From 221beea478b7bd30762b5ed15ae15ea756b6d783 Mon Sep 17 00:00:00 2001
From: Michael Zhang <mail@mzhang.io>
Date: Sun, 17 Jul 2022 21:13:09 -0500
Subject: [PATCH] Variables

---
 src/codegen/llvm_ir/expr.rs  | 11 ++++++++---
 src/codegen/llvm_ir/mod.rs   |  6 +++---
 src/codegen/llvm_ir/stmts.rs |  9 ++++++++-
 src/utils.rs                 |  8 +++++++-
 4 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/src/codegen/llvm_ir/expr.rs b/src/codegen/llvm_ir/expr.rs
index da1de0e..efa0830 100644
--- a/src/codegen/llvm_ir/expr.rs
+++ b/src/codegen/llvm_ir/expr.rs
@@ -19,11 +19,11 @@ impl<W: Write> LlvmIrCodegen<W> {
     &mut self,
     expr: &'a Expr<Type>,
   ) -> Result<ExprLlvm<'a>> {
-    let expr_id = self.gensym("expr");
+    let ty_str = type_to_llvm(&expr.ty);
+    let mut expr_id = self.gensym("expr");
 
     match &expr.kind {
       ExprKind::Int(n) => {
-        let ty_str = type_to_llvm(&expr.ty);
         writeln!(self.writer, "%{} = alloca {}", expr_id, ty_str)?;
         writeln!(
           self.writer,
@@ -31,7 +31,12 @@ impl<W: Write> LlvmIrCodegen<W> {
           ty_str, n, ty_str, expr_id
         )?;
       }
-      ExprKind::Var(_) => todo!(),
+      ExprKind::Var(name) => match self.var_env.lookup(name) {
+        Some((_, name)) => {
+          expr_id = name.clone();
+        }
+        None => bail!("Unbound name {name:?}"),
+      },
       ExprKind::BinOp(_, _, _) => todo!(),
       ExprKind::Call(_, _) => todo!(),
     }
diff --git a/src/codegen/llvm_ir/mod.rs b/src/codegen/llvm_ir/mod.rs
index 6bab4a5..52a0909 100644
--- a/src/codegen/llvm_ir/mod.rs
+++ b/src/codegen/llvm_ir/mod.rs
@@ -13,16 +13,16 @@ use super::CodegenBackend;
 
 pub struct LlvmIrCodegen<W> {
   ctr: usize,
-  env: LayeredEnv<String, ()>,
+  var_env: LayeredEnv<String, (Type, String)>,
   writer: W,
 }
 
 impl<W> LlvmIrCodegen<W> {
   pub fn new(writer: W) -> Self {
-    let env = LayeredEnv::default();
+    let env = LayeredEnv::new();
     LlvmIrCodegen {
       ctr: 0,
-      env,
+      var_env: env,
       writer,
     }
   }
diff --git a/src/codegen/llvm_ir/stmts.rs b/src/codegen/llvm_ir/stmts.rs
index 3bc1f99..5126f48 100644
--- a/src/codegen/llvm_ir/stmts.rs
+++ b/src/codegen/llvm_ir/stmts.rs
@@ -15,7 +15,14 @@ impl<W: Write> LlvmIrCodegen<W> {
 
     for stmt in stmts.iter() {
       match stmt {
-        Stmt::Let(_, _, _) => todo!(),
+        Stmt::Let(name, _, expr) => {
+          let ty = expr.ty.clone();
+          let expr = self.convert_expr(&expr)?;
+          let new_name = expr.name().to_owned();
+
+          // TODO:
+          self.var_env.insert(name.clone(), (ty, new_name));
+        }
         Stmt::Return(expr) => match expr {
           Some(ret_val) => {
             let ret_ty = type_to_llvm(&ret_val.ty);
diff --git a/src/utils.rs b/src/utils.rs
index 6e9baa2..805d500 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -1,13 +1,19 @@
 use std::collections::HashMap;
 use std::hash::Hash;
 
-#[derive(Default)]
 pub struct LayeredEnv<K, V> {
   parent: Option<Box<LayeredEnv<K, V>>>,
   inner_map: HashMap<K, V>,
 }
 
 impl<K: Hash + Eq, V> LayeredEnv<K, V> {
+  pub fn new() -> Self {
+    LayeredEnv {
+      parent: None,
+      inner_map: HashMap::new(),
+    }
+  }
+
   pub fn insert(&mut self, key: K, value: V) {
     self.inner_map.insert(key, value);
   }