AI Updates #7: span the data-derive impls, and catalog the equality-pinned abstract-type error

crates/macros/cgp-macro-core/src/types/cgp_data/derive_builder/finalize_build_impl.rs

@@ -4,6 +4,7 @@ use syn::token::Comma;
 use syn::{FieldValue, Ident, ItemImpl, ItemStruct, Type};
 
 use crate::exports::{FinalizeBuild, IsPresent};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{field_to_member, field_value_expr, to_generic_args};
 
@@ -49,5 +50,7 @@ pub fn derive_finalize_build_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the struct name the user wrote, not the whole
+    // derive. See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_builder/has_builder_impl.rs

@@ -4,6 +4,7 @@ use syn::token::Comma;
 use syn::{FieldValue, Ident, ItemImpl, ItemStruct};
 
 use crate::exports::{HasBuilder, IsNothing};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{field_to_member, field_value_expr, to_generic_args};
 
@@ -44,5 +45,7 @@ pub fn derive_has_builder_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the struct name the user wrote, not the whole
+    // derive. See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_builder/has_field_impls.rs

@@ -1,6 +1,8 @@
+use syn::spanned::Spanned;
 use syn::{Ident, ItemImpl, ItemStruct};
 
 use crate::exports::{HasField, IsPresent, MapType};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{
     field_to_member, field_to_tag, index_to_generic_ident, to_generic_args,
@@ -55,7 +57,13 @@ pub fn derive_has_field_impls(
             }
         };
 
-        item_impls.push(item_impl);
+        // Point an error on this per-field impl at the field the user wrote
+        // rather than at the whole derive. See docs/implementation/README.md#spans.
+        let field_span = current_field
+            .ident
+            .as_ref()
+            .map_or_else(|| current_field.span(), |ident| ident.span());
+        item_impls.push(override_item_span(field_span, &item_impl)?);
     }
 
     Ok(item_impls)

crates/macros/cgp-macro-core/src/types/cgp_data/derive_builder/into_builder_impl.rs

@@ -4,6 +4,7 @@ use syn::token::Comma;
 use syn::{FieldValue, Ident, ItemImpl, ItemStruct};
 
 use crate::exports::{IntoBuilder, IsPresent};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{field_to_member, field_value_expr, to_generic_args};
 
@@ -47,5 +48,7 @@ pub fn derive_into_builder_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the struct name the user wrote, not the whole
+    // derive. See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_builder/partial_data.rs

@@ -1,6 +1,7 @@
 use syn::{Ident, ItemImpl, ItemStruct};
 
 use crate::exports::{MapType, PartialData};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::index_to_generic_ident;
 
@@ -32,5 +33,7 @@ pub fn derive_partial_data_impl_from_struct(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the struct name the user wrote, not the whole
+    // derive. See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_builder/update_field_impls.rs

@@ -1,9 +1,11 @@
 use quote::quote;
 use syn::punctuated::Punctuated;
+use syn::spanned::Spanned;
 use syn::token::Comma;
 use syn::{FieldValue, GenericArgument, Ident, ItemImpl, ItemStruct, Type};
 
 use crate::exports::{MapType, UpdateField};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{
     field_to_member, field_to_tag, field_value_expr, index_to_generic_ident, to_generic_args,
@@ -99,7 +101,13 @@ pub fn derive_update_field_impls(
             }
         };
 
-        item_impls.push(item_impl);
+        // Point an error on this per-field impl at the field the user wrote
+        // rather than at the whole derive. See docs/implementation/README.md#spans.
+        let field_span = current_field
+            .ident
+            .as_ref()
+            .map_or_else(|| current_field.span(), |ident| ident.span());
+        item_impls.push(override_item_span(field_span, &item_impl)?);
     }
 
     Ok(item_impls)

crates/macros/cgp-macro-core/src/types/cgp_data/derive_extractor/extract_field_impls.rs

@@ -1,6 +1,7 @@
 use syn::{Arm, GenericArgument, Ident, ItemEnum, ItemImpl, Type};
 
 use crate::exports::{ExtractField, IsPresent, IsVoid, MapType, MapTypeRef};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{get_variant_type, index_to_generic_ident, to_generic_args};
 use crate::types::field::Symbol;
@@ -116,7 +117,12 @@ pub fn derive_extract_field_impls(
             }
         };
 
-        item_impls.push(item_impl);
+        // Point an error on this per-variant impl at the variant the user wrote
+        // rather than at the whole derive. See docs/implementation/README.md#spans.
+        item_impls.push(override_item_span(
+            current_variant.ident.span(),
+            &item_impl,
+        )?);
     }
 
     Ok(item_impls)

crates/macros/cgp-macro-core/src/types/cgp_data/derive_extractor/finalize_extract_impl.rs

@@ -1,6 +1,7 @@
 use syn::{Ident, ItemEnum, ItemImpl, Type};
 
 use crate::exports::{FinalizeExtract, IsVoid, MapTypeRef};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::to_generic_args;
 
@@ -61,5 +62,7 @@ pub fn derive_finalize_extract_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the enum name the user wrote, not the whole derive.
+    // See docs/implementation/README.md#spans.
+    override_item_span(context_enum.ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_extractor/has_extractor_impl.rs

@@ -2,6 +2,7 @@ use quote::quote;
 use syn::{Arm, Ident, ItemEnum, ItemImpl};
 
 use crate::exports::{HasExtractor, HasExtractorMut, HasExtractorRef, IsMut, IsPresent, IsRef};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::to_generic_args;
 
@@ -62,7 +63,9 @@ pub fn derive_has_extractor_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the enum name the user wrote, not the whole derive.
+    // See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }
 
 /// Emit the `HasExtractorRef` impl over the borrowed partial enum (`IsRef`). Its
@@ -137,7 +140,9 @@ pub fn derive_has_extractor_ref_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the enum name the user wrote, not the whole derive.
+    // See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }
 
 /// Emit the `HasExtractorMut` impl: the `IsMut` mirror of
@@ -209,5 +214,7 @@ pub fn derive_has_extractor_mut_impl(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the enum name the user wrote, not the whole derive.
+    // See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_extractor/partial_data.rs

@@ -1,6 +1,7 @@
 use syn::{Ident, ItemEnum, ItemImpl};
 
 use crate::exports::{MapType, MapTypeRef, PartialData};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::index_to_generic_ident;
 
@@ -56,5 +57,7 @@ pub fn derive_partial_data_impl_from_enum(
         }
     };
 
-    Ok(item_impl)
+    // Key the error span on the enum name the user wrote, not the whole derive.
+    // See docs/implementation/README.md#spans.
+    override_item_span(context_ident.span(), &item_impl)
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_from_variant.rs

@@ -1,6 +1,7 @@
 use syn::{ItemEnum, ItemImpl};
 
 use crate::exports::FromVariant;
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::get_variant_type;
 use crate::types::field::Symbol;
@@ -32,7 +33,11 @@ pub fn derive_from_variant_from_enum(item_enum: &ItemEnum) -> syn::Result<Vec<It
             }
         };
 
-        item_impls.push(item_impl);
+        // Aim a compiler error on this impl at the variant the user wrote rather
+        // than at the whole `#[derive(...)]`, which is where the impl's
+        // `call_site`-spanned boundary would otherwise put the caret. See
+        // docs/implementation/README.md#spans.
+        item_impls.push(override_item_span(variant_ident.span(), &item_impl)?);
     }
 
     Ok(item_impls)

crates/macros/cgp-macro-core/src/types/cgp_data/derive_has_field.rs

@@ -2,6 +2,7 @@ use syn::spanned::Spanned;
 use syn::{Fields, ItemImpl, ItemStruct, LitInt};
 
 use crate::exports::{HasField, HasFieldMut};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::field::{Index, Symbol};
 
@@ -17,6 +18,14 @@ pub fn derive_has_field_impls_from_struct(item_struct: &ItemStruct) -> syn::Resu
             for field in fields.named.iter() {
                 let field_ident = field.ident.as_ref().unwrap();
 
+                // Aim a compiler error on either generated impl — a coherence
+                // conflict (`E0119`) with a hand-written `HasField` impl for the
+                // same tag, say — at the field the user wrote rather than at the
+                // whole `#[derive(HasField)]`, which is where the impl's
+                // `call_site`-spanned `impl`/`{ … }` boundary would otherwise put
+                // the caret. See docs/implementation/README.md#spans.
+                let field_span = field_ident.span();
+
                 let field_symbol = Symbol::from_ident(field_ident.clone());
 
                 let field_type = &field.ty;
@@ -53,18 +62,23 @@ pub fn derive_has_field_impls_from_struct(item_struct: &ItemStruct) -> syn::Resu
                     }
                 };
 
-                item_impls.push(has_field_impl);
-                item_impls.push(has_field_mut_impl);
+                item_impls.push(override_item_span(field_span, &has_field_impl)?);
+                item_impls.push(override_item_span(field_span, &has_field_mut_impl)?);
             }
         }
         Fields::Unnamed(fields) => {
             for (i, field) in fields.unnamed.iter().enumerate() {
+                // A tuple field has no identifier, so its whole `syn::Field` span
+                // is the narrowest token the user wrote; re-span each generated
+                // impl onto it for the same reason as the named case above.
+                let field_span = field.span();
+
                 let field_tag = Index {
                     index: i,
-                    span: field.span(),
+                    span: field_span,
                 };
 
-                let field_ident = LitInt::new(&format!("{i}"), field.span());
+                let field_ident = LitInt::new(&format!("{i}"), field_span);
 
                 let field_type = &field.ty;
 
@@ -100,8 +114,8 @@ pub fn derive_has_field_impls_from_struct(item_struct: &ItemStruct) -> syn::Resu
                     }
                 };
 
-                item_impls.push(has_field_impl);
-                item_impls.push(has_field_mut_impl);
+                item_impls.push(override_item_span(field_span, &has_field_impl)?);
+                item_impls.push(override_item_span(field_span, &has_field_mut_impl)?);
             }
         }
         _ => {}

crates/macros/cgp-macro-core/src/types/cgp_data/derive_has_fields/derive_enum.rs

@@ -3,6 +3,7 @@ use quote::quote;
 use syn::{ItemEnum, ItemImpl};
 
 use crate::exports::{HasFields, HasFieldsRef};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{
     derive_from_fields_for_enum, derive_to_fields_for_enum, derive_to_fields_ref_for_enum,
@@ -45,11 +46,17 @@ pub fn derive_has_fields_impls_from_enum(item_enum: &ItemEnum) -> syn::Result<Ve
 
     let to_fields_ref_impl = derive_to_fields_ref_for_enum(item_enum)?;
 
-    Ok(vec![
+    // These impls are all keyed on the whole enum, so aim an error on any of
+    // their headers at the enum name the user wrote rather than at the whole
+    // `#[derive(...)]`. See docs/implementation/README.md#spans.
+    [
         has_fields_impl,
         has_fields_ref_impl,
         from_fields_impl,
         to_fields_impl,
         to_fields_ref_impl,
-    ])
+    ]
+    .into_iter()
+    .map(|item_impl| override_item_span(struct_name.span(), &item_impl))
+    .collect()
 }

crates/macros/cgp-macro-core/src/types/cgp_data/derive_has_fields/derive_struct.rs

@@ -3,6 +3,7 @@ use quote::quote;
 use syn::{ItemImpl, ItemStruct};
 
 use crate::exports::{HasFields, HasFieldsRef};
+use crate::functions::override_item_span;
 use crate::parse_internal;
 use crate::types::cgp_data::{
     derive_from_fields_for_struct, derive_to_fields_for_struct, derive_to_fields_ref_for_struct,
@@ -46,11 +47,17 @@ pub fn derive_has_fields_impls_from_struct(item_struct: &ItemStruct) -> syn::Res
 
     let to_fields_ref_impl = derive_to_fields_ref_for_struct(item_struct)?;
 
-    Ok(vec![
+    // These impls are all keyed on the whole struct, so aim an error on any of
+    // their headers at the struct name the user wrote rather than at the whole
+    // `#[derive(...)]`. See docs/implementation/README.md#spans.
+    [
         has_fields_impl,
         has_fields_ref_impl,
         from_fields_impl,
         to_fields_impl,
         to_fields_ref_impl,
-    ])
+    ]
+    .into_iter()
+    .map(|item_impl| override_item_span(struct_name.span(), &item_impl))
+    .collect()
 }