doc

src/if_type.rs

@@ -1,13 +1,14 @@
 use std::any::TypeId;
 
+/// run if types are identical
 #[inline]
 pub fn if_type<Specific: 'static, T: 'static>(f: impl FnOnce() -> Specific) -> Option<T> {
     if TypeId::of::<T>() == TypeId::of::<Specific>() {
         let typed = f();
-        let erased: T = unsafe{ std::mem::transmute_copy(&typed) };
-        std::mem::forget(typed);
+        let erased: T = unsafe{ std::mem::transmute_copy(&typed) }; //type and alignment ensured by identical type
+        std::mem::forget(typed); //else we get some fancy double free
         Some(erased)
     }else{
         None
     }
-}
+}