serialize: Change some FnOnce bounds to FnMut

Relax some of the bounds on the decoder methods back to FnMut to help accomodate
some more flavorful variants of decoders which may need to run the closure more
than once when it, for example, attempts to find the first successful enum to
decode.

This a breaking change due to the bounds for the trait switching, and clients
will need to update from `FnOnce` to `FnMut` as well as likely making the local
function binding mutable in order to call the function.

[breaking-change]

2 files changed, 9 insertions, 8 deletions

diff --git a/src/libserialize/json.rs b/src/libserialize/json.rs
index d34828ccee3..6047c76d093 100644
--- a/src/libserialize/json.rs
+++ b/src/libserialize/json.rs
@@ -2082,8 +2082,9 @@ impl ::Decoder<DecoderError> for Decoder {
         f(self)
     }
 
-    fn read_enum_variant<T, F>(&mut self, names: &[&str], f: F) -> DecodeResult<T> where
-        F: FnOnce(&mut Decoder, uint) -> DecodeResult<T>,
+    fn read_enum_variant<T, F>(&mut self, names: &[&str],
+                               mut f: F) -> DecodeResult<T>
+        where F: FnMut(&mut Decoder, uint) -> DecodeResult<T>,
     {
         debug!("read_enum_variant(names={})", names);
         let name = match self.pop() {
@@ -2133,7 +2134,7 @@ impl ::Decoder<DecoderError> for Decoder {
     }
 
     fn read_enum_struct_variant<T, F>(&mut self, names: &[&str], f: F) -> DecodeResult<T> where
-        F: FnOnce(&mut Decoder, uint) -> DecodeResult<T>,
+        F: FnMut(&mut Decoder, uint) -> DecodeResult<T>,
     {
         debug!("read_enum_struct_variant(names={})", names);
         self.read_enum_variant(names, f)
@@ -2230,8 +2231,8 @@ impl ::Decoder<DecoderError> for Decoder {
         self.read_tuple_arg(idx, f)
     }
 
-    fn read_option<T, F>(&mut self, f: F) -> DecodeResult<T> where
-        F: FnOnce(&mut Decoder, bool) -> DecodeResult<T>,
+    fn read_option<T, F>(&mut self, mut f: F) -> DecodeResult<T> where
+        F: FnMut(&mut Decoder, bool) -> DecodeResult<T>,
     {
         debug!("read_option()");
         match self.pop() {
diff --git a/src/libserialize/serialize.rs b/src/libserialize/serialize.rs
index 98bd2f6bc93..0e0d3b4115b 100644
--- a/src/libserialize/serialize.rs
+++ b/src/libserialize/serialize.rs
@@ -120,12 +120,12 @@ pub trait Decoder<E> {
         F: FnOnce(&mut Self) -> Result<T, E>;
 
     fn read_enum_variant<T, F>(&mut self, names: &[&str], f: F) -> Result<T, E> where
-        F: FnOnce(&mut Self, uint) -> Result<T, E>;
+        F: FnMut(&mut Self, uint) -> Result<T, E>;
     fn read_enum_variant_arg<T, F>(&mut self, a_idx: uint, f: F) -> Result<T, E> where
         F: FnOnce(&mut Self) -> Result<T, E>;
 
     fn read_enum_struct_variant<T, F>(&mut self, names: &[&str], f: F) -> Result<T, E> where
-        F: FnOnce(&mut Self, uint) -> Result<T, E>;
+        F: FnMut(&mut Self, uint) -> Result<T, E>;
     fn read_enum_struct_variant_field<T, F>(&mut self,
                                             &f_name: &str,
                                             f_idx: uint,
@@ -154,7 +154,7 @@ pub trait Decoder<E> {
 
     // Specialized types:
     fn read_option<T, F>(&mut self, f: F) -> Result<T, E> where
-        F: FnOnce(&mut Self, bool) -> Result<T, E>;
+        F: FnMut(&mut Self, bool) -> Result<T, E>;
 
     fn read_seq<T, F>(&mut self, f: F) -> Result<T, E> where
         F: FnOnce(&mut Self, uint) -> Result<T, E>;