READY: Attribute macros phantom implementation

module/core/derive_tools/Cargo.toml

@@ -72,6 +72,8 @@ default = [
   "derive_inner_from",
   "derive_new",
 
+  "derive_phantom"
+
   # "use_std",
 ]
 
@@ -117,6 +119,8 @@ full = [
   "derive_inner_from",
   "derive_new",
 
+  "derive_phantom"
+
   # "use_std",
 ]
 no_std = []
@@ -177,6 +181,8 @@ derive_from = [ "derive_tools_meta/derive_from" ]
 derive_inner_from = [ "derive_tools_meta/derive_inner_from" ]
 derive_new = [ "derive_tools_meta/derive_new" ]
 
+derive_phantom = [ "derive_tools_meta/derive_phantom" ]
+
 parse_display = [ "parse-display" ]
 
 

module/core/derive_tools/tests/inc/mod.rs

@@ -31,6 +31,7 @@ mod all_manual_test;
 		feature = "derive_deref_mut",
 		feature = "derive_from",
 		feature = "derive_inner_from",
+        feature = "derive_phantom"
 	)
 )]
 mod all_test;
@@ -252,3 +253,16 @@ mod inner_from_tests
 	mod multiple_unnamed_test;
 
 }
+
+#[ cfg( feature = "derive_phantom" ) ]
+#[ path = "phantom" ]
+mod phantom_tests
+{
+  #[ allow( unused_imports ) ]
+  use super::*;
+
+  mod struct_named;
+  mod struct_named_manual;
+  mod struct_tuple;
+  mod struct_tuple_manual;
+}

module/core/derive_tools/tests/inc/phantom/only_test/struct_named.rs

@@ -0,0 +1,5 @@
+#[ test ]
+fn phantom()
+{
+  let _ = StructNamed::< bool >{ a : "boo".into(), b : 3, _phantom: Default::default() };
+}

module/core/derive_tools/tests/inc/phantom/only_test/struct_tuple.rs

@@ -0,0 +1,5 @@
+#[ test ]
+fn phantom()
+{
+  let _ = StructTuple::< bool >( "boo".into(), 3, Default::default() );
+}

module/core/derive_tools/tests/inc/phantom/struct_named.rs

@@ -0,0 +1,11 @@
+use super::*;
+
+#[ allow( dead_code ) ]
+#[ the_module::phantom ]
+struct StructNamed< T >
+{
+  a : String,
+  b : i32,
+}
+
+include!( "./only_test/struct_named.rs" );

module/core/derive_tools/tests/inc/phantom/struct_named_manual.rs

@@ -0,0 +1,12 @@
+use super::*;
+use std::marker::PhantomData;
+
+#[ allow( dead_code ) ]
+struct StructNamed< T >
+{
+  a : String,
+  b : i32,
+  _phantom : PhantomData< T >,
+}
+
+include!( "./only_test/struct_named.rs" );

module/core/derive_tools/tests/inc/phantom/struct_tuple.rs

@@ -0,0 +1,7 @@
+use super::*;
+
+#[ allow( dead_code ) ]
+#[ the_module::phantom ]
+struct StructTuple< T >( String, i32 );
+
+include!( "./only_test/struct_tuple.rs" );

module/core/derive_tools/tests/inc/phantom/struct_tuple_manual.rs

@@ -0,0 +1,7 @@
+use std::marker::PhantomData;
+use super::*;
+
+#[ allow( dead_code ) ]
+struct StructTuple< T >( String, i32, PhantomData< T > );
+
+include!( "./only_test/struct_tuple.rs" );

module/core/derive_tools_meta/Cargo.toml

@@ -40,6 +40,7 @@ default = [
   "derive_as_ref",
   "derive_as_mut",
   "derive_variadic_from",
+  "derive_phantom"
 ]
 full = [
   "enabled",
@@ -51,6 +52,7 @@ full = [
   "derive_as_ref",
   "derive_as_mut",
   "derive_variadic_from",
+  "derive_phantom"
 ]
 enabled = [ "macro_tools/enabled", "iter_tools/enabled", "former_types/enabled" ]
 
@@ -62,6 +64,7 @@ derive_from = []
 derive_new = []
 derive_inner_from = []
 derive_variadic_from = []
+derive_phantom = []
 
 [dependencies]
 # zzz : qqq : optimize features set

module/core/derive_tools_meta/src/derive.rs

@@ -26,3 +26,5 @@ pub mod new;
 pub mod variadic_from;
 #[ cfg( feature = "derive_reflect" ) ]
 pub mod reflect;
+#[ cfg( feature = "derive_phantom" ) ]
+pub mod phantom;

module/core/derive_tools_meta/src/derive/phantom.rs

@@ -0,0 +1,28 @@
+use super::*;
+use macro_tools::
+{
+  attr,
+  diag,
+  Result,
+  phantom::add_to_item,
+  quote::ToTokens,
+  syn::ItemStruct,
+};
+
+pub fn phantom( input : proc_macro::TokenStream  ) -> Result< proc_macro2::TokenStream >
+{
+  let original_input = input.clone();
+  let parsed = syn::parse::< ItemStruct >( input )?;
+  let has_debug = attr::has_debug( parsed.attrs.iter() )?;
+  let item_name = &parsed.ident;
+
+  let result = add_to_item( &parsed ).to_token_stream();
+
+  if has_debug
+  {
+    let about = format!( "derive : PhantomData\nstructure : {item_name}" );
+    diag::report_print( about, &original_input, &result );
+  }
+
+  Ok( result )
+}

module/core/derive_tools_meta/src/lib.rs

@@ -15,6 +15,7 @@
     feature = "derive_from",
     feature = "derive_inner_from",
     feature = "derive_variadic_from",
+    feature = "derive_phantom"
   )
 )]
 #[ cfg( feature = "enabled" ) ]
@@ -30,6 +31,7 @@ mod derive;
 //     feature = "derive_from",
 //     feature = "derive_inner_from",
 //     feature = "derive_variadic_from",
+//     feature = "derive_phantom"
 //   )
 // )]
 // #[ cfg( feature = "enabled" ) ]
@@ -517,3 +519,52 @@ pub fn derive_variadic_from( input : proc_macro::TokenStream ) -> proc_macro::To
     Err( err ) => err.to_compile_error().into(),
   }
 }
+
+///
+/// Provides an automatic `PhantomData` field for a struct based on its generic types.
+///
+/// This macro simplifies the addition of a `PhantomData` field to a struct
+/// to indicate that the struct logically owns instances of the generic types,
+/// even though it does not store them.
+///
+/// ## Example Usage
+///
+/// Instead of manually adding `PhantomData<T>` to `MyStruct`:
+///
+/// ```rust
+/// use std::marker::PhantomData;
+///
+/// pub struct MyStruct<T>
+/// {
+///     data: i32,
+///     _phantom: PhantomData<T>,
+/// }
+/// ```
+///
+/// Use `#[ phantom ]` to automatically generate the `PhantomData` field:
+///
+/// ```rust
+/// use derive_tools_meta::*;
+///
+/// #[ phantom ]
+/// pub struct MyStruct< T >
+/// {
+///     data: i32,
+/// }
+/// ```
+///
+/// The macro facilitates the addition of the `PhantomData` field without additional boilerplate code.
+///
+
+#[ cfg( feature = "enabled" ) ]
+#[ cfg ( feature = "derive_phantom" ) ]
+#[ proc_macro_attribute ]
+pub fn phantom( _attr: proc_macro::TokenStream, input : proc_macro::TokenStream ) -> proc_macro::TokenStream
+{
+  let result = derive::phantom::phantom( input );
+  match result
+  {
+    Ok( stream ) => stream.into(),
+    Err( err ) => err.to_compile_error().into(),
+  }
+}