From ab0da5eebfdb6bd4340dfae1136b4c189494f3bd Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sat, 31 Jan 2026 21:25:37 +0100
Subject: [PATCH 01/11] Parse optional associated type in auto getter trait

---
 .../src/derive_getter/blanket.rs              | 20 ++++++++--
 .../src/derive_getter/constraint.rs           | 14 ++++---
 .../cgp-macro-lib/src/derive_getter/parse.rs  | 40 ++++++++++++++++++-
 .../src/derive_getter/use_field.rs            |  2 +-
 .../src/derive_getter/use_fields.rs           |  2 +-
 .../src/entrypoints/cgp_auto_getter.rs        |  4 +-
 .../src/entrypoints/cgp_getter.rs             |  2 +-
 7 files changed, 68 insertions(+), 16 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/blanket.rs b/crates/cgp-macro-lib/src/derive_getter/blanket.rs
index bbe9e7cb..e887746b 100644
--- a/crates/cgp-macro-lib/src/derive_getter/blanket.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/blanket.rs
@@ -14,12 +14,13 @@ pub fn derive_blanket_impl(
     context_type: &Ident,
     consumer_trait: &ItemTrait,
     fields: &[GetterField],
+    field_assoc_type: &Option<Ident>,
 ) -> syn::Result<ItemImpl> {
     let consumer_name = &consumer_trait.ident;
 
     let supertrait_constraints = consumer_trait.supertraits.clone();
 
-    let mut methods: TokenStream = TokenStream::new();
+    let mut items: TokenStream = TokenStream::new();
 
     let mut generics = consumer_trait.generics.clone();
 
@@ -27,6 +28,16 @@ pub fn derive_blanket_impl(
         .params
         .insert(0, parse2(context_type.to_token_stream())?);
 
+    if let Some(field_assoc_type) = field_assoc_type {
+        generics
+            .params
+            .push(parse2(field_assoc_type.to_token_stream())?);
+
+        items.extend(quote! {
+            type #field_assoc_type = #field_assoc_type;
+        });
+    }
+
     let where_clause = generics.make_where_clause();
 
     if !supertrait_constraints.is_empty() {
@@ -53,9 +64,10 @@ pub fn derive_blanket_impl(
             None,
         );
 
-        methods.extend(method);
+        items.extend(method);
 
-        let constraint = derive_getter_constraint(field, quote! { #field_symbol })?;
+        let constraint =
+            derive_getter_constraint(field, quote! { #field_symbol }, field_assoc_type)?;
 
         where_clause.predicates.push(parse2(quote! {
             #receiver_type: #constraint
@@ -69,7 +81,7 @@ pub fn derive_blanket_impl(
         impl #impl_generics #consumer_name #type_generics for #context_type
         #where_clause
         {
-            #methods
+            #items
         }
     })?;
 
diff --git a/crates/cgp-macro-lib/src/derive_getter/constraint.rs b/crates/cgp-macro-lib/src/derive_getter/constraint.rs
index 8f977e6c..543c5d4d 100644
--- a/crates/cgp-macro-lib/src/derive_getter/constraint.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/constraint.rs
@@ -1,28 +1,32 @@
 use proc_macro2::TokenStream;
 use quote::quote;
-use syn::{TypeParamBound, parse2};
+use syn::{Ident, TypeParamBound, parse_quote, parse2};
 
 use crate::derive_getter::{FieldMode, GetterField};
 
 pub fn derive_getter_constraint(
     spec: &GetterField,
     field_symbol: TokenStream,
+    field_assoc_type: &Option<Ident>,
 ) -> syn::Result<TypeParamBound> {
-    let provider_type = &spec.field_type;
+    let field_type = match field_assoc_type {
+        Some(field_assoc_type) => parse_quote! { #field_assoc_type },
+        None => spec.field_type.clone(),
+    };
 
     let constraint = if spec.field_mut.is_none() {
         if let FieldMode::Slice = spec.field_mode {
             quote! {
-                HasField< #field_symbol, Value: AsRef< [ #provider_type ] > + 'static >
+                HasField< #field_symbol, Value: AsRef< [ #field_type ] > + 'static >
             }
         } else {
             quote! {
-                HasField< #field_symbol, Value = #provider_type >
+                HasField< #field_symbol, Value = #field_type >
             }
         }
     } else {
         quote! {
-            HasFieldMut< #field_symbol, Value = #provider_type >
+            HasFieldMut< #field_symbol, Value = #field_type >
         }
     };
 
diff --git a/crates/cgp-macro-lib/src/derive_getter/parse.rs b/crates/cgp-macro-lib/src/derive_getter/parse.rs
index d19a8e2b..e6b82f2b 100644
--- a/crates/cgp-macro-lib/src/derive_getter/parse.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/parse.rs
@@ -16,8 +16,9 @@ use crate::replace_self::replace_self_type;
 pub fn parse_getter_fields(
     context_type: &Ident,
     consumer_trait: &ItemTrait,
-) -> syn::Result<Vec<GetterField>> {
+) -> syn::Result<(Vec<GetterField>, Option<Ident>)> {
     let mut fields = Vec::new();
+    let mut field_type = None;
 
     for item in consumer_trait.items.iter() {
         match item {
@@ -26,6 +27,23 @@ pub fn parse_getter_fields(
 
                 fields.push(getter_spec);
             }
+            TraitItem::Type(item_type) => {
+                if field_type.is_some() {
+                    return Err(Error::new(
+                        item_type.span(),
+                        "at most one associated type is allowed in getter trait",
+                    ));
+                }
+
+                if item_type.generics.params.len() > 0 {
+                    return Err(Error::new(
+                        item_type.generics.params.span(),
+                        "associated type in getter trait must not contain generic params",
+                    ));
+                }
+
+                field_type = Some(item_type.ident.clone());
+            }
             _ => {
                 return Err(Error::new(
                     item.span(),
@@ -35,7 +53,25 @@ pub fn parse_getter_fields(
         }
     }
 
-    Ok(fields)
+    match (&field_type, fields.first(), fields.len()) {
+        (None, _, _) => {}
+        (Some(field_type), Some(field), 1) => {
+            if field.field_type != parse_quote! { Self :: #field_type } {
+                return Err(Error::new(
+                    field.field_type.span(),
+                    "getter method return type must match the associated type",
+                ));
+            }
+        }
+        _ => {
+            return Err(Error::new(
+                consumer_trait.span(),
+                "if associated type is defined, exactly one getter method must be defined",
+            ));
+        }
+    }
+
+    Ok((fields, field_type))
 }
 
 fn parse_getter_method(context_type: &Ident, method: &TraitItemFn) -> syn::Result<GetterField> {
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_field.rs b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
index 740a777c..5bb00280 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_field.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
@@ -28,7 +28,7 @@ pub fn derive_use_field_impl(
 
     let method = derive_getter_method(&ContextArg::Ident(receiver_type.clone()), field, None, None);
 
-    let constraint = derive_getter_constraint(field, quote! { #tag_type })?;
+    let constraint = derive_getter_constraint(field, quote! { #tag_type }, &None)?;
 
     field_constraints.push(constraint);
 
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
index 6a40cbd6..0052374c 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
@@ -42,7 +42,7 @@ pub fn derive_use_fields_impl(
 
         methods.extend(method);
 
-        let constraint = derive_getter_constraint(field, quote! { #field_symbol })?;
+        let constraint = derive_getter_constraint(field, quote! { #field_symbol }, &None)?;
 
         where_clause
             .predicates
diff --git a/crates/cgp-macro-lib/src/entrypoints/cgp_auto_getter.rs b/crates/cgp-macro-lib/src/entrypoints/cgp_auto_getter.rs
index c6100f0e..ba6a72c7 100644
--- a/crates/cgp-macro-lib/src/entrypoints/cgp_auto_getter.rs
+++ b/crates/cgp-macro-lib/src/entrypoints/cgp_auto_getter.rs
@@ -16,9 +16,9 @@ pub fn cgp_auto_getter(attr: TokenStream, body: TokenStream) -> syn::Result<Toke
 
     let context_type = Ident::new("__Context__", Span::call_site());
 
-    let fields = parse_getter_fields(&context_type, &consumer_trait)?;
+    let (fields, field_type) = parse_getter_fields(&context_type, &consumer_trait)?;
 
-    let blanket_impl = derive_blanket_impl(&context_type, &consumer_trait, &fields)?;
+    let blanket_impl = derive_blanket_impl(&context_type, &consumer_trait, &fields, &field_type)?;
 
     Ok(quote! {
         #consumer_trait
diff --git a/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs b/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs
index e38b1a75..fb9ca719 100644
--- a/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs
+++ b/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs
@@ -39,7 +39,7 @@ pub fn cgp_getter(attr: TokenStream, body: TokenStream) -> syn::Result<TokenStre
 
     let derived_component = derive_component_with_ast(&spec, consumer_trait.clone())?;
 
-    let fields = parse_getter_fields(&spec.context_type, &consumer_trait)?;
+    let (fields, _field_type) = parse_getter_fields(&spec.context_type, &consumer_trait)?;
 
     let use_fields_impl =
         derive_use_fields_impl(&spec, &derived_component.provider_trait, &fields)?;

From 065dd7e7408de01c3827fa4ecfe5a1b86c637571 Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sat, 31 Jan 2026 21:26:35 +0100
Subject: [PATCH 02/11] Move getter tests

---
 crates/cgp-tests/src/tests/mod.rs                                | 1 -
 crates/cgp-tests/tests/getter.rs                                 | 1 +
 .../{src/tests/getter => tests/getter_tests}/abstract_type.rs    | 0
 .../{src/tests/getter => tests/getter_tests}/auto_generics.rs    | 0
 .../cgp-tests/{src/tests/getter => tests/getter_tests}/clone.rs  | 0
 crates/cgp-tests/{src/tests/getter => tests/getter_tests}/mod.rs | 0
 .../cgp-tests/{src/tests/getter => tests/getter_tests}/mref.rs   | 0
 .../{src/tests/getter => tests/getter_tests}/non_self.rs         | 0
 .../{src/tests/getter => tests/getter_tests}/non_self_auto.rs    | 0
 .../cgp-tests/{src/tests/getter => tests/getter_tests}/option.rs | 0
 .../cgp-tests/{src/tests/getter => tests/getter_tests}/slice.rs  | 0
 .../cgp-tests/{src/tests/getter => tests/getter_tests}/string.rs | 0
 12 files changed, 1 insertion(+), 1 deletion(-)
 create mode 100644 crates/cgp-tests/tests/getter.rs
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/abstract_type.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/auto_generics.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/clone.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/mod.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/mref.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/non_self.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/non_self_auto.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/option.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/slice.rs (100%)
 rename crates/cgp-tests/{src/tests/getter => tests/getter_tests}/string.rs (100%)

diff --git a/crates/cgp-tests/src/tests/mod.rs b/crates/cgp-tests/src/tests/mod.rs
index 86fdc838..cfb6745f 100644
--- a/crates/cgp-tests/src/tests/mod.rs
+++ b/crates/cgp-tests/src/tests/mod.rs
@@ -3,7 +3,6 @@ pub mod blanket_trait;
 pub mod check_components;
 pub mod compose;
 pub mod delegate_and_check_components;
-pub mod getter;
 pub mod has_field;
 pub mod has_fields;
 pub mod monad;
diff --git a/crates/cgp-tests/tests/getter.rs b/crates/cgp-tests/tests/getter.rs
new file mode 100644
index 00000000..359a2dc2
--- /dev/null
+++ b/crates/cgp-tests/tests/getter.rs
@@ -0,0 +1 @@
+pub mod getter_tests;
diff --git a/crates/cgp-tests/src/tests/getter/abstract_type.rs b/crates/cgp-tests/tests/getter_tests/abstract_type.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/abstract_type.rs
rename to crates/cgp-tests/tests/getter_tests/abstract_type.rs
diff --git a/crates/cgp-tests/src/tests/getter/auto_generics.rs b/crates/cgp-tests/tests/getter_tests/auto_generics.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/auto_generics.rs
rename to crates/cgp-tests/tests/getter_tests/auto_generics.rs
diff --git a/crates/cgp-tests/src/tests/getter/clone.rs b/crates/cgp-tests/tests/getter_tests/clone.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/clone.rs
rename to crates/cgp-tests/tests/getter_tests/clone.rs
diff --git a/crates/cgp-tests/src/tests/getter/mod.rs b/crates/cgp-tests/tests/getter_tests/mod.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/mod.rs
rename to crates/cgp-tests/tests/getter_tests/mod.rs
diff --git a/crates/cgp-tests/src/tests/getter/mref.rs b/crates/cgp-tests/tests/getter_tests/mref.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/mref.rs
rename to crates/cgp-tests/tests/getter_tests/mref.rs
diff --git a/crates/cgp-tests/src/tests/getter/non_self.rs b/crates/cgp-tests/tests/getter_tests/non_self.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/non_self.rs
rename to crates/cgp-tests/tests/getter_tests/non_self.rs
diff --git a/crates/cgp-tests/src/tests/getter/non_self_auto.rs b/crates/cgp-tests/tests/getter_tests/non_self_auto.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/non_self_auto.rs
rename to crates/cgp-tests/tests/getter_tests/non_self_auto.rs
diff --git a/crates/cgp-tests/src/tests/getter/option.rs b/crates/cgp-tests/tests/getter_tests/option.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/option.rs
rename to crates/cgp-tests/tests/getter_tests/option.rs
diff --git a/crates/cgp-tests/src/tests/getter/slice.rs b/crates/cgp-tests/tests/getter_tests/slice.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/slice.rs
rename to crates/cgp-tests/tests/getter_tests/slice.rs
diff --git a/crates/cgp-tests/src/tests/getter/string.rs b/crates/cgp-tests/tests/getter_tests/string.rs
similarity index 100%
rename from crates/cgp-tests/src/tests/getter/string.rs
rename to crates/cgp-tests/tests/getter_tests/string.rs

From 733dcc59a3ab9c1a5e7189f2802808f4b2774ea0 Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sat, 31 Jan 2026 21:46:08 +0100
Subject: [PATCH 03/11] Auto getter with assoc type is working

---
 .../cgp-macro-lib/src/derive_getter/parse.rs  | 41 +++++++++++++------
 .../tests/getter_tests/assoc_type.rs          |  8 ++++
 crates/cgp-tests/tests/getter_tests/mod.rs    |  1 +
 3 files changed, 37 insertions(+), 13 deletions(-)
 create mode 100644 crates/cgp-tests/tests/getter_tests/assoc_type.rs

diff --git a/crates/cgp-macro-lib/src/derive_getter/parse.rs b/crates/cgp-macro-lib/src/derive_getter/parse.rs
index e6b82f2b..b86341df 100644
--- a/crates/cgp-macro-lib/src/derive_getter/parse.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/parse.rs
@@ -18,17 +18,17 @@ pub fn parse_getter_fields(
     consumer_trait: &ItemTrait,
 ) -> syn::Result<(Vec<GetterField>, Option<Ident>)> {
     let mut fields = Vec::new();
-    let mut field_type = None;
+    let mut field_assoc_type = None;
 
     for item in consumer_trait.items.iter() {
         match item {
             TraitItem::Fn(method) => {
-                let getter_spec = parse_getter_method(context_type, method)?;
+                let getter_spec = parse_getter_method(context_type, method, &field_assoc_type)?;
 
                 fields.push(getter_spec);
             }
             TraitItem::Type(item_type) => {
-                if field_type.is_some() {
+                if field_assoc_type.is_some() {
                     return Err(Error::new(
                         item_type.span(),
                         "at most one associated type is allowed in getter trait",
@@ -42,7 +42,7 @@ pub fn parse_getter_fields(
                     ));
                 }
 
-                field_type = Some(item_type.ident.clone());
+                field_assoc_type = Some(item_type.ident.clone());
             }
             _ => {
                 return Err(Error::new(
@@ -53,13 +53,20 @@ pub fn parse_getter_fields(
         }
     }
 
-    match (&field_type, fields.first(), fields.len()) {
+    match (&field_assoc_type, fields.first(), fields.len()) {
         (None, _, _) => {}
-        (Some(field_type), Some(field), 1) => {
-            if field.field_type != parse_quote! { Self :: #field_type } {
+        (Some(field_assoc_type), Some(field), 1) => {
+            let field_type = &field.field_type;
+
+            if field_type != &parse_quote! { Self :: #field_assoc_type }
+                && field_type != &parse_quote! { #context_type :: #field_assoc_type }
+            {
                 return Err(Error::new(
                     field.field_type.span(),
-                    "getter method return type must match the associated type",
+                    format!(
+                        "getter method return type must match the associated type. {}",
+                        field_type.to_token_stream()
+                    ),
                 ));
             }
         }
@@ -71,10 +78,14 @@ pub fn parse_getter_fields(
         }
     }
 
-    Ok((fields, field_type))
+    Ok((fields, field_assoc_type))
 }
 
-fn parse_getter_method(context_type: &Ident, method: &TraitItemFn) -> syn::Result<GetterField> {
+fn parse_getter_method(
+    context_type: &Ident,
+    method: &TraitItemFn,
+    field_assoc_type: &Option<Ident>,
+) -> syn::Result<GetterField> {
     let signature = &method.sig;
 
     validate_getter_method_signature(signature)?;
@@ -85,7 +96,7 @@ fn parse_getter_method(context_type: &Ident, method: &TraitItemFn) -> syn::Resul
 
     let (receiver_mode, field_mut) = parse_receiver(context_type, arg)?;
 
-    let return_type = parse_return_type(context_type, &signature.output)?;
+    let return_type = parse_return_type(context_type, &signature.output, field_assoc_type)?;
 
     let (field_type, field_mode) = parse_field_type(&return_type, &field_mut)?;
 
@@ -223,12 +234,16 @@ fn parse_receiver(context_ident: &Ident, arg: &FnArg) -> syn::Result<(ReceiverMo
     }
 }
 
-fn parse_return_type(context_type: &Ident, return_type: &ReturnType) -> syn::Result<Type> {
+fn parse_return_type(
+    context_type: &Ident,
+    return_type: &ReturnType,
+    field_assoc_type: &Option<Ident>,
+) -> syn::Result<Type> {
     match return_type {
         ReturnType::Type(_, ty) => parse2(replace_self_type(
             ty.to_token_stream(),
             context_type.to_token_stream(),
-            &Vec::new(),
+            &field_assoc_type.iter().cloned().collect::<Vec<_>>(),
         )),
         _ => Err(Error::new(
             return_type.span(),
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type.rs b/crates/cgp-tests/tests/getter_tests/assoc_type.rs
new file mode 100644
index 00000000..0e98def4
--- /dev/null
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type.rs
@@ -0,0 +1,8 @@
+use cgp::prelude::*;
+
+#[cgp_auto_getter]
+pub trait HasName {
+    type Name;
+
+    fn name(&self) -> &Self::Name;
+}
diff --git a/crates/cgp-tests/tests/getter_tests/mod.rs b/crates/cgp-tests/tests/getter_tests/mod.rs
index 2d113d64..30fc034d 100644
--- a/crates/cgp-tests/tests/getter_tests/mod.rs
+++ b/crates/cgp-tests/tests/getter_tests/mod.rs
@@ -1,4 +1,5 @@
 pub mod abstract_type;
+pub mod assoc_type;
 pub mod auto_generics;
 pub mod clone;
 pub mod mref;

From 73372cb8fff0a7e73e03b8eb0210547c0c12703c Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 17:36:59 +0100
Subject: [PATCH 04/11] Support assoc type in `Allow abstract types to be
 defined in `#[cgp_getter]`

---
 .../src/derive_getter/use_field.rs            | 23 +++++++++++---
 .../src/derive_getter/use_fields.rs           | 25 +++++++++++----
 .../src/derive_getter/with_provider.rs        | 31 ++++++++++++++-----
 .../src/entrypoints/cgp_getter.rs             | 28 ++++++++++++-----
 .../auto_getter.rs}                           |  0
 .../tests/getter_tests/assoc_type/getter.rs   |  8 +++++
 .../tests/getter_tests/assoc_type/mod.rs      |  2 ++
 7 files changed, 91 insertions(+), 26 deletions(-)
 rename crates/cgp-tests/tests/getter_tests/{assoc_type.rs => assoc_type/auto_getter.rs} (100%)
 create mode 100644 crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
 create mode 100644 crates/cgp-tests/tests/getter_tests/assoc_type/mod.rs

diff --git a/crates/cgp-macro-lib/src/derive_getter/use_field.rs b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
index 5bb00280..691cdf19 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_field.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
@@ -1,7 +1,7 @@
 use quote::{ToTokens, quote};
 use syn::punctuated::Punctuated;
 use syn::token::Plus;
-use syn::{Generics, ItemImpl, ItemTrait, TypeParamBound, parse2};
+use syn::{Generics, Ident, ItemImpl, ItemTrait, TypeParamBound, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{
@@ -13,6 +13,7 @@ pub fn derive_use_field_impl(
     spec: &ComponentSpec,
     provider_trait: &ItemTrait,
     field: &GetterField,
+    field_assoc_type: &Option<Ident>,
 ) -> syn::Result<ItemImpl> {
     let context_type = &spec.context_type;
     let provider_name = &provider_trait.ident;
@@ -26,20 +27,32 @@ pub fn derive_use_field_impl(
 
     let tag_type = quote! { __Tag__ };
 
-    let method = derive_getter_method(&ContextArg::Ident(receiver_type.clone()), field, None, None);
+    let mut items =
+        derive_getter_method(&ContextArg::Ident(receiver_type.clone()), field, None, None);
 
-    let constraint = derive_getter_constraint(field, quote! { #tag_type }, &None)?;
+    let constraint = derive_getter_constraint(field, quote! { #tag_type }, field_assoc_type)?;
 
     field_constraints.push(constraint);
 
     let mut provider_generics = provider_trait.generics.clone();
 
+    if let Some(field_assoc_type) = field_assoc_type {
+        provider_generics
+            .params
+            .push(parse2(field_assoc_type.to_token_stream())?);
+
+        items.extend(quote! {
+            type #field_assoc_type = #field_assoc_type;
+        });
+    }
+
     let mut where_clause = provider_generics.make_where_clause().clone();
     where_clause
         .predicates
         .push(parse2(quote! { #receiver_type: #field_constraints })?);
 
-    let (impl_generics, type_generics, _) = provider_generics.split_for_impl();
+    let (_, type_generics, _) = provider_trait.generics.split_for_impl();
+    let (impl_generics, _, _) = provider_generics.split_for_impl();
 
     let impl_generics = {
         let mut generics: Generics = parse2(impl_generics.to_token_stream())?;
@@ -51,7 +64,7 @@ pub fn derive_use_field_impl(
         impl #impl_generics #provider_name #type_generics for UseField< #tag_type >
         #where_clause
         {
-            #method
+            #items
         }
     })?;
 
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
index 0052374c..57682de3 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
@@ -2,7 +2,7 @@ use alloc::string::ToString;
 
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
-use syn::{ItemImpl, ItemTrait, parse2};
+use syn::{Ident, ItemImpl, ItemTrait, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{
@@ -15,16 +15,27 @@ pub fn derive_use_fields_impl(
     spec: &ComponentSpec,
     provider_trait: &ItemTrait,
     fields: &[GetterField],
+    field_assoc_type: &Option<Ident>,
 ) -> syn::Result<ItemImpl> {
     let context_type = &spec.context_type;
 
     let provider_name = &spec.provider_name;
 
-    let mut methods: TokenStream = TokenStream::new();
+    let mut items: TokenStream = TokenStream::new();
 
     let mut provider_generics = provider_trait.generics.clone();
     let mut where_clause = provider_generics.make_where_clause().clone();
 
+    if let Some(field_assoc_type) = field_assoc_type {
+        provider_generics
+            .params
+            .push(parse2(field_assoc_type.to_token_stream())?);
+
+        items.extend(quote! {
+            type #field_assoc_type = #field_assoc_type;
+        });
+    }
+
     for field in fields {
         let receiver_type = match &field.receiver_mode {
             ReceiverMode::SelfReceiver => context_type.to_token_stream(),
@@ -40,22 +51,24 @@ pub fn derive_use_fields_impl(
             None,
         );
 
-        methods.extend(method);
+        items.extend(method);
 
-        let constraint = derive_getter_constraint(field, quote! { #field_symbol }, &None)?;
+        let constraint =
+            derive_getter_constraint(field, quote! { #field_symbol }, field_assoc_type)?;
 
         where_clause
             .predicates
             .push(parse2(quote! { #receiver_type: #constraint })?);
     }
 
-    let (impl_generics, type_generics, _) = provider_generics.split_for_impl();
+    let (_, type_generics, _) = provider_trait.generics.split_for_impl();
+    let (impl_generics, _, _) = provider_generics.split_for_impl();
 
     let out = parse2(quote! {
         impl #impl_generics #provider_name #type_generics for UseFields
         #where_clause
         {
-            #methods
+            #items
         }
     })?;
 
diff --git a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
index 6805fb45..1efe567f 100644
--- a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
@@ -1,6 +1,6 @@
 use proc_macro2::Span;
 use quote::{ToTokens, quote};
-use syn::{Generics, Ident, ItemImpl, ItemTrait, parse2};
+use syn::{Generics, Ident, ItemImpl, ItemTrait, parse_quote, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{ContextArg, FieldMode, ReceiverMode, derive_getter_method};
@@ -10,6 +10,7 @@ pub fn derive_with_provider_impl(
     spec: &ComponentSpec,
     provider_trait: &ItemTrait,
     field: &GetterField,
+    field_assoc_type: &Option<Ident>,
 ) -> syn::Result<ItemImpl> {
     let component_name = &spec.component_name;
     let component_params = &spec.component_params;
@@ -22,7 +23,10 @@ pub fn derive_with_provider_impl(
         ReceiverMode::Type(ty) => ty.to_token_stream(),
     };
 
-    let provider_type = &field.field_type;
+    let field_type = match field_assoc_type {
+        Some(field_assoc_type) => parse_quote! { #field_assoc_type },
+        None => field.field_type.clone(),
+    };
 
     let provider_ident = Ident::new("__Provider__", Span::call_site());
 
@@ -31,20 +35,20 @@ pub fn derive_with_provider_impl(
     let provider_constraint = if field.field_mut.is_none() {
         if let FieldMode::Slice = field.field_mode {
             quote! {
-                FieldGetter< #receiver_type, #component_type, Value: AsRef< [ #provider_type ] > + 'static >
+                FieldGetter< #receiver_type, #component_type, Value: AsRef< [ #field_type ] > + 'static >
             }
         } else {
             quote! {
-                FieldGetter< #receiver_type, #component_type , Value = #provider_type >
+                FieldGetter< #receiver_type, #component_type , Value = #field_type >
             }
         }
     } else {
         quote! {
-            MutFieldGetter< #receiver_type, #component_type, Value = #provider_type >
+            MutFieldGetter< #receiver_type, #component_type, Value = #field_type >
         }
     };
 
-    let method = derive_getter_method(
+    let mut items = derive_getter_method(
         &ContextArg::Ident(receiver_type),
         field,
         None,
@@ -53,12 +57,23 @@ pub fn derive_with_provider_impl(
 
     let mut provider_generics = provider_trait.generics.clone();
 
+    if let Some(field_assoc_type) = field_assoc_type {
+        provider_generics
+            .params
+            .push(parse2(field_assoc_type.to_token_stream())?);
+
+        items.extend(quote! {
+            type #field_assoc_type = #field_assoc_type;
+        });
+    }
+
     let mut where_clause = provider_generics.make_where_clause().clone();
     where_clause
         .predicates
         .push(parse2(quote! { #provider_ident : #provider_constraint })?);
 
-    let (impl_generics, type_generics, _) = provider_generics.split_for_impl();
+    let (_, type_generics, _) = provider_trait.generics.split_for_impl();
+    let (impl_generics, _, _) = provider_generics.split_for_impl();
 
     let impl_generics = {
         let mut generics: Generics = parse2(impl_generics.to_token_stream())?;
@@ -70,7 +85,7 @@ pub fn derive_with_provider_impl(
         impl #impl_generics #provider_name #type_generics for WithProvider< #provider_ident >
         #where_clause
         {
-            #method
+            #items
         }
     })?;
 
diff --git a/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs b/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs
index fb9ca719..3d20f1f5 100644
--- a/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs
+++ b/crates/cgp-macro-lib/src/entrypoints/cgp_getter.rs
@@ -39,10 +39,14 @@ pub fn cgp_getter(attr: TokenStream, body: TokenStream) -> syn::Result<TokenStre
 
     let derived_component = derive_component_with_ast(&spec, consumer_trait.clone())?;
 
-    let (fields, _field_type) = parse_getter_fields(&spec.context_type, &consumer_trait)?;
+    let (fields, field_assoc_type) = parse_getter_fields(&spec.context_type, &consumer_trait)?;
 
-    let use_fields_impl =
-        derive_use_fields_impl(&spec, &derived_component.provider_trait, &fields)?;
+    let use_fields_impl = derive_use_fields_impl(
+        &spec,
+        &derived_component.provider_trait,
+        &fields,
+        &field_assoc_type,
+    )?;
 
     let component_name_type: Type = {
         let component_name = &spec.component_name;
@@ -64,13 +68,23 @@ pub fn cgp_getter(attr: TokenStream, body: TokenStream) -> syn::Result<TokenStre
     };
 
     if let Some([field]) = m_field {
-        let use_field_impl =
-            derive_use_field_impl(&spec, &derived_component.provider_trait, &field)?;
+        let use_field_impl = derive_use_field_impl(
+            &spec,
+            &derived_component.provider_trait,
+            &field,
+            &field_assoc_type,
+        )?;
+
         let is_provider_use_field_impl =
             derive_is_provider_for(&component_name_type, &use_field_impl)?;
 
-        let use_provider_impl =
-            derive_with_provider_impl(&spec, &derived_component.provider_trait, &field)?;
+        let use_provider_impl = derive_with_provider_impl(
+            &spec,
+            &derived_component.provider_trait,
+            &field,
+            &field_assoc_type,
+        )?;
+
         let is_provider_use_provider_impl =
             derive_is_provider_for(&component_name_type, &use_provider_impl)?;
 
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
similarity index 100%
rename from crates/cgp-tests/tests/getter_tests/assoc_type.rs
rename to crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
new file mode 100644
index 00000000..fcc84989
--- /dev/null
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
@@ -0,0 +1,8 @@
+use cgp::prelude::*;
+
+#[cgp_getter]
+pub trait HasName {
+    type Name;
+
+    fn name(&self) -> &Self::Name;
+}
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type/mod.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/mod.rs
new file mode 100644
index 00000000..98e2c237
--- /dev/null
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type/mod.rs
@@ -0,0 +1,2 @@
+pub mod auto_getter;
+pub mod getter;

From f866bce477575c4dd25d3491a19d6eb7c7fa3b3d Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 17:40:35 +0100
Subject: [PATCH 05/11] Rearrange generated assoc type definition

---
 .../src/derive_getter/use_field.rs            | 19 +++++++----
 .../src/derive_getter/with_provider.rs        | 32 ++++++++++---------
 2 files changed, 30 insertions(+), 21 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/use_field.rs b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
index 691cdf19..f2846f2b 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_field.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
@@ -1,3 +1,4 @@
+use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
 use syn::punctuated::Punctuated;
 use syn::token::Plus;
@@ -27,12 +28,7 @@ pub fn derive_use_field_impl(
 
     let tag_type = quote! { __Tag__ };
 
-    let mut items =
-        derive_getter_method(&ContextArg::Ident(receiver_type.clone()), field, None, None);
-
-    let constraint = derive_getter_constraint(field, quote! { #tag_type }, field_assoc_type)?;
-
-    field_constraints.push(constraint);
+    let mut items = TokenStream::new();
 
     let mut provider_generics = provider_trait.generics.clone();
 
@@ -46,6 +42,17 @@ pub fn derive_use_field_impl(
         });
     }
 
+    items.extend(derive_getter_method(
+        &ContextArg::Ident(receiver_type.clone()),
+        field,
+        None,
+        None,
+    ));
+
+    let constraint = derive_getter_constraint(field, quote! { #tag_type }, field_assoc_type)?;
+
+    field_constraints.push(constraint);
+
     let mut where_clause = provider_generics.make_where_clause().clone();
     where_clause
         .predicates
diff --git a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
index 1efe567f..275603b8 100644
--- a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
@@ -1,4 +1,4 @@
-use proc_macro2::Span;
+use proc_macro2::{Span, TokenStream};
 use quote::{ToTokens, quote};
 use syn::{Generics, Ident, ItemImpl, ItemTrait, parse_quote, parse2};
 
@@ -32,6 +32,20 @@ pub fn derive_with_provider_impl(
 
     let component_type = quote! { #component_name < #component_params > };
 
+    let mut items = TokenStream::new();
+
+    let mut provider_generics = provider_trait.generics.clone();
+
+    if let Some(field_assoc_type) = field_assoc_type {
+        provider_generics
+            .params
+            .push(parse2(field_assoc_type.to_token_stream())?);
+
+        items.extend(quote! {
+            type #field_assoc_type = #field_assoc_type;
+        });
+    }
+
     let provider_constraint = if field.field_mut.is_none() {
         if let FieldMode::Slice = field.field_mode {
             quote! {
@@ -48,24 +62,12 @@ pub fn derive_with_provider_impl(
         }
     };
 
-    let mut items = derive_getter_method(
+    items.extend(derive_getter_method(
         &ContextArg::Ident(receiver_type),
         field,
         None,
         Some(provider_ident.clone()),
-    );
-
-    let mut provider_generics = provider_trait.generics.clone();
-
-    if let Some(field_assoc_type) = field_assoc_type {
-        provider_generics
-            .params
-            .push(parse2(field_assoc_type.to_token_stream())?);
-
-        items.extend(quote! {
-            type #field_assoc_type = #field_assoc_type;
-        });
-    }
+    ));
 
     let mut where_clause = provider_generics.make_where_clause().clone();
     where_clause

From 0efd65af418551963a1a0b341fe48f5a8e9f5cff Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 17:54:14 +0100
Subject: [PATCH 06/11] Forward whole TraitItemType

---
 .../src/derive_getter/blanket.rs              | 16 ++++++++++------
 .../cgp-macro-lib/src/derive_getter/parse.rs  | 19 ++++++++++++-------
 .../src/derive_getter/use_field.rs            | 16 +++++++++++-----
 .../src/derive_getter/use_fields.rs           | 17 +++++++++++------
 .../src/derive_getter/with_provider.rs        | 15 ++++++++++-----
 5 files changed, 54 insertions(+), 29 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/blanket.rs b/crates/cgp-macro-lib/src/derive_getter/blanket.rs
index e887746b..b3d74528 100644
--- a/crates/cgp-macro-lib/src/derive_getter/blanket.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/blanket.rs
@@ -2,7 +2,7 @@ use alloc::string::ToString;
 
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
-use syn::{Ident, ItemImpl, ItemTrait, parse2};
+use syn::{Ident, ItemImpl, ItemTrait, TraitItemType, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{
@@ -14,7 +14,7 @@ pub fn derive_blanket_impl(
     context_type: &Ident,
     consumer_trait: &ItemTrait,
     fields: &[GetterField],
-    field_assoc_type: &Option<Ident>,
+    field_assoc_type: &Option<TraitItemType>,
 ) -> syn::Result<ItemImpl> {
     let consumer_name = &consumer_trait.ident;
 
@@ -29,12 +29,13 @@ pub fn derive_blanket_impl(
         .insert(0, parse2(context_type.to_token_stream())?);
 
     if let Some(field_assoc_type) = field_assoc_type {
+        let field_assoc_type_ident = &field_assoc_type.ident;
         generics
             .params
-            .push(parse2(field_assoc_type.to_token_stream())?);
+            .push(parse2(field_assoc_type_ident.to_token_stream())?);
 
         items.extend(quote! {
-            type #field_assoc_type = #field_assoc_type;
+            type #field_assoc_type_ident = #field_assoc_type_ident;
         });
     }
 
@@ -66,8 +67,11 @@ pub fn derive_blanket_impl(
 
         items.extend(method);
 
-        let constraint =
-            derive_getter_constraint(field, quote! { #field_symbol }, field_assoc_type)?;
+        let constraint = derive_getter_constraint(
+            field,
+            quote! { #field_symbol },
+            &field_assoc_type.as_ref().map(|item| item.ident.clone()),
+        )?;
 
         where_clause.predicates.push(parse2(quote! {
             #receiver_type: #constraint
diff --git a/crates/cgp-macro-lib/src/derive_getter/parse.rs b/crates/cgp-macro-lib/src/derive_getter/parse.rs
index b86341df..e05f84fc 100644
--- a/crates/cgp-macro-lib/src/derive_getter/parse.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/parse.rs
@@ -6,7 +6,7 @@ use syn::spanned::Spanned;
 use syn::token::{Comma, Mut};
 use syn::{
     Error, FnArg, GenericArgument, Ident, ItemTrait, PathArguments, PathSegment, ReturnType,
-    Signature, TraitItem, TraitItemFn, Type, TypePath, parse_quote, parse2,
+    Signature, TraitItem, TraitItemFn, TraitItemType, Type, TypePath, parse_quote, parse2,
 };
 
 use crate::derive_getter::getter_field::GetterField;
@@ -16,14 +16,18 @@ use crate::replace_self::replace_self_type;
 pub fn parse_getter_fields(
     context_type: &Ident,
     consumer_trait: &ItemTrait,
-) -> syn::Result<(Vec<GetterField>, Option<Ident>)> {
+) -> syn::Result<(Vec<GetterField>, Option<TraitItemType>)> {
     let mut fields = Vec::new();
-    let mut field_assoc_type = None;
+    let mut field_assoc_type: Option<TraitItemType> = None;
 
     for item in consumer_trait.items.iter() {
         match item {
             TraitItem::Fn(method) => {
-                let getter_spec = parse_getter_method(context_type, method, &field_assoc_type)?;
+                let getter_spec = parse_getter_method(
+                    context_type,
+                    method,
+                    &field_assoc_type.as_ref().map(|item| item.ident.clone()),
+                )?;
 
                 fields.push(getter_spec);
             }
@@ -42,7 +46,7 @@ pub fn parse_getter_fields(
                     ));
                 }
 
-                field_assoc_type = Some(item_type.ident.clone());
+                field_assoc_type = Some(item_type.clone());
             }
             _ => {
                 return Err(Error::new(
@@ -56,10 +60,11 @@ pub fn parse_getter_fields(
     match (&field_assoc_type, fields.first(), fields.len()) {
         (None, _, _) => {}
         (Some(field_assoc_type), Some(field), 1) => {
+            let field_assoc_type_ident = &field_assoc_type.ident;
             let field_type = &field.field_type;
 
-            if field_type != &parse_quote! { Self :: #field_assoc_type }
-                && field_type != &parse_quote! { #context_type :: #field_assoc_type }
+            if field_type != &parse_quote! { Self :: #field_assoc_type_ident }
+                && field_type != &parse_quote! { #context_type :: #field_assoc_type_ident }
             {
                 return Err(Error::new(
                     field.field_type.span(),
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_field.rs b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
index f2846f2b..55124412 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_field.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
@@ -2,7 +2,7 @@ use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
 use syn::punctuated::Punctuated;
 use syn::token::Plus;
-use syn::{Generics, Ident, ItemImpl, ItemTrait, TypeParamBound, parse2};
+use syn::{Generics, ItemImpl, ItemTrait, TraitItemType, TypeParamBound, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{
@@ -14,7 +14,7 @@ pub fn derive_use_field_impl(
     spec: &ComponentSpec,
     provider_trait: &ItemTrait,
     field: &GetterField,
-    field_assoc_type: &Option<Ident>,
+    field_assoc_type: &Option<TraitItemType>,
 ) -> syn::Result<ItemImpl> {
     let context_type = &spec.context_type;
     let provider_name = &provider_trait.ident;
@@ -33,12 +33,14 @@ pub fn derive_use_field_impl(
     let mut provider_generics = provider_trait.generics.clone();
 
     if let Some(field_assoc_type) = field_assoc_type {
+        let field_assoc_type_ident = &field_assoc_type.ident;
+
         provider_generics
             .params
-            .push(parse2(field_assoc_type.to_token_stream())?);
+            .push(parse2(field_assoc_type_ident.to_token_stream())?);
 
         items.extend(quote! {
-            type #field_assoc_type = #field_assoc_type;
+            type #field_assoc_type_ident = #field_assoc_type_ident;
         });
     }
 
@@ -49,7 +51,11 @@ pub fn derive_use_field_impl(
         None,
     ));
 
-    let constraint = derive_getter_constraint(field, quote! { #tag_type }, field_assoc_type)?;
+    let constraint = derive_getter_constraint(
+        field,
+        quote! { #tag_type },
+        &field_assoc_type.as_ref().map(|item| item.ident.clone()),
+    )?;
 
     field_constraints.push(constraint);
 
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
index 57682de3..4aa64185 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
@@ -2,7 +2,7 @@ use alloc::string::ToString;
 
 use proc_macro2::TokenStream;
 use quote::{ToTokens, quote};
-use syn::{Ident, ItemImpl, ItemTrait, parse2};
+use syn::{ItemImpl, ItemTrait, TraitItemType, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{
@@ -15,7 +15,7 @@ pub fn derive_use_fields_impl(
     spec: &ComponentSpec,
     provider_trait: &ItemTrait,
     fields: &[GetterField],
-    field_assoc_type: &Option<Ident>,
+    field_assoc_type: &Option<TraitItemType>,
 ) -> syn::Result<ItemImpl> {
     let context_type = &spec.context_type;
 
@@ -27,12 +27,14 @@ pub fn derive_use_fields_impl(
     let mut where_clause = provider_generics.make_where_clause().clone();
 
     if let Some(field_assoc_type) = field_assoc_type {
+        let field_assoc_type_ident = &field_assoc_type.ident;
+
         provider_generics
             .params
-            .push(parse2(field_assoc_type.to_token_stream())?);
+            .push(parse2(field_assoc_type_ident.to_token_stream())?);
 
         items.extend(quote! {
-            type #field_assoc_type = #field_assoc_type;
+            type #field_assoc_type_ident = #field_assoc_type_ident;
         });
     }
 
@@ -53,8 +55,11 @@ pub fn derive_use_fields_impl(
 
         items.extend(method);
 
-        let constraint =
-            derive_getter_constraint(field, quote! { #field_symbol }, field_assoc_type)?;
+        let constraint = derive_getter_constraint(
+            field,
+            quote! { #field_symbol },
+            &field_assoc_type.as_ref().map(|item| item.ident.clone()),
+        )?;
 
         where_clause
             .predicates
diff --git a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
index 275603b8..f5f06f1b 100644
--- a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
@@ -1,6 +1,6 @@
 use proc_macro2::{Span, TokenStream};
 use quote::{ToTokens, quote};
-use syn::{Generics, Ident, ItemImpl, ItemTrait, parse_quote, parse2};
+use syn::{Generics, Ident, ItemImpl, ItemTrait, TraitItemType, parse_quote, parse2};
 
 use crate::derive_getter::getter_field::GetterField;
 use crate::derive_getter::{ContextArg, FieldMode, ReceiverMode, derive_getter_method};
@@ -10,7 +10,7 @@ pub fn derive_with_provider_impl(
     spec: &ComponentSpec,
     provider_trait: &ItemTrait,
     field: &GetterField,
-    field_assoc_type: &Option<Ident>,
+    field_assoc_type: &Option<TraitItemType>,
 ) -> syn::Result<ItemImpl> {
     let component_name = &spec.component_name;
     let component_params = &spec.component_params;
@@ -24,7 +24,10 @@ pub fn derive_with_provider_impl(
     };
 
     let field_type = match field_assoc_type {
-        Some(field_assoc_type) => parse_quote! { #field_assoc_type },
+        Some(field_assoc_type) => {
+            let field_assoc_type_ident = &field_assoc_type.ident;
+            parse_quote! { #field_assoc_type_ident }
+        }
         None => field.field_type.clone(),
     };
 
@@ -37,12 +40,14 @@ pub fn derive_with_provider_impl(
     let mut provider_generics = provider_trait.generics.clone();
 
     if let Some(field_assoc_type) = field_assoc_type {
+        let field_assoc_type_ident = &field_assoc_type.ident;
+
         provider_generics
             .params
-            .push(parse2(field_assoc_type.to_token_stream())?);
+            .push(parse2(field_assoc_type_ident.to_token_stream())?);
 
         items.extend(quote! {
-            type #field_assoc_type = #field_assoc_type;
+            type #field_assoc_type_ident = #field_assoc_type_ident;
         });
     }
 

From 6836df28061c7e859fa969a1ff29c8e6098dd2fb Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 18:01:07 +0100
Subject: [PATCH 07/11] Support associated type constraints

---
 crates/cgp-macro-lib/src/derive_getter/blanket.rs  |  7 +++++++
 .../cgp-macro-lib/src/derive_getter/use_field.rs   |  9 +++++++++
 .../cgp-macro-lib/src/derive_getter/use_fields.rs  | 14 ++++++++++++--
 .../src/derive_getter/with_provider.rs             |  9 +++++++++
 .../tests/getter_tests/assoc_type/auto_getter.rs   |  4 +++-
 .../tests/getter_tests/assoc_type/getter.rs        |  4 +++-
 6 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/blanket.rs b/crates/cgp-macro-lib/src/derive_getter/blanket.rs
index b3d74528..db383649 100644
--- a/crates/cgp-macro-lib/src/derive_getter/blanket.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/blanket.rs
@@ -30,6 +30,7 @@ pub fn derive_blanket_impl(
 
     if let Some(field_assoc_type) = field_assoc_type {
         let field_assoc_type_ident = &field_assoc_type.ident;
+
         generics
             .params
             .push(parse2(field_assoc_type_ident.to_token_stream())?);
@@ -37,6 +38,12 @@ pub fn derive_blanket_impl(
         items.extend(quote! {
             type #field_assoc_type_ident = #field_assoc_type_ident;
         });
+
+        let field_constraints = &field_assoc_type.bounds;
+
+        generics.make_where_clause().predicates.push(parse2(quote! {
+            #field_assoc_type_ident: #field_constraints
+        })?);
     }
 
     let where_clause = generics.make_where_clause();
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_field.rs b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
index 55124412..ac118dbf 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_field.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_field.rs
@@ -42,6 +42,15 @@ pub fn derive_use_field_impl(
         items.extend(quote! {
             type #field_assoc_type_ident = #field_assoc_type_ident;
         });
+
+        let field_constraints = &field_assoc_type.bounds;
+
+        provider_generics
+            .make_where_clause()
+            .predicates
+            .push(parse2(quote! {
+                #field_assoc_type_ident: #field_constraints
+            })?);
     }
 
     items.extend(derive_getter_method(
diff --git a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
index 4aa64185..d83bdce6 100644
--- a/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/use_fields.rs
@@ -24,7 +24,6 @@ pub fn derive_use_fields_impl(
     let mut items: TokenStream = TokenStream::new();
 
     let mut provider_generics = provider_trait.generics.clone();
-    let mut where_clause = provider_generics.make_where_clause().clone();
 
     if let Some(field_assoc_type) = field_assoc_type {
         let field_assoc_type_ident = &field_assoc_type.ident;
@@ -36,8 +35,19 @@ pub fn derive_use_fields_impl(
         items.extend(quote! {
             type #field_assoc_type_ident = #field_assoc_type_ident;
         });
+
+        let field_constraints = &field_assoc_type.bounds;
+
+        provider_generics
+            .make_where_clause()
+            .predicates
+            .push(parse2(quote! {
+                #field_assoc_type_ident: #field_constraints
+            })?);
     }
 
+    let where_clause = provider_generics.make_where_clause();
+
     for field in fields {
         let receiver_type = match &field.receiver_mode {
             ReceiverMode::SelfReceiver => context_type.to_token_stream(),
@@ -67,7 +77,7 @@ pub fn derive_use_fields_impl(
     }
 
     let (_, type_generics, _) = provider_trait.generics.split_for_impl();
-    let (impl_generics, _, _) = provider_generics.split_for_impl();
+    let (impl_generics, _, where_clause) = provider_generics.split_for_impl();
 
     let out = parse2(quote! {
         impl #impl_generics #provider_name #type_generics for UseFields
diff --git a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
index f5f06f1b..ee7c2fe5 100644
--- a/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/with_provider.rs
@@ -49,6 +49,15 @@ pub fn derive_with_provider_impl(
         items.extend(quote! {
             type #field_assoc_type_ident = #field_assoc_type_ident;
         });
+
+        let field_constraints = &field_assoc_type.bounds;
+
+        provider_generics
+            .make_where_clause()
+            .predicates
+            .push(parse2(quote! {
+                #field_assoc_type_ident: #field_constraints
+            })?);
     }
 
     let provider_constraint = if field.field_mut.is_none() {
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
index 0e98def4..32f5438c 100644
--- a/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
@@ -1,8 +1,10 @@
+use core::fmt::Display;
+
 use cgp::prelude::*;
 
 #[cgp_auto_getter]
 pub trait HasName {
-    type Name;
+    type Name: Display;
 
     fn name(&self) -> &Self::Name;
 }
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
index fcc84989..6497a445 100644
--- a/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
@@ -1,8 +1,10 @@
+use core::fmt::Display;
+
 use cgp::prelude::*;
 
 #[cgp_getter]
 pub trait HasName {
-    type Name;
+    type Name: Display;
 
     fn name(&self) -> &Self::Name;
 }

From 2127cade25f1813e4289e47a7a4279d057a8ca6b Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 18:04:45 +0100
Subject: [PATCH 08/11] Allow associated type to be defined after getter method

---
 .../cgp-macro-lib/src/derive_getter/parse.rs  | 28 +++++++++++++------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/parse.rs b/crates/cgp-macro-lib/src/derive_getter/parse.rs
index e05f84fc..b27beca2 100644
--- a/crates/cgp-macro-lib/src/derive_getter/parse.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/parse.rs
@@ -20,17 +20,9 @@ pub fn parse_getter_fields(
     let mut fields = Vec::new();
     let mut field_assoc_type: Option<TraitItemType> = None;
 
+    // Extract optional associated type first
     for item in consumer_trait.items.iter() {
         match item {
-            TraitItem::Fn(method) => {
-                let getter_spec = parse_getter_method(
-                    context_type,
-                    method,
-                    &field_assoc_type.as_ref().map(|item| item.ident.clone()),
-                )?;
-
-                fields.push(getter_spec);
-            }
             TraitItem::Type(item_type) => {
                 if field_assoc_type.is_some() {
                     return Err(Error::new(
@@ -48,6 +40,24 @@ pub fn parse_getter_fields(
 
                 field_assoc_type = Some(item_type.clone());
             }
+            _ => {}
+        }
+    }
+
+    for item in consumer_trait.items.iter() {
+        match item {
+            TraitItem::Fn(method) => {
+                let getter_spec = parse_getter_method(
+                    context_type,
+                    method,
+                    &field_assoc_type.as_ref().map(|item| item.ident.clone()),
+                )?;
+
+                fields.push(getter_spec);
+            }
+            TraitItem::Type(_) => {
+                // Already processed in the previous loop
+            }
             _ => {
                 return Err(Error::new(
                     item.span(),

From d6800c7ac63bf17929b8b116dd074f8ac87d4b3e Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 18:05:05 +0100
Subject: [PATCH 09/11] Fix clippy

---
 .../cgp-macro-lib/src/derive_getter/parse.rs  | 33 +++++++++----------
 1 file changed, 15 insertions(+), 18 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/parse.rs b/crates/cgp-macro-lib/src/derive_getter/parse.rs
index b27beca2..fb37c983 100644
--- a/crates/cgp-macro-lib/src/derive_getter/parse.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/parse.rs
@@ -22,25 +22,22 @@ pub fn parse_getter_fields(
 
     // Extract optional associated type first
     for item in consumer_trait.items.iter() {
-        match item {
-            TraitItem::Type(item_type) => {
-                if field_assoc_type.is_some() {
-                    return Err(Error::new(
-                        item_type.span(),
-                        "at most one associated type is allowed in getter trait",
-                    ));
-                }
-
-                if item_type.generics.params.len() > 0 {
-                    return Err(Error::new(
-                        item_type.generics.params.span(),
-                        "associated type in getter trait must not contain generic params",
-                    ));
-                }
-
-                field_assoc_type = Some(item_type.clone());
+        if let TraitItem::Type(item_type) = item {
+            if field_assoc_type.is_some() {
+                return Err(Error::new(
+                    item_type.span(),
+                    "at most one associated type is allowed in getter trait",
+                ));
+            }
+
+            if !item_type.generics.params.is_empty() {
+                return Err(Error::new(
+                    item_type.generics.params.span(),
+                    "associated type in getter trait must not contain generic params",
+                ));
             }
-            _ => {}
+
+            field_assoc_type = Some(item_type.clone());
         }
     }
 

From 039476e7754381964e9fb60ea6ef26f76d74fac0 Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 19:16:28 +0100
Subject: [PATCH 10/11] Add more tests

---
 crates/cgp-macro-lib/src/derive_getter/parse.rs   |  5 +----
 .../tests/getter_tests/assoc_type/auto_getter.rs  |  8 ++++++++
 .../tests/getter_tests/assoc_type/getter.rs       | 15 +++++++++++++++
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/crates/cgp-macro-lib/src/derive_getter/parse.rs b/crates/cgp-macro-lib/src/derive_getter/parse.rs
index fb37c983..947efecb 100644
--- a/crates/cgp-macro-lib/src/derive_getter/parse.rs
+++ b/crates/cgp-macro-lib/src/derive_getter/parse.rs
@@ -75,10 +75,7 @@ pub fn parse_getter_fields(
             {
                 return Err(Error::new(
                     field.field_type.span(),
-                    format!(
-                        "getter method return type must match the associated type. {}",
-                        field_type.to_token_stream()
-                    ),
+                    "getter method return type must match the associated type",
                 ));
             }
         }
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
index 32f5438c..ad6c03a5 100644
--- a/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type/auto_getter.rs
@@ -8,3 +8,11 @@ pub trait HasName {
 
     fn name(&self) -> &Self::Name;
 }
+
+#[derive(HasField)]
+pub struct Person {
+    pub name: String,
+}
+
+pub trait CheckHasName: HasName<Name = String> {}
+impl CheckHasName for Person {}
diff --git a/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs b/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
index 6497a445..441a4941 100644
--- a/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
+++ b/crates/cgp-tests/tests/getter_tests/assoc_type/getter.rs
@@ -8,3 +8,18 @@ pub trait HasName {
 
     fn name(&self) -> &Self::Name;
 }
+
+#[derive(HasField)]
+pub struct Person {
+    pub first_name: String,
+}
+
+delegate_components! {
+    Person {
+        NameGetterComponent:
+            UseField<Symbol!("first_name")>,
+    }
+}
+
+pub trait CheckHasName: HasName<Name = String> {}
+impl CheckHasName for Person {}

From ee5726e800d6124dabec0bdf6f56d846f035969a Mon Sep 17 00:00:00 2001
From: Soares Chen <soares.chen@maybevoid.com>
Date: Sun, 1 Feb 2026 19:30:18 +0100
Subject: [PATCH 11/11] Fix clippy

---
 crates/cgp-tests/tests/getter.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crates/cgp-tests/tests/getter.rs b/crates/cgp-tests/tests/getter.rs
index 359a2dc2..7bc4e98e 100644
--- a/crates/cgp-tests/tests/getter.rs
+++ b/crates/cgp-tests/tests/getter.rs
@@ -1 +1,3 @@
+#![allow(clippy::disallowed_names)]
+
 pub mod getter_tests;