Remove the missing_copy_implementations lint.

compiler/rustc_lint/messages.ftl

@@ -110,8 +110,6 @@ lint_builtin_link_section_fn = declaration of a function with `link_section`
 
 lint_builtin_link_section_static = declaration of a static with `link_section`
 
-lint_builtin_missing_copy_impl = type could implement `Copy`; consider adding `impl Copy`
-
 lint_builtin_missing_debug_impl =
     type does not implement `{$debug}`; consider adding `#[derive(Debug)]` or a manual implementation
 

compiler/rustc_lint/src/builtin.rs

@@ -29,11 +29,11 @@ use crate::{
         BuiltinDerefNullptr, BuiltinEllipsisInclusiveRangePatternsLint, BuiltinExplicitOutlives,
         BuiltinExplicitOutlivesSuggestion, BuiltinFeatureIssueNote, BuiltinIncompleteFeatures,
         BuiltinIncompleteFeaturesHelp, BuiltinInternalFeatures, BuiltinKeywordIdents,
-        BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
-        BuiltinMutablesTransmutes, BuiltinNamedAsmLabel, BuiltinNoMangleGeneric,
-        BuiltinNonShorthandFieldPatterns, BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds,
-        BuiltinTypeAliasGenericBounds, BuiltinTypeAliasGenericBoundsSuggestion,
-        BuiltinTypeAliasWhereClause, BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit,
+        BuiltinMissingDebugImpl, BuiltinMissingDoc, BuiltinMutablesTransmutes,
+        BuiltinNamedAsmLabel, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
+        BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasGenericBounds,
+        BuiltinTypeAliasGenericBoundsSuggestion, BuiltinTypeAliasWhereClause,
+        BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit,
         BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub, BuiltinUnsafe,
         BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
         BuiltinWhileTrue, SuggestChangingAssocTypes,
@@ -54,11 +54,9 @@ use rustc_hir::intravisit::FnKind as HirFnKind;
 use rustc_hir::{Body, FnDecl, GenericParamKind, PatKind, PredicateOrigin};
 use rustc_middle::bug;
 use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::TypeVisitableExt;
-use rustc_middle::ty::Upcast;
 use rustc_middle::ty::{self, Ty, TyCtxt, VariantDef};
 use rustc_session::lint::FutureIncompatibilityReason;
 use rustc_session::{declare_lint, declare_lint_pass, impl_lint_pass};
@@ -67,9 +65,6 @@ use rustc_span::source_map::Spanned;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{BytePos, InnerSpan, Span};
 use rustc_target::abi::Abi;
-use rustc_trait_selection::infer::{InferCtxtExt, TyCtxtInferExt};
-use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
-use rustc_trait_selection::traits::{self, misc::type_allowed_to_implement_copy};
 use tracing::debug;
 
 use crate::nonstandard_style::{method_context, MethodLateContext};
@@ -598,148 +593,6 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
     }
 }
 
-declare_lint! {
-    /// The `missing_copy_implementations` lint detects potentially-forgotten
-    /// implementations of [`Copy`] for public types.
-    ///
-    /// [`Copy`]: https://doc.rust-lang.org/std/marker/trait.Copy.html
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![deny(missing_copy_implementations)]
-    /// pub struct Foo {
-    ///     pub field: i32
-    /// }
-    /// # fn main() {}
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// Historically (before 1.0), types were automatically marked as `Copy`
-    /// if possible. This was changed so that it required an explicit opt-in
-    /// by implementing the `Copy` trait. As part of this change, a lint was
-    /// added to alert if a copyable type was not marked `Copy`.
-    ///
-    /// This lint is "allow" by default because this code isn't bad; it is
-    /// common to write newtypes like this specifically so that a `Copy` type
-    /// is no longer `Copy`. `Copy` types can result in unintended copies of
-    /// large data which can impact performance.
-    pub MISSING_COPY_IMPLEMENTATIONS,
-    Allow,
-    "detects potentially-forgotten implementations of `Copy`"
-}
-
-declare_lint_pass!(MissingCopyImplementations => [MISSING_COPY_IMPLEMENTATIONS]);
-
-impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
-    fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
-        if !cx.effective_visibilities.is_reachable(item.owner_id.def_id) {
-            return;
-        }
-        let (def, ty) = match item.kind {
-            hir::ItemKind::Struct(_, ast_generics) => {
-                if !ast_generics.params.is_empty() {
-                    return;
-                }
-                let def = cx.tcx.adt_def(item.owner_id);
-                (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
-            }
-            hir::ItemKind::Union(_, ast_generics) => {
-                if !ast_generics.params.is_empty() {
-                    return;
-                }
-                let def = cx.tcx.adt_def(item.owner_id);
-                (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
-            }
-            hir::ItemKind::Enum(_, ast_generics) => {
-                if !ast_generics.params.is_empty() {
-                    return;
-                }
-                let def = cx.tcx.adt_def(item.owner_id);
-                (def, Ty::new_adt(cx.tcx, def, ty::List::empty()))
-            }
-            _ => return,
-        };
-        if def.has_dtor(cx.tcx) {
-            return;
-        }
-
-        // If the type contains a raw pointer, it may represent something like a handle,
-        // and recommending Copy might be a bad idea.
-        for field in def.all_fields() {
-            let did = field.did;
-            if cx.tcx.type_of(did).instantiate_identity().is_unsafe_ptr() {
-                return;
-            }
-        }
-        if ty.is_copy_modulo_regions(cx.tcx, cx.param_env) {
-            return;
-        }
-        if type_implements_negative_copy_modulo_regions(cx.tcx, ty, cx.param_env) {
-            return;
-        }
-        if def.is_variant_list_non_exhaustive()
-            || def.variants().iter().any(|variant| variant.is_field_list_non_exhaustive())
-        {
-            return;
-        }
-
-        // We shouldn't recommend implementing `Copy` on stateful things,
-        // such as iterators.
-        if let Some(iter_trait) = cx.tcx.get_diagnostic_item(sym::Iterator)
-            && cx
-                .tcx
-                .infer_ctxt()
-                .build()
-                .type_implements_trait(iter_trait, [ty], cx.param_env)
-                .must_apply_modulo_regions()
-        {
-            return;
-        }
-
-        // Default value of clippy::trivially_copy_pass_by_ref
-        const MAX_SIZE: u64 = 256;
-
-        if let Some(size) = cx.layout_of(ty).ok().map(|l| l.size.bytes()) {
-            if size > MAX_SIZE {
-                return;
-            }
-        }
-
-        if type_allowed_to_implement_copy(
-            cx.tcx,
-            cx.param_env,
-            ty,
-            traits::ObligationCause::misc(item.span, item.owner_id.def_id),
-        )
-        .is_ok()
-        {
-            cx.emit_span_lint(MISSING_COPY_IMPLEMENTATIONS, item.span, BuiltinMissingCopyImpl);
-        }
-    }
-}
-
-/// Check whether a `ty` has a negative `Copy` implementation, ignoring outlives constraints.
-fn type_implements_negative_copy_modulo_regions<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    ty: Ty<'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
-) -> bool {
-    let trait_ref = ty::TraitRef::new(tcx, tcx.require_lang_item(hir::LangItem::Copy, None), [ty]);
-    let pred = ty::TraitPredicate { trait_ref, polarity: ty::PredicatePolarity::Negative };
-    let obligation = traits::Obligation {
-        cause: traits::ObligationCause::dummy(),
-        param_env,
-        recursion_depth: 0,
-        predicate: pred.upcast(tcx),
-    };
-
-    tcx.infer_ctxt().build().predicate_must_hold_modulo_regions(&obligation)
-}
-
 declare_lint! {
     /// The `missing_debug_implementations` lint detects missing
     /// implementations of [`fmt::Debug`] for public types.
@@ -1644,7 +1497,6 @@ declare_lint_pass!(
         NON_SHORTHAND_FIELD_PATTERNS,
         UNSAFE_CODE,
         MISSING_DOCS,
-        MISSING_COPY_IMPLEMENTATIONS,
         MISSING_DEBUG_IMPLEMENTATIONS,
         ANONYMOUS_PARAMETERS,
         UNUSED_DOC_COMMENTS,

compiler/rustc_lint/src/lib.rs

@@ -195,8 +195,6 @@ late_lint_methods!(
             NonUpperCaseGlobals: NonUpperCaseGlobals,
             NonShorthandFieldPatterns: NonShorthandFieldPatterns,
             UnusedAllocation: UnusedAllocation,
-            // Depends on types used in type definitions
-            MissingCopyImplementations: MissingCopyImplementations,
             // Depends on referenced function signatures in expressions
             PtrNullChecks: PtrNullChecks,
             MutableTransmutes: MutableTransmutes,
@@ -549,6 +547,11 @@ fn register_builtins(store: &mut LintStore) {
         "converted into hard error, see RFC #3535 \
          <https://rust-lang.github.io/rfcs/3535-constants-in-patterns.html> for more information",
     );
+    store.register_removed(
+        "missing_copy_implementations",
+        "it existed mostly for historical reasons, \
+         and not implementing `Copy` is common and reasonable",
+    );
 }
 
 fn register_internals(store: &mut LintStore) {

compiler/rustc_lint/src/lints.rs

@@ -133,10 +133,6 @@ pub struct BuiltinMissingDoc<'a> {
     pub desc: &'a str,
 }
 
-#[derive(LintDiagnostic)]
-#[diag(lint_builtin_missing_copy_impl)]
-pub struct BuiltinMissingCopyImpl;
-
 pub struct BuiltinMissingDebugImpl<'a> {
     pub tcx: TyCtxt<'a>,
     pub def_id: DefId,

library/std/src/io/util.rs

@@ -1,5 +1,3 @@
-#![allow(missing_copy_implementations)]
-
 #[cfg(test)]
 mod tests;
 

src/tools/rust-analyzer/crates/ide-db/src/generated/lints.rs

@@ -305,10 +305,6 @@ pub const DEFAULT_LINTS: &[Lint] = &[
         description: r##"possible meta-variable misuse at macro definition"##,
     },
     Lint { label: "missing_abi", description: r##"No declared ABI for extern declaration"## },
-    Lint {
-        label: "missing_copy_implementations",
-        description: r##"detects potentially-forgotten implementations of `Copy`"##,
-    },
     Lint {
         label: "missing_debug_implementations",
         description: r##"detects missing implementations of Debug"##,

tests/ui/lint/issue-111359.rs

@@ -1,12 +1,10 @@
 #[deny(missing_debug_implementations)]
-#[deny(missing_copy_implementations)]
 
 mod priv_mod {
     use std::convert::TryFrom;
 
     pub struct BarPub;
     //~^ ERROR type does not implement `Debug`; consider adding `#[derive(Debug)]` or a manual implementation
-    //~| ERROR type could implement `Copy`; consider adding `impl Copy`
     struct BarPriv;
 
     impl<'a> TryFrom<BarPriv> for u8 {

tests/ui/lint/issue-111359.stderr

@@ -1,17 +1,5 @@
-error: type could implement `Copy`; consider adding `impl Copy`
-  --> $DIR/issue-111359.rs:7:5
-   |
-LL |     pub struct BarPub;
-   |     ^^^^^^^^^^^^^^^^^^
-   |
-note: the lint level is defined here
-  --> $DIR/issue-111359.rs:2:8
-   |
-LL | #[deny(missing_copy_implementations)]
-   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
 error: type does not implement `Debug`; consider adding `#[derive(Debug)]` or a manual implementation
-  --> $DIR/issue-111359.rs:7:5
+  --> $DIR/issue-111359.rs:6:5
    |
 LL |     pub struct BarPub;
    |     ^^^^^^^^^^^^^^^^^^
@@ -22,5 +10,5 @@ note: the lint level is defined here
 LL | #[deny(missing_debug_implementations)]
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 1 previous error