Provide more context on trait bounds being unmet due to imperfect derive

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -1256,7 +1256,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 self.suggest_cloning_inner(err, ty, expr);
             }
         } else if let ty::Adt(def, args) = ty.kind()
-            && def.did().as_local().is_some()
+            && let Some(local_did) = def.did().as_local()
             && def.variants().iter().all(|variant| {
                 variant
                     .fields
@@ -1266,12 +1266,50 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         {
             let ty_span = self.infcx.tcx.def_span(def.did());
             let mut span: MultiSpan = ty_span.into();
-            span.push_span_label(ty_span, "consider implementing `Clone` for this type");
-            span.push_span_label(expr.span, "you could clone this value");
-            err.span_note(
-                span,
-                format!("if `{ty}` implemented `Clone`, you could clone the value"),
+            let mut derive_clone = false;
+            self.infcx.tcx.for_each_relevant_impl(
+                self.infcx.tcx.lang_items().clone_trait().unwrap(),
+                ty,
+                |def_id| {
+                    if self.infcx.tcx.is_automatically_derived(def_id) {
+                        derive_clone = true;
+                        span.push_span_label(
+                            self.infcx.tcx.def_span(def_id),
+                            "derived `Clone` adds implicit bounds on type parameters",
+                        );
+                        if let Some(generics) = self.infcx.tcx.hir_get_generics(local_did) {
+                            for param in generics.params {
+                                if let hir::GenericParamKind::Type { .. } = param.kind {
+                                    span.push_span_label(
+                                        param.span,
+                                        format!(
+                                            "introduces an implicit `{}: Clone` bound",
+                                            param.name.ident()
+                                        ),
+                                    );
+                                }
+                            }
+                        }
+                    }
+                },
             );
+            let msg = if !derive_clone {
+                span.push_span_label(
+                    ty_span,
+                    format!(
+                        "consider {}implementing `Clone` for this type",
+                        if derive_clone { "manually " } else { "" }
+                    ),
+                );
+                format!("if `{ty}` implemented `Clone`, you could clone the value")
+            } else {
+                format!("if all bounds were met, you could clone the value")
+            };
+            span.push_span_label(expr.span, "you could clone this value");
+            err.span_note(span, msg);
+            if derive_clone {
+                err.help("consider manually implementing `Clone` to avoid undesired bounds");
+            }
         } else if let ty::Param(param) = ty.kind()
             && let Some(_clone_trait_def) = self.infcx.tcx.lang_items().clone_trait()
             && let generics = self.infcx.tcx.generics_of(self.mir_def_id())

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -638,27 +638,27 @@ impl<'a> TraitDef<'a> {
                 GenericParamKind::Type { .. } => {
                     // Extra restrictions on the generics parameters to the
                     // type being derived upon.
+                    let span = param.ident.span.with_ctxt(ctxt);
                     let bounds: Vec<_> = self
                         .additional_bounds
                         .iter()
                         .map(|p| {
-                            cx.trait_bound(
-                                p.to_path(cx, self.span, type_ident, generics),
-                                self.is_const,
-                            )
+                            cx.trait_bound(p.to_path(cx, span, type_ident, generics), self.is_const)
                         })
                         .chain(
                             // Add a bound for the current trait.
-                            self.skip_path_as_bound
-                                .not()
-                                .then(|| cx.trait_bound(trait_path.clone(), self.is_const)),
+                            self.skip_path_as_bound.not().then(|| {
+                                let mut trait_path = trait_path.clone();
+                                trait_path.span = span;
+                                cx.trait_bound(trait_path, self.is_const)
+                            }),
                         )
                         .chain({
                             // Add a `Copy` bound if required.
                             if is_packed && self.needs_copy_as_bound_if_packed {
                                 let p = deriving::path_std!(marker::Copy);
                                 Some(cx.trait_bound(
-                                    p.to_path(cx, self.span, type_ident, generics),
+                                    p.to_path(cx, span, type_ident, generics),
                                     self.is_const,
                                 ))
                             } else {
@@ -671,7 +671,7 @@ impl<'a> TraitDef<'a> {
                         )
                         .collect();
 
-                    cx.typaram(param.ident.span.with_ctxt(ctxt), param.ident, bounds, None)
+                    cx.typaram(span, param.ident, bounds, None)
                 }
                 GenericParamKind::Const { ty, span, .. } => {
                     let const_nodefault_kind = GenericParamKind::Const {
@@ -791,7 +791,8 @@ impl<'a> TraitDef<'a> {
             .collect();
 
         // Create the type of `self`.
-        let path = cx.path_all(self.span, false, vec![type_ident], self_params);
+        let path =
+            cx.path_all(type_ident.span.with_ctxt(ctxt), false, vec![type_ident], self_params);
         let self_type = cx.ty_path(path);
         let rustc_const_unstable =
             cx.path_ident(self.span, Ident::new(sym::rustc_const_unstable, self.span));

compiler/rustc_hir/src/hir.rs

@@ -1,6 +1,7 @@
 // ignore-tidy-filelength
 use std::borrow::Cow;
 use std::fmt;
+use std::ops::Not;
 
 use rustc_abi::ExternAbi;
 use rustc_ast::attr::AttributeExt;
@@ -1012,10 +1013,14 @@ impl<'hir> Generics<'hir> {
 
                 span_for_parentheses.map_or_else(
                     || {
-                        // We include bounds that come from a `#[derive(_)]` but point at the user's code,
-                        // as we use this method to get a span appropriate for suggestions.
+                        // We include bounds that come from a `#[derive(_)]` but point at the user's
+                        // code, as we use this method to get a span appropriate for suggestions.
                         let bs = bound.span();
-                        bs.can_be_used_for_suggestions().then(|| (bs.shrink_to_hi(), None))
+                        // We use `from_expansion` instead of `can_be_used_for_suggestions` because
+                        // the trait bound from imperfect derives do point at the type parameter,
+                        // but expanded to a where clause, so we want to ignore those. This is only
+                        // true for derive intrinsics.
+                        bs.from_expansion().not().then(|| (bs.shrink_to_hi(), None))
                     },
                     |span| Some((span.shrink_to_hi(), Some(span.shrink_to_lo()))),
                 )

compiler/rustc_hir_analysis/messages.ftl

@@ -142,6 +142,7 @@ hir_analysis_copy_impl_on_non_adt =
 hir_analysis_copy_impl_on_type_with_dtor =
     the trait `Copy` cannot be implemented for this type; the type has a destructor
     .label = `Copy` not allowed on types with destructors
+    .note = destructor declared here
 
 hir_analysis_cross_crate_traits = cross-crate traits with a default impl, like `{$traits}`, can only be implemented for a struct/enum type, not `{$self_ty}`
     .label = can't implement cross-crate trait with a default impl for non-struct/enum type

compiler/rustc_hir_analysis/src/coherence/builtin.rs

@@ -121,9 +121,10 @@ fn visit_implementation_of_copy(checker: &Checker<'_>) -> Result<(), ErrorGuaran
             let span = tcx.hir_expect_item(impl_did).expect_impl().self_ty.span;
             Err(tcx.dcx().emit_err(errors::CopyImplOnNonAdt { span }))
         }
-        Err(CopyImplementationError::HasDestructor) => {
+        Err(CopyImplementationError::HasDestructor(did)) => {
             let span = tcx.hir_expect_item(impl_did).expect_impl().self_ty.span;
-            Err(tcx.dcx().emit_err(errors::CopyImplOnTypeWithDtor { span }))
+            let impl_ = tcx.def_span(did);
+            Err(tcx.dcx().emit_err(errors::CopyImplOnTypeWithDtor { span, impl_ }))
         }
         Err(CopyImplementationError::HasUnsafeFields) => {
             let span = tcx.hir_expect_item(impl_did).expect_impl().self_ty.span;

compiler/rustc_hir_analysis/src/errors.rs

@@ -278,6 +278,8 @@ pub(crate) struct CopyImplOnTypeWithDtor {
     #[primary_span]
     #[label]
     pub span: Span,
+    #[note]
+    pub impl_: Span,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_hir_analysis/src/hir_ty_lowering/dyn_trait.rs

@@ -592,7 +592,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
             if span.can_be_used_for_suggestions()
                 && poly_trait_ref.trait_ref.trait_def_id().is_some()
                 && !self.maybe_suggest_impl_trait(span, hir_id, hir_bounds, &mut diag)
-                && !self.maybe_suggest_dyn_trait(hir_id, sugg, &mut diag)
+                && !self.maybe_suggest_dyn_trait(hir_id, span, sugg, &mut diag)
             {
                 self.maybe_suggest_add_generic_impl_trait(span, hir_id, &mut diag);
             }
@@ -750,10 +750,14 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
     fn maybe_suggest_dyn_trait(
         &self,
         hir_id: hir::HirId,
+        span: Span,
         sugg: Vec<(Span, String)>,
         diag: &mut Diag<'_>,
     ) -> bool {
         let tcx = self.tcx();
+        if span.in_derive_expansion() {
+            return false;
+        }
 
         // Look at the direct HIR parent, since we care about the relationship between
         // the type and the thing that directly encloses it.

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1932,25 +1932,94 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     None,
                 );
             } else {
+                let mut suggest_derive = true;
                 if let Some(errors) =
                     self.type_implements_trait_shallow(clone_trait_did, expected_ty, self.param_env)
                 {
+                    let manually_impl = "consider manually implementing `Clone` to avoid the \
+                        implicit type parameter bounds";
                     match &errors[..] {
                         [] => {}
                         [error] => {
-                            diag.help(format!(
-                                "`Clone` is not implemented because the trait bound `{}` is \
-                                 not satisfied",
-                                error.obligation.predicate,
-                            ));
+                            let msg = "`Clone` is not implemented because a trait bound is not \
+                                satisfied";
+                            if let traits::ObligationCauseCode::ImplDerived(data) =
+                                error.obligation.cause.code()
+                            {
+                                let mut span: MultiSpan = data.span.into();
+                                if self.tcx.is_automatically_derived(data.impl_or_alias_def_id) {
+                                    span.push_span_label(
+                                        data.span,
+                                        format!(
+                                            "derive introduces an implicit `{}` bound",
+                                            error.obligation.predicate
+                                        ),
+                                    );
+                                }
+                                diag.span_help(span, msg);
+                                if self.tcx.is_automatically_derived(data.impl_or_alias_def_id)
+                                    && data.impl_or_alias_def_id.is_local()
+                                {
+                                    diag.help(manually_impl);
+                                    suggest_derive = false;
+                                }
+                            } else {
+                                diag.help(msg);
+                            }
                         }
                         _ => {
-                            diag.help(format!(
-                                "`Clone` is not implemented because the following trait bounds \
-                                 could not be satisfied: {}",
-                                listify(&errors, |e| format!("`{}`", e.obligation.predicate))
-                                    .unwrap(),
-                            ));
+                            let unsatisfied_bounds: Vec<_> = errors
+                                .iter()
+                                .filter_map(|error| match error.obligation.cause.code() {
+                                    traits::ObligationCauseCode::ImplDerived(data) => {
+                                        let pre = if self
+                                            .tcx
+                                            .is_automatically_derived(data.impl_or_alias_def_id)
+                                        {
+                                            "derive introduces an implicit "
+                                        } else {
+                                            ""
+                                        };
+                                        Some((
+                                            data.span,
+                                            format!(
+                                                "{pre}unsatisfied trait bound `{}`",
+                                                error.obligation.predicate
+                                            ),
+                                        ))
+                                    }
+                                    _ => None,
+                                })
+                                .collect();
+                            let msg = "`Clone` is not implemented because the some trait bounds \
+                                could not be satisfied";
+                            if errors.len() == unsatisfied_bounds.len() {
+                                let mut unsatisfied_bounds_spans: MultiSpan = unsatisfied_bounds
+                                    .iter()
+                                    .map(|(span, _)| *span)
+                                    .collect::<Vec<Span>>()
+                                    .into();
+                                for (span, label) in unsatisfied_bounds {
+                                    unsatisfied_bounds_spans.push_span_label(span, label);
+                                }
+                                diag.span_help(unsatisfied_bounds_spans, msg);
+                                if errors.iter().all(|error| match error.obligation.cause.code() {
+                                    traits::ObligationCauseCode::ImplDerived(data) => {
+                                        self.tcx.is_automatically_derived(data.impl_or_alias_def_id)
+                                            && data.impl_or_alias_def_id.is_local()
+                                    }
+                                    _ => false,
+                                }) {
+                                    diag.help(manually_impl);
+                                    suggest_derive = false;
+                                }
+                            } else {
+                                diag.help(format!(
+                                    "{msg}: {}",
+                                    listify(&errors, |e| format!("`{}`", e.obligation.predicate))
+                                        .unwrap(),
+                                ));
+                            }
                         }
                     }
                     for error in errors {
@@ -1968,7 +2037,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         }
                     }
                 }
-                self.suggest_derive(diag, &vec![(trait_ref.upcast(self.tcx), None, None)]);
+                if suggest_derive {
+                    self.suggest_derive(diag, &vec![(trait_ref.upcast(self.tcx), None, None)]);
+                }
             }
         }
     }