Use E0665 for missing `#[default]` error

Use orphaned error code for the same error it belonged to before.

```
error[E0665]: `#[derive(Default)]` on enum with no `#[default]`
  --> $DIR/macros-nonfatal-errors.rs:42:10
   |
LL |   #[derive(Default)]
   |            ^^^^^^^
LL | / enum NoDeclaredDefault {
LL | |     Foo,
LL | |     Bar,
LL | | }
   | |_- this enum needs a unit variant marked with `#[default]`
   |
   = note: this error originates in the derive macro `Default` (in Nightly builds, run with -Z macro-backtrace for more info)
help: make this unit variant default by placing `#[default]` on it
   |
LL |     #[default] Foo,
   |     ~~~~~~~~~~~~~~
help: make this unit variant default by placing `#[default]` on it
   |
LL |     #[default] Bar,
   |     ~~~~~~~~~~~~~~
```

2 files changed, 13 insertions, 13 deletions

diff --git a/compiler/rustc_builtin_macros/src/deriving/default.rs b/compiler/rustc_builtin_macros/src/deriving/default.rs
index a7d9f608cbd..3c7bebd0f19 100644
--- a/compiler/rustc_builtin_macros/src/deriving/default.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/default.rs
@@ -42,7 +42,9 @@ pub(crate) fn expand_deriving_default(
                     StaticStruct(_, fields) => {
                         default_struct_substructure(cx, trait_span, substr, fields)
                     }
-                    StaticEnum(enum_def, _) => default_enum_substructure(cx, trait_span, enum_def),
+                    StaticEnum(enum_def, _) => {
+                        default_enum_substructure(cx, trait_span, enum_def, item.span())
+                    }
                     _ => cx.dcx().span_bug(trait_span, "method in `derive(Default)`"),
                 }
             })),
@@ -96,9 +98,10 @@ fn default_enum_substructure(
     cx: &ExtCtxt<'_>,
     trait_span: Span,
     enum_def: &EnumDef,
+    item_span: Span,
 ) -> BlockOrExpr {
     let expr = match try {
-        let default_variant = extract_default_variant(cx, enum_def, trait_span)?;
+        let default_variant = extract_default_variant(cx, enum_def, trait_span, item_span)?;
         validate_default_attribute(cx, default_variant)?;
         default_variant
     } {
@@ -146,6 +149,7 @@ fn extract_default_variant<'a>(
     cx: &ExtCtxt<'_>,
     enum_def: &'a EnumDef,
     trait_span: Span,
+    item_span: Span,
 ) -> Result<&'a rustc_ast::Variant, ErrorGuaranteed> {
     let default_variants: SmallVec<[_; 1]> = enum_def
         .variants
@@ -163,9 +167,10 @@ fn extract_default_variant<'a>(
                 .filter(|variant| !attr::contains_name(&variant.attrs, sym::non_exhaustive));
 
             let suggs = possible_defaults
-                .map(|v| errors::NoDefaultVariantSugg { span: v.span, ident: v.ident })
+                .map(|v| errors::NoDefaultVariantSugg { span: v.span.shrink_to_lo() })
                 .collect();
-            let guar = cx.dcx().emit_err(errors::NoDefaultVariant { span: trait_span, suggs });
+            let guar =
+                cx.dcx().emit_err(errors::NoDefaultVariant { span: trait_span, item_span, suggs });
 
             return Err(guar);
         }
diff --git a/compiler/rustc_builtin_macros/src/errors.rs b/compiler/rustc_builtin_macros/src/errors.rs
index b3198e7743d..1abdfdb9c65 100644
--- a/compiler/rustc_builtin_macros/src/errors.rs
+++ b/compiler/rustc_builtin_macros/src/errors.rs
@@ -369,26 +369,21 @@ pub(crate) struct DerivePathArgsValue {
 }
 
 #[derive(Diagnostic)]
-#[diag(builtin_macros_no_default_variant)]
-#[help]
+#[diag(builtin_macros_no_default_variant, code = E0665)]
 pub(crate) struct NoDefaultVariant {
     #[primary_span]
     pub(crate) span: Span,
+    #[label]
+    pub(crate) item_span: Span,
     #[subdiagnostic]
     pub(crate) suggs: Vec<NoDefaultVariantSugg>,
 }
 
 #[derive(Subdiagnostic)]
-#[suggestion(
-    builtin_macros_suggestion,
-    code = "#[default] {ident}",
-    applicability = "maybe-incorrect",
-    style = "tool-only"
-)]
+#[suggestion(builtin_macros_suggestion, code = "#[default] ", applicability = "maybe-incorrect")]
 pub(crate) struct NoDefaultVariantSugg {
     #[primary_span]
     pub(crate) span: Span,
-    pub(crate) ident: Ident,
 }
 
 #[derive(Diagnostic)]