diff --git a/programs/aidl/assets/core.idl b/programs/aidl/assets/core.idl
index 508ba9c..1067197 100644
--- a/programs/aidl/assets/core.idl
+++ b/programs/aidl/assets/core.idl
@@ -1,19 +1,21 @@
-Type Byte = U8;
-Type Int = U32;
-Type String = Vector<Byte>;
+Alias Byte = U8;
+Alias Int = U32;
+Alias String = Vector<Byte>;
 
-Enumurate Boolean {
+Enumeration Boolean {
     False = 0,
     True = 1,
 }
 
-Union Option<T>{
-    None,
-    Some<T>
+Enumeration Nothing {}
+
+Enumeration Option<T> {
+  None,
+  Some(T)
 }
 
 Structure Version {
     major: Byte,
     minor: Byte,
     patch: Byte,
-};
+}
diff --git a/programs/aidl/assets/why.idl b/programs/aidl/assets/why.idl
index e1ca115..e39c329 100644
--- a/programs/aidl/assets/why.idl
+++ b/programs/aidl/assets/why.idl
@@ -5,7 +5,25 @@ Constant Hi = "WHY???/\n";
 Alias Yo = Byte;
 
 Constant Version = Make Version {
-  major: 1,
-  minor: 0,
+  major: 1
+  minor: 0
   patch: 0
 };
+
+Interface Iface {
+  Function hello Takes(Int Boolean) Returns(Int);
+}
+
+Function a_free_function Returns(Boolean);
+
+Structure Hello {
+  world: Boolean prompt: Option<String>
+}
+
+Enumeration Reality {
+  Dead(Boolean Boolean),
+  Alive {
+    health: Int
+    dying: Boolean
+  }
+}
diff --git a/programs/aidl/src/ast.rs b/programs/aidl/src/ast.rs
index 9c18491..78b7ee3 100644
--- a/programs/aidl/src/ast.rs
+++ b/programs/aidl/src/ast.rs
@@ -17,20 +17,60 @@ pub struct IDLModule {
 
 #[derive(Debug)]
 pub enum Item {
-    _Interface(ItemInterface),
+    Interface(ItemInterface),
     Alias(ItemAlias),
     Constant(ItemConstant),
+    Function(Function),
+    Structure(ItemStructure),
+    Enumeration(ItemEnumeration)
 }
 
-#[derive(Debug)]
+#[derive(Debug, Default)]
 pub struct Function {
     pub name: String,
     pub takes: Vec<Type>,
-    pub returns: Type
+    pub returns: Type,
 }
 
-// why
-pub type Type = String;
+#[derive(Debug)]
+pub struct Type {
+    pub name: String,
+    pub arguments: TypeArguments,
+}
+
+impl Type {
+    pub fn infer() -> Self {
+        Self {
+            name: String::from(INFER_TYPE),
+            arguments: TypeArguments::None
+        }
+    }
+}
+
+pub const NOTHING_TYPE: &str = "Nothing";
+pub const INFER_TYPE: &str = "_";
+
+impl Default for Type {
+    fn default() -> Self {
+        Self {
+            name: String::from(NOTHING_TYPE),
+            arguments: TypeArguments::None,
+        }
+    }
+}
+
+#[derive(Debug, Default)]
+pub enum TypeArguments {
+    /// TypeName
+    #[default]
+    None,
+    /// TypeName<T1, T2, T3, TN>
+    AngleBracketed(Vec<Box<Type>>),
+}
+
+pub fn nothing() -> Type {
+    Type::default()
+}
 
 #[derive(Debug)]
 pub struct ItemInterface {
@@ -38,16 +78,44 @@ pub struct ItemInterface {
     pub functions: Vec<Function>,
 }
 
+#[derive(Debug)]
+pub struct ItemStructure {
+    pub name: String,
+    pub fields: HashMap<String, Type>,
+}
+
 #[derive(Debug)]
 pub struct ItemAlias {
     pub name: String,
-    pub referree: String,
+    pub referree: Type,
 }
 
 #[derive(Debug)]
 pub struct ItemConstant {
     pub name: String,
-    pub expr: Expr
+    pub expr: Expr,
+}
+
+#[derive(Debug)]
+pub struct ItemEnumeration {
+    pub name: String,
+    pub arguments: TypeArguments,
+    pub variants: Vec<EnumerationVariant>
+}
+
+#[derive(Debug)]
+pub struct EnumerationVariant {
+    pub name: String,
+    pub content: EnumerationContent
+}
+
+#[derive(Debug, Default)]
+pub enum EnumerationContent {
+    #[default]
+    None,
+    Tuple(Vec<Type>),
+    Structure(HashMap<String, Type>),
+    Value(NumberLiteral)
 }
 
 #[derive(Debug)]
@@ -59,20 +127,20 @@ pub struct UseDecl {
 pub enum Expr {
     Literal(Literal),
     _IdentAccess(String),
-    Make(Box<ExprMake>)
+    Make(Box<ExprMake>),
 }
 
 #[derive(Debug)]
 pub struct ExprMake {
     pub name: String,
-    pub params: HashMap<String, Expr>
+    pub params: HashMap<String, Expr>,
 }
 
 #[derive(Debug)]
 pub enum Literal {
     String(String),
     Number(NumberLiteral),
-    Char(char)
+    Char(char),
 }
 
 #[derive(Debug)]
diff --git a/programs/aidl/src/lexer.rs b/programs/aidl/src/lexer.rs
index d169678..0e11bd6 100644
--- a/programs/aidl/src/lexer.rs
+++ b/programs/aidl/src/lexer.rs
@@ -1,6 +1,6 @@
 use std::{
     fmt::Display,
-    ops::{Add, Range, AddAssign},
+    ops::{Add, AddAssign, Range},
 };
 
 use logos::Logos;
@@ -51,7 +51,10 @@ pub enum Token {
     #[regex(r#"(-)?\d+"#, |lex| lex.slice().parse().ok())]
     NumberLiteral(i64),
 
-    #[regex(r"(ptr|u8|i8|u16|i16|u32|i32|u64|i64|f32|f64)", |lex| NumberSuffix::lexer(lex.slice()).next().and_then(Result::ok))]
+    #[regex(
+        r"(ptr|u8|i8|u16|i16|u32|i32|u64|i64|f32|f64)",
+        |lex| NumberSuffix::lexer(lex.slice()).next().and_then(Result::ok)
+    )]
     NumberSuffix(NumberSuffix),
 
     #[regex(r#"[a-zA-Z_][a-zA-Z\d_]*"#, |lex| Ident::lexer(lex.slice()).next().and_then(Result::ok))]
@@ -73,10 +76,18 @@ pub enum Ident {
     Structure,
     #[token("Alias")]
     Alias,
+    #[token("Enumeration")]
+    Enumeration,
     #[token("Use")]
     Use,
     #[token("Make")]
     Make,
+    #[token("Takes")]
+    Takes,
+    #[token("Returns")]
+    Returns,
+    #[token("_")]
+    Underscore,
     #[regex(r"[a-zA-Z_][a-zA-Z\d_]*", |lex| lex.slice().parse().ok())]
     Other(String),
 }
diff --git a/programs/aidl/src/main.rs b/programs/aidl/src/main.rs
index 179bd3e..62527ba 100644
--- a/programs/aidl/src/main.rs
+++ b/programs/aidl/src/main.rs
@@ -36,9 +36,15 @@ fn main() {
                     parser::ParserError::UnexpectedEOF => Label::primary(
                         (),
                         (codespan_file.source().len() - 1)..codespan_file.source().len(),
-                    ).with_message("Unexpected end of file here"),
-                    parser::ParserError::Unexpected(expected, Spanned(got, span)) => Label::primary((), span.0).with_message(format!("Unexpected `{got}`, expected {expected}")),
-                    parser::ParserError::PleaseStopParsingUse => unreachable!()
+                    )
+                    .with_message("Unexpected end of file here"),
+                    parser::ParserError::Unexpected(expected, Spanned(got, span)) => {
+                        Label::primary((), span.0)
+                            .with_message(format!("Unexpected `{got}`, expected {expected}"))
+                    }
+                    parser::ParserError::PleaseStopParsingUse => unsafe {
+                        std::hint::unreachable_unchecked()
+                    },
                 };
                 let diagnostic = codespan_reporting::diagnostic::Diagnostic::error()
                     .with_message(msg)
@@ -52,6 +58,8 @@ fn main() {
                 .unwrap();
             }
         }
+    } else {
+        eprintln!("No file given. Aborting.");
     }
 }
 
diff --git a/programs/aidl/src/parser/enumeration.rs b/programs/aidl/src/parser/enumeration.rs
new file mode 100644
index 0000000..c6d728c
--- /dev/null
+++ b/programs/aidl/src/parser/enumeration.rs
@@ -0,0 +1,133 @@
+use std::collections::HashMap;
+
+use crate::{
+    ast::{EnumerationContent, EnumerationVariant, ItemEnumeration, Type},
+    lexer::{Ident, Spanned, Token},
+};
+
+use super::{Parser, ParserError};
+
+impl<'a> Parser<'a> {
+    pub fn ask_enumeration(&mut self) -> Result<Spanned<ItemEnumeration>, ParserError> {
+        let Spanned(_, span) = self.get_real(
+            |token| matches!(token, Token::Ident(Ident::Enumeration)),
+            "the `Enumeration` keyword",
+        )?;
+
+        let Spanned(Type { name, arguments }, _) = self.ask_type()?;
+
+        self.get_real(
+            |token| matches!(token, Token::LeftCurly),
+            "an opening curly brace",
+        )?;
+
+        let mut variants = vec![];
+
+        loop {
+            match self.tokens.peek()?.0 {
+                Token::Ident(Ident::Other(_)) => {
+                    let Spanned(variant_name, _) = self.ask_ident()?;
+
+                    let mut content = EnumerationContent::None;
+
+                    loop {
+                        match self.tokens.peek()?.0 {
+                            Token::LeftParen => {
+                                self.eat();
+
+                                let mut tuple = vec![];
+
+                                loop {
+                                    match self.tokens.peek()?.0 {
+                                        Token::Ident(Ident::Other(_)) => {
+                                            tuple.push(self.ask_type()?.0);
+                                            if let Token::Comma = self.tokens.peek()?.0 {
+                                                self.eat();
+                                            };
+                                        }
+                                        Token::RightParen => {
+                                            self.eat();
+                                            break;
+                                        }
+                                        _ => {
+                                            return Err(
+                                                self.expected("closing parentheses or a type")
+                                            )
+                                        }
+                                    }
+                                }
+                                content = EnumerationContent::Tuple(tuple);
+                            }
+                            Token::LeftCurly => {
+                                self.eat();
+
+                                let mut structure = HashMap::<String, Type>::new();
+
+                                loop {
+                                    match self.tokens.peek()?.0 {
+                                        Token::Ident(Ident::Other(_)) => {
+                                            let Spanned(field_name, _) = self.ask_ident()?;
+
+                                            self.get_real(
+                                                |token| matches!(token, Token::Colon),
+                                                "a colon",
+                                            )?;
+
+                                            structure.insert(field_name, self.ask_type()?.0);
+                                            if let Token::Comma = self.tokens.peek()?.0 {
+                                                self.eat();
+                                            };
+                                        }
+                                        Token::RightCurly => {
+                                            self.eat();
+                                            break;
+                                        }
+                                        _ => {
+                                            return Err(
+                                                self.expected("closing parentheses or a type")
+                                            )
+                                        }
+                                    }
+                                }
+
+                                content = EnumerationContent::Structure(structure);
+                            }
+                            Token::Equals => {
+                                self.eat();
+
+                                content = EnumerationContent::Value(self._ask_number_literal()?.0);
+                            }
+                            _ => break,
+                        }
+                    }
+
+                    if let Spanned(Token::Comma, _) = self.tokens.peek()? {
+                        self.eat();
+                    }
+
+                    variants.push(EnumerationVariant {
+                        name: variant_name,
+                        content,
+                    });
+                }
+                Token::RightCurly => break,
+                _ => return Err(self.expected("a closing curly brace or a variant")),
+            }
+        }
+
+        if let Spanned(Token::RightCurly, _) = self.tokens.peek()? {
+            self.eat();
+
+            return Ok(Spanned(
+                ItemEnumeration {
+                    name,
+                    arguments,
+                    variants,
+                },
+                span + self.tokens.span(),
+            ));
+        };
+
+        Err(self.expected("???"))
+    }
+}
diff --git a/programs/aidl/src/parser/expr.rs b/programs/aidl/src/parser/expr.rs
index c793206..ff2632c 100644
--- a/programs/aidl/src/parser/expr.rs
+++ b/programs/aidl/src/parser/expr.rs
@@ -17,26 +17,20 @@ impl<'a> Parser<'a> {
             }
             Token::Ident(Ident::Make) => {
                 self.eat();
-                self._ask_struct_init()?
-                    .map(Box::new)
-                    .map(Expr::Make)
+                self._ask_struct_init()?.map(Box::new).map(Expr::Make)
             }
             _ => return Err(self.expected("an expression")),
         })
     }
 
-    fn _ask_literal(&mut self) -> Result<Spanned<Literal>, ParserError> {
-        let Spanned(token, mut span) = self.tokens.next()?;
-        Ok(match token {
-            Token::StringLiteral(string) => Spanned(Literal::String(string), span),
-            Token::CharLiteral(chr) => Spanned(Literal::Char(chr), span),
-            Token::NumberLiteral(number) => {
+    pub fn _ask_number_literal(&mut self) -> Result<Spanned<NumberLiteral>, ParserError> {
+        match self.tokens.next()? {
+            Spanned(Token::NumberLiteral(number), mut span) => {
                 let lit = if let Spanned(Token::NumberSuffix(_), sp) = self.tokens.peek()? {
                     span += sp;
 
                     use NumberLiteral::*;
-                    Literal::Number(
-                        match unwrap_match!(
+                    match unwrap_match!(
                             self.tokens.next()?, Spanned(Token::NumberSuffix(suffering), _) => suffering) // eat suffix
                         {
                             NumberSuffix::Ptr => Ptr(number as usize),
@@ -49,14 +43,26 @@ impl<'a> Parser<'a> {
                             NumberSuffix::U64 => U64(number as u64),
                             NumberSuffix::I64 => I64(number),
                             _ => return Err(self.expected("a non-floating number suffix"))
-                        },
-                    )
+                        }
                 } else {
-                    Literal::Number(NumberLiteral::Infer(number))
+                    NumberLiteral::Infer(number)
                 };
 
-                Spanned(lit, span)
+                Ok(Spanned(lit, span))
             }
+            _ => Err(self.expected("a number literal")),
+        }
+    }
+
+    pub fn _ask_literal(&mut self) -> Result<Spanned<Literal>, ParserError> {
+        if let Spanned(Token::NumberLiteral(_), _) = self.tokens.peek()? {
+            return Ok(self._ask_number_literal()?.map(Literal::Number));
+        };
+        let Spanned(token, span) = self.tokens.next()?;
+        Ok(match token {
+            Token::StringLiteral(string) => Spanned(Literal::String(string), span),
+            Token::CharLiteral(chr) => Spanned(Literal::Char(chr), span),
+
             _ => return Err(self.expected("a literal")),
         })
     }
@@ -90,6 +96,6 @@ impl<'a> Parser<'a> {
             return Ok(Spanned(ExprMake { name, params }, nSp + ccSp));
         };
 
-        Err(self.expected("something"))
+        Err(self.expected("closing curly braces"))
     }
 }
diff --git a/programs/aidl/src/parser/interface.rs b/programs/aidl/src/parser/interface.rs
index e69de29..651ad18 100644
--- a/programs/aidl/src/parser/interface.rs
+++ b/programs/aidl/src/parser/interface.rs
@@ -0,0 +1,140 @@
+use crate::{
+    ast::{nothing, Function, ItemInterface},
+    lexer::{Ident, Span, Spanned, Token},
+};
+
+use super::{Parser, ParserError};
+
+impl<'a> Parser<'a> {
+    pub fn ask_interface(&mut self) -> Result<Spanned<ItemInterface>, ParserError> {
+        // Interface
+        let Spanned(_, mut span) = self.get_real(
+            |token| matches!(token, Token::Ident(Ident::Interface)),
+            "the `Interface` keyword",
+        )?;
+        // InterfaceName
+        let Spanned(name, _) = self.ask_ident()?;
+
+        // {
+        self.get_real(
+            |token| matches!(token, Token::LeftCurly),
+            "opening curly brackets",
+        )?;
+
+        let mut functions = vec![];
+
+        loop {
+            match self.tokens.peek()? {
+                Spanned(Token::RightCurly, end) => {
+                    self.eat();
+                    span += end;
+                    break;
+                }
+                Spanned(Token::Ident(Ident::Function), _) => functions.push(self.ask_function()?.0),
+                _ => return Err(self.expected("A function or closing curly braces")),
+            }
+        }
+
+        Ok(Spanned(ItemInterface { name, functions }, span))
+    }
+
+    pub fn ask_function(&mut self) -> Result<Spanned<Function>, ParserError> {
+        let Spanned(_, bsp) = self.get_real(
+            |token| matches!(token, Token::Ident(Ident::Function)),
+            "the `Function` keyword",
+        )?;
+
+        let Spanned(name, _) = self.ask_ident()?;
+
+        let Spanned(next, esp) = self.tokens.next()?;
+        match next {
+            Token::Ident(Ident::Takes) => {
+                self.get_real(
+                    |token| matches!(token, Token::LeftParen),
+                    "Opening parentheses",
+                )?;
+
+                let mut takes = vec![];
+                let mut returns = nothing();
+                loop {
+                    let Spanned(peeked, _) = self.tokens.peek()?;
+                    match peeked {
+                        Token::Ident(_) => {
+                            takes.push(self.ask_type()?.0);
+                            if let Token::Comma = self.tokens.peek()?.0 {
+                                self.eat();
+                            };
+                        }
+                        Token::RightParen => {
+                            self.eat();
+                            break;
+                        }
+                        _ => return Err(self.expected("closing parentheses or a type name")),
+                    }
+                }
+
+                match self.tokens.next()?.0 {
+                    Token::Semicolon => {}
+                    Token::Ident(Ident::Returns) => {
+                        self.get_real(
+                            |token| matches!(token, Token::LeftParen),
+                            "Opening parentheses",
+                        )?;
+
+                        let Spanned(returns_, _) = self.ask_type()?;
+
+                        returns = returns_;
+
+                        self.get_real(
+                            |token| matches!(token, Token::RightParen),
+                            "Closing parentheses",
+                        )?;
+
+                        self.semi()?;
+                    }
+                    _ => return Err(self.expected("a semicolon or a Returns clause")),
+                }
+
+                Ok(Spanned(
+                    Function {
+                        name,
+                        takes,
+                        returns,
+                    },
+                    bsp + Span(self.tokens.lexer.span()),
+                ))
+            }
+            Token::Ident(Ident::Returns) => {
+                self.get_real(
+                    |token| matches!(token, Token::LeftParen),
+                    "Opening parentheses",
+                )?;
+
+                let Spanned(returns, _) = self.ask_type()?;
+
+                self.get_real(
+                    |token| matches!(token, Token::RightParen),
+                    "Closing parentheses",
+                )?;
+
+                Ok(Spanned(
+                    Function {
+                        name,
+                        takes: Vec::new(),
+                        returns,
+                    },
+                    bsp + self.semi()?,
+                ))
+            }
+            Token::Semicolon => Ok(Spanned(
+                Function {
+                    name,
+                    takes: Vec::new(),
+                    returns: nothing(),
+                },
+                bsp + esp,
+            )),
+            _ => Err(self.expected("a Takes clause, a Returns clause or a semicolon")),
+        }
+    }
+}
diff --git a/programs/aidl/src/parser/mod.rs b/programs/aidl/src/parser/mod.rs
index 29b5eb0..b443b6b 100644
--- a/programs/aidl/src/parser/mod.rs
+++ b/programs/aidl/src/parser/mod.rs
@@ -1,11 +1,13 @@
+mod enumeration;
 mod expr;
 mod interface;
 mod structure;
+mod types;
 
 use logos::{Lexer, Logos};
 
 use crate::{
-    ast::{IDLModule, Item, ItemAlias, ItemConstant, ItemInterface, ModulePath, UseDecl},
+    ast::{IDLModule, Item, ItemAlias, ItemConstant, ModulePath, UseDecl},
     lexer::{Ident, Span, Spanned, Token},
 };
 use std::iter::Iterator;
@@ -52,7 +54,11 @@ impl<'a> TokenIterator<'a> {
     }
 
     pub fn current(&self) -> Spanned<String> {
-        Spanned(self.lexer.slice().to_owned(), Span(self.lexer.span()))
+        Spanned(self.lexer.slice().to_owned(), self.span())
+    }
+
+    pub fn span(&self) -> Span {
+        Span(self.lexer.span())
     }
 }
 
@@ -94,11 +100,16 @@ impl<'a> Parser<'a> {
     }
 
     fn ask_ident(&mut self) -> Result<Spanned<String>, ParserError> {
-        Ok(crate::unwrap_match!(
-            self.get_real(|token| matches!(token, Token::Ident(Ident::Other(_))), "an identifier")?,
-            Spanned(Token::Ident(Ident::Other(ident)), span) =>
-            Spanned(ident, span)
-        ))
+        Ok(
+            match self.get_real(
+                |token| matches!(token, Token::Ident(Ident::Other(_) | Ident::Underscore)),
+                "an identifier",
+            )? {
+                Spanned(Token::Ident(Ident::Other(ident)), span) => Spanned(ident, span),
+                Spanned(Token::Ident(Ident::Underscore), span) => Spanned("_".to_owned(), span),
+                _ => unreachable!(),
+            },
+        )
     }
 
     fn ask_modpath(
@@ -115,18 +126,18 @@ impl<'a> Parser<'a> {
                 Spanned(Token::Ident(Ident::Other(ident)), span_span)
                     if !in_path_seg && waiting_next_seg =>
                 {
-                    span = span + span_span;
+                    span += span_span;
                     segments.push(ident);
                     in_path_seg = true;
                     waiting_next_seg = false;
                 }
                 Spanned(Token::Dot, span_span) if in_path_seg && !waiting_next_seg => {
-                    span = span + span_span;
+                    span += span_span;
                     waiting_next_seg = true;
                     in_path_seg = false;
                 }
                 v if end(&v.0) && (in_path_seg || !waiting_next_seg) => {
-                    span = span + v.1;
+                    span += v.1;
                     break;
                 }
                 _ => return Err(self.expected("a path segment")),
@@ -136,22 +147,6 @@ impl<'a> Parser<'a> {
         Ok(Spanned(ModulePath { segments }, span))
     }
 
-    fn _ask_interface(&mut self) -> Result<Spanned<ItemInterface>, ParserError> {
-        let Spanned(_, kSp) = self.get_real(
-            |token| matches!(token, Token::Ident(Ident::Interface)),
-            "`Interface`",
-        )?;
-        let Spanned(ident, iSp) = self.ask_ident()?;
-
-        Ok(Spanned::new(
-            ItemInterface {
-                name: ident,
-                functions: vec![],
-            },
-            [kSp, iSp, self.semi()?],
-        ))
-    }
-
     fn ask_alias(&mut self) -> Result<Spanned<ItemAlias>, ParserError> {
         let Spanned(_, kSp) = self.get_real(
             |token| matches!(token, Token::Ident(Ident::Alias)),
@@ -160,7 +155,7 @@ impl<'a> Parser<'a> {
         let Spanned(name, nSp) = self.ask_ident()?;
 
         let Spanned(_, eqSp) = self.get_real(|token| matches!(token, Token::Equals), "`=`")?;
-        let Spanned(referree, rSp) = self.ask_ident()?;
+        let Spanned(referree, rSp) = self.ask_type()?;
 
         Ok(Spanned::new(
             ItemAlias { name, referree },
@@ -177,7 +172,10 @@ impl<'a> Parser<'a> {
         let Spanned(_, eqSp) = self.get_real(|token| matches!(token, Token::Equals), "`=`")?;
         let Spanned(expr, exprSp) = self.ask_expr()?;
 
-        Ok(Spanned::new(ItemConstant { name, expr }, [kSp, nSp, eqSp, exprSp, self.semi()?]))
+        Ok(Spanned::new(
+            ItemConstant { name, expr },
+            [kSp, nSp, eqSp, exprSp, self.semi()?],
+        ))
     }
 
     fn ask_item(&mut self) -> Result<Spanned<Item>, ParserError> {
@@ -186,10 +184,13 @@ impl<'a> Parser<'a> {
                 Err(self.expected("a keyword, not just an identifier"))?
             }
             Token::Ident(keyword) => match keyword {
-                //Ident::Interface => self.ask_interface()?.map(Item::Interface),
+                Ident::Interface => self.ask_interface()?.map(Item::Interface),
+                Ident::Structure => self.ask_structure()?.map(Item::Structure),
                 Ident::Alias => self.ask_alias()?.map(Item::Alias),
                 Ident::Constant => self.ask_constant()?.map(Item::Constant),
-                _ => Err(self.expected("`Alias` or `Constant`"))?,
+                Ident::Function => self.ask_function()?.map(Item::Function),
+                Ident::Enumeration => self.ask_enumeration()?.map(Item::Enumeration),
+                _ => Err(self.expected("an item denoting keyword (Interface, Structure, Alias, Constant, Function, Enumeration)"))?,
             },
             _ => Err(self.expected("a keyword"))?,
         })
diff --git a/programs/aidl/src/parser/structure.rs b/programs/aidl/src/parser/structure.rs
index e69de29..32db118 100644
--- a/programs/aidl/src/parser/structure.rs
+++ b/programs/aidl/src/parser/structure.rs
@@ -0,0 +1,44 @@
+use std::collections::HashMap;
+
+use crate::{lexer::{Ident, Spanned, Token}, ast::{Type, ItemStructure}};
+
+use super::{Parser, ParserError};
+
+impl<'a> Parser<'a> {
+    pub fn ask_structure(&mut self) -> Result<Spanned<ItemStructure>, ParserError> {
+        let Spanned(_, span) = self.get_real(
+            |token| matches!(token, Token::Ident(Ident::Structure)),
+            "the `Structure` keyword",
+        )?;
+
+        let Spanned(name, _) = self.ask_ident()?;
+        let Spanned(_, _) = self.get_real(
+            |token| matches!(token, Token::LeftCurly),
+            "an opening curly brace (`{`)",
+        )?;
+
+        let mut fields = HashMap::<String, Type>::new();
+
+        loop {
+            match self.tokens.peek()?.0 {
+                Token::Ident(_) => {
+                    let Spanned(ident, _) = self.ask_ident().unwrap();
+                    self.get_real(|token| matches!(token, Token::Colon), "a colon")?;
+                    let Spanned(value, _) = self.ask_type()?;
+                    fields.insert(ident, value);
+                    if let Token::Comma = self.tokens.peek()?.0 {
+                        self.eat();
+                    };
+                }
+                Token::RightCurly => break,
+                _ => return Err(self.expected("an identifier or a closing curly brace (`}`)")),
+            }
+        }
+
+        if let Spanned(Token::RightCurly, end) = self.tokens.next()? {
+            return Ok(Spanned(ItemStructure { name, fields }, span + end));
+        };
+
+        Err(self.expected("closing curly braces"))
+    }
+}
diff --git a/programs/aidl/src/parser/types.rs b/programs/aidl/src/parser/types.rs
new file mode 100644
index 0000000..27180c0
--- /dev/null
+++ b/programs/aidl/src/parser/types.rs
@@ -0,0 +1,45 @@
+use crate::{
+    ast::{Type, TypeArguments, INFER_TYPE},
+    lexer::{Spanned, Token},
+};
+
+use super::{Parser, ParserError};
+
+impl<'a> Parser<'a> {
+    pub fn ask_type(&mut self) -> Result<Spanned<Type>, ParserError> {
+        let Spanned(name, span) = self.ask_ident()?;
+
+        if name == INFER_TYPE {
+            return Ok(Spanned(Type::infer(), span));
+        }
+
+        let mut arguments = TypeArguments::None;
+
+        if let Spanned(crate::lexer::Token::LeftArrow, _) = self.tokens.peek()? {
+            self.eat(); // eat `<`
+
+            let mut args = vec![];
+
+            args.push(Box::new(self.ask_type()?.0));
+
+            if let Spanned(Token::Comma, _) = self.tokens.peek()? {
+                self.eat(); // skip comma, allow trailing comma
+            };
+
+            loop {
+                match self.tokens.peek()? {
+                    Spanned(Token::Ident(_), _) => args.push(Box::new(self.ask_type()?.0)),
+                    Spanned(Token::RightArrow, _) => {
+                        self.eat();
+                        break;
+                    }
+                    _ => return Err(self.expected("closing angle brackets or a type name")),
+                }
+            }
+
+            arguments = TypeArguments::AngleBracketed(args);
+        };
+
+        Ok(Spanned(Type { name, arguments }, span + self.tokens.span()))
+    }
+}