Giant overhaul, still doesn't work tho

.gitignore

@@ -3,3 +3,5 @@ result*
 
 *.bc
 *.ll
+
+a.out

examples/conditions.e0

@@ -0,0 +1,11 @@
+fn main() -> int {
+  let x = 5;
+
+  if x < 3 {
+    return 3;
+  } else if x > 10 {
+    return 10;
+  } else {
+    return x;
+  }
+}

src/ast/llvm.rs

@@ -1,4 +1,4 @@
-use std::{collections::HashMap, marker::PhantomData};
+use std::collections::HashMap;
 
 use anyhow::Result;
 use inkwell::{
@@ -6,31 +6,72 @@ use inkwell::{
   context::Context,
   module::Module,
   types::{BasicMetadataTypeEnum, BasicTypeEnum, FunctionType},
-  values::{AnyValueEnum, BasicValueEnum, PointerValue},
+  values::{BasicValueEnum, FunctionValue, IntValue, PointerValue},
+  IntPredicate,
 };
 
-use super::{Decl, Expr, Stmt, Type};
+use super::{Decl, ElseClause, Expr, ExprKind, IfElse, Op, Stmt, Type};
 
-impl Expr {
+impl Expr<Type> {
   fn into_llvm<'ctx>(
     &self,
     context: &'ctx Context,
-    builder: &Builder,
+    builder: &'ctx Builder,
     env: &Env<'_, 'ctx>,
   ) -> Result<BasicValueEnum<'ctx>> {
-    match self {
-      Expr::Var(name) => {
+    let int_ty = context.i64_type();
+    let bool_ty = context.bool_type();
+
+    match &self.kind {
+      ExprKind::Var(name) => {
         let (_, value) = match env.lookup(&name) {
           Some(v) => v,
           None => bail!("Unbound name {name:?}"),
         };
 
-        Ok(BasicValueEnum::PointerValue(*value))
+        Ok(builder.build_load(*value, ""))
       }
 
-      Expr::Int(n) => Ok(BasicValueEnum::IntValue(
-        context.i64_type().const_int(*n as u64, false),
-      )),
+      ExprKind::Int(n) => {
+        Ok(BasicValueEnum::IntValue(int_ty.const_int(*n as u64, false)))
+      }
+
+      ExprKind::BinOp(left, op, right) => {
+        if !op.check_types(&left.ty, &right.ty) {
+          // TODO: detailed error message
+          bail!("Invalid types on operation.");
+        }
+
+        match op {
+          Op::LessThan => {
+            let left_val =
+              left.into_llvm(context, builder, env)?.into_int_value();
+            let right_val =
+              right.into_llvm(context, builder, env)?.into_int_value();
+            let result: IntValue = builder.build_int_compare(
+              IntPredicate::SLT,
+              left_val,
+              right_val,
+              "",
+            );
+            Ok(BasicValueEnum::IntValue(result))
+          }
+
+          Op::GreaterThan => {
+            let left_val =
+              left.into_llvm(context, builder, env)?.into_int_value();
+            let right_val =
+              right.into_llvm(context, builder, env)?.into_int_value();
+            let result: IntValue = builder.build_int_compare(
+              IntPredicate::SGT,
+              left_val,
+              right_val,
+              "",
+            );
+            Ok(BasicValueEnum::IntValue(result))
+          }
+        }
+      }
     }
   }
 }
@@ -42,6 +83,8 @@ impl Type {
   ) -> BasicTypeEnum<'ctx> {
     match self {
       Type::Int => BasicTypeEnum::IntType(context.i64_type()),
+      Type::Bool => BasicTypeEnum::IntType(context.bool_type()),
+      _ => panic!("Tried to convert a function type into a LLVM basic type"),
     }
   }
 }
@@ -65,7 +108,7 @@ type EnvValue<'a, 'ctx> = (&'a Type, PointerValue<'ctx>);
 
 #[derive(Default)]
 struct Env<'a, 'ctx> {
-  parent: Option<Box<Env<'a, 'ctx>>>,
+  parent: Option<&'a Env<'a, 'ctx>>,
   local_type_map: HashMap<String, EnvValue<'a, 'ctx>>,
 }
 
@@ -81,23 +124,72 @@ impl<'a, 'ctx> Env<'a, 'ctx> {
   }
 }
 
-fn convert_lexical_block(
+fn convert_if_else(
   context: &Context,
+  module: &Module,
   builder: &Builder,
-  parent_env: Env,
-  stmts: impl AsRef<[Stmt]>,
+  function: &FunctionValue,
+  if_else: &IfElse<Type>,
+  env: &Env,
+) -> Result<()> {
+  let success_branch = context.append_basic_block(*function, "success");
+  let fail_branch = context.append_basic_block(*function, "fail");
+  let exit_block = context.append_basic_block(*function, "exit");
+
+  let cond = if_else
+    .cond
+    .into_llvm(context, builder, env)?
+    .into_int_value();
+  builder.build_conditional_branch(cond, success_branch, fail_branch);
+
+  // build success branch
+  builder.position_at_end(success_branch);
+  convert_stmts(context, module, function, builder, env, &if_else.body)?;
+  // builder.build_unconditional_branch(exit_branch);
+
+  // build fail branch
+  builder.position_at_end(fail_branch);
+  match &if_else.else_clause {
+    Some(ElseClause::If(if_else2)) => {
+      println!("SUB-IF CLAUSE {if_else2:?}");
+      convert_if_else(context, module, builder, function, if_else2, env)?;
+    }
+    Some(ElseClause::Body(body)) => {
+      println!("STMTS {body:?}");
+      convert_stmts(context, module, function, builder, env, body)?;
+    }
+    None => {
+      println!("NOTHING");
+    }
+  }
+  builder.build_unconditional_branch(exit_block);
+
+  builder.position_at_end(exit_block);
+
+  Ok(())
+}
+
+fn convert_stmts(
+  context: &Context,
+  module: &Module,
+  function: &FunctionValue,
+  builder: &Builder,
+  parent_env: &Env,
+  stmts: impl AsRef<[Stmt<Type>]>,
 ) -> Result<()> {
   let stmts = stmts.as_ref();
   let mut scope_env = Env {
-    parent: Some(Box::new(parent_env)),
+    parent: Some(parent_env),
     ..Default::default()
   };
 
   for stmt in stmts.iter() {
     match stmt {
-      Stmt::Let(name, ty, expr) => {
+      Stmt::Let(name, _, expr) => {
+        let ty = &expr.ty;
         let llvm_ty = ty.into_llvm_basic_type(context);
-        let alloca = builder.build_alloca(llvm_ty, name);
+        // Empty variable name gets LLVM to generate a unique name
+        let alloca = builder.build_alloca(llvm_ty, "");
 
         let expr_val = expr.into_llvm(context, builder, &scope_env)?;
         builder.build_store(alloca, expr_val);
@@ -114,17 +206,30 @@ fn convert_lexical_block(
         }
         println!("Emitted return.");
       }
+
+      Stmt::IfElse(if_else) => {
+        convert_if_else(
+          context, module, builder, function, if_else, &scope_env,
+        )?;
+      }
     }
   }
 
   Ok(())
 }
 
-pub fn convert(context: &mut Context, program: Vec<Decl>) -> Result<Module> {
-  let module = context.create_module("program");
+pub fn convert(
+  file_name: String,
+  context: &Context,
+  program: Vec<Decl<Type>>,
+) -> Result<Module> {
+  let module = context.create_module(&file_name);
   let builder = context.create_builder();
 
-  for func in program.iter().filter_map(Decl::unwrap_func) {
+  for func in program.iter().filter_map(|decl| match decl {
+    Decl::Func(v) => Some(v),
+    _ => None,
+  }) {
     let return_ty = func.return_ty.into_llvm_basic_type(context);
     let llvm_func_ty = fn_type_basic(return_ty, &[], false);
 
@@ -134,7 +239,7 @@ pub fn convert(context: &mut Context, program: Vec<Decl>) -> Result<Module> {
     builder.position_at_end(entry_block);
 
     let env = Env::default();
-    convert_lexical_block(context, &builder, env, &func.stmts)?;
+    convert_stmts(&context, &module, &llvm_func, &builder, &env, &func.stmts)?;
   }
 
   Ok(module)

src/ast/mod.rs

@@ -1,39 +1,69 @@
 pub mod llvm;
+pub mod typed;
 
 #[derive(Debug)]
-pub enum Decl {
-  Func(Func),
-}
-
-impl Decl {
-  pub fn unwrap_func(&self) -> Option<&Func> {
-    match self {
-      Decl::Func(func) => Some(func),
-      _ => None,
-    }
-  }
+pub enum Decl<T> {
+  Func(Func<T>),
 }
 
 #[derive(Debug)]
-pub struct Func {
+pub struct Func<T> {
   pub name: String,
   pub return_ty: Type,
-  pub stmts: Vec<Stmt>,
+  pub stmts: Vec<Stmt<T>>,
 }
 
 #[derive(Debug)]
-pub enum Stmt {
-  Let(String, Type, Expr),
-  Return(Option<Expr>),
+pub enum Stmt<T> {
+  Let(String, Option<Type>, Expr<T>),
+  Return(Option<Expr<T>>),
+  IfElse(IfElse<T>),
 }
 
 #[derive(Debug)]
-pub enum Expr {
+pub struct IfElse<T> {
+  pub cond: Expr<T>,
+  pub body: Vec<Stmt<T>>,
+  pub else_clause: Option<ElseClause<T>>,
+}
+
+#[derive(Debug)]
+pub enum ElseClause<T> {
+  Body(Vec<Stmt<T>>),
+  If(Box<IfElse<T>>),
+}
+
+#[derive(Debug)]
+pub struct Expr<T> {
+  pub kind: ExprKind<T>,
+  pub ty: T,
+}
+
+#[derive(Debug)]
+pub enum ExprKind<T> {
   Int(i64),
   Var(String),
+  BinOp(Box<Expr<T>>, Op, Box<Expr<T>>),
 }
 
-#[derive(Debug)]
+#[derive(Copy, Clone, Debug)]
+pub enum Op {
+  LessThan,
+  GreaterThan,
+}
+
+impl Op {
+  pub fn check_types(&self, left_ty: &Type, right_ty: &Type) -> bool {
+    // TODO: since only binops work on integers right now, just check that the two sides are both
+    // integers. this will have to change once && gets added.
+    matches!(left_ty, Type::Int) && matches!(right_ty, Type::Int)
+  }
+}
+
+#[derive(Clone, Debug, Hash, Eq, PartialEq)]
 pub enum Type {
   Int,
+  Bool,
+
+  Func(Vec<Type>, Box<Type>),
 }

src/ast/typed.rs

@@ -0,0 +1,437 @@
+use std::collections::{HashMap, HashSet};
+
+use anyhow::Result;
+
+use crate::ast::Expr;
+
+use super::{Decl, ElseClause, ExprKind, Func, IfElse, Op, Stmt, Type};
+
+#[derive(Clone, Debug, Hash, Eq, PartialEq)]
+pub enum Type_ {
+  Var(usize),
+
+  Int,
+  Bool,
+
+  Func(Vec<Type_>, Box<Type_>),
+}
+
+impl Type_ {
+  fn from_type(ty: Type) -> Self {
+    match ty {
+      Type::Int => Type_::Int,
+      Type::Bool => Type_::Bool,
+
+      Type::Func(args, ret) => {
+        let args = args.into_iter().map(|arg| Type_::from_type(arg)).collect();
+        let ret = Type_::from_type(*ret);
+        Type_::Func(args, Box::new(ret))
+      }
+    }
+  }
+
+  fn convert(&self, assignments: &Assignments) -> Result<Type> {
+    Ok(match self {
+      Type_::Var(n) => match assignments.get(&n) {
+        Some(v) => v.convert(assignments)?,
+        None => bail!("Unsolved constraint variable {n}"),
+      },
+
+      Type_::Int => Type::Int,
+      Type_::Bool => Type::Bool,
+
+      Type_::Func(args, ret) => {
+        let args = args
+          .into_iter()
+          .map(|arg| arg.convert(assignments))
+          .collect::<Result<_>>()?;
+        let ret = ret.convert(assignments)?;
+        Type::Func(args, Box::new(ret))
+      }
+    })
+  }
+}
+
+impl Op {
+  fn constraints(
+    &self,
+    ctx: &mut AnnotationContext,
+    left: &Type_,
+    right: &Type_,
+    output: &Type_,
+  ) {
+    match self {
+      Op::LessThan | Op::GreaterThan => {
+        ctx.constrain(left.clone(), Type_::Int);
+        ctx.constrain(right.clone(), Type_::Int);
+        ctx.constrain(output.clone(), Type_::Bool);
+      }
+    }
+  }
+}
+
+#[derive(Debug, Hash, Eq, PartialEq)]
+struct Constraint(Type_, Type_);
+
+#[derive(Default)]
+struct Env {
+  parent: Option<Box<Env>>,
+  local_type_map: HashMap<String, Type_>,
+}
+
+impl Env {
+  pub fn lookup(&self, name: impl AsRef<str>) -> Option<&Type_> {
+    match self.local_type_map.get(name.as_ref()) {
+      Some(v) => Some(v),
+      None => match &self.parent {
+        Some(p) => p.lookup(name),
+        None => None,
+      },
+    }
+  }
+}
+
+struct AnnotationContext<'a> {
+  counter: usize,
+  constraints: &'a mut HashSet<Constraint>,
+  current_env: Option<Env>,
+}
+
+impl<'a> AnnotationContext<'a> {
+  pub fn type_var(&mut self) -> Type_ {
+    Type_::Var(self.gen_int())
+  }
+
+  pub fn gen_int(&mut self) -> usize {
+    let id = self.counter;
+    self.counter += 1;
+    id
+  }
+
+  pub fn constrain(&mut self, left: Type_, right: Type_) {
+    if left == right {
+      // No op, return now
+      return;
+    }
+    self.constraints.insert(Constraint(left, right));
+  }
+
+  pub fn lookup(&self, name: impl AsRef<str>) -> Option<&Type_> {
+    self.current_env.as_ref().unwrap().lookup(name)
+  }
+
+  pub fn define_var(&mut self, name: impl AsRef<str>, ty: Type_) {
+    self
+      .current_env
+      .as_mut()
+      .unwrap()
+      .local_type_map
+      .insert(name.as_ref().to_string(), ty);
+  }
+
+  pub fn push_scope(&mut self) {
+    self.current_env = Some(Env {
+      parent: Some(Box::new(self.current_env.take().unwrap())),
+      local_type_map: Default::default(),
+    });
+  }
+
+  pub fn pop_scope(&mut self) {
+    self.current_env =
+      Some(*self.current_env.take().unwrap().parent.take().unwrap());
+  }
+}
+
+fn annotate_stmts(
+  ctx: &mut AnnotationContext,
+  stmts: impl AsRef<[Stmt<()>]>,
+) -> Vec<Stmt<Type_>> {
+  let stmts = stmts.as_ref();
+  let mut new_stmts = Vec::new();
+  ctx.push_scope();
+
+  for stmt in stmts.iter() {
+    match stmt {
+      Stmt::Return(ret_val) => {
+        let new_stmt =
+          Stmt::Return(ret_val.as_ref().map(|expr| annotate_expr(ctx, expr)));
+        new_stmts.push(new_stmt);
+      }
+
+      Stmt::Let(name, ty, body) => {
+        let new_stmt =
+          Stmt::Let(name.clone(), ty.clone(), annotate_expr(ctx, body));
+        let ty = match ty {
+          Some(v) => Type_::from_type(v.clone()),
+          None => ctx.type_var(),
+        };
+        ctx.define_var(name, ty);
+        new_stmts.push(new_stmt);
+      }
+
+      Stmt::IfElse(if_else) => {
+        let new_stmt = Stmt::IfElse(annotate_if_else(ctx, &if_else));
+        new_stmts.push(new_stmt);
+      }
+    }
+  }
+
+  ctx.pop_scope();
+  new_stmts
+}
+
+fn annotate_expr(ctx: &mut AnnotationContext, expr: &Expr<()>) -> Expr<Type_> {
+  match &expr.kind {
+    ExprKind::Int(n) => Expr {
+      kind: ExprKind::Int(*n),
+      ty: Type_::Int,
+    },
+
+    ExprKind::Var(name) => {
+      let ty = match ctx.lookup(name) {
+        Some(v) => v.clone(),
+        None => ctx.type_var(),
+      };
+      Expr {
+        kind: ExprKind::Var(name.clone()),
+        ty,
+      }
+    }
+
+    ExprKind::BinOp(left, op, right) => {
+      let left = annotate_expr(ctx, left);
+      let right = annotate_expr(ctx, right);
+      let output = ctx.type_var();
+
+      op.constraints(ctx, &left.ty, &right.ty, &output);
+
+      Expr {
+        kind: ExprKind::BinOp(Box::new(left), *op, Box::new(right)),
+        ty: output,
+      }
+    }
+  }
+}
+
+fn annotate_if_else(
+  ctx: &mut AnnotationContext,
+  if_else: &IfElse<()>,
+) -> IfElse<Type_> {
+  let converted_cond = annotate_expr(ctx, &if_else.cond);
+  let converted_body = annotate_stmts(ctx, &if_else.body);
+
+  let else_clause = match &if_else.else_clause {
+    Some(ElseClause::If(if_else2)) => {
+      Some(ElseClause::If(Box::new(annotate_if_else(ctx, &if_else2))))
+    }
+    Some(ElseClause::Body(stmts)) => {
+      Some(ElseClause::Body(annotate_stmts(ctx, &stmts)))
+    }
+    None => None,
+  };
+
+  IfElse {
+    cond: converted_cond,
+    body: converted_body,
+    else_clause,
+  }
+}
+
+fn collect_info(func: &Func<()>) -> (Func<Type_>, HashSet<Constraint>) {
+  let mut constraints = HashSet::new();
+  let mut ctx = AnnotationContext {
+    counter: 0,
+    constraints: &mut constraints,
+    current_env: Some(Env::default()),
+  };
+  let new_stmts = annotate_stmts(&mut ctx, &func.stmts);
+
+  let func = Func {
+    name: func.name.clone(),
+    return_ty: func.return_ty.clone(),
+    stmts: new_stmts,
+  };
+
+  (func, constraints)
+}
+
+type Assignments = HashMap<usize, Type_>;
+
+fn substitute_types(assignments: &Assignments, ty: &Type_) -> Type_ {
+  match ty {
+    Type_::Var(n) => match assignments.get(&n) {
+      Some(ty2) => ty2.clone(),
+      None => ty.clone(),
+    },
+    Type_::Func(args, ret) => {
+      let args = args
+        .into_iter()
+        .map(|arg| substitute_types(assignments, arg))
+        .collect();
+      let ret = substitute_types(assignments, &*ret);
+      Type_::Func(args, Box::new(ret))
+    }
+    Type_::Int | Type_::Bool => ty.clone(),
+  }
+}
+
+fn unify_constraints(constraints: &HashSet<Constraint>) -> Result<Assignments> {
+  let mut assignments = HashMap::new();
+
+  for Constraint(left, right) in constraints {
+    let left = substitute_types(&assignments, left);
+    let right = substitute_types(&assignments, right);
+    unify_single(&mut assignments, left, right)?;
+  }
+
+  Ok(assignments)
+}
+
+fn unify_single(
+  assignments: &mut Assignments,
+  left: Type_,
+  right: Type_,
+) -> Result<()> {
+  match (left, right) {
+    (Type_::Int, Type_::Int) | (Type_::Bool, Type_::Bool) => {}
+
+    (Type_::Var(n), o) | (o, Type_::Var(n)) => {
+      assignments.insert(n, o);
+    }
+
+    (Type_::Func(left_args, left_ret), Type_::Func(right_args, right_ret)) => {
+      let mut new_constraints = HashSet::new();
+      for (left_arg, right_arg) in
+        left_args.into_iter().zip(right_args.into_iter())
+      {
+        new_constraints.insert(Constraint(left_arg, right_arg));
+      }
+      new_constraints.insert(Constraint(*left_ret, *right_ret));
+      assignments.extend(unify_constraints(&new_constraints)?);
+    }
+
+    (left, right) => bail!("Mismatching types {left:?} vs. {right:?}"),
+  };
+
+  Ok(())
+}
+
+fn substitute_in_expr_kind(
+  assignments: &Assignments,
+  expr_kind: ExprKind<Type_>,
+) -> Result<ExprKind<Type>> {
+  Ok(match expr_kind {
+    ExprKind::Int(n) => ExprKind::Int(n),
+    ExprKind::Var(name) => ExprKind::Var(name),
+    ExprKind::BinOp(left, op, right) => {
+      let left = substitute_in_expr(assignments, *left)?;
+      let right = substitute_in_expr(assignments, *right)?;
+      ExprKind::BinOp(Box::new(left), op, Box::new(right))
+    }
+  })
+}
+
+fn substitute_in_expr(
+  assignments: &Assignments,
+  expr: Expr<Type_>,
+) -> Result<Expr<Type>> {
+  Ok(Expr {
+    kind: substitute_in_expr_kind(assignments, expr.kind)?,
+    ty: expr.ty.convert(assignments)?,
+  })
+}
+
+fn substitute_in_if_else(
+  assignments: &Assignments,
+  if_else: IfElse<Type_>,
+) -> Result<IfElse<Type>> {
+  let cond = substitute_in_expr(assignments, if_else.cond)?;
+  let body = substitute_in_stmts(assignments, if_else.body)?;
+
+  let else_clause = match if_else.else_clause {
+    Some(ElseClause::If(if_else2)) => Some(ElseClause::If(Box::new(
+      substitute_in_if_else(assignments, *if_else2)?,
+    ))),
+    Some(ElseClause::Body(body)) => {
+      Some(ElseClause::Body(substitute_in_stmts(assignments, body)?))
+    }
+    None => None,
+  };
+
+  Ok(IfElse {
+    cond,
+    body,
+    else_clause,
+  })
+}
+
+fn substitute_in_stmts(
+  assignments: &Assignments,
+  stmts: Vec<Stmt<Type_>>,
+) -> Result<Vec<Stmt<Type>>> {
+  stmts
+    .into_iter()
+    .map(|stmt| {
+      Ok(match stmt {
+        Stmt::Let(name, ty, body) => {
+          Stmt::Let(name, ty, substitute_in_expr(assignments, body)?)
+        }
+
+        Stmt::Return(ret_val) => Stmt::Return(match ret_val {
+          Some(v) => Some(substitute_in_expr(assignments, v)?),
+          None => None,
+        }),
+
+        Stmt::IfElse(if_else) => {
+          Stmt::IfElse(substitute_in_if_else(assignments, if_else)?)
+        }
+      })
+    })
+    .collect()
+}
+
+fn substitute_in_func(
+  assignments: &Assignments,
+  func: Func<Type_>,
+) -> Result<Func<Type>> {
+  Ok(Func {
+    name: func.name,
+    return_ty: func.return_ty,
+    stmts: substitute_in_stmts(assignments, func.stmts)?,
+  })
+}
+
+pub fn convert(ast: Vec<Decl<()>>) -> Result<Vec<Decl<Type>>> {
+  // First pass, gather all of the type signatures in the top level
+  let mut top_level_signatures = HashMap::new();
+  for decl in ast.iter() {
+    match decl {
+      super::Decl::Func(func) => {
+        let name = func.name.clone();
+        let ty = Type::Func(Vec::new(), Box::new(func.return_ty.clone()));
+        top_level_signatures.insert(name, ty);
+      }
+    }
+  }
+
+  // Now, type-check each function separately
+  let mut new_decl = Vec::new();
+  for decl in ast.iter() {
+    match decl {
+      Decl::Func(func) => {
+        let (decorated_func, constraints) = collect_info(func);
+        println!("func: {:?}", decorated_func);
+        println!("constraints: {:?}", constraints);
+
+        let assignments = unify_constraints(&constraints)?;
+        println!("assignments: {:?}", assignments);
+
+        let typed_func = substitute_in_func(&assignments, decorated_func)?;
+        println!("typed: {:?}", typed_func);
+        new_decl.push(Decl::Func(typed_func));
+      }
+    }
+  }
+
+  Ok(new_decl)
+}

src/main.rs

@@ -6,6 +6,7 @@ extern crate anyhow;
 lalrpop_mod!(parser);
 
 mod ast;
+mod utils;
 
 use std::fs::{self, File};
 use std::path::PathBuf;
@@ -32,14 +33,16 @@ struct Opt {
 fn main() -> Result<()> {
   let opts = Opt::parse();
 
-  let contents = fs::read_to_string(opts.path)?;
+  let contents = fs::read_to_string(&opts.path)?;
 
   let parser = ProgramParser::new();
   let ast = parser.parse(&contents).unwrap();
-  println!("AST: {ast:?}");
 
-  let mut context = Context::create();
-  let module = ast::llvm::convert(&mut context, ast)?;
+  let typed_ast = ast::typed::convert(ast)?;
+
+  let context = Context::create();
+  let module =
+    ast::llvm::convert(opts.path.display().to_string(), &context, typed_ast)?;
 
   {
     let file = File::create(&opts.out_path)?;

src/parser.lalrpop

@@ -2,31 +2,57 @@ use crate::ast::*;
 
 grammar;
 
-pub Program: Vec<Decl> = Decl* => <>;
+pub Program: Vec<Decl<()>> = Decl* => <>;
 
-Decl: Decl = {
+Decl: Decl<()> = {
   Func => Decl::Func(<>),
 };
 
-Func: Func = {
+Func: Func<()> = {
   "fn" <name:Ident> "(" ")" "->" <return_ty:Type> "{" <stmts:Stmt*> "}" =>
     Func { name, return_ty, stmts },
 };
 
-Stmt: Stmt = {
-  "let" <name:Ident> ":" <ty:Type> "=" <expr:Expr> ";" =>
+Stmt: Stmt<()> = {
+  "let" <name:Ident> <ty:ColonType?> "=" <expr:Expr> ";" =>
     Stmt::Let(name, ty, expr),
   "return" <expr:Expr?> ";" => Stmt::Return(expr),
+  IfElse => Stmt::IfElse(<>),
 };
 
-Expr: Expr = {
-  Expr1 => <>,
+ColonType: Type = ":" <ty:Type> => ty;
+
+IfElse: IfElse<()> =
+  "if" <cond:Expr> "{" <body:Stmt*> "}" <else_clause:Else?> =>
+    IfElse { cond, body, else_clause };
+
+Else: ElseClause<()> = "else" <else_clause:Else_> => else_clause;
+Else_: ElseClause<()> = {
+  IfElse => ElseClause::If(Box::new(<>)),
+  "{" <body:Stmt*> "}" => ElseClause::Body(body),
 };
 
-Expr1: Expr = {
-  r"[0-9]+" => Expr::Int(<>.parse::<i64>().unwrap()),
-  Ident => Expr::Var(<>),
+Expr: Expr<()> = {
+  #[precedence(level = "0")]
   "(" <expr:Expr> ")" => expr,
+
+  #[precedence(level = "0")]
+  r"[0-9]+" => Expr { kind: ExprKind::Int(<>.parse::<i64>().unwrap()), ty: () },
+
+  #[precedence(level = "0")]
+  Ident => Expr { kind: ExprKind::Var(<>), ty: () },
+
+  #[precedence(level = "13")]
+  #[assoc(side = "none")]
+  <left:Expr> <op:CompareOp> <right:Expr> => Expr {
+    kind: ExprKind::BinOp(Box::new(left), op, Box::new(right)),
+    ty: (),
+  },
+};
+
+CompareOp: Op = {
+  "<" => Op::LessThan,
+  ">" => Op::GreaterThan,
 };
 
 Type: Type = {

src/utils.rs

@@ -0,0 +1 @@
+// TODO: put layered environment here?