Moved the conversion into the function.

src/morethantext/error.rs

@@ -41,8 +41,8 @@ impl Generic {
         }
     }
 
-    fn add_source(&mut self, source: MTTError) {
-        self.source = Some(Arc::new(source));
+    fn add_source<E: Into<MTTError>>(&mut self, source: E) {
+        self.source = Some(Arc::new(source.into()));
     }
 }
 
@@ -94,7 +94,7 @@ mod generics {
         let cld_detail = "child error";
         let par_err = Generic::new(par_detail);
         let mut cld_err = Generic::new(cld_detail);
-        cld_err.add_source(par_err.into());
+        cld_err.add_source(par_err);
         assert!(
             cld_err.source().unwrap().to_string() == par_detail,
             "/n/nGot:  {}\nWant: {}\n\n",