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/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());
                     }
                 }