diff --git a/Cargo.toml b/Cargo.toml
index accd96c5..923d719d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -38,6 +38,7 @@ categories = ["command-line-interface"]
 description = """
 A simple to use, efficient, and full featured Command Line Argument Parser
 """
+edition = "2018"
 
 [badges]
 travis-ci = { repository = "clap-rs/clap" }
diff --git a/src/build/arg/long.rs b/src/build/arg/key/long.rs
similarity index 100%
rename from src/build/arg/long.rs
rename to src/build/arg/key/long.rs
diff --git a/src/build/arg/key.rs b/src/build/arg/key/mod.rs
similarity index 100%
rename from src/build/arg/key.rs
rename to src/build/arg/key/mod.rs
diff --git a/src/build/arg/key/position.rs b/src/build/arg/key/position.rs
new file mode 100644
index 00000000..15474daf
--- /dev/null
+++ b/src/build/arg/key/position.rs
@@ -0,0 +1,13 @@
+pub struct Position(u64);
+
+impl Default for Position {
+    fn default() -> Self {
+        Position(1)
+    }
+}
+
+impl Position {
+    fn new() -> Self {
+        Position(1)
+    }
+}
\ No newline at end of file
diff --git a/src/build/arg/short.rs b/src/build/arg/key/short.rs
similarity index 100%
rename from src/build/arg/short.rs
rename to src/build/arg/key/short.rs
diff --git a/src/build/arg/position.rs b/src/build/arg/position.rs
deleted file mode 100644
index e05c91b9..00000000
--- a/src/build/arg/position.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-pub struct Position {
-    index: u64
-}
\ No newline at end of file
diff --git a/src/build/arg/default_values.rs b/src/build/arg/value/default_values.rs
similarity index 62%
rename from src/build/arg/default_values.rs
rename to src/build/arg/value/default_values.rs
index c3aabfe6..aab161ca 100644
--- a/src/build/arg/default_values.rs
+++ b/src/build/arg/value/default_values.rs
@@ -1,13 +1,14 @@
-pub struct DefaultValue<'help> {
-    value: &'help str,
+pub struct EnvDefaultValue<'help> {
+    key: &'help OsStr,
+    value: Option<OsString>
 }
-
 pub struct ConditionalDefault<'help> {
-    value: DefaultValue<'help>,
+    value: &'help str,
     other_arg: Option<u64>,
     other_value: Option<&'help str>,
 }
 
 pub struct DefaultValues<'help> {
     defaults: Vec<ConditionalDefault<'help>>,
+    env: Option<EnvDefaultValue<'help>>,
 }
\ No newline at end of file
diff --git a/src/build/arg/delimiter.rs b/src/build/arg/value/delimiter.rs
similarity index 100%
rename from src/build/arg/delimiter.rs
rename to src/build/arg/value/delimiter.rs
diff --git a/src/build/arg/filter.rs b/src/build/arg/value/filter.rs
similarity index 100%
rename from src/build/arg/filter.rs
rename to src/build/arg/value/filter.rs
diff --git a/src/build/arg/value.rs b/src/build/arg/value/mod.rs
similarity index 84%
rename from src/build/arg/value.rs
rename to src/build/arg/value/mod.rs
index 603404d2..e7df2950 100644
--- a/src/build/arg/value.rs
+++ b/src/build/arg/value/mod.rs
@@ -1,6 +1,5 @@
 pub struct Value<'help> {
     defaults: Option<DefaultValues>,
-    name: Option<&'help str>,
     filter: Filter,
     occurrence: Occurrence,
     requires_equals: bool,
diff --git a/src/build/arg/possible_values.rs b/src/build/arg/value/possible_values.rs
similarity index 100%
rename from src/build/arg/possible_values.rs
rename to src/build/arg/value/possible_values.rs
diff --git a/src/build/arg/terminator.rs b/src/build/arg/value/terminator.rs
similarity index 100%
rename from src/build/arg/terminator.rs
rename to src/build/arg/value/terminator.rs
diff --git a/src/build/arg/value/value_name.rs b/src/build/arg/value/value_name.rs
new file mode 100644
index 00000000..7e21581f
--- /dev/null
+++ b/src/build/arg/value/value_name.rs
@@ -0,0 +1,15 @@
+use std::io;
+
+pub struct ValueName<'help>(&'help str);
+
+impl<'help> ValueName<'help> {
+    fn write_as_required<W: io::Write>(&self, w: W) -> io::Result {
+        write!(w, "<{}>", self.0)
+    }
+    fn write_as_optional<W: io::Write>(&self, w: W) -> io::Result {
+        write!(w, "[{}]", self.0)
+    }
+    fn write<W: io::Write>(&self, w: W) -> io::Result {
+        write!(w, "{}", self.0)
+    }
+}
\ No newline at end of file
diff --git a/src/build/arg/value_name.rs b/src/build/arg/value_name.rs
deleted file mode 100644
index cb2c0e1c..00000000
--- a/src/build/arg/value_name.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-pub struct ValueName<'help> {
-    name: &'help str,
-}
\ No newline at end of file