diff --git a/src/ast/walk.rs b/src/ast/walk.rs
index d67422f..bce4ad9 100644
--- a/src/ast/walk.rs
+++ b/src/ast/walk.rs
@@ -124,9 +124,9 @@ pub trait Walker {
 
 // TODO this would be better implemented as a Trait I think.
 pub struct AstWalker<'a> {
-    handle_value: Option<&'a Fn(&mut Value)>,
-    handle_expression: Option<&'a Fn(&mut Expression)>,
-    handle_statment: Option<&'a Fn(&mut Statement)>,
+    handle_value: Option<&'a dyn Fn(&mut Value)>,
+    handle_expression: Option<&'a dyn Fn(&mut Expression)>,
+    handle_statment: Option<&'a dyn Fn(&mut Statement)>,
 }
 
 impl<'a> AstWalker<'a> {
@@ -138,17 +138,17 @@ impl<'a> AstWalker<'a> {
         }
     }
 
-    pub fn with_value_handler(mut self, h: &'a Fn(&mut Value)) -> Self {
+    pub fn with_value_handler(mut self, h: &'a dyn Fn(&mut Value)) -> Self {
         self.handle_value = Some(h);
         self
     }
 
-    pub fn with_expr_handler(mut self, h: &'a Fn(&mut Expression)) -> Self {
+    pub fn with_expr_handler(mut self, h: &'a dyn Fn(&mut Expression)) -> Self {
         self.handle_expression = Some(h);
         self
     }
 
-    pub fn with_stmt_handler(mut self, h: &'a Fn(&mut Statement)) -> Self {
+    pub fn with_stmt_handler(mut self, h: &'a dyn Fn(&mut Statement)) -> Self {
         self.handle_statment = Some(h);
         self
     }
diff --git a/src/convert/env.rs b/src/convert/env.rs
index a01848c..0d83196 100644
--- a/src/convert/env.rs
+++ b/src/convert/env.rs
@@ -28,7 +28,7 @@ impl EnvConverter {
         EnvConverter {}
     }
 
-    fn convert_tuple(&self, flds: &Vec<(String, Rc<Val>)>, w: &mut IOWrite) -> ConvertResult {
+    fn convert_tuple(&self, flds: &Vec<(String, Rc<Val>)>, w: &mut dyn IOWrite) -> ConvertResult {
         for &(ref name, ref val) in flds.iter() {
             if val.is_tuple() {
                 eprintln!("Skipping embedded tuple...");
@@ -44,12 +44,12 @@ impl EnvConverter {
         Ok(())
     }
 
-    fn convert_list(&self, _items: &Vec<Rc<Val>>, _w: &mut IOWrite) -> ConvertResult {
+    fn convert_list(&self, _items: &Vec<Rc<Val>>, _w: &mut dyn IOWrite) -> ConvertResult {
         eprintln!("Skipping List...");
         Ok(())
     }
 
-    fn write(&self, v: &Val, w: &mut IOWrite) -> ConvertResult {
+    fn write(&self, v: &Val, w: &mut dyn IOWrite) -> ConvertResult {
         match v {
             &Val::Empty => {
                 // Empty is a noop.
@@ -91,7 +91,7 @@ impl EnvConverter {
 }
 
 impl Converter for EnvConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut IOWrite) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn IOWrite) -> ConvertResult {
         self.write(&v, &mut w)
     }
 
diff --git a/src/convert/exec.rs b/src/convert/exec.rs
index 3b9bc81..bff2762 100644
--- a/src/convert/exec.rs
+++ b/src/convert/exec.rs
@@ -37,7 +37,7 @@ impl ExecConverter {
     }
 
     #[allow(unused_assignments)]
-    fn write(&self, v: &Val, w: &mut Write) -> ConvertResult {
+    fn write(&self, v: &Val, w: &mut dyn Write) -> ConvertResult {
         // We always expect the Val to be a Tuple.
         if let &Tuple(ref fields) = v {
             // We expect no more than three fields in our exec tuple.
@@ -173,7 +173,7 @@ impl ExecConverter {
 }
 
 impl Converter for ExecConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut Write) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
         self.write(&v, &mut w)
     }
 
diff --git a/src/convert/flags.rs b/src/convert/flags.rs
index db3a7b0..3d57974 100644
--- a/src/convert/flags.rs
+++ b/src/convert/flags.rs
@@ -36,7 +36,7 @@ impl FlagConverter {
         self
     }
 
-    fn write_flag_name(&self, pfx: &str, name: &str, w: &mut Write) -> ConvertResult {
+    fn write_flag_name(&self, pfx: &str, name: &str, w: &mut dyn Write) -> ConvertResult {
         if name.chars().count() > 1 || pfx.chars().count() > 0 {
             write!(w, "--{}{} ", pfx, name)?;
         } else {
@@ -50,7 +50,7 @@ impl FlagConverter {
         pfx: &str,
         name: &str,
         def: &Vec<Rc<Val>>,
-        w: &mut Write,
+        w: &mut dyn Write,
     ) -> ConvertResult {
         // first of all we need to make sure that each &Val is only a primitive type.
         for v in def.iter() {
@@ -68,7 +68,7 @@ impl FlagConverter {
         return Ok(());
     }
 
-    fn write_simple_value(&self, v: &Val, w: &mut Write) -> ConvertResult {
+    fn write_simple_value(&self, v: &Val, w: &mut dyn Write) -> ConvertResult {
         match v {
             &Val::Empty => {
                 // Empty is a noop.
@@ -94,7 +94,7 @@ impl FlagConverter {
         Ok(())
     }
 
-    fn write(&self, pfx: &str, flds: &Vec<(String, Rc<Val>)>, w: &mut Write) -> ConvertResult {
+    fn write(&self, pfx: &str, flds: &Vec<(String, Rc<Val>)>, w: &mut dyn Write) -> ConvertResult {
         for &(ref name, ref val) in flds.iter() {
             if let &Val::Empty = val.as_ref() {
                 self.write_flag_name(pfx, name, w)?;
@@ -118,7 +118,7 @@ impl FlagConverter {
 }
 
 impl Converter for FlagConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut Write) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
         if let &Val::Tuple(ref flds) = v.as_ref() {
             self.write("", flds, &mut w)
         } else {
diff --git a/src/convert/json.rs b/src/convert/json.rs
index f8fe83e..3d6efc7 100644
--- a/src/convert/json.rs
+++ b/src/convert/json.rs
@@ -116,7 +116,7 @@ impl JsonConverter {
         })
     }
 
-    fn write(&self, v: &Val, w: &mut Write) -> ConvertResult {
+    fn write(&self, v: &Val, w: &mut dyn Write) -> ConvertResult {
         let jsn_val = self.convert_value(v)?;
         serde_json::to_writer_pretty(w, &jsn_val)?;
         Ok(())
@@ -124,7 +124,7 @@ impl JsonConverter {
 }
 
 impl Converter for JsonConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut Write) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
         self.write(&v, &mut w)
     }
 
diff --git a/src/convert/mod.rs b/src/convert/mod.rs
index bec447c..975757e 100644
--- a/src/convert/mod.rs
+++ b/src/convert/mod.rs
@@ -55,15 +55,15 @@ impl ConverterRegistry {
         registry
     }
 
-    pub fn register<S: Into<String>>(&mut self, typ: S, converter: Box<traits::Converter>) {
+    pub fn register<S: Into<String>>(&mut self, typ: S, converter: Box<dyn traits::Converter>) {
         self.converters.insert(typ.into(), converter);
     }
 
-    pub fn get_converter(&self, typ: &str) -> Option<&traits::Converter> {
+    pub fn get_converter(&self, typ: &str) -> Option<&dyn traits::Converter> {
         self.converters.get(typ).map(|c| c.as_ref())
     }
 
-    pub fn get_converter_list(&self) -> Vec<(&String, &Box<traits::Converter>)> {
+    pub fn get_converter_list(&self) -> Vec<(&String, &Box<dyn traits::Converter>)> {
         self.converters.iter().collect()
     }
 }
diff --git a/src/convert/toml.rs b/src/convert/toml.rs
index a925000..0c65ee1 100644
--- a/src/convert/toml.rs
+++ b/src/convert/toml.rs
@@ -26,7 +26,7 @@ use crate::convert::traits::{ConvertResult, Converter, ImportResult, Importer};
 
 pub struct TomlConverter {}
 
-type Result = std::result::Result<toml::Value, Box<error::Error>>;
+type Result = std::result::Result<toml::Value, Box<dyn error::Error>>;
 
 impl TomlConverter {
     pub fn new() -> Self {
@@ -107,7 +107,7 @@ impl TomlConverter {
         })
     }
 
-    fn write(&self, v: &Val, w: &mut Write) -> ConvertResult {
+    fn write(&self, v: &Val, w: &mut dyn Write) -> ConvertResult {
         let toml_val = self.convert_value(v)?;
         let toml_bytes = toml::ser::to_string_pretty(&toml_val)?;
         write!(w, "{}", toml_bytes)?;
@@ -116,7 +116,7 @@ impl TomlConverter {
 }
 
 impl Converter for TomlConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut Write) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
         self.write(&v, &mut w)
     }
 
diff --git a/src/convert/traits.rs b/src/convert/traits.rs
index 10dba11..a4f07e5 100644
--- a/src/convert/traits.rs
+++ b/src/convert/traits.rs
@@ -27,7 +27,7 @@ pub type ImportResult = result::Result<Rc<Val>, Box<dyn 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: &mut Write) -> ConvertResult;
+    fn convert(&self, vs: Rc<Val>, w: &mut dyn Write) -> ConvertResult;
     fn file_ext(&self) -> String;
     fn description(&self) -> String;
     fn help(&self) -> String;
diff --git a/src/convert/xml.rs b/src/convert/xml.rs
index 55b421c..edfc256 100644
--- a/src/convert/xml.rs
+++ b/src/convert/xml.rs
@@ -153,7 +153,7 @@ impl XmlConverter {
         Ok(())
     }
 
-    fn write(&self, v: &Val, w: &mut Write) -> ConvertResult {
+    fn write(&self, v: &Val, w: &mut dyn Write) -> ConvertResult {
         if let Val::Tuple(ref fs) = v {
             let mut version: Option<&str> = None;
             let mut encoding: Option<&str> = None;
@@ -223,7 +223,7 @@ impl XmlConverter {
 }
 
 impl Converter for XmlConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut Write) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
         self.write(&v, &mut w)
     }
 
diff --git a/src/convert/yaml.rs b/src/convert/yaml.rs
index 54ba689..1b17a16 100644
--- a/src/convert/yaml.rs
+++ b/src/convert/yaml.rs
@@ -139,7 +139,7 @@ impl YamlConverter {
         })
     }
 
-    fn write(&self, v: &Val, w: &mut Write) -> ConvertResult {
+    fn write(&self, v: &Val, w: &mut dyn Write) -> ConvertResult {
         let jsn_val = self.convert_value(v)?;
         serde_yaml::to_writer(w, &jsn_val)?;
         Ok(())
@@ -147,7 +147,7 @@ impl YamlConverter {
 }
 
 impl Converter for YamlConverter {
-    fn convert(&self, v: Rc<Val>, mut w: &mut Write) -> ConvertResult {
+    fn convert(&self, v: Rc<Val>, mut w: &mut dyn Write) -> ConvertResult {
         self.write(&v, &mut w)
     }
 
diff --git a/src/main.rs b/src/main.rs
index 4ce1b24..8446196 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -80,8 +80,8 @@ fn do_flags<'a, 'b>() -> clap::App<'a, 'b> {
     )
 }
 
-fn run_converter(c: &traits::Converter, v: Rc<Val>, f: Option<&str>) -> traits::ConvertResult {
-    let mut file: Box<std::io::Write> = match f {
+fn run_converter(c: &dyn traits::Converter, v: Rc<Val>, f: Option<&str>) -> traits::ConvertResult {
+    let mut file: Box<dyn std::io::Write> = match f {
         Some(f) => {
             let mut path_buf = PathBuf::from(f);
             path_buf.set_extension(c.file_ext());