rust - Trying to implement core::fmt::Show -

i trying implement core::fmt::show binary tree. implement code :

impl<t: partialeq + partialord + show> show node<t> {     fn fmt(&self, f: &mut formatter) -> result<(), &str>     {         match self.left {             some(ref x) => {x.fmt(f);},             none => {}         };         match self.value {             some(ref x) => {                 write!(f, "{}", x.to_string().as_slice());             },             none => {}         };         match self.right {             some(ref x) => {x.fmt(f);},             none => {}         };         ok(())     } } 

but compiler throw following error :

compiling binary_tree v0.0.1 (file:///home/guillaume/projects/binary_tree) src/binary_tree.rs:60:2: 77:3 error: method fmt has incompatible type trait: expected enum core::fmt::formaterror, found &-ptr [e0053] src/binary_tree.rs:60 fn fmt(&self, f: &mut formatter) -> result<(), &str> src/binary_tree.rs:61 { src/binary_tree.rs:62 match self.left { src/binary_tree.rs:63 some(ref x) => {x.fmt(f);}, src/binary_tree.rs:64 none => {} src/binary_tree.rs:65 };

i can't understand why. complete code found here. comments code welcome.

the error telling method fmt not have type expects, , in particular found &-ptr (i.e., &str) there should formaterror.

changing method signature fix compilation error:

  fn fmt(&self, f: &mut formatter) -> result<(), fmt::formaterror> 

i have sent pull request on github makes change (and fixes test verify work)