::from_param("Test2").expect("Should be valid");
     assert_eq!(test2, Test::Test2);
+
+    let test3 = Test::from_param("not_test");
+    assert!(test3.is_err())
 }

core/codegen/tests/ui-fail/from_param.rs

@@ -0,0 +1,9 @@
+use rocket::request::FromParam;
+
+#[derive(FromParam)]
+enum Foo1 {
+    A,
+    B
+}
+
+fn main() {}