diff --git a/examples/ackermann.sb b/examples/ackermann.sb
index c07a96f..8d1437b 100644
--- a/examples/ackermann.sb
+++ b/examples/ackermann.sb
@@ -4,7 +4,7 @@ fn main() {
     println(ackermann(m, n))
 }
 
-fn ackermann(m int, n int) {
+fn ackermann(m: int, n: int) {
     if m == 0 {
         return n + 1
     } else if n == 0 {
diff --git a/examples/fib.sb b/examples/fib.sb
index 7f7011a..895c78c 100644
--- a/examples/fib.sb
+++ b/examples/fib.sb
@@ -3,7 +3,7 @@ fn main() {
     println(fib(num))
 }
 
-fn fib(n int) { 
+fn fib(n: int) { 
     if 1 >= n {
         return n
     }
diff --git a/examples/greeter.sb b/examples/greeter.sb
index c2597b8..bd72412 100644
--- a/examples/greeter.sb
+++ b/examples/greeter.sb
@@ -2,6 +2,6 @@ fn main() {
     println(greet("World"))
 }
 
-fn greet(name string) {
+fn greet(name: string) {
     return "Hello " + name
 }
diff --git a/examples/playground.sb b/examples/playground.sb
index 31265c6..78cfac5 100644
--- a/examples/playground.sb
+++ b/examples/playground.sb
@@ -1,3 +1,5 @@
-fn main() {
-    let arr = [1, 4, 2, 5, 3]
-}
+fn main(n: int) {
+    if n {
+        return n
+    }
+}
\ No newline at end of file
diff --git a/lib/stdio.sb b/lib/stdio.sb
index 25fa46e..b86fec7 100644
--- a/lib/stdio.sb
+++ b/lib/stdio.sb
@@ -1,16 +1,16 @@
 // Raw wrapper around _printf builtin function.
 // Writes the given content to stdout
-fn print(msg string) {
-    _printf(msg)
+fn print(arg: string) {
+    _printf(arg)
 }
 
 // Like print(), but with an extra newline ('\n') character
-fn println(msg string) {
+fn println(msg: string) {
     print(msg + "\n")
 }
 
 // Prints the size of an array
-fn len(arr int[]) {
+fn len(arr: int[]) {
     let c = 0
     while arr[c] {
         c = c + 1
@@ -21,7 +21,7 @@ fn len(arr int[]) {
 
 // Reverses an array
 // TODO: fix me!
-fn rev(arr int[]) {
+fn rev(arr: int[]) {
 
     let l = len(arr)
     let new_arr = []
diff --git a/playground.js b/playground.js
new file mode 100644
index 0000000..6bfc3a0
--- /dev/null
+++ b/playground.js
@@ -0,0 +1,38 @@
+/* START builtins */
+
+function _printf(msg) {
+  process.stdout.write(msg);
+}
+
+/* END builtins */
+function print(msg){
+_printf(msg);
+}
+function println(msg){
+print(msg + "\n");
+}
+function len(arr){
+var c = 0;
+while (arr[c]) {
+c = c + 1;
+}
+;
+return c;
+}
+function rev(arr){
+var l = len(arr);
+var new_arr = [];
+var i = 0;
+var j = l;
+while (i < l) {
+new_arr[i] = arr[j];
+i = i - 1;
+j = j - 1;
+}
+;
+return new_arr;
+}
+function main(){
+var arr = [1, 4, 2, 5, 3];
+}
+main();
\ No newline at end of file
diff --git a/src/lexer/mod.rs b/src/lexer/mod.rs
index 3da70c3..5a65d5e 100644
--- a/src/lexer/mod.rs
+++ b/src/lexer/mod.rs
@@ -161,6 +161,10 @@ pub fn first_token(input: &str, pos: &mut Position) -> Token {
 pub fn is_whitespace(c: char) -> bool {
     match c {
         ' ' | '\n' | '\r' | '\t' => true,
+        '\u{00A0}' => {
+            dbg!("Non-standard unicode character found: '\u{00A0}'");
+            true
+        }
         _ => false,
     }
 }
diff --git a/src/main.rs b/src/main.rs
index b44b359..03f0b03 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -67,7 +67,6 @@ fn main() -> Result<(), String> {
 
     let tokens = lexer::tokenize(&contents);
     let program = parser::parse(tokens, Some(contents))?;
-    dbg!(&program);
 
     let output = generator::js::JsGenerator::generate(program);
     let mut file = std::fs::File::create(out_file).expect("create failed");
diff --git a/src/parser/rules.rs b/src/parser/rules.rs
index 4fce8ed..b9e04e2 100644
--- a/src/parser/rules.rs
+++ b/src/parser/rules.rs
@@ -80,10 +80,12 @@ impl Parser {
                 TokenKind::Comma => {
                     continue;
                 }
-                TokenKind::Identifier(name) => args.push(Variable {
-                    name: name,
-                    ty: Some(self.parse_type()?),
-                }),
+                TokenKind::Identifier(name) => {
+                    args.push(Variable {
+                        name: name,
+                        ty: Some(self.parse_type()?),
+                    });
+                }
                 _ => return Err(self.make_error(TokenKind::Identifier("Argument".into()), next)),
             }
         }
@@ -92,13 +94,14 @@ impl Parser {
     }
 
     fn parse_type(&mut self) -> Result<Type, String> {
-        let next = self.next()?;
+        self.match_token(TokenKind::Colon)?;
+        let next = self.peek()?;
         let typ = match next.kind {
-            TokenKind::Identifier(t) => Type::try_from(t),
+            TokenKind::Identifier(_) => Type::try_from(self.next()?.raw),
             _ => Err("Expected type".into()),
         }?;
         if let Ok(_) = self.peek_token(TokenKind::SquareBraceOpen) {
-            self.drop(1);
+            self.match_token(TokenKind::SquareBraceOpen)?;
             self.match_token(TokenKind::SquareBraceClose)?;
             Ok(Type::Array(Box::new(typ)))
         } else {
@@ -242,16 +245,20 @@ impl Parser {
     fn parse_array(&mut self) -> Result<Expression, String> {
         let mut elements = Vec::new();
         loop {
-            let next = self.next()?;
+            let next = self.peek()?;
             match next.kind {
+                TokenKind::SquareBraceClose => {}
                 TokenKind::Literal(Value::Int) => {
-                    let value = next.raw.parse::<u32>().map_err(|e| e.to_string())?;
+                    let value = self.next()?.raw.parse::<u32>().map_err(|e| e.to_string())?;
                     elements.push(Expression::Int(value));
                 }
                 TokenKind::Literal(Value::Str) => {
-                    elements.push(Expression::Str(next.raw));
+                    elements.push(Expression::Str(self.next()?.raw));
+                }
+                _ => {
+                    let n = self.next()?;
+                    return Err(self.make_error(TokenKind::Identifier("Argument".into()), n));
                 }
-                _ => return Err(self.make_error(TokenKind::Identifier("Argument".into()), next)),
             };
             if self.peek_token(TokenKind::SquareBraceClose).is_ok() {
                 break;
@@ -347,17 +354,14 @@ impl Parser {
 
     fn parse_declare(&mut self) -> Result<Statement, String> {
         self.match_keyword(Keyword::Let)?;
-        match (self.next()?.kind, self.peek()?.kind) {
-            (TokenKind::Identifier(name), TokenKind::SemiColon) => {
-                Ok(Statement::Declare(Variable { name, ty: None }, None))
-            }
-            (TokenKind::Identifier(name), TokenKind::Assign) => {
-                self.drop(1);
-                let exp = self.parse_expression().ok();
-                Ok(Statement::Declare(Variable { name, ty: None }, exp))
-            }
-            other => Err(format!("Expected identifier, found {:?}", other)),
-        }
+        let name = self.match_identifier()?;
+        let ty = match self.peek()?.kind {
+            TokenKind::Colon => Some(self.parse_type()?),
+            _ => None,
+        };
+        self.match_token(TokenKind::Assign)?;
+        let expr = self.parse_expression()?;
+        Ok(Statement::Declare(Variable { name, ty }, Some(expr)))
     }
 
     fn parse_assignent(&mut self, name: Option<Expression>) -> Result<Statement, String> {
diff --git a/src/parser/tests.rs b/src/parser/tests.rs
index 74c0c53..baf3258 100644
--- a/src/parser/tests.rs
+++ b/src/parser/tests.rs
@@ -120,7 +120,7 @@ fn test_parse_variable_declaration_added() {
 #[test]
 fn test_parse_function_with_args() {
     let raw = "
-    fn main(foo int) {
+    fn main(foo: int) {
         return foo
     }
     ";
@@ -132,7 +132,7 @@ fn test_parse_function_with_args() {
 #[test]
 fn test_parse_function_call() {
     let raw = "
-    fn main(foo int) {
+    fn main(foo: int) {
         foo()
     }
 
@@ -184,7 +184,7 @@ fn test_parse_nexted_function_call() {
         fib(fib(2), 2)
     }
 
-    fn fib(n int) {
+    fn fib(n: int) {
         return 2
     }
     ";
@@ -244,7 +244,7 @@ fn test_parse_compound_ops_with_strings() {
 #[test]
 fn test_parse_compound_ops_with_identifier() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         return 2 * n
     }
     ";
@@ -256,7 +256,7 @@ fn test_parse_compound_ops_with_identifier() {
 #[test]
 fn test_parse_compound_ops_with_identifier_first() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         return n * 2
     }
     ";
@@ -268,7 +268,7 @@ fn test_parse_compound_ops_with_identifier_first() {
 #[test]
 fn test_parse_compound_ops_return() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         return 2 * n
     }
     ";
@@ -280,7 +280,7 @@ fn test_parse_compound_ops_return() {
 #[test]
 fn test_parse_basic_conditional() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         if n {
             return n
         }
@@ -294,7 +294,7 @@ fn test_parse_basic_conditional() {
 #[test]
 fn test_parse_basic_conditional_with_multiple_statements() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         if n {
             let x = 2 * n
             return x
@@ -309,7 +309,7 @@ fn test_parse_basic_conditional_with_multiple_statements() {
 #[test]
 fn test_parse_conditional_else_if_branch() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         if n > 10 {
             let x = 2 * n
             return x
@@ -326,7 +326,7 @@ fn test_parse_conditional_else_if_branch() {
 #[test]
 fn test_parse_conditional_multiple_else_if_branch_branches() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         if n > 10 {
             let x = 2 * n
             return x
@@ -345,7 +345,7 @@ fn test_parse_conditional_multiple_else_if_branch_branches() {
 #[test]
 fn test_parse_conditional_else_branch() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         if n > 10 {
             let x = 2 * n
             return x
@@ -362,7 +362,7 @@ fn test_parse_conditional_else_branch() {
 #[test]
 fn test_parse_conditional_elseif_else_branch() {
     let raw = "
-    fn main(n int) {
+    fn main(n: int) {
         if n > 10 {
             let x = 2 * n
             return x
@@ -383,7 +383,7 @@ fn test_parse_conditional_elseif_else_branch() {
 #[test]
 fn test_int_array() {
     let raw = "
-    fn main(n int) {
+    fn main() {
         let arr = [1, 2, 3]
         return arr
     }
@@ -396,7 +396,7 @@ fn test_int_array() {
 #[test]
 fn test_string_array() {
     let raw = "
-    fn main(n int) {
+    fn main(n:int) {
         return [\"Foo\", \"Bar\", \"Baz\"]
     }
     ";
@@ -533,7 +533,7 @@ fn test_uninitialized_variables() {
 #[test]
 fn test_function_call_math() {
     let raw = "
-    fn main(m int) {
+    fn main(m: int) {
         main(m - 1)
     }
     ";
@@ -545,7 +545,7 @@ fn test_function_call_math() {
 #[test]
 fn test_function_multiple_args() {
     let raw = "
-    fn main(m int, n int) {
+    fn main(m: int, n: int) {
         main(m, n)
     }
     ";
@@ -565,3 +565,29 @@ fn test_array_position_assignment() {
     let tree = parse(tokens, Some(raw.to_string()));
     assert!(tree.is_ok())
 }
+
+#[test]
+fn test_typed_declare() {
+    let raw = "
+    fn main() {
+        let x = 5
+        let y: int = 1
+        let z: bool = false
+    }
+    ";
+    let tokens = tokenize(raw);
+    let tree = parse(tokens, Some(raw.to_string()));
+    assert!(tree.is_ok())
+}
+
+#[test]
+fn test_no_function_args_without_type() {
+    let raw = "
+    fn main(x) {
+        return n
+    }
+    ";
+    let tokens = tokenize(raw);
+    let tree = parse(tokens, Some(raw.to_string()));
+    assert!(tree.is_err())
+}