Use small integer repr for gen_program! enum

Remove the default __FallBack variant and Debug derive from pack types.

4 files changed, 25 insertions, 10 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7ba069e..eb30d4b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@
 1. Fixed a build failure on **Windows** caused by `mingling_core/src/program.rs`
 2. **\[picker\]** Fixed an issue where the `Pickable` trait for `Yes` and `True` types could not correctly parse explicit boolean `--value true`
 
+#### Optimizings:
+
+1. **\[macros\]** Optimized the memory usage of the `gen_program!()` macro: the internal generated enum now uses the smallest possible integer representation (`u8`, `u16`, `u32`, or `u128`) based on the number of packed types, instead of always using `u32`.
+
 #### Features:
 
 1. **\[mingling\]** Added the scaffolding tool `mling`, which can quickly deploy and test your command-line programs
@@ -164,6 +168,10 @@ let (name, age) = Picker::new(prev.inner)
     .unpack(); // will return Result<Value, Route>
 ```
 
+7. **\[macros\]** The enum generated by `gen_program!()` no longer has a default variant (`__FallBack`), and the `#[default]` attribute has been removed accordingly.
+
+8. **\[macros\]** Removed `#[derive(Debug)]` from generated pack types to remove unnecessary trait bounds.
+
 ---
 
 ### Release 0.1.6 **\[YANKED\]**
diff --git a/dev_tools/src/bin/docsify-sidebar-gen.rs b/dev_tools/src/bin/docsify-sidebar-gen.rs
index 9020ca4..a525283 100644
--- a/dev_tools/src/bin/docsify-sidebar-gen.rs
+++ b/dev_tools/src/bin/docsify-sidebar-gen.rs
@@ -31,10 +31,10 @@ fn gen_sidebar() {
                 if !entries.is_empty() {
                     sub_dirs.insert(dir_name, entries);
                 }
-            } else if path.extension().map_or(false, |ext| ext == "md") {
+            } else if path.extension().is_some_and(|ext| ext == "md") {
                 let title = extract_title(&path);
                 let relative = path
-                    .strip_prefix(&repo_root.join("docs"))
+                    .strip_prefix(repo_root.join("docs"))
                     .unwrap()
                     .to_string_lossy()
                     .replace('\\', "/");
@@ -87,7 +87,7 @@ fn collect_markdown_files(dir: &Path) -> Vec<SidebarEntry> {
     if let Ok(read_dir) = std::fs::read_dir(dir) {
         for entry in read_dir.flatten() {
             let path = entry.path();
-            if path.extension().map_or(false, |ext| ext == "md") {
+            if path.extension().is_some_and(|ext| ext == "md") {
                 let title = extract_title(&path);
                 let relative = path
                     .strip_prefix(&docs_root)
diff --git a/mingling_macros/src/lib.rs b/mingling_macros/src/lib.rs
index 8ba028b..a8b3b15 100644
--- a/mingling_macros/src/lib.rs
+++ b/mingling_macros/src/lib.rs
@@ -346,19 +346,27 @@ pub fn program_final_gen(input: TokenStream) -> TokenStream {
         .map(|s| syn::parse_str::<proc_macro2::TokenStream>(s).unwrap())
         .collect();
 
+    let num_variants = packed_types.len();
+    let repr_type = if num_variants <= u8::MAX as usize {
+        quote! { u8 }
+    } else if num_variants <= u16::MAX as usize {
+        quote! { u16 }
+    } else if num_variants <= u32::MAX as usize {
+        quote! { u32 }
+    } else {
+        quote! { u128 }
+    };
+
     let expanded = quote! {
-        #[derive(Debug, Default, PartialEq, Eq, Clone)]
-        #[repr(u32)]
+        #[derive(Debug, PartialEq, Eq, Clone)]
+        #[repr(#repr_type)]
         pub enum #name {
-            #[default]
-            __FallBack,
             #(#packed_types),*
         }
 
         impl ::std::fmt::Display for #name {
             fn fmt(&self, f: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
                 match self {
-                    #name::__FallBack => write!(f, "__FallBack"),
                     #(#name::#packed_types => write!(f, stringify!(#packed_types)),)*
                 }
             }
diff --git a/mingling_macros/src/pack.rs b/mingling_macros/src/pack.rs
index 9da16de..f7bdfe3 100644
--- a/mingling_macros/src/pack.rs
+++ b/mingling_macros/src/pack.rs
@@ -79,7 +79,6 @@ pub fn pack(input: TokenStream) -> TokenStream {
     // Generate the struct definition
     #[cfg(not(feature = "general_renderer"))]
     let struct_def = quote! {
-        #[derive(Debug)]
         pub struct #type_name {
             pub(crate) inner: #inner_type,
         }
@@ -87,7 +86,7 @@ pub fn pack(input: TokenStream) -> TokenStream {
 
     #[cfg(feature = "general_renderer")]
     let struct_def = quote! {
-        #[derive(Debug, serde::Serialize)]
+        #[derive(serde::Serialize)]
         pub struct #type_name {
             pub(crate) inner: #inner_type,
         }