From de83eb6fcdda458f0ec159e03d94fc55355b1e09 Mon Sep 17 00:00:00 2001
From: Dustin Swan <dustin@dustinswan.com>
Date: Thu, 26 Mar 2026 20:01:06 -0600
Subject: [PATCH] More type checking

---
 src/cg/01-stdlib.cg |  5 +++++
 src/typechecker.ts  | 17 +++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/cg/01-stdlib.cg b/src/cg/01-stdlib.cg
index d4cd726..9e68ca6 100644
--- a/src/cg/01-stdlib.cg
+++ b/src/cg/01-stdlib.cg
@@ -1,3 +1,8 @@
+point : Int \ Int \ { x : Int, y : Int } = x y \ { x = x, y = y };
+getX : { x : Int, y : Int } \ Int = p \ p.x;
+setX : Int \ { x : Int, y : Int } \ { x : Int, y : Int } = newX p \ p.{ x = newX };
+myPoint = point 3 "a";
+
 # builtins
 # TODO: once we get typeclasses, make these the actual types
 cat : a \ a \ a;
diff --git a/src/typechecker.ts b/src/typechecker.ts
index 9f97ff7..da00fe0 100644
--- a/src/typechecker.ts
+++ b/src/typechecker.ts
@@ -127,6 +127,23 @@ function infer(expr: AST, env: TypeEnv, subst: Subst): TypeAST | null {
             return null;
         }
 
+        case 'record-update': {
+            const recType = infer(expr.record, env, subst);
+            if (!recType) return null;
+            const resolved = applySubst(recType, subst);
+            if (resolved.kind !== 'type-record') return null;
+
+            for (const [key, value] of Object.entries(expr.updates)) {
+                const field = resolved.fields.find(f => f.name === key);
+                if (field) {
+                    const err = check(value, field.type, env, subst);
+                    if (err) warn(err, value);
+                }
+            }
+
+            return resolved;
+        }
+
         case 'apply': {
             const funcType = infer(expr.func, env, subst);
             if (!funcType) return null;