From 5394268ca379538f0f96d8083be7ec9c7558dace Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Sun, 5 Apr 2026 14:26:40 -0400
Subject: [PATCH] Mark method receivers in builtin derives as being from the
 derive.

---
 compiler/rustc_builtin_macros/src/deriving/generic/mod.rs | 2 +-
 compiler/rustc_expand/src/build.rs                        | 2 +-
 tests/ui/associated-types/issue-38821.stderr              | 2 ++
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
index b392a9623d05..63c06e672727 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
+++ b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
@@ -1052,7 +1052,7 @@ fn create_method(
 
         let args = {
             let self_arg = explicit_self.map(|explicit_self| {
-                let ident = Ident::with_dummy_span(kw::SelfLower).with_span_pos(span);
+                let ident = Ident::new(kw::SelfLower, span);
                 ast::Param::from_self(ast::AttrVec::default(), explicit_self, ident)
             });
             let nonself_args =
diff --git a/compiler/rustc_expand/src/build.rs b/compiler/rustc_expand/src/build.rs
index 3680f24707df..05e6b78132ae 100644
--- a/compiler/rustc_expand/src/build.rs
+++ b/compiler/rustc_expand/src/build.rs
@@ -315,7 +315,7 @@ pub fn expr_ident(&self, span: Span, id: Ident) -> Box<ast::Expr> {
         self.expr_path(self.path_ident(span, id))
     }
     pub fn expr_self(&self, span: Span) -> Box<ast::Expr> {
-        self.expr_ident(span, Ident::with_dummy_span(kw::SelfLower))
+        self.expr_ident(span, Ident::new(kw::SelfLower, span))
     }
 
     pub fn expr_macro_call(&self, span: Span, call: Box<ast::MacCall>) -> Box<ast::Expr> {
diff --git a/tests/ui/associated-types/issue-38821.stderr b/tests/ui/associated-types/issue-38821.stderr
index 07b146f8bfca..e3398f0e2390 100644
--- a/tests/ui/associated-types/issue-38821.stderr
+++ b/tests/ui/associated-types/issue-38821.stderr
@@ -272,6 +272,7 @@ LL | impl<T: NotNull> IntoNullable for T {
    |         -------  ^^^^^^^^^^^^     ^
    |         |
    |         unsatisfied trait bound introduced here
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0277]: the trait bound `<Col as Expression>::SqlType: NotNull` is not satisfied
   --> $DIR/issue-38821.rs:23:23
@@ -301,6 +302,7 @@ LL | impl<T: NotNull> IntoNullable for T {
    |         -------  ^^^^^^^^^^^^     ^
    |         |
    |         unsatisfied trait bound introduced here
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0277]: the trait bound `<Col as Expression>::SqlType: NotNull` is not satisfied
   --> $DIR/issue-38821.rs:23:10