lower FnMut to FnOnce since json-hack is no longer required

Author: Oliver Schneider

src/librbml/lib.rs

@@ -1055,8 +1055,8 @@ pub mod writer {
             self.end_tag()
         }
 
-        fn emit_map_elt_key<F>(&mut self, _idx: uint, mut f: F) -> EncodeResult where
-            F: FnMut(&mut Encoder<'a, W>) -> EncodeResult,
+        fn emit_map_elt_key<F>(&mut self, _idx: uint, f: F) -> EncodeResult where
+            F: FnOnce(&mut Encoder<'a, W>) -> EncodeResult,
         {
 
             try!(self.start_tag(EsMapKey as uint));

src/libserialize/json.rs

@@ -635,8 +635,8 @@ impl<'a> ::Encoder<io::IoError> for Encoder<'a> {
         write!(self.writer, "}}")
     }
 
-    fn emit_map_elt_key<F>(&mut self, idx: uint, mut f: F) -> EncodeResult where
-        F: FnMut(&mut Encoder<'a>) -> EncodeResult,
+    fn emit_map_elt_key<F>(&mut self, idx: uint, f: F) -> EncodeResult where
+        F: FnOnce(&mut Encoder<'a>) -> EncodeResult,
     {
         if idx != 0 { try!(write!(self.writer, ",")) }
         self.emitting_map_key = EmittingMapKeyState::Emitting;
@@ -901,8 +901,8 @@ impl<'a> ::Encoder<io::IoError> for PrettyEncoder<'a> {
         }
     }
 
-    fn emit_map_elt_key<F>(&mut self, idx: uint, mut f: F) -> EncodeResult where
-        F: FnMut(&mut PrettyEncoder<'a>) -> EncodeResult,
+    fn emit_map_elt_key<F>(&mut self, idx: uint, f: F) -> EncodeResult where
+        F: FnOnce(&mut PrettyEncoder<'a>) -> EncodeResult,
     {
         if idx == 0 {
             try!(write!(self.writer, "\n"));

src/libserialize/serialize.rs

@@ -91,7 +91,7 @@ pub trait Encoder<E> {
     fn emit_map<F>(&mut self, len: uint, f: F) -> Result<(), E> where
         F: FnOnce(&mut Self) -> Result<(), E>;
     fn emit_map_elt_key<F>(&mut self, idx: uint, f: F) -> Result<(), E> where
-        F: FnMut(&mut Self) -> Result<(), E>;
+        F: FnOnce(&mut Self) -> Result<(), E>;
     fn emit_map_elt_val<F>(&mut self, idx: uint, f: F) -> Result<(), E> where
         F: FnOnce(&mut Self) -> Result<(), E>;
 }