nix: replace rust-overlay with fenix

Signed-off-by: Amneesh Singh <natto@weirdnatto.in>

.github/workflows/ci.yml

@@ -0,0 +1,34 @@
+name: CI
+
+on: [ push, pull_request, workflow_dispatch ]
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: cachix/install-nix-action@v20
+        with:
+          extra_nix_config: |
+            auto-optimise-store = true
+            experimental-features = nix-command flakes
+      - uses: cachix/cachix-action@v12
+        with:
+          name: pain
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+
+      - name: fmt checks
+        run: nix build .#checks.fmt -L
+
+      - name: clippy checks
+        run: nix build .#checks.clippy -L
+        
+      - name: nextest checks
+        run: nix build .#checks.nextest -L
+
+      - name: doc checks
+        run: nix build .#checks.doc -L
+
+      - name: build
+        run: nix build .#tricc -L

README.org

@@ -2,6 +2,6 @@ tricc (pronounced "trick-c" or "trixie" like pixie) is a WIP toy compiler I am
 writing to understand compilers better, that's it. Will probably use LLVM as
 the backend.
 
-Notes:
+** Notes:
-- Does not work
++ Does not work
-- Is WIP
++ Is WIP

flake.lock

@@ -10,11 +10,11 @@
         "rust-overlay": "rust-overlay"
       },
       "locked": {
-        "lastModified": 1680584903,
+        "lastModified": 1688772518,
-        "narHash": "sha256-uraq+D3jcLzw/UVk0xMHcnfILfIMa0DLrtAEq2nNlxU=",
+        "narHash": "sha256-ol7gZxwvgLnxNSZwFTDJJ49xVY5teaSvF7lzlo3YQfM=",
         "owner": "ipetkov",
         "repo": "crane",
-        "rev": "65d3f6a3970cd46bef5eedfd458300f72c56b3c5",
+        "rev": "8b08e96c9af8c6e3a2b69af5a7fa168750fcf88e",
         "type": "github"
       },
       "original": {
@@ -40,12 +40,15 @@
       }
     },
     "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
       "locked": {
-        "lastModified": 1678901627,
+        "lastModified": 1687709756,
-        "narHash": "sha256-U02riOqrKKzwjsxc/400XnElV+UtPUQWpANPlyazjH0=",
+        "narHash": "sha256-Y5wKlQSkgEK2weWdOu4J3riRd+kV/VCgHsqLNTTWQ/0=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "93a2b84fc4b70d9e089d029deacc3583435c2ed6",
+        "rev": "dbabf0ca0c0c4bce6ea5eaf65af5cb694d2082c7",
         "type": "github"
       },
       "original": {
@@ -55,12 +58,15 @@
       }
     },
     "flake-utils_2": {
+      "inputs": {
+        "systems": "systems_2"
+      },
       "locked": {
-        "lastModified": 1678901627,
+        "lastModified": 1689068808,
-        "narHash": "sha256-U02riOqrKKzwjsxc/400XnElV+UtPUQWpANPlyazjH0=",
+        "narHash": "sha256-6ixXo3wt24N/melDWjq70UuHQLxGV8jZvooRanIHXw0=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "93a2b84fc4b70d9e089d029deacc3583435c2ed6",
+        "rev": "919d646de7be200f3bf08cb76ae1f09402b6f9b4",
         "type": "github"
       },
       "original": {
@@ -70,12 +76,15 @@
       }
     },
     "flake-utils_3": {
+      "inputs": {
+        "systems": "systems_3"
+      },
       "locked": {
-        "lastModified": 1659877975,
+        "lastModified": 1681202837,
-        "narHash": "sha256-zllb8aq3YO3h8B/U0/J1WBgAL8EX5yWf5pMj3G0NAmc=",
+        "narHash": "sha256-H+Rh19JDwRtpVPAWp64F+rlEtxUWBAQW28eAi3SRSzg=",
         "owner": "numtide",
         "repo": "flake-utils",
-        "rev": "c0e246b9b83f637f4681389ecabcb2681b4f3af0",
+        "rev": "cfacdce06f30d2b68473a46042957675eebb3401",
         "type": "github"
       },
       "original": {
@@ -86,11 +95,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1680724564,
+        "lastModified": 1688392541,
-        "narHash": "sha256-eeUUGOTKTelYKDbUxKs0V7GUa186L2fym7jM2QQ4Oss=",
+        "narHash": "sha256-lHrKvEkCPTUO+7tPfjIcb7Trk6k31rz18vkyqmkeJfY=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "36adaa6aaa6b03e59102df0c1b12cdc3f23fd112",
+        "rev": "ea4c80b39be4c09702b0cb3b42eab59e2ba4f24b",
         "type": "github"
       },
       "original": {
@@ -120,11 +129,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1680488274,
+        "lastModified": 1688351637,
-        "narHash": "sha256-0vYMrZDdokVmPQQXtFpnqA2wEgCCUXf5a3dDuDVshn0=",
+        "narHash": "sha256-CLTufJ29VxNOIZ8UTg0lepsn3X03AmopmaLTTeHDCL4=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "7ec2ff598a172c6e8584457167575b3a1a5d80d8",
+        "rev": "f9b92316727af9e6c7fee4a761242f7f46880329",
         "type": "github"
       },
       "original": {
@@ -141,11 +150,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1680660688,
+        "lastModified": 1690252178,
-        "narHash": "sha256-XeQTCxWBR0Ai1VMzI5ZXYpA2lu1F8FzZKjw8RtByZOg=",
+        "narHash": "sha256-9oEz822bvbHobfCUjJLDor2BqW3I5tycIauzDlzOALY=",
         "owner": "oxalica",
         "repo": "rust-overlay",
-        "rev": "2f40052be98347b479c820c00fb2fc1d87b3aa28",
+        "rev": "8d64353ca827002fb8459e44d49116c78d868eba",
         "type": "github"
       },
       "original": {
@@ -153,6 +162,51 @@
         "repo": "rust-overlay",
         "type": "github"
       }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "systems_2": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    },
+    "systems_3": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
     }
   },
   "root": "root",

flake.nix

@@ -9,25 +9,28 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
-    rust-overlay = {
+    fenix = {
-      url = github:oxalica/rust-overlay;
+      url = github:nix-community/fenix;
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
     flake-utils.url = github:numtide/flake-utils;
   };
 
-  outputs = inputs@{ self, nixpkgs, crane, rust-overlay, flake-utils }:
+  outputs = inputs@{ self, nixpkgs, crane, fenix, flake-utils }:
     flake-utils.lib.eachDefaultSystem (system:
       let
         pkgs = import nixpkgs {
           inherit system;
-          overlays = [ rust-overlay.overlays.default ];
+          overlays = [ fenix.overlays.default ];
         };
 
         inherit (pkgs) lib;
 
-        toolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+        toolchain = pkgs.fenix.fromToolchainFile {
+          file = ./rust-toolchain.toml;
+          sha256 = "sha256-n8LtGbpj/yCUGo0NFJ7FNv9fSdT9oKEUl+EPLg06JdQ=";
+        };
 
         craneLib = (crane.mkLib pkgs).overrideToolchain toolchain;
         src = craneLib.cleanCargoSource (craneLib.path ./.);
@@ -38,25 +41,34 @@
 
         tricc = craneLib.buildPackage (commonArgs // {
           inherit cargoArtifacts;
+          doCheck = false;
         });
       in
       {
-        checks = {
-          inherit tricc;
-
-          clippy = craneLib.cargoClippy (commonArgs // {
-            inherit cargoArtifacts;
-            cargoClippyExtraArgs = "--all-targets -- --deny warnings";
-          });
-
-          fmt = craneLib.cargoFmt {
-            inherit src;
-          };
-        };
-
         packages = {
           inherit tricc;
           default = tricc;
+
+          # not using flake checks to run them individually
+          checks = {
+            clippy = craneLib.cargoClippy (commonArgs // {
+              inherit cargoArtifacts;
+            });
+
+            fmt = craneLib.cargoFmt {
+              inherit src;
+            };
+
+            doc = craneLib.cargoDoc (commonArgs // {
+              inherit cargoArtifacts;
+            });
+
+            nextest = craneLib.cargoNextest (commonArgs // {
+              inherit cargoArtifacts;
+              partitions = 1;
+              partitionType = "count";
+            });
+          };
         };
 
         devShells.default = pkgs.mkShell {

rust-toolchain.toml

@@ -1,3 +1,3 @@
 [toolchain]
-channel = "nightly-2023-04-01"
+channel = "nightly-2023-07-15"
 components = [ "rustfmt", "clippy", "rust-analyzer", "rust-src" ]

rustfmt.toml

@@ -0,0 +1,5 @@
+comment_width = 99
+format_code_in_doc_comments = true
+imports_granularity = "Module"
+imports_layout = "Vertical"
+wrap_comments = true

src/args.rs

@@ -1,50 +1,62 @@
 use std::env;
+use std::path::PathBuf;
 use std::process::exit;
 
 const VERSION: &str = env!("CARGO_PKG_VERSION");
 const CRATE: &str = env!("CARGO_CRATE_NAME");
 
+/// A naive argument handler
 #[derive(Default)]
-struct Options {
+pub struct Args {
     version: bool,
-    file: String,
+    file: Option<PathBuf>,
 }
 
-// naive argument handling
+impl Args {
-pub fn handle() -> String {
+    /// Creates a new [`Args`] instance
-    let args: Vec<String> = env::args().collect();
+    pub fn new() -> Args {
-
+        Args::default()
-    if args.len() < 2 {
-        println!("Usage: {} [-v] <file>", CRATE);
-        exit(0);
     }
 
-    let mut options: Options = Default::default();
+    /// Checks for various arguments
+    pub fn handle(&mut self) {
+        let args: Vec<String> = env::args().collect();
 
-    for arg in &args[1..] {
+        if args.len() < 2 {
-        match arg.as_str() {
+            println!("Usage: {} [-v] <file>", CRATE);
-            "-v" | "--version" => options.version = true,
+            exit(0);
-            flag if flag.starts_with('-') => panic!("option {} not implemented!", flag),
+        }
-            file => {
+
-                if !options.file.is_empty() {
+        for arg in &args[1..] {
-                    panic!("please specify only a single source file!");
+            match arg.as_str() {
+                "-v" | "--version" => self.version = true,
+                flag if flag.starts_with('-') => panic!("option {} not implemented!", flag),
+                file => {
+                    if self.file.is_some() {
+                        panic!("please specify only a single source file!");
+                    }
+                    self.file = Some(PathBuf::from(file));
                 }
-                options.file = file.to_string();
+            }
+        }
+
+        if self.version {
+            println!("{} version: {}", CRATE, VERSION);
+        }
+
+        if self.file.is_none() {
+            if self.version {
+                exit(0);
+            } else {
+                panic!("no file supplied!");
             }
         }
     }
 
-    if options.version {
+    /// Fetches the file from the arguments.
-        println!("{} version: {}", CRATE, VERSION);
+    /// Panics if there is no file in the arguments
+    #[inline]
+    pub fn get_file(self) -> PathBuf {
+        self.file.expect("no file supplied!")
     }
-
-    if options.file.is_empty() {
-        if options.version {
-            exit(0);
-        } else {
-            panic!("no file supplied!");
-        }
-    }
-
-    options.file
 }

src/ast.rs

@@ -0,0 +1,132 @@
+//! A very naive AST definition using recursive enums
+//!
+//! See the parser for implementation
+
+use std::rc::Rc;
+
+pub type Parent = Vec<Entity>;
+
+/// Entities are functions, classes, and modules
+#[derive(Debug, PartialEq)]
+pub enum Entity {
+    Fn(Fn),
+    Class(Class),
+    Module(Module),
+    Static(Let),
+}
+
+/// A module just provides an additional scope
+///
+/// TODO: Add exporting and importing modules
+#[derive(Debug, PartialEq)]
+pub struct Module {
+    /// Name of module
+    pub name: Rc<str>,
+    /// Everything inside the module
+    pub children: Vec<ModuleChildren>,
+}
+
+/// Modules contain functions, classes and statements
+#[derive(Debug, PartialEq)]
+pub enum ModuleChildren {
+    Fn(Fn),
+    Class(Class),
+    Module(Module),
+    Static(Let),
+}
+
+/// Classes encapsulate functions and definitions.
+#[derive(Debug, PartialEq)]
+pub struct Class {
+    /// Name of class
+    pub name: Rc<str>,
+    /// Everything inside the class
+    pub children: Vec<ClassChildren>,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ClassChildren {
+    Fn(Fn),
+    Let(Let),
+    Static(Let),
+}
+
+/// A Function
+#[derive(Debug, PartialEq)]
+pub struct Fn {
+    /// Name of the function
+    pub name: Rc<str>,
+    /// Optional return type
+    pub return_ty: Option<Ty>,
+    /// Parameters
+    pub params: Vec<(Rc<str>, Ty)>,
+    /// The function block
+    pub children: Vec<Statement>,
+}
+
+/// Statements encapsulate expressions and definitions
+#[derive(Debug, PartialEq)]
+pub enum Statement {
+    Static(Let),
+    Let(Let),
+    Expr(Expr),
+}
+
+/// A variable definition
+#[derive(Debug, PartialEq)]
+pub struct Let {
+    /// Name of variabe
+    pub name: Rc<str>,
+    /// Type of variable
+    pub ty: Ty,
+    /// Value of variable
+    pub expr: Option<Expr>,
+}
+
+/// Primitives
+///
+/// TODO: add arrays and pointers maybe
+#[derive(Debug, PartialEq)]
+pub enum Ty {
+    Int,
+    Float,
+    Char,
+}
+
+#[derive(Debug, PartialEq)]
+pub struct If {
+    pub cond: Box<Expr>,
+    pub then: Vec<Statement>,
+    pub or: Option<Box<ElseType>>,
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ElseType {
+    If(If),
+    Else(Vec<Statement>),
+}
+
+pub(crate) type Op = crate::lexer::TokenSymbol;
+
+#[derive(Debug, PartialEq)]
+pub enum Literal {
+    Int(i32),
+    Float(f32),
+    Char(char),
+}
+
+/// Lowest form of expression
+///
+/// TODO: refine
+#[derive(Debug, PartialEq)]
+pub enum Expr {
+    Literal(Literal),
+    Identifier(Rc<str>),
+    Op(Op, Box<Expr>, Option<Box<Expr>>),
+    If(If),
+    Block(Vec<Statement>),
+    Loop(Vec<Statement>),
+    Break,
+    Continue,
+    Return(Option<Box<Expr>>),
+}

src/lexer.rs

@@ -1,5 +1,565 @@
-use nix::
+use std::collections::VecDeque;
+use std::iter::Peekable;
+use std::rc::Rc;
+use std::str;
 
-fn threads(){
+/// All token literals
-    println!({},"aa");
+///
-}
+/// TODO: Add string
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum TokenLiteral {
+    Int,
+    Float,
+    Char,
+}
+
+/// All token symbols
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum TokenSymbol {
+    // arithmetic
+    Plus,
+    Minus,
+    Star,
+    Slash,
+    Percent,
+    Caret,
+    Tilde,
+
+    // bitwise
+    Shl,
+    Shr,
+    And,
+    Or,
+
+    // logical
+    Not,
+    AndAnd,
+    OrOr,
+
+    // relational
+    Gt,
+    Lt,
+    GtEq,
+    LtEq,
+    EqEq,
+    Ne,
+
+    // assignment
+    Eq,
+    PlusEq,
+    MinusEq,
+    StarEq,
+    SlashEq,
+    PercentEq,
+    CaretEq,
+    ShlEq,
+    ShrEq,
+    AndEq,
+    OrEq,
+
+    //misc
+    Colon,
+    Dot,
+    Comma,
+    Hash,
+}
+
+/// All token keywod
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum TokenKeyword {
+    // parents
+    Fn,
+    Class,
+    Module,
+
+    // statements
+    Static,
+    Let,
+    Ret,
+
+    // conditionals
+    If,
+    Else,
+    Elif,
+
+    // control flow
+    Loop,
+    Break,
+    Continue,
+    Return,
+
+    // primitives
+    Int,
+    Float,
+    Char,
+}
+
+/// All token delimiters
+///
+/// TODO: Maybe add \[ and \]
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum TokenDelimiter {
+    BraceOpen,
+    BraceClose,
+    ParenOpen,
+    ParenClose,
+}
+
+/// All tokens
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum TokenKind {
+    Newline,
+    Eof,
+    Literal(TokenLiteral),
+    Symbol(TokenSymbol),
+    Keyword(TokenKeyword),
+    Delimiter(TokenDelimiter),
+    Identifier,
+    Invalid,
+}
+
+#[derive(Debug)]
+pub struct Token {
+    pub kind: TokenKind,
+    /// Holds the reference to the tokenized string
+    ///
+    /// For example, if `kind` is of type [`TokenKind::Identifier`], this would contain the value
+    /// of that identifier
+    pub val: Rc<str>,
+}
+
+pub struct Lexer<'a> {
+    /// The entire text to be tokenized
+    text: &'a str,
+    /// A peekable iterate for `text`
+    chars: Peekable<str::Chars<'a>>,
+    /// A peekable double ended queue for the tokens
+    tokens: VecDeque<Token>,
+    /// Current line number
+    pub(crate) line: usize,
+    pub(crate) col: usize,
+    /// Start character index for the current token
+    start: usize,
+    /// End character index for the current token
+    end: usize,
+}
+
+impl<'a> Lexer<'a> {
+    /// Creates a new [`Lexer`] instance with the provided content.
+    ///
+    /// The `Lexer` is responsible for tokenizing the given text, making it easier to
+    /// perform various parsing operations.
+    ///
+    /// # Arguments
+    ///
+    /// * `content`: The text to tokenize.
+    ///
+    /// # Returns
+    ///
+    /// A new instance of `Lexer` initialized with the provided `content`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use tricc::lexer::Lexer;
+    ///
+    /// let lexer = Lexer::new("let example: int = 4");
+    /// ```
+    pub fn new(content: &'a str) -> Self {
+        Lexer {
+            text: content,
+            chars: content.chars().peekable(),
+            tokens: VecDeque::new(),
+            line: 1,
+            col: 1,
+            start: 0,
+            end: 0,
+        }
+    }
+
+    #[inline]
+    fn new_token(&self, kind: TokenKind) -> Token {
+        Token {
+            kind,
+            val: Rc::from(&self.text[self.start..self.end]),
+        }
+    }
+
+    #[inline]
+    fn error(&self, msg: &str) {
+        eprintln!("Lexer: {}, at \"{}:{}\"", msg, self.line, self.end);
+    }
+
+    #[inline]
+    fn peek(&mut self) -> Option<&char> {
+        self.chars.peek()
+    }
+
+    #[inline]
+    fn next(&mut self) -> Option<char> {
+        self.end += 1;
+        self.col += 1;
+        self.chars.next()
+    }
+
+    fn skip_whitespace(&mut self) {
+        let mut ignore_nl: bool = false;
+
+        while let Some(c) = self.peek() {
+            match c {
+                '\r' | '\t' | ' ' => {
+                    self.next();
+                }
+                '\n' => {
+                    if ignore_nl {
+                        ignore_nl = false;
+                        self.next();
+                    } else {
+                        break;
+                    }
+                }
+                '\\' => {
+                    self.next();
+                    ignore_nl = true;
+                }
+                _ => break,
+            }
+        }
+    }
+
+    fn get_numeric(&mut self) -> Token {
+        let mut is_float: bool = false;
+        while let Some(c) = self.peek() {
+            match c {
+                '0'..='9' => {}
+                '.' => {
+                    if is_float {
+                        self.error("multiple decimals encountered");
+                        return self.new_token(TokenKind::Invalid);
+                    }
+                    is_float = true;
+                }
+                'e' | 'E' => {
+                    self.next();
+                    is_float = true;
+                    break;
+                }
+                _ => break,
+            }
+            self.next();
+        }
+
+        self.new_token(TokenKind::Literal(if is_float {
+            TokenLiteral::Float
+        } else {
+            TokenLiteral::Int
+        }))
+    }
+
+    fn get_char(&mut self) -> Token {
+        // skip '
+        self.next();
+
+        if matches!(self.next(), Some('\'') | None) {
+            self.error("Expected character literal");
+            return self.new_token(TokenKind::Invalid);
+        }
+
+        if self.peek() != Some(&'\'') {
+            self.error("Expected '");
+            return self.new_token(TokenKind::Invalid);
+        }
+
+        // skip '
+        self.next();
+
+        self.new_token(TokenKind::Literal(TokenLiteral::Char))
+    }
+
+    fn get_alphanumeric(&mut self) -> Token {
+        while let Some(c) = self.peek() {
+            match c {
+                'a'..='z' | 'A'..='Z' | '0'..='9' | '_' => {}
+                _ => break,
+            }
+            self.next();
+        }
+
+        use TokenKeyword::*;
+        use TokenKind::Keyword;
+
+        self.new_token(match &self.text[self.start..self.end] {
+            "fn" => Keyword(Fn),
+            "class" => Keyword(Class),
+            "module" => Keyword(Module),
+            "static" => Keyword(Static),
+            "let" => Keyword(Let),
+            "ret" => Keyword(Ret),
+            "if" => Keyword(If),
+            "else" => Keyword(Else),
+            "elif" => Keyword(Elif),
+            "loop" => Keyword(Loop),
+            "break" => Keyword(Break),
+            "continue" => Keyword(Continue),
+            "return" => Keyword(Return),
+            "int" => Keyword(Int),
+            "float" => Keyword(Float),
+            "char" => Keyword(Char),
+            _ => TokenKind::Identifier,
+        })
+    }
+
+    fn get_symbol(&mut self) -> Token {
+        let c = self.next().unwrap();
+
+        use TokenDelimiter::*;
+        use TokenKind::{
+            Delimiter,
+            Symbol,
+        };
+        use TokenSymbol::*;
+
+        // handle +, +=, -, -=, *, *=, /, /=, %, %=, ^, ^=, !, !=
+        macro_rules! token_symbol_eq {
+            ($a:expr, $b:expr) => {
+                match self.peek() {
+                    Some('=') => {
+                        self.next();
+                        Symbol($b)
+                    }
+                    _ => Symbol($a),
+                }
+            };
+        }
+
+        // handle &, |, ||, &&, &=, |=
+        macro_rules! token_symbol_logical {
+            ($a:expr, $b:expr, $c:expr, $d:expr) => {
+                match self.peek() {
+                    Some('=') => {
+                        self.next();
+                        Symbol($c)
+                    }
+                    Some($d) => {
+                        self.next();
+                        Symbol($b)
+                    }
+                    _ => Symbol($a),
+                }
+            };
+        }
+
+        // handle <, <=, >, >=, <<, >>, <<=, >>=
+        macro_rules! token_symbol_compare {
+            ($a:expr, $b:expr, $c:expr, $d:expr, $e:expr) => {
+                match self.peek() {
+                    Some('=') => {
+                        self.next();
+                        Symbol($d)
+                    }
+                    Some($e) => {
+                        self.next();
+                        token_symbol_eq!($b, $c)
+                    }
+                    _ => Symbol($a),
+                }
+            };
+        }
+
+        let typ = match c {
+            '{' => Delimiter(BraceOpen),
+            '}' => Delimiter(BraceClose),
+            '(' => Delimiter(ParenOpen),
+            ')' => Delimiter(ParenClose),
+            '+' => token_symbol_eq!(Plus, PlusEq),
+            '-' => token_symbol_eq!(Minus, MinusEq),
+            '*' => token_symbol_eq!(Star, StarEq),
+            '/' => token_symbol_eq!(Slash, SlashEq),
+            '%' => token_symbol_eq!(Percent, PercentEq),
+            '^' => token_symbol_eq!(Caret, CaretEq),
+            '!' => token_symbol_eq!(Not, Ne),
+            '=' => token_symbol_eq!(Eq, EqEq),
+            '&' => token_symbol_logical!(And, AndAnd, AndEq, '&'),
+            '|' => token_symbol_logical!(Or, OrOr, OrEq, '|'),
+            '<' => token_symbol_compare!(Lt, Shl, ShlEq, LtEq, '<'),
+            '>' => token_symbol_compare!(Gt, Shr, ShrEq, GtEq, '>'),
+            '~' => Symbol(Tilde),
+            ':' => Symbol(Colon),
+            '.' => Symbol(Dot),
+            ',' => Symbol(Comma),
+            '#' => Symbol(Hash),
+            _ => {
+                self.error("Unknown character encountered");
+                TokenKind::Invalid
+            }
+        };
+        self.new_token(typ)
+    }
+
+    fn lex(&mut self) {
+        self.skip_whitespace();
+        self.start = self.end;
+
+        let token = if let Some(c) = self.peek() {
+            match c {
+                '\n' => {
+                    self.next();
+                    self.line += 1;
+                    self.col = 0;
+                    self.new_token(TokenKind::Newline)
+                }
+                '0'..='9' => self.get_numeric(),
+                'a'..='z' | 'A'..='Z' | '_' => self.get_alphanumeric(),
+                '\'' => self.get_char(),
+                _ => self.get_symbol(),
+            }
+        } else {
+            self.new_token(TokenKind::Eof)
+        };
+        self.tokens.push_back(token);
+    }
+
+    /// Peeks at the next token and returns a reference to it
+    pub fn peek_token(&mut self) -> &Token {
+        if self.tokens.is_empty() {
+            self.lex();
+        }
+        &self.tokens[0]
+    }
+
+    /// Returns the next token, moving the lexer forward
+    pub fn next_token(&mut self) -> Token {
+        if self.tokens.is_empty() {
+            self.lex();
+        }
+        self.tokens.pop_front().unwrap()
+    }
+}
+
+#[test]
+fn test_peek_next() {
+    let mut lexer = Lexer::new("test01");
+    assert_eq!(lexer.peek(), Some(&'t'));
+    assert_eq!(lexer.next(), Some('t'));
+    assert_eq!(lexer.peek(), Some(&'e'));
+    assert_eq!(lexer.peek(), Some(&'e'));
+    assert_eq!(lexer.next(), Some('e'));
+    assert_eq!(lexer.next(), Some('s'));
+    assert_eq!(lexer.next(), Some('t'));
+    assert_eq!(lexer.next(), Some('0'));
+    assert_eq!(lexer.peek(), Some(&'1'));
+    assert_eq!(lexer.next(), Some('1'));
+    assert_eq!(lexer.peek(), None);
+    assert_eq!(lexer.next(), None);
+    assert_eq!(lexer.peek(), None);
+}
+
+#[test]
+fn test_tokens() {
+    let mut lexer = Lexer::new("let test02 = 4 << 1");
+
+    use TokenKind::*;
+
+    assert_eq!(lexer.peek_token().kind, Keyword(TokenKeyword::Let));
+    assert_eq!(lexer.next_token().kind, Keyword(TokenKeyword::Let));
+
+    let mut token = lexer.next_token();
+    assert_eq!(token.kind, Identifier);
+    assert_eq!(*token.val, *"test02");
+
+    assert_eq!(lexer.next_token().kind, Symbol(TokenSymbol::Eq));
+
+    token = lexer.next_token();
+    assert_eq!(token.kind, Literal(TokenLiteral::Int));
+    assert_eq!(*token.val, *"4");
+
+    assert_eq!(lexer.next_token().kind, Symbol(TokenSymbol::Shl));
+
+    assert_eq!(lexer.peek_token().kind, Literal(TokenLiteral::Int));
+    assert_eq!(*lexer.peek_token().val, *"1");
+    token = lexer.next_token();
+    assert_eq!(token.kind, Literal(TokenLiteral::Int));
+    assert_eq!(*token.val, *"1");
+
+    assert_eq!(lexer.peek_token().kind, Eof);
+    assert_eq!(lexer.next_token().kind, Eof);
+    assert_eq!(lexer.peek_token().kind, Eof);
+    assert_eq!(lexer.next_token().kind, Eof);
+}
+
+#[test]
+fn test_tokens_2() {
+    let mut lexer = Lexer::new("let test03: char = 'h'");
+
+    use TokenKind::*;
+
+    assert_eq!(lexer.peek_token().kind, Keyword(TokenKeyword::Let));
+    assert_eq!(lexer.next_token().kind, Keyword(TokenKeyword::Let));
+
+    let mut token = lexer.next_token();
+    assert_eq!(token.kind, Identifier);
+    assert_eq!(*token.val, *"test03");
+
+    assert_eq!(lexer.next_token().kind, Symbol(TokenSymbol::Colon));
+    assert_eq!(lexer.next_token().kind, Keyword(TokenKeyword::Char));
+    assert_eq!(lexer.next_token().kind, Symbol(TokenSymbol::Eq));
+
+    assert_eq!(lexer.peek_token().kind, Literal(TokenLiteral::Char));
+    assert_eq!(*lexer.peek_token().val, *"'h'");
+    token = lexer.next_token();
+    assert_eq!(token.kind, Literal(TokenLiteral::Char));
+    assert_eq!(*token.val, *"'h'");
+
+    assert_eq!(lexer.peek_token().kind, Eof);
+    assert_eq!(lexer.next_token().kind, Eof);
+}
+
+#[test]
+fn test_tokens_eof() {
+    let mut lexer = Lexer::new("");
+
+    assert_eq!(lexer.peek_token().kind, TokenKind::Eof);
+    assert_eq!(lexer.next_token().kind, TokenKind::Eof);
+}
+
+#[test]
+fn test_tokens_numeric() {
+    let mut lexer = Lexer::new("3342");
+
+    let token = lexer.next_token();
+    assert_eq!(token.kind, TokenKind::Literal(TokenLiteral::Int));
+    assert_eq!(*token.val, *"3342");
+
+    assert_eq!(lexer.next_token().kind, TokenKind::Eof);
+}
+
+#[test]
+fn test_tokens_numeric_2() {
+    let mut lexer = Lexer::new("334.2e");
+
+    let token = lexer.next_token();
+    assert_eq!(token.kind, TokenKind::Literal(TokenLiteral::Float));
+    assert_eq!(*token.val, *"334.2e");
+
+    assert_eq!(lexer.next_token().kind, TokenKind::Eof);
+}
+
+#[test]
+fn test_tokens_numeric_3() {
+    let mut lexer = Lexer::new("334.2e-5");
+
+    let mut token = lexer.next_token();
+    assert_eq!(token.kind, TokenKind::Literal(TokenLiteral::Float));
+    assert_eq!(*token.val, *"334.2e");
+
+    assert_eq!(
+        lexer.next_token().kind,
+        TokenKind::Symbol(TokenSymbol::Minus)
+    );
+
+    token = lexer.next_token();
+    assert_eq!(token.kind, TokenKind::Literal(TokenLiteral::Int));
+    assert_eq!(*token.val, *"5");
+
+    assert_eq!(lexer.next_token().kind, TokenKind::Eof);
+}

src/lib.rs

@@ -1 +1,4 @@
 pub mod args;
+pub mod ast;
+pub mod lexer;
+pub mod parser;

src/main.rs

@@ -1,7 +1,40 @@
-use tricc::args;
+use std::{
-use tricc::lexer;
+    fs,
+    panic,
+};
+
+use tricc::args::Args;
+use tricc::parser::Parser;
 
 fn main() {
-    let file: String = args::handle();
+    panic::set_hook(Box::new(|panic_info| {
-    println!("{}", file);
+        if let Some(msg) = panic_info.payload().downcast_ref::<&str>() {
+            eprintln!("{}", msg);
+        } else if let Some(msg) = panic_info.payload().downcast_ref::<String>() {
+            eprintln!("{}", msg);
+        } else if let Some(location) = panic_info.location() {
+            eprintln!(
+                "panic occurred in file '{}' at line {}",
+                location.file(),
+                location.line(),
+            );
+        } else {
+            eprintln!("panic occurred");
+        }
+    }));
+
+    let mut args = Args::default();
+    args.handle();
+
+    let file = args.get_file();
+    let content = fs::read_to_string(&file).expect("Couldn't read the file");
+    let mut parser = Parser::new(&content);
+    let Some(parent) = parser.parse() else {
+        eprintln!(
+            "Failed to parse {} - See the errors above",
+            file.to_string_lossy()
+        );
+        std::process::exit(1);
+    };
+    println!("Parsed AST:\n{:#?}", parent);
 }

src/parser/entity.rs

@@ -0,0 +1,215 @@
+use super::Parser;
+use crate::ast::*;
+use crate::lexer::{
+    TokenDelimiter,
+    TokenKeyword,
+    TokenKind,
+    TokenSymbol,
+};
+use std::rc::Rc;
+
+impl<'a> Parser<'a> {
+    /// entity ::= module | class | fn | static
+    pub(super) fn parse_entity(&mut self) -> Option<Entity> {
+        use TokenKeyword::*;
+        let token = self.peek_token();
+
+        if let TokenKind::Keyword(keyword) = &token.kind {
+            Some(match keyword {
+                Module => Entity::Module(self.parse_module()?),
+                Class => Entity::Class(self.parse_class()?),
+                Fn => Entity::Fn(self.parse_fn()?),
+                Static => Entity::Static(self.parse_static()?),
+                _ => {
+                    self.error_expected_peek("entity");
+                    return None;
+                }
+            })
+        } else {
+            self.error_expected_peek("entity");
+            None
+        }
+    }
+
+    /// module ::= "module" ident "{" { module | fn | static | class } "}"
+    fn parse_module(&mut self) -> Option<Module> {
+        self.next_token();
+
+        let name = self.parse_ident()?;
+        let mut children = vec![];
+
+        if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceOpen)) {
+            self.error_expected_peek("{");
+            return None;
+        }
+
+        loop {
+            use TokenKeyword::*;
+            self.trim_newlines();
+            if let TokenKind::Keyword(keyword) = &self.peek_token().kind {
+                children.push(match keyword {
+                    Module => ModuleChildren::Module(self.parse_module()?),
+                    Fn => ModuleChildren::Fn(self.parse_fn()?),
+                    Static => ModuleChildren::Static(self.parse_static()?),
+                    Class => ModuleChildren::Class(self.parse_class()?),
+                    _ => {
+                        self.error_expected_peek("module child");
+                        return None;
+                    }
+                });
+                if !self.check_newline_or_tok(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                    self.error_expected_peek("newline or }");
+                    return None;
+                }
+            } else if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                self.error_expected_peek("}");
+                return None;
+            } else {
+                break;
+            }
+        }
+
+        Some(Module { name, children })
+    }
+
+    /// class ::= "class" ident "{" { fn | static | let } "}"
+    fn parse_class(&mut self) -> Option<Class> {
+        self.next_token();
+
+        let name = self.parse_ident()?;
+        let mut children = vec![];
+
+        if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceOpen)) {
+            self.error_expected_peek("{");
+            return None;
+        }
+
+        loop {
+            use TokenKeyword::*;
+            self.trim_newlines();
+            if let TokenKind::Keyword(keyword) = &self.peek_token().kind {
+                children.push(match keyword {
+                    Fn => ClassChildren::Fn(self.parse_fn()?),
+                    Static => ClassChildren::Static(self.parse_static()?),
+                    Let => ClassChildren::Let(self.parse_let()?),
+                    _ => {
+                        self.error_expected_peek("class child");
+                        return None;
+                    }
+                });
+                if !self.check_newline_or_tok(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                    self.error_expected_peek("newline or }");
+                    return None;
+                }
+            } else if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                self.error_expected_peek("}");
+                return None;
+            } else {
+                break;
+            }
+        }
+
+        Some(Class { name, children })
+    }
+
+    /// fn ::= "fn" ident "(" [ identWithTy { "," identWithTy } ] ")" [ ":" ty ]
+    ///        "{" { statement } "}"
+    fn parse_fn(&mut self) -> Option<Fn> {
+        self.next_token();
+
+        let name = self.parse_ident()?;
+        let mut params: Vec<(Rc<str>, Ty)> = vec![];
+        let mut return_typ: Option<Ty> = None;
+        let mut children: Vec<Statement> = vec![];
+
+        if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::ParenOpen)) {
+            self.error_expected_peek("(");
+            return None;
+        }
+
+        loop {
+            if self.peek_token().kind == TokenKind::Identifier {
+                params.push(self.parse_ident_with_ty()?);
+            }
+
+            if !self.skip_token(TokenKind::Symbol(TokenSymbol::Comma)) {
+                if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::ParenClose)) {
+                    self.error_expected_peek(", or )");
+                    return None;
+                } else {
+                    break;
+                }
+            }
+        }
+
+        if self.skip_token(TokenKind::Symbol(TokenSymbol::Colon)) {
+            return_typ = Some(self.parse_ty()?);
+        }
+
+        if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceOpen)) {
+            self.error_expected_peek("{");
+            return None;
+        }
+
+        loop {
+            self.trim_newlines();
+            if self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                break;
+            }
+            children.push(self.parse_statement()?);
+            if !self.check_newline_or_tok(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                self.error_expected_peek("newline or }");
+                return None;
+            }
+        }
+
+        Some(Fn {
+            name,
+            return_ty: return_typ,
+            params,
+            children,
+        })
+    }
+}
+
+#[test]
+fn test_parse_entity() {
+    let mut parser = Parser::new(
+        r#"module module01 {
+             class class01 {
+               fn fn01(param01: char, param02: float) {
+                 static let let01: int = 4
+               }
+             }
+
+             fn fn02 (): int { }
+          }"#,
+    );
+    assert_eq!(
+        parser.parse_entity(),
+        Some(Entity::Module(Module {
+            name: "module01".into(),
+            children: vec![
+                ModuleChildren::Class(Class {
+                    name: "class01".into(),
+                    children: vec![ClassChildren::Fn(Fn {
+                        name: "fn01".into(),
+                        return_ty: None,
+                        params: vec![("param01".into(), Ty::Char), ("param02".into(), Ty::Float)],
+                        children: vec![Statement::Static(Let {
+                            name: "let01".into(),
+                            ty: Ty::Int,
+                            expr: Some(Expr::Literal(Literal::Int(4)))
+                        })]
+                    })]
+                }),
+                ModuleChildren::Fn(Fn {
+                    name: "fn02".into(),
+                    return_ty: Some(Ty::Int),
+                    params: vec![],
+                    children: vec![]
+                })
+            ]
+        }))
+    );
+}

src/parser/expr.rs

@@ -0,0 +1,435 @@
+use super::Parser;
+use crate::ast::{
+    self,
+    *,
+};
+use crate::lexer::{
+    TokenDelimiter,
+    TokenKeyword,
+    TokenKind,
+    TokenLiteral,
+    TokenSymbol,
+};
+use std::rc::Rc;
+
+impl<'a> Parser<'a> {
+    /// exprIf ::= "if" expr block [ else (block | exprIf ) ]
+    fn parse_expr_if(&mut self) -> Option<If> {
+        // skip "if"
+        self.next_token();
+
+        let cond = Box::new(self.parse_expr()?);
+        let then = self.parse_expr_block()?;
+
+        if !self.skip_token(TokenKind::Keyword(TokenKeyword::Else)) {
+            return Some(If {
+                cond,
+                then,
+                or: None,
+            });
+        }
+
+        if self.peek_token().kind != TokenKind::Keyword(TokenKeyword::If) {
+            return Some(If {
+                cond,
+                then,
+                or: Some(Box::new(ElseType::Else(self.parse_expr_block()?))),
+            });
+        }
+
+        Some(If {
+            cond,
+            then,
+            or: Some(Box::new(ElseType::If(self.parse_expr_if()?))),
+        })
+    }
+
+    /// exprBlock ::= "{" { statement } "}"
+    fn parse_expr_block(&mut self) -> Option<Vec<Statement>> {
+        let mut statements = vec![];
+
+        // skip {
+        self.next_token();
+
+        loop {
+            self.trim_newlines();
+            if self.skip_token(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                break;
+            }
+            statements.push(self.parse_statement()?);
+            if !self.check_newline_or_tok(TokenKind::Delimiter(TokenDelimiter::BraceClose)) {
+                self.error_expected_peek("newline or }");
+                return None;
+            }
+        }
+
+        Some(statements)
+    }
+
+    /// exprLoop ::= "loop" exprBlock
+    fn parse_expr_loop(&mut self) -> Option<Vec<Statement>> {
+        self.next_token();
+        if self.peek_token().kind != TokenKind::Delimiter(TokenDelimiter::BraceOpen) {
+            self.error_expected_peek("{");
+            return None;
+        }
+
+        self.parse_expr_block()
+    }
+
+    /// exprAtom ::= ( "(" expr ")" ) | ident | int | float | char | exprBlock | exprLoop | exprIf
+    fn parse_expr_atom(&mut self) -> Option<Expr> {
+        use ast::Literal::*;
+        use TokenKind::*;
+
+        // TODO: check lvalue validity in the analysis phase
+        Some(match self.peek_token().kind {
+            Delimiter(TokenDelimiter::ParenOpen) => {
+                self.next_token(); // skip (
+
+                let expr = self.parse_expr()?;
+
+                if !self.skip_token(TokenKind::Delimiter(TokenDelimiter::ParenClose)) {
+                    self.error_expected_peek(")");
+                    return None;
+                }
+
+                expr
+            }
+            Identifier => {
+                let token = self.next_token();
+                Expr::Identifier(Rc::clone(&token.val))
+            }
+            Literal(TokenLiteral::Int) => Expr::Literal(Int(self.parse_int()?)),
+            Literal(TokenLiteral::Float) => Expr::Literal(Float(self.parse_float()?)),
+            Literal(TokenLiteral::Char) => Expr::Literal(Char(self.parse_char()?)),
+            Delimiter(TokenDelimiter::BraceOpen) => Expr::Block(self.parse_expr_block()?),
+            Keyword(TokenKeyword::Loop) => Expr::Loop(self.parse_expr_loop()?),
+            Keyword(TokenKeyword::If) => Expr::If(self.parse_expr_if()?),
+            _ => {
+                self.error_expected_peek("expression");
+                return None;
+            }
+        })
+    }
+
+    /// exprUnary ::= [ unaryOp ] exprAtom
+    /// unaryOp   ::= "+" | "-" | "~"
+    fn parse_expr_unary(&mut self) -> Option<Expr> {
+        use TokenSymbol::*;
+        Some(match self.peek_token().kind {
+            TokenKind::Symbol(symbol @ (Minus | Plus | Tilde)) => {
+                self.next_token();
+                Expr::Op(symbol, Box::new(self.parse_expr_atom()?), None)
+            }
+            _ => self.parse_expr_atom()?,
+        })
+    }
+
+    /// exprArithmeticMul ::= exprUnary [ arithmeticMulOp exprArithmeticMul ]
+    /// arithmeticMulOp   ::= "*" | "/" | "%"
+    fn parse_expr_arithmetic_mul(&mut self) -> Option<Expr> {
+        use TokenSymbol::*;
+        let lhs = self.parse_expr_unary()?;
+
+        Some(match self.peek_token().kind {
+            TokenKind::Symbol(symbol @ (Star | Slash | Percent)) => {
+                self.next_token();
+                Expr::Op(
+                    symbol,
+                    Box::new(lhs),
+                    Some(Box::new(self.parse_expr_arithmetic_mul()?)),
+                )
+            }
+            _ => lhs,
+        })
+    }
+
+    /// exprArithmeticAdd ::= exprArithmeticMul [ arithmeticAddOp exprArithmeticAdd ]
+    /// arithmeticAddOp   ::= "+" | "-"
+    fn parse_expr_arithmetic_add(&mut self) -> Option<Expr> {
+        use TokenSymbol::*;
+        let lhs = self.parse_expr_arithmetic_mul()?;
+
+        Some(match self.peek_token().kind {
+            TokenKind::Symbol(symbol @ (Plus | Minus)) => {
+                self.next_token();
+                Expr::Op(
+                    symbol,
+                    Box::new(lhs),
+                    Some(Box::new(self.parse_expr_arithmetic_add()?)),
+                )
+            }
+            _ => lhs,
+        })
+    }
+
+    /// exprBitwiseShift ::= exprArithmeticAdd [ bitwiseShiftOp exprBitwiseShift ]
+    /// bitwiseShiftOp   ::= "<<" | ">>"
+    fn parse_expr_bitwise_shift(&mut self) -> Option<Expr> {
+        use TokenSymbol::*;
+        let lhs = self.parse_expr_arithmetic_add()?;
+
+        Some(match self.peek_token().kind {
+            TokenKind::Symbol(symbol @ (Shl | Shr)) => {
+                self.next_token();
+                Expr::Op(
+                    symbol,
+                    Box::new(lhs),
+                    Some(Box::new(self.parse_expr_bitwise_shift()?)),
+                )
+            }
+            _ => lhs,
+        })
+    }
+
+    /// exprBitwiseAnd ::= exprBitwiseShift [ "&" exprBitwiseAnd ]
+    fn parse_expr_bitwise_and(&mut self) -> Option<Expr> {
+        let lhs = self.parse_expr_bitwise_shift()?;
+        let symbol = TokenSymbol::And;
+
+        if !self.skip_token(TokenKind::Symbol(symbol)) {
+            return Some(lhs);
+        }
+
+        Some(Expr::Op(
+            symbol,
+            Box::new(lhs),
+            Some(Box::new(self.parse_expr_bitwise_and()?)),
+        ))
+    }
+
+    /// exprBitwiseXor ::= exprBitwiseAnd [ "^" exprBitwiseXor ]
+    fn parse_expr_bitwise_xor(&mut self) -> Option<Expr> {
+        let lhs = self.parse_expr_bitwise_and()?;
+        let symbol = TokenSymbol::Caret;
+
+        if !self.skip_token(TokenKind::Symbol(symbol)) {
+            return Some(lhs);
+        }
+
+        Some(Expr::Op(
+            symbol,
+            Box::new(lhs),
+            Some(Box::new(self.parse_expr_bitwise_xor()?)),
+        ))
+    }
+
+    /// exprBiwiseOr ::= exprBitwiseXor [ "|" exprBitwiseOr ]
+    fn parse_expr_bitwise_or(&mut self) -> Option<Expr> {
+        let lhs = self.parse_expr_bitwise_xor()?;
+        let symbol = TokenSymbol::Or;
+
+        if !self.skip_token(TokenKind::Symbol(symbol)) {
+            return Some(lhs);
+        }
+
+        Some(Expr::Op(
+            symbol,
+            Box::new(lhs),
+            Some(Box::new(self.parse_expr_bitwise_or()?)),
+        ))
+    }
+
+    /// exprAssign   ::= exprBitwiseOr [ relationalOp exprRelational ]
+    /// relationalOp ::= ">" | "<" | ">=" | "<=" | "==" | "!="
+    fn parse_expr_relational(&mut self) -> Option<Expr> {
+        use TokenSymbol::*;
+        let lhs = self.parse_expr_bitwise_or()?;
+
+        Some(match self.peek_token().kind {
+            TokenKind::Symbol(symbol @ (Gt | Lt | GtEq | LtEq | EqEq | Ne)) => {
+                self.next_token();
+                Expr::Op(
+                    symbol,
+                    Box::new(lhs),
+                    Some(Box::new(self.parse_expr_relational()?)),
+                )
+            }
+            _ => lhs,
+        })
+    }
+
+    /// exprLogicalAnd ::= exprLogicalRelational [ "&&" exprLogicalAnd ]
+    fn parse_expr_logical_and(&mut self) -> Option<Expr> {
+        let lhs = self.parse_expr_relational()?;
+        let symbol = TokenSymbol::AndAnd;
+
+        if !self.skip_token(TokenKind::Symbol(symbol)) {
+            return Some(lhs);
+        }
+
+        Some(Expr::Op(
+            symbol,
+            Box::new(lhs),
+            Some(Box::new(self.parse_expr_logical_and()?)),
+        ))
+    }
+
+    /// exprLogicalOr ::= exprLogicalAnd [ "||" exprLogicalOr ]
+    fn parse_expr_logical_or(&mut self) -> Option<Expr> {
+        let lhs = self.parse_expr_logical_and()?;
+        let symbol = TokenSymbol::OrOr;
+
+        if !self.skip_token(TokenKind::Symbol(symbol)) {
+            return Some(lhs);
+        }
+
+        Some(Expr::Op(
+            symbol,
+            Box::new(lhs),
+            Some(Box::new(self.parse_expr_logical_or()?)),
+        ))
+    }
+
+    /// exprAssign ::= exprLogicalOr [ assignOp exprAssign ]
+    /// assignOp   ::= "=" | "+=" | "-=" | "*=" | "/=" | "%=" | "^=" | "<<=" | ">>=" | "&=" | "|="
+    fn parse_expr_assign(&mut self) -> Option<Expr> {
+        use TokenSymbol::*;
+        let lhs = self.parse_expr_logical_or()?;
+
+        Some(match self.peek_token().kind {
+            TokenKind::Symbol(
+                symbol @ (Eq | PlusEq | MinusEq | StarEq | SlashEq | PercentEq | CaretEq | ShlEq
+                | ShrEq | AndEq | OrEq),
+            ) => {
+                self.next_token();
+                Expr::Op(
+                    symbol,
+                    Box::new(lhs),
+                    Some(Box::new(self.parse_expr_assign()?)),
+                )
+            }
+            _ => lhs,
+        })
+    }
+
+    /// exprControl ::= "continue" | "break" | "return" [ exprControl ] | exprAssign
+    fn parse_expr_control(&mut self) -> Option<Expr> {
+        use TokenKeyword::*;
+
+        Some(match self.peek_token().kind {
+            TokenKind::Keyword(Continue) => {
+                self.next_token();
+                Expr::Continue
+            }
+            TokenKind::Keyword(Break) => {
+                self.next_token();
+                Expr::Break
+            }
+            TokenKind::Keyword(Return) => {
+                self.next_token();
+                Expr::Return(self.parse_expr_control().map(Box::new))
+            }
+            _ => self.parse_expr_assign()?,
+        })
+    }
+
+    /// entrypoint for expression parsing using recursive descent parsing
+    ///
+    /// <https://en.wikipedia.org/wiki/Recursive_descent_parser>
+    /// expr ::= exprControl
+    pub(super) fn parse_expr(&mut self) -> Option<Expr> {
+        self.parse_expr_control()
+    }
+}
+
+#[test]
+fn test_parse_expr() {
+    use Literal::*;
+    use TokenSymbol::*;
+
+    macro_rules! b {
+        ($expr:expr) => {
+            Box::new($expr)
+        };
+    }
+
+    let mut parser = Parser::new(
+        r#"if if 1 { 1 } else { 0 } + 9 {
+             a = 4
+           } else if 1 {
+             a = 5
+           } else {
+           }
+          amul ^= (4 + 93 * (1 << 3) / 1.44) ^ bhatura
+          stove = { 44 } + amul"#,
+    );
+
+    assert_eq!(
+        parser.parse_expr(),
+        Some(Expr::If(If {
+            cond: b!(Expr::Op(
+                Plus,
+                b!(Expr::If(If {
+                    cond: b!(Expr::Literal(Int(1))),
+                    then: vec![Statement::Expr(Expr::Literal(Int(1)))],
+                    or: Some(b!(ElseType::Else(vec![Statement::Expr(Expr::Literal(
+                        Int(0)
+                    ))])))
+                })),
+                Some(b!(Expr::Literal(Int(9))))
+            )),
+            then: vec![Statement::Expr(Expr::Op(
+                Eq,
+                b!(Expr::Identifier("a".into())),
+                Some(b!(Expr::Literal(Int(4))))
+            ))],
+            or: Some(b!(ElseType::If(If {
+                cond: b!(Expr::Literal(Int(1))),
+                then: vec![Statement::Expr(Expr::Op(
+                    Eq,
+                    b!(Expr::Identifier("a".into())),
+                    Some(b!(Expr::Literal(Int(5))))
+                ))],
+                or: Some(b!(ElseType::Else(vec![])))
+            })))
+        }))
+    );
+
+    assert_eq!(parser.skip_token(TokenKind::Newline), true);
+
+    assert_eq!(
+        parser.parse_expr(),
+        Some(Expr::Op(
+            CaretEq,
+            b!(Expr::Identifier("amul".into())),
+            Some(b!(Expr::Op(
+                Caret,
+                b!(Expr::Op(
+                    Plus,
+                    b!(Expr::Literal(Int(4))),
+                    Some(b!(Expr::Op(
+                        Star,
+                        b!(Expr::Literal(Int(93))),
+                        Some(b!(Expr::Op(
+                            Slash,
+                            b!(Expr::Op(
+                                Shl,
+                                b!(Expr::Literal(Int(1))),
+                                Some(b!(Expr::Literal(Int(3))))
+                            )),
+                            Some(b!(Expr::Literal(Float(1.44))))
+                        )))
+                    )))
+                )),
+                Some(b!(Expr::Identifier("bhatura".into())))
+            )))
+        ))
+    );
+
+    assert_eq!(parser.skip_token(TokenKind::Newline), true);
+
+    assert_eq!(
+        parser.parse_expr(),
+        Some(Expr::Op(
+            Eq,
+            b!(Expr::Identifier("stove".into())),
+            Some(b!(Expr::Op(
+                Plus,
+                b!(Expr::Block(vec![Statement::Expr(Expr::Literal(Int(44)))])),
+                Some(b!(Expr::Identifier("amul".into())))
+            )))
+        ))
+    );
+}

src/parser/literal.rs

@@ -0,0 +1,121 @@
+use super::Parser;
+use crate::lexer::{
+    TokenKind,
+    TokenLiteral,
+    TokenSymbol,
+};
+
+impl<'a> Parser<'a> {
+    /// int ::= digit { digit }
+    pub(super) fn parse_int(&mut self) -> Option<i32> {
+        let val = self.next_token().val;
+        let mut integer: i32 = 0;
+        let error = || {
+            self.error(&format!(
+                "integer values must be in range [{}, {}]",
+                i32::MIN,
+                i32::MAX
+            ))
+        };
+
+        for c in val.chars() {
+            // c is always ['0'..='9']
+            let d = c.to_digit(10)?;
+
+            match integer.checked_mul(10) {
+                Some(m) => integer = m,
+                None => {
+                    error();
+                    return None;
+                }
+            }
+
+            match integer.checked_add(d as i32) {
+                Some(a) => integer = a,
+                None => {
+                    error();
+                    return None;
+                }
+            }
+        }
+
+        Some(integer)
+    }
+
+    // didnt use parse() because i wanted to do this myself for some reason
+    /// f32 can be NaN and inf as well
+    /// float ::= int [ "." { digit } ] [ "e" { digit } ]
+    pub(super) fn parse_float(&mut self) -> Option<f32> {
+        let token = self.next_token();
+        let mut chars = token.val.chars();
+        let mut float: f32 = 0.0;
+        let mut fraction: f32 = 0.0;
+        let mut prec: i32 = 0;
+        let mut exp: i32 = 0;
+        let mut decimal: bool = false;
+
+        // lexer takes care of multiple decimals and non digit characters
+        for c in chars.by_ref() {
+            match c {
+                '.' => decimal = true,
+                'e' | 'E' => {
+                    // lexer takes care that decimal doesnt come after e
+                    let s;
+                    match self.peek_token().kind {
+                        TokenKind::Symbol(TokenSymbol::Minus) => {
+                            s = -1;
+                            self.next_token();
+                        }
+                        TokenKind::Symbol(TokenSymbol::Plus) => {
+                            s = 1;
+                            self.next_token();
+                        }
+                        _ => s = 1,
+                    }
+
+                    if self.peek_token().kind != TokenKind::Literal(TokenLiteral::Int) {
+                        break;
+                    }
+
+                    exp = self.parse_int()? * s;
+                    break;
+                }
+                _ => {
+                    // c is always ['0'..='9']
+                    let d = c.to_digit(10)? as f32;
+                    if decimal {
+                        fraction *= 10.0;
+                        fraction += d;
+                        prec += 1;
+                    } else {
+                        float *= 10.0;
+                        float += d;
+                    }
+                }
+            }
+        }
+
+        fraction /= 10f32.powi(prec);
+        float += fraction;
+        float *= 10f32.powi(exp);
+
+        Some(float)
+    }
+
+    /// char ::= "'" letter "'"
+    pub(super) fn parse_char(&mut self) -> Option<char> {
+        // the lexer ensures that the 0th and 2nd characters are both '
+        self.next_token().val.chars().nth(1)
+    }
+}
+
+#[test]
+fn test_parse_literals() {
+    let mut parser = Parser::new("4524 3123.15e4 9e2 9083482.429455 'c' 3331.13.1");
+    assert_eq!(parser.parse_int(), Some(4524));
+    assert_eq!(parser.parse_float(), Some(3123.15e4));
+    assert_eq!(parser.parse_float(), Some(9e2));
+    assert_eq!(parser.parse_float(), Some(9083482.429455));
+    assert_eq!(parser.parse_char(), Some('c'));
+    assert_eq!(parser.next_token().kind, TokenKind::Invalid);
+}

src/parser/mod.rs

@@ -0,0 +1,156 @@
+//! A naive parser just to get started
+//!
+//! Can only parse module, class and function declaration now along with let statements
+
+mod entity;
+mod expr;
+mod literal;
+mod statement;
+
+use crate::ast::{
+    Parent,
+    Ty,
+};
+use crate::lexer::{
+    Lexer,
+    Token,
+    TokenKeyword,
+    TokenKind,
+    TokenSymbol,
+};
+use std::rc::Rc;
+
+pub struct Parser<'a> {
+    pub lexer: Lexer<'a>,
+}
+
+impl<'a> Parser<'a> {
+    /// Creates a new [`Parser`] instance.
+    pub fn new(contents: &'a str) -> Parser<'a> {
+        Parser {
+            lexer: Lexer::new(contents),
+        }
+    }
+
+    #[inline]
+    fn error(&self, message: &str) {
+        eprintln!(
+            "Parser: {}, at \"{}:{}\"",
+            message, self.lexer.line, self.lexer.col
+        );
+    }
+
+    #[inline]
+    fn error_expected(&self, expected: &str, found: &str) {
+        self.error(&format!("expected {}, found {}", expected, found));
+    }
+
+    #[inline]
+    fn error_expected_peek(&mut self, expected: &str) {
+        let found = &Rc::clone(&self.peek_token().val);
+        self.error_expected(expected, found);
+    }
+
+    #[inline]
+    fn next_token(&mut self) -> Token {
+        let t = self.lexer.next_token();
+        println!("{:?}", t);
+        t
+    }
+
+    #[inline]
+    fn peek_token(&mut self) -> &Token {
+        return self.lexer.peek_token();
+    }
+
+    /// newline ::= "}\n"
+    fn trim_newlines(&mut self) {
+        while self.peek_token().kind == TokenKind::Newline {
+            self.next_token();
+        }
+    }
+
+    fn skip_token(&mut self, kind: TokenKind) -> bool {
+        if self.peek_token().kind == kind {
+            self.next_token();
+            return true;
+        }
+
+        false
+    }
+
+    fn check_newline_or_tok(&mut self, token: TokenKind) -> bool {
+        match self.peek_token().kind {
+            TokenKind::Newline => true,
+            d if d == token => true,
+            _ => false,
+        }
+    }
+
+    /// ty ::= "int" | "float" | "char"
+    fn parse_ty(&mut self) -> Option<Ty> {
+        let ty: Ty;
+
+        if let TokenKind::Keyword(keyword) = &self.peek_token().kind {
+            ty = match keyword {
+                TokenKeyword::Int => Ty::Int,
+                TokenKeyword::Char => Ty::Char,
+                TokenKeyword::Float => Ty::Float,
+                _ => {
+                    self.error_expected_peek("ty");
+                    return None;
+                }
+            };
+        } else {
+            self.error_expected_peek("ty");
+            return None;
+        }
+        self.next_token();
+        Some(ty)
+    }
+
+    /// ident ::= ( letter | "_" ) { letter | digit | "_" }
+    fn parse_ident(&mut self) -> Option<Rc<str>> {
+        if self.peek_token().kind != TokenKind::Identifier {
+            self.error_expected_peek("identifier");
+            return None;
+        }
+
+        Some(Rc::clone(&self.next_token().val))
+    }
+
+    /// identWithTy ::= letter ":" ty
+    fn parse_ident_with_ty(&mut self) -> Option<(Rc<str>, Ty)> {
+        let ident = self.parse_ident()?;
+
+        if !self.skip_token(TokenKind::Symbol(TokenSymbol::Colon)) {
+            self.error_expected_peek(":");
+            return None;
+        }
+
+        Some((ident, self.parse_ty()?))
+    }
+
+    /// Returns an [`Entity`] vector after parsing
+    ///
+    /// parent ::= { entity }
+    /// [`Entity`]: crate::ast::Entity
+    pub fn parse(&mut self) -> Option<Parent> {
+        let mut parent = vec![];
+
+        loop {
+            match self.peek_token().kind {
+                TokenKind::Newline => self.trim_newlines(),
+                TokenKind::Eof => break,
+                _ => {
+                    parent.push(self.parse_entity()?);
+                    if !self.check_newline_or_tok(TokenKind::Eof) {
+                        self.error_expected_peek("newline or end of file");
+                        return None;
+                    }
+                }
+            }
+        }
+        Some(parent)
+    }
+}

src/parser/statement.rs

@@ -0,0 +1,91 @@
+use super::Parser;
+use crate::ast::*;
+use crate::lexer::{
+    TokenKeyword,
+    TokenKind,
+    TokenSymbol,
+};
+
+impl<'a> Parser<'a> {
+    /// statement ::= static | let | expr
+    pub(super) fn parse_statement(&mut self) -> Option<Statement> {
+        use TokenKeyword::*;
+        println!("STMT");
+
+        Some(match self.peek_token().kind {
+            TokenKind::Keyword(Static) => Statement::Static(self.parse_static()?),
+            TokenKind::Keyword(Let) => Statement::Let(self.parse_let()?),
+            _ => Statement::Expr(self.parse_expr()?),
+        })
+    }
+
+    /// static ::="static" let
+    pub(super) fn parse_static(&mut self) -> Option<Let> {
+        self.next_token();
+
+        if self.peek_token().kind != TokenKind::Keyword(TokenKeyword::Let) {
+            self.error_expected_peek("let");
+            return None;
+        }
+
+        self.parse_let()
+    }
+
+    /// let ::= "let" identWithTy "=" expr
+    pub(super) fn parse_let(&mut self) -> Option<Let> {
+        self.next_token();
+
+        let (name, ty) = self.parse_ident_with_ty()?;
+
+        let expr = if self.skip_token(TokenKind::Symbol(TokenSymbol::Eq)) {
+            self.parse_expr()
+        } else if self.peek_token().kind == TokenKind::Newline {
+            None
+        } else {
+            self.error_expected_peek("= or newline");
+            return None;
+        };
+
+        Some(Let { name, ty, expr })
+    }
+}
+
+#[test]
+fn test_parse_let() {
+    use Literal::*;
+
+    let mut parser = Parser::new(
+        r#"static let test01: int = 4
+           let test02: char = '6'
+           static let test03: float
+           let test04 = 9"#,
+    );
+    assert_eq!(
+        parser.parse_static(),
+        Some(Let {
+            name: "test01".into(),
+            ty: Ty::Int,
+            expr: Some(Expr::Literal(Int(4)))
+        })
+    );
+    assert_eq!(parser.skip_token(TokenKind::Newline), true);
+    assert_eq!(
+        parser.parse_let(),
+        Some(Let {
+            name: "test02".into(),
+            ty: Ty::Char,
+            expr: Some(Expr::Literal(Char('6')))
+        })
+    );
+    assert_eq!(parser.skip_token(TokenKind::Newline), true);
+    assert_eq!(
+        parser.parse_static(),
+        Some(Let {
+            name: "test03".into(),
+            ty: Ty::Float,
+            expr: None
+        })
+    );
+    assert_eq!(parser.skip_token(TokenKind::Newline), true);
+    assert_eq!(parser.parse_let(), None);
+}