From cd642bb6f95767991625d6be37bdc05ce957077b Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <n.nethercote@gmail.com>
Date: Wed, 1 Jul 2026 08:36:07 +1000
Subject: [PATCH] Remove unnecessary `Clone` derives on resolver types

The starting point of this commit is that `ModuleData`, `ImportData`,
and `DeclData` are all interned, and don't need to be `Clone`.

Then there are various types nestled within these types that also don't
need to be `Clone`.
---
 compiler/rustc_expand/src/base.rs              | 2 +-
 compiler/rustc_resolve/src/error_helper.rs     | 2 +-
 compiler/rustc_resolve/src/imports.rs          | 9 ++++-----
 compiler/rustc_resolve/src/late/diagnostics.rs | 2 +-
 compiler/rustc_resolve/src/lib.rs              | 4 ++--
 5 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/compiler/rustc_expand/src/base.rs b/compiler/rustc_expand/src/base.rs
index 31c776f3fef00..821f541170f62 100644
--- a/compiler/rustc_expand/src/base.rs
+++ b/compiler/rustc_expand/src/base.rs
@@ -1199,7 +1199,7 @@ pub trait LintStoreExpand {
 
 type LintStoreExpandDyn<'a> = Option<&'a (dyn LintStoreExpand + 'a)>;
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Default)]
 pub struct ModuleData {
     /// Path to the module starting from the crate name, like `my_crate::foo::bar`.
     pub mod_path: Vec<Ident>,
diff --git a/compiler/rustc_resolve/src/error_helper.rs b/compiler/rustc_resolve/src/error_helper.rs
index 1b7d799cadd35..c8abc3556f8fe 100644
--- a/compiler/rustc_resolve/src/error_helper.rs
+++ b/compiler/rustc_resolve/src/error_helper.rs
@@ -109,7 +109,7 @@ impl TypoSuggestion {
 }
 
 /// A free importable items suggested in case of resolution failure.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub(crate) struct ImportSuggestion {
     pub did: Option<DefId>,
     pub descr: &'static str,
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index a3cb526e60a87..303e333c4100e 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -69,7 +69,6 @@ impl<'ra> PendingDecl<'ra> {
 }
 
 /// Contains data for specific kinds of imports.
-#[derive(Clone)]
 pub(crate) enum ImportKind<'ra> {
     Single {
         /// `source` in `use prefix::source as target`.
@@ -157,7 +156,7 @@ impl<'ra> std::fmt::Debug for ImportKind<'ra> {
 }
 
 /// One import.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub(crate) struct ImportData<'ra> {
     pub kind: ImportKind<'ra>,
 
@@ -280,7 +279,7 @@ impl<'ra> ImportData<'ra> {
 }
 
 /// Records information about the resolution of a name in a namespace of a module.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub(crate) struct NameResolution<'ra> {
     /// Single imports that may define the name in the namespace.
     /// Imports are arena-allocated, so it's ok to use pointers as keys.
@@ -322,7 +321,7 @@ impl<'ra> NameResolution<'ra> {
 
 /// An error that may be transformed into a diagnostic later. Used to combine multiple unresolved
 /// import errors within the same use tree into a single diagnostic.
-#[derive(Debug, Clone)]
+#[derive(Debug)]
 pub(crate) struct UnresolvedImportError {
     pub(crate) span: Span,
     pub(crate) label: Option<String>,
@@ -341,7 +340,7 @@ fn pub_use_of_private_extern_crate_hack(
     import: ImportSummary,
     decl: Decl<'_>,
 ) -> Option<LocalDefId> {
-    match (import.is_single, decl.kind) {
+    match (import.is_single, &decl.kind) {
         (true, DeclKind::Import { import: decl_import, .. })
             if let ImportKind::ExternCrate { def_id, .. } = decl_import.kind
                 && import.vis.is_public() =>
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index 045e0ff523c7d..8c5c7f5b2d76d 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -133,7 +133,7 @@ pub(super) struct MissingLifetime {
 
 /// Description of the lifetimes appearing in a function parameter.
 /// This is used to provide a literal explanation to the elision failure.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub(super) struct ElisionFnParameter {
     /// The index of the argument in the original definition.
     pub index: usize,
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index e6cfa469e91d0..382a3eecb455f 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -992,7 +992,7 @@ impl<'ra> fmt::Debug for LocalModule<'ra> {
 }
 
 /// Data associated with any name declaration.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 struct DeclData<'ra> {
     kind: DeclKind<'ra>,
     ambiguity: CmCell<Option<(Decl<'ra>, bool /*warning*/)>>,
@@ -1026,7 +1026,7 @@ impl std::hash::Hash for DeclData<'_> {
 }
 
 /// Name declaration kind.
-#[derive(Clone, Copy, Debug)]
+#[derive(Debug)]
 enum DeclKind<'ra> {
     /// The name declaration is a definition (possibly without a `DefId`),
     /// can be provided by source code or built into the language.