fix: let

nix-js/src/codegen.rs

@@ -194,11 +194,18 @@ impl<Ctx: CodegenContext> Compile<Ctx> for Let {
                 for &expr in scc_exprs {
                     let ir = ctx.get_ir(expr);
                     let value = if let Ir::Thunk(inner) = ir {
-                        ctx.get_ir(*inner).compile(ctx)
+                        let inner_ir = ctx.get_ir(*inner);
+                        // Don't unwrap Thunk if inner is a Let expression
+                        // to avoid generating IIFE that executes immediately
+                        if matches!(inner_ir, Ir::Let(_)) {
+                            ir.compile(ctx)
+                        } else {
+                            inner_ir.compile(ctx)
+                        }
                     } else {
                         ir.compile(ctx)
                     };
-                    js_statements.push(format!("let expr{}={}", expr.0, value));
+                    js_statements.push(format!("const expr{}={}", expr.0, value));
                 }
             }
         }