Refactor AST substitution logic

This commit refactors the AST substitution logic to correctly handle
nested expansions and improve the inlining of lambda expressions.

The changes include:
- Extracting the core value from potentially expanded AST nodes before
  checking their kind.
- Ensuring that lambda expressions with empty upvalues are correctly
  substituted.
- Adding support for inlining global get expressions as AST
  substitutions.
- Improving the `UsageInfo` collection to correctly track assigned
  values.

src/ast/compiler/optimizer/engine.rs

@@ -504,17 +504,29 @@ impl Optimizer {
                         }
                     }
 
+                    let unmapped_addr = if let BoundKind::Define { addr, .. } = &e.kind {
+                        Some(*addr)
+                    } else {
+                        None
+                    };
+
                     let opt = self.visit_node(e.clone(), sub, path);
                     
-                    if let BoundKind::Define { addr, value, .. } = &opt.kind
-                        && !info.assigned.contains(addr)
+                    if let BoundKind::Define { value, .. } = &opt.kind
+                        && let Some(orig_addr) = unmapped_addr
+                        && !info.assigned.contains(&orig_addr)
                     {
-                        if let BoundKind::Constant(val) = &value.kind {
-                            sub.add_value(*addr, val.clone());
-                        } else if let BoundKind::Lambda { upvalues, .. } = &value.kind
+                        let mut core_value = value.as_ref();
+                        while let BoundKind::Expansion { bound_expanded, .. } = &core_value.kind {
+                            core_value = bound_expanded.as_ref();
+                        }
+
+                        if let BoundKind::Constant(val) = &core_value.kind {
+                            sub.add_value(orig_addr, val.clone());
+                        } else if let BoundKind::Lambda { upvalues, .. } = &core_value.kind
                             && upvalues.is_empty()
                         {
-                            sub.add_ast_substitution(*addr, (**value).clone());
+                            sub.add_ast_substitution(orig_addr, core_value.clone());
                         }
                     }
 
@@ -560,10 +572,13 @@ impl Optimizer {
 
                 for (old_idx, capture_addr) in upvalues.iter().enumerate() {
                     let mut inlined_val = None;
-                    if !sub.assigned.contains(capture_addr)
-                        && let Some(val) = sub.get_value(capture_addr)
-                    {
-                        inlined_val = Some(val.clone());
+                    let mut inlined_ast = None;
+                    if !sub.assigned.contains(capture_addr) {
+                        if let Some(val) = sub.get_value(capture_addr) {
+                            inlined_val = Some(val.clone());
+                        } else if let Some(ast) = sub.ast_substitutions.get(capture_addr) {
+                            inlined_ast = Some(Rc::clone(ast));
+                        }
                     }
 
                     if let Address::Local(slot) = capture_addr {
@@ -575,6 +590,11 @@ impl Optimizer {
                             .add_value(Address::Upvalue(UpvalueIdx(old_idx as u32)), val);
                         mapping.push(None);
                         upvalues_changed = true;
+                    } else if let Some(ast) = inlined_ast {
+                        next_inner_subs
+                            .add_ast_substitution(Address::Upvalue(UpvalueIdx(old_idx as u32)), (*ast).clone());
+                        mapping.push(None);
+                        upvalues_changed = true;
                     } else {
                         mapping.push(Some(new_upvalues.len() as u32));
                         let mapped = sub.map_address(*capture_addr);

src/ast/compiler/optimizer/inliner.rs

@@ -112,18 +112,23 @@ impl<'a> Inliner<'a> {
                 if let Some(arg) = args.get(*offset)
                     && !body_usage.is_assigned(addr)
                 {
-                    if let BoundKind::Constant(val) = &arg.kind {
+                    let mut core_arg = arg.as_ref();
+                    while let BoundKind::Expansion { bound_expanded, .. } = &core_arg.kind {
+                        core_arg = bound_expanded.as_ref();
+                    }
+
+                    if let BoundKind::Constant(val) = &core_arg.kind {
                         sub.add_value(*addr, val.clone());
-                    } else if let BoundKind::Lambda { upvalues, .. } = &arg.kind
+                    } else if let BoundKind::Lambda { upvalues, .. } = &core_arg.kind
                         && upvalues.is_empty()
                     {
-                        sub.add_ast_substitution(*addr, (**arg).clone());
+                        sub.add_ast_substitution(*addr, core_arg.clone());
                     } else if let BoundKind::Get {
                         addr: Address::Global(_),
                         ..
-                    } = &arg.kind
+                    } = &core_arg.kind
                     {
-                        sub.add_ast_substitution(*addr, (**arg).clone());
+                        sub.add_ast_substitution(*addr, core_arg.clone());
                     }
                 }
 

src/ast/compiler/optimizer/utils.rs

@@ -143,8 +143,7 @@ impl UsageInfo {
                     self.collect(v);
                 }
             }
-            BoundKind::Define { addr, value, .. } => {
-                self.assigned.insert(*addr);
+            BoundKind::Define { value, .. } => {
                 self.collect(value);
             }
             BoundKind::Expansion { bound_expanded, .. } => {