From d04eb536459e742b0b1f71c1bb50f39d6128b9d2 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 24 Dec 2025 06:02:18 +0000
Subject: [PATCH 1/3] Initial plan


From 22764e9870cbc58b8179d53551493e83227cf16c Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 24 Dec 2025 06:07:41 +0000
Subject: [PATCH 2/3] Add diagnostic::on_unimplemented attributes to
 Transmogrifier and ByNameFieldPlucker traits

Co-authored-by: lloydmeta <914805+lloydmeta@users.noreply.github.com>
---
 core/src/labelled.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/core/src/labelled.rs b/core/src/labelled.rs
index 938e4a6d..fc48498b 100644
--- a/core/src/labelled.rs
+++ b/core/src/labelled.rs
@@ -586,6 +586,12 @@ where
 }
 
 /// Trait for plucking out a `Field` from a type by type-level `TargetKey`.
+#[diagnostic::on_unimplemented(
+    message = "Cannot find field with key `{TargetKey}` in `{Self}`",
+    label = "Field not found",
+    note = "The source type does not contain a field with the target key.",
+    note = "Make sure the field name exists in the source struct and matches exactly."
+)]
 pub trait ByNameFieldPlucker<TargetKey, Index> {
     type TargetValue;
     type Remainder;
@@ -752,6 +758,13 @@ where
 ///
 /// Credit:
 /// 1. Haskell "transmogrify" Github repo: <https://github.com/ivan-m/transmogrify>
+#[diagnostic::on_unimplemented(
+    message = "Cannot transmogrify `{Self}` into `{Target}`",
+    label = "Cannot convert this type into the target type",
+    note = "Transmogrify requires that the source and target types have compatible structures.",
+    note = "The source type must have all the fields needed for the target type, possibly in a different order or nested structure.",
+    note = "Check that field names match and types are compatible between the source and target."
+)]
 pub trait Transmogrifier<Target, TransmogrifyIndexIndices> {
     /// Consume this current object and return an object of the Target type.
     ///

From 1be8690399fa38dd56800ffc5e5e265eafd4be19 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Wed, 24 Dec 2025 06:22:49 +0000
Subject: [PATCH 3/3] Add diagnostic attributes to LabelledGeneric and Sculptor
 traits, fix clippy unused imports warning

Co-authored-by: lloydmeta <914805+lloydmeta@users.noreply.github.com>
---
 core/src/hlist.rs    | 6 ++++++
 core/src/labelled.rs | 6 ++++++
 core/src/tuples.rs   | 1 -
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/core/src/hlist.rs b/core/src/hlist.rs
index 3771544e..e03c7b85 100644
--- a/core/src/hlist.rs
+++ b/core/src/hlist.rs
@@ -970,6 +970,12 @@ where
 /// then `list.sculpt()` should "just work" even without the trait.
 ///
 /// [`HCons::sculpt`]: struct.HCons.html#method.sculpt
+#[diagnostic::on_unimplemented(
+    message = "Cannot sculpt `{Self}` into the target HList shape",
+    label = "Sculpture failed",
+    note = "The source HList must contain all the types needed for the target HList.",
+    note = "Make sure all required types are present in the source, possibly in a different order."
+)]
 pub trait Sculptor<Target, Indices> {
     type Remainder;
 
diff --git a/core/src/labelled.rs b/core/src/labelled.rs
index fc48498b..1506a2f6 100644
--- a/core/src/labelled.rs
+++ b/core/src/labelled.rs
@@ -195,6 +195,12 @@ use core::marker::PhantomData;
 /// // representation of the source object to that of the target type
 /// let s_user: SavedUser = frunk::transform_from(n_user); // done
 /// # }
+#[diagnostic::on_unimplemented(
+    message = "Cannot derive labelled generic representation for `{Self}`",
+    label = "LabelledGeneric not implemented",
+    note = "The type must have a LabelledGeneric instance to be used with transform_from or transmogrify.",
+    note = "Derive LabelledGeneric using #[derive(LabelledGeneric)] on your struct or enum."
+)]
 pub trait LabelledGeneric {
     /// The labelled generic representation type.
     type Repr;
diff --git a/core/src/tuples.rs b/core/src/tuples.rs
index b259875d..2911aad6 100644
--- a/core/src/tuples.rs
+++ b/core/src/tuples.rs
@@ -17,7 +17,6 @@
 //! ```
 
 use crate::generic::Generic;
-use crate::{hlist, HList};
 
 macro_rules! tup_def {
     ( $($dtype: ident),* ; ; ) => {};