From 90f7d7e07475697fa5b9eedd26d74f2a309b4d31 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Mon, 9 Mar 2026 15:47:34 +0100
Subject: [PATCH] clean up some unused leftovers

---
 compiler/rustc_const_eval/src/errors.rs    |  2 --
 compiler/rustc_middle/src/error.rs         | 26 +---------------------
 compiler/rustc_middle/src/ty/consts/int.rs |  9 --------
 3 files changed, 1 insertion(+), 36 deletions(-)

diff --git a/compiler/rustc_const_eval/src/errors.rs b/compiler/rustc_const_eval/src/errors.rs
index 1097eecf3121..3943be0cf15e 100644
--- a/compiler/rustc_const_eval/src/errors.rs
+++ b/compiler/rustc_const_eval/src/errors.rs
@@ -383,8 +383,6 @@ pub struct RawBytesNote {
     pub bytes: String,
 }
 
-// FIXME(fee1-dead) do not use stringly typed `ConstContext`
-
 #[derive(Diagnostic)]
 #[diag(
     r#"cannot match on `{$ty}` in {$kind ->
diff --git a/compiler/rustc_middle/src/error.rs b/compiler/rustc_middle/src/error.rs
index dfb99fb98513..d173335e9aa2 100644
--- a/compiler/rustc_middle/src/error.rs
+++ b/compiler/rustc_middle/src/error.rs
@@ -1,8 +1,7 @@
+use std::io;
 use std::path::Path;
-use std::{fmt, io};
 
 use rustc_errors::codes::*;
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_span::{Span, Symbol};
 
@@ -114,29 +113,6 @@ pub(super) struct ConstNotUsedTraitAlias {
     pub span: Span,
 }
 
-pub struct CustomSubdiagnostic<'a> {
-    pub msg: fn() -> DiagMessage,
-    pub add_args: Box<dyn FnOnce(&mut dyn FnMut(DiagArgName, DiagArgValue)) + 'a>,
-}
-
-impl<'a> CustomSubdiagnostic<'a> {
-    pub fn label(x: fn() -> DiagMessage) -> Self {
-        Self::label_and_then(x, |_| {})
-    }
-    pub fn label_and_then<F: FnOnce(&mut dyn FnMut(DiagArgName, DiagArgValue)) + 'a>(
-        msg: fn() -> DiagMessage,
-        f: F,
-    ) -> Self {
-        Self { msg, add_args: Box::new(move |x| f(x)) }
-    }
-}
-
-impl fmt::Debug for CustomSubdiagnostic<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("CustomSubdiagnostic").finish_non_exhaustive()
-    }
-}
-
 #[derive(Diagnostic)]
 pub enum LayoutError<'tcx> {
     #[diag("the type `{$ty}` has an unknown layout")]
diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index eaf67ae23ad2..180ccd9301c4 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -4,7 +4,6 @@
 use rustc_abi::Size;
 use rustc_apfloat::Float;
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
-use rustc_errors::{DiagArgValue, IntoDiagArg};
 use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 
 use crate::ty::TyCtxt;
@@ -137,14 +136,6 @@ fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
     }
 }
 
-impl IntoDiagArg for ConstInt {
-    // FIXME this simply uses the Debug impl, but we could probably do better by converting both
-    // to an inherent method that returns `Cow`.
-    fn into_diag_arg(self, _: &mut Option<std::path::PathBuf>) -> DiagArgValue {
-        DiagArgValue::Str(format!("{self:?}").into())
-    }
-}
-
 /// The raw bytes of a simple value.
 ///
 /// This is a packed struct in order to allow this type to be optimally embedded in enums