REFACTOR: Don't presume io::Result for the converter Result.

src/convert/env.rs

@@ -13,13 +13,12 @@
 //  limitations under the License.
 
 //! An environment variable converter.
-use std::io::Result;
 use std::io::Write;
 use std::rc::Rc;
 
 use ast::Positioned;
 use build::Val;
-use convert::traits::Converter;
+use convert::traits::{Converter, Result};
 
 /// EnvConverter implements the conversion logic for converting a Val into a set of environment variables.
 pub struct EnvConverter {}
@@ -29,11 +28,7 @@ impl EnvConverter {
         EnvConverter {}
     }
 
-    fn convert_tuple(
-        &self,
-        flds: &Vec<(Positioned<String>, Rc<Val>)>,
-        w: &mut Write,
-    ) -> Result<()> {
+    fn convert_tuple(&self, flds: &Vec<(Positioned<String>, Rc<Val>)>, w: &mut Write) -> Result {
         for &(ref name, ref val) in flds.iter() {
             if val.is_tuple() {
                 eprintln!("Skipping embedded tuple...");
@@ -49,12 +44,12 @@ impl EnvConverter {
         Ok(())
     }
 
-    fn convert_list(&self, _items: &Vec<Rc<Val>>, _w: &mut Write) -> Result<()> {
+    fn convert_list(&self, _items: &Vec<Rc<Val>>, _w: &mut Write) -> Result {
         eprintln!("Skipping List...");
         Ok(())
     }
 
-    fn write(&self, v: &Val, w: &mut Write) -> Result<()> {
+    fn write(&self, v: &Val, w: &mut Write) -> Result {
         match v {
             &Val::Empty => {
                 // Empty is a noop.
@@ -88,7 +83,7 @@ impl EnvConverter {
 }
 
 impl Converter for EnvConverter {
-    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result<()> {
+    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result {
         self.write(&v, &mut w)
     }
 }

src/convert/flags.rs

@@ -13,12 +13,11 @@
 //  limitations under the License.
 
 //! Contains code for converting a UCG Val into the command line flag output target.
-use std::io::Result;
 use std::io::Write;
 use std::rc::Rc;
 
 use build::Val;
-use convert::traits::Converter;
+use convert::traits::{Converter, Result};
 
 /// FlagConverter implements the conversion logic for converting a Val into a set of command line flags.
 pub struct FlagConverter {}
@@ -28,7 +27,7 @@ impl FlagConverter {
         FlagConverter {}
     }
 
-    fn write_flag_name(&self, pfx: &str, name: &str, w: &mut Write) -> Result<()> {
+    fn write_flag_name(&self, pfx: &str, name: &str, w: &mut Write) -> Result {
         if name.chars().count() > 1 || pfx.chars().count() > 0 {
             try!(write!(w, "--{}{} ", pfx, name));
         } else {
@@ -37,13 +36,7 @@ impl FlagConverter {
         return Ok(());
     }
 
-    fn write_list_flag(
-        &self,
-        pfx: &str,
-        name: &str,
-        def: &Vec<Rc<Val>>,
-        w: &mut Write,
-    ) -> Result<()> {
+    fn write_list_flag(&self, pfx: &str, name: &str, def: &Vec<Rc<Val>>, w: &mut Write) -> Result {
         // first of all we need to make sure that each &Val is only a primitive type.
         for v in def.iter() {
             let vref = v.as_ref();
@@ -60,7 +53,7 @@ impl FlagConverter {
         return Ok(());
     }
 
-    fn write(&self, pfx: &str, v: &Val, w: &mut Write) -> Result<()> {
+    fn write(&self, pfx: &str, v: &Val, w: &mut Write) -> Result {
         match v {
             &Val::Empty => {
                 // Empty is a noop.
@@ -110,7 +103,7 @@ impl FlagConverter {
 }
 
 impl Converter for FlagConverter {
-    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result<()> {
+    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result {
         self.write("", &v, &mut w)
     }
 }

src/convert/json.rs

@@ -8,7 +8,7 @@
 //  See the License for the specific language governing permissions and
 //  limitations under the License.
 //! Flags contains code for converting a UCG Val into the json output target.
-use std::io::Result;
+use std;
 use std::io::Write;
 use std::rc::Rc;
 
@@ -16,7 +16,7 @@ use serde_json;
 
 use ast;
 use build::Val;
-use convert::traits::Converter;
+use convert::traits::{Converter, Result};
 
 /// JsonConverter implements the logic for converting a Val into the json output format.
 pub struct JsonConverter {}
@@ -26,7 +26,7 @@ impl JsonConverter {
         JsonConverter {}
     }
 
-    fn convert_list(&self, items: &Vec<Rc<Val>>) -> Result<serde_json::Value> {
+    fn convert_list(&self, items: &Vec<Rc<Val>>) -> std::io::Result<serde_json::Value> {
         let mut v = Vec::new();
         for val in items.iter() {
             v.push(try!(self.convert_value(val)));
@@ -37,7 +37,7 @@ impl JsonConverter {
     fn convert_tuple(
         &self,
         items: &Vec<(ast::Positioned<String>, Rc<Val>)>,
-    ) -> Result<serde_json::Value> {
+    ) -> std::io::Result<serde_json::Value> {
         let mut mp = serde_json::Map::new();
         for &(ref k, ref v) in items.iter() {
             mp.entry(k.val.clone())
@@ -46,7 +46,7 @@ impl JsonConverter {
         Ok(serde_json::Value::Object(mp))
     }
 
-    fn convert_value(&self, v: &Val) -> Result<serde_json::Value> {
+    fn convert_value(&self, v: &Val) -> std::io::Result<serde_json::Value> {
         let jsn_val = match v {
             &Val::Boolean(b) => serde_json::Value::Bool(b),
             &Val::Empty => serde_json::Value::Null,
@@ -77,7 +77,7 @@ impl JsonConverter {
         Ok(jsn_val)
     }
 
-    fn write(&self, v: &Val, w: &mut Write) -> Result<()> {
+    fn write(&self, v: &Val, w: &mut Write) -> Result {
         let jsn_val = try!(self.convert_value(v));
         try!(serde_json::to_writer(w, &jsn_val));
         Ok(())
@@ -85,7 +85,7 @@ impl JsonConverter {
 }
 
 impl Converter for JsonConverter {
-    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result<()> {
+    fn convert(&self, v: Rc<Val>, mut w: Box<Write>) -> Result {
         self.write(&v, &mut w)
     }
 }

src/convert/mod.rs

@@ -18,7 +18,6 @@ pub mod flags;
 pub mod json;
 pub mod traits;
 
-use std::io;
 use std::io::Write;
 use std::rc::Rc;
 
@@ -54,7 +53,7 @@ impl ConverterRunner {
     }
 
     /// convert runs the Converter on a Val and writes the output to the provided writer.
-    pub fn convert(&self, v: Rc<Val>, w: Box<Write>) -> io::Result<()> {
+    pub fn convert(&self, v: Rc<Val>, w: Box<Write>) -> traits::Result {
         self.converter.convert(v, w)
     }
 }

src/convert/traits.rs

@@ -13,14 +13,17 @@
 //  limitations under the License.
 
 //! The traits used by the ucg compiler for converting Val intermediate format into the output formats..
-use std::io::Result;
+use std::error::Error;
 use std::io::Write;
 use std::rc::Rc;
+use std::result;
 
 use build::Val;
 
+pub type Result = result::Result<(), Box<Error>>;
+
 /// The trait that Converters from Val to different output formats for the
 /// final conversion stage of the ucg compiler.
 pub trait Converter {
-    fn convert(&self, vs: Rc<Val>, w: Box<Write>) -> Result<()>;
+    fn convert(&self, vs: Rc<Val>, w: Box<Write>) -> Result;
 }

src/main.rs

@@ -23,6 +23,7 @@ use std::rc::Rc;
 
 use ucglib::build;
 use ucglib::build::Val;
+use ucglib::convert::traits;
 use ucglib::convert::ConverterRunner;
 
 // TODO(jwall): List the target output types automatically.
@@ -46,7 +47,7 @@ fn do_flags<'a>() -> clap::ArgMatches<'a> {
     ).get_matches()
 }
 
-fn run_converter(c: ConverterRunner, v: Rc<Val>, f: Option<&str>) -> io::Result<()> {
+fn run_converter(c: ConverterRunner, v: Rc<Val>, f: Option<&str>) -> traits::Result {
     let file: Box<std::io::Write> = match f {
         Some(f) => Box::new(try!(File::create(f))),
         None => Box::new(io::stdout()),