diff --git a/schala-lang/language/src/parser.rs b/schala-lang/language/src/parser.rs
index d0b9548..6a3cff7 100644
--- a/schala-lang/language/src/parser.rs
+++ b/schala-lang/language/src/parser.rs
@@ -457,8 +457,10 @@ fn formal_params(text: &str) -> ParseResult<Vec<FormalParam>> {
 }
 
 fn formal_param(text: &str) -> ParseResult<FormalParam> {
-  let p = tuple((identifier, opt(type_anno)));
-  //TODO handle default arg
+  let default = opt(preceded(ws(tag("=")), expression));
+  let p = tuple((ws(identifier), opt(ws(type_anno)), default));
+  map(p, |(name, anno, default)|
+    FormalParam { name, anno, default })(text)
 }
 
 fn type_declaration(text: &str) -> ParseResult<Declaration> {
@@ -466,7 +468,7 @@ fn type_declaration(text: &str) -> ParseResult<Declaration> {
 }
 
 fn type_declaration_body(text: &str) -> ParseResult<Declaration> {
-  let t = tuple((opt(tag("mut"))), ws(type_singleton_name), ws(tag("=")), ws(type_body));
+  let t = tuple((opt(tag("mut")), ws(type_singleton_name), ws(tag("=")), ws(type_body)));
   alt((
     preceded(tag("alias"), ws(type_alias)),
     map(t, |(mut_kw, name, _, body)| {
@@ -475,10 +477,29 @@ fn type_declaration_body(text: &str) -> ParseResult<Declaration> {
   ))(text)
 }
 
+fn type_body(text: &str) -> ParseResult<TypeBody> {
+  let p = separated_nonempty_list(ws(tag("|")), variant_specifier);
+  map(p, TypeBody)(text)
+}
+
+fn variant_specifier(text: &str) -> ParseResult<Variant> {
+  use self::Variant::*;
+  let tuple_struct =
+    delimited(tag("("), separated_nonempty_list(ws(tag(",")), type_name), ws(tag(")")));
+  //TODO record
+
+  let p = tuple((identifier, opt(tuple_struct)));
+  map(p, |(name, maybe_tuple_members)| match maybe_tuple_members {
+    Some(members) => TupleStruct(name, members),
+    None => UnitStruct(name),
+  })(text)
+}
+
 fn type_singleton_name(text: &str) -> ParseResult<TypeSingletonName> {
-  tuple((identifier, opt(delimited(tag("<"),
+  let p = tuple((identifier, opt(delimited(tag("<"),
     separated_nonempty_list(tag(","), ws(type_name)),
-  tag(">")))))(text)
+  tag(">")))));
+  map(p, |(name, params)| TypeSingletonName { name, params: params.unwrap_or(vec![]) })(text)
 }
 
 fn type_alias(text: &str) -> ParseResult<Declaration> {