From efcb4e368509e3c7e84b2fc7a43fb9fc26016b67 Mon Sep 17 00:00:00 2001
From: Michael Schimmel <schimmel@mycelium.de>
Date: Tue, 10 Mar 2026 20:25:04 +0100
Subject: [PATCH] feat: Add stack size to runtime metadata

Store the pre-calculated stack size of lambda bodies in the
RuntimeMetadata. This allows the VM to directly access this information
without recalculating it.
---
 src/ast/compiler/tco.rs | 13 +++++++++++++
 src/ast/vm.rs           |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/ast/compiler/tco.rs b/src/ast/compiler/tco.rs
index b362cca..71aac68 100644
--- a/src/ast/compiler/tco.rs
+++ b/src/ast/compiler/tco.rs
@@ -10,6 +10,7 @@ pub struct RuntimeMetadata {
     pub is_tail: bool,
     /// The analyzed node, containing metrics and a link to the original TypedNode.
     pub original: Rc<AnalyzedNode>,
+    pub stack_size: u32,
 }
 
 impl Debug for RuntimeMetadata {
@@ -17,6 +18,7 @@ impl Debug for RuntimeMetadata {
         f.debug_struct("Metadata")
             .field("ty", &self.ty)
             .field("is_tail", &self.is_tail)
+            .field("stack_size", &self.stack_size)
             .finish()
     }
 }
@@ -174,6 +176,16 @@ impl TCO {
             BoundKind::Error => BoundKind::Error,
         };
 
+        let stack_size = match &new_kind {
+            BoundKind::Lambda { .. } => {
+                // Pre-calculate stack size for the lambda body.
+                // Note: 'node' here is AnalyzedNode (Node<BoundKind<NodeMetrics>, NodeMetrics>)
+                // 'calculate_stack_size' works for any T.
+                node.calculate_stack_size()
+            }
+            _ => 0,
+        };
+
         Node {
             identity: node.identity.clone(),
             kind: new_kind,
@@ -181,6 +193,7 @@ impl TCO {
                 ty: node.ty.original.ty.clone(),
                 is_tail: is_tail_position,
                 original: node_rc,
+                stack_size,
             },
         }
     }
diff --git a/src/ast/vm.rs b/src/ast/vm.rs
index 06aab04..30e0f93 100644
--- a/src/ast/vm.rs
+++ b/src/ast/vm.rs
@@ -508,7 +508,7 @@ impl VM {
                 for addr in upvalues {
                     captured.push(self.capture_upvalue(*addr)?);
                 }
-                let stack_size = body.calculate_stack_size();
+                let stack_size = node.ty.stack_size;
                 let closure = Closure::new(
                     params.ty.original.clone(),
                     body.ty.original.clone(),