Suggest Pin::as_mut when encountering borrow error

compiler/rustc_borrowck/src/diagnostics/mod.rs

@@ -6,7 +6,7 @@ use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, Namespace};
 use rustc_hir::GeneratorKind;
-use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::infer::{LateBoundRegionConversionTime, TyCtxtInferExt};
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::{
     AggregateKind, Constant, FakeReadCause, Field, Local, LocalInfo, LocalKind, Location, Operand,
@@ -18,7 +18,10 @@ use rustc_mir_dataflow::move_paths::{InitLocation, LookupResult};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{symbol::sym, Span, Symbol, DUMMY_SP};
 use rustc_target::abi::VariantIdx;
-use rustc_trait_selection::traits::type_known_to_meet_bound_modulo_regions;
+use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
+use rustc_trait_selection::traits::{
+    type_known_to_meet_bound_modulo_regions, Obligation, ObligationCause,
+};
 
 use super::borrow_set::BorrowData;
 use super::MirBorrowckCtxt;
@@ -1131,13 +1134,19 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 place_name, partially_str, loop_message
                             ),
                         );
-                        let ty = tcx.erase_regions(moved_place.ty(self.body, self.infcx.tcx).ty);
+                        let infcx = tcx.infer_ctxt().build();
+                        let ty = infcx.freshen(moved_place.ty(self.body, tcx).ty);
                         if let ty::Adt(def, substs) = ty.kind()
-                            && Some(def.did()) == self.infcx.tcx.lang_items().pin_type()
+                            && Some(def.did()) == tcx.lang_items().pin_type()
                             && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()
-                            // FIXME: this is a hack because we can't call `can_eq`
-                            && ty.to_string() ==
-                                tcx.fn_sig(method_did).input(0).skip_binder().to_string()
+                            && let self_ty = infcx.freshen(
+                                infcx.replace_bound_vars_with_fresh_vars(
+                                    fn_call_span,
+                                    LateBoundRegionConversionTime::FnCall,
+                                    tcx.fn_sig(method_did).input(0),
+                                )
+                            )
+                            && infcx.can_eq(self.param_env, ty, self_ty).is_ok()
                         {
                             err.span_suggestion_verbose(
                                 fn_call_span.shrink_to_lo(),
@@ -1146,28 +1155,23 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 Applicability::MaybeIncorrect,
                             );
                         }
-                        if let Some(clone_trait) = tcx.lang_items().clone_trait() {
-                            // We can't use `predicate_may_hold` or `can_eq` without ICEs in
-                            // borrowck because of the inference context, so we do a poor-man's
-                            // version here.
-                            for impl_def_id in tcx.all_impls(clone_trait) {
-                                if let Some(def_id) = impl_def_id.as_local()
-                                    && let hir_id = tcx.hir().local_def_id_to_hir_id(def_id)
-                                    && let hir::Node::Item(hir::Item {
-                                        kind: hir::ItemKind::Impl(_),
-                                        ..
-                                    }) = tcx.hir().get(hir_id)
-                                    && tcx.type_of(impl_def_id) == ty
-                                {
-                                    err.span_suggestion_verbose(
-                                        fn_call_span.shrink_to_lo(),
-                                        "you can `clone` the value and consume it, but this might \
-                                         not be your desired behavior",
-                                        "clone().".to_string(),
-                                        Applicability::MaybeIncorrect,
-                                    );
-                                }
-                            }
+                        if let Some(clone_trait) = tcx.lang_items().clone_trait()
+                            && let trait_ref = tcx.mk_trait_ref(clone_trait, [ty])
+                            && let o = Obligation::new(
+                                tcx,
+                                ObligationCause::dummy(),
+                                self.param_env,
+                                ty::Binder::dummy(trait_ref),
+                            )
+                            && infcx.predicate_must_hold_modulo_regions(&o)
+                        {
+                            err.span_suggestion_verbose(
+                                fn_call_span.shrink_to_lo(),
+                                "you can `clone` the value and consume it, but this might not be \
+                                 your desired behavior",
+                                "clone().".to_string(),
+                                Applicability::MaybeIncorrect,
+                            );
                         }
                     }
                     // Avoid pointing to the same function in multiple different

src/test/ui/borrowck/borrowck-move-out-of-overloaded-auto-deref.stderr

@@ -9,6 +9,10 @@ LL |     let _x = Rc::new(vec![1, 2]).into_iter();
    |
 note: `into_iter` takes ownership of the receiver `self`, which moves value
   --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     let _x = Rc::new(vec![1, 2]).clone().into_iter();
+   |                                  ++++++++
 
 error: aborting due to previous error
 

src/test/ui/borrowck/unboxed-closures-move-upvar-from-non-once-ref-closure.fixed

@@ -0,0 +1,15 @@
+// run-rustfix
+// Test that a by-ref `FnMut` closure gets an error when it tries to
+// consume a value.
+
+fn call<F>(f: F) where F : Fn() {
+    f();
+}
+
+fn main() {
+    let y = vec![format!("World")];
+    call(|| {
+        y.clone().into_iter();
+        //~^ ERROR cannot move out of `y`, a captured variable in an `Fn` closure
+    });
+}

src/test/ui/borrowck/unboxed-closures-move-upvar-from-non-once-ref-closure.rs

@@ -1,3 +1,4 @@
+// run-rustfix
 // Test that a by-ref `FnMut` closure gets an error when it tries to
 // consume a value.
 

src/test/ui/borrowck/unboxed-closures-move-upvar-from-non-once-ref-closure.stderr

@@ -1,5 +1,5 @@
 error[E0507]: cannot move out of `y`, a captured variable in an `Fn` closure
-  --> $DIR/unboxed-closures-move-upvar-from-non-once-ref-closure.rs:11:9
+  --> $DIR/unboxed-closures-move-upvar-from-non-once-ref-closure.rs:12:9
    |
 LL |     let y = vec![format!("World")];
    |         - captured outer variable
@@ -12,6 +12,10 @@ LL |         y.into_iter();
    |
 note: `into_iter` takes ownership of the receiver `self`, which moves `y`
   --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |         y.clone().into_iter();
+   |           ++++++++
 
 error: aborting due to previous error
 

src/test/ui/codemap_tests/tab_3.stderr

@@ -16,6 +16,10 @@ help: consider cloning the value if the performance cost is acceptable
    |
 LL |     some_vec.clone().into_iter();
    |             ++++++++
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     some_vec.clone().into_iter();
+   |              ++++++++
 
 error: aborting due to previous error
 

src/test/ui/moves/move-fn-self-receiver.stderr

@@ -9,6 +9,10 @@ LL |     val.0;
 note: `into_iter` takes ownership of the receiver `self`, which moves `val.0`
   --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
    = note: move occurs because `val.0` has type `Vec<bool>`, which does not implement the `Copy` trait
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     val.0.clone().into_iter().next();
+   |           ++++++++
 
 error[E0382]: use of moved value: `foo`
   --> $DIR/move-fn-self-receiver.rs:34:5
@@ -97,6 +101,10 @@ help: consider cloning the value if the performance cost is acceptable
    |
 LL |     rc_foo.clone().use_rc_self();
    |           ++++++++
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     rc_foo.clone().use_rc_self();
+   |            ++++++++
 
 error[E0382]: use of moved value: `foo_add`
   --> $DIR/move-fn-self-receiver.rs:59:5
@@ -140,6 +148,10 @@ help: consider cloning the value if the performance cost is acceptable
    |
 LL |     for _val in explicit_into_iter.clone().into_iter() {}
    |                                   ++++++++
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     for _val in explicit_into_iter.clone().into_iter() {}
+   |                                    ++++++++
 
 error[E0382]: use of moved value: `container`
   --> $DIR/move-fn-self-receiver.rs:71:5

src/test/ui/moves/moves-based-on-type-access-to-field.stderr

@@ -14,6 +14,10 @@ help: consider cloning the value if the performance cost is acceptable
    |
 LL |     consume(x.clone().into_iter().next().unwrap());
    |              ++++++++
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     consume(x.clone().into_iter().next().unwrap());
+   |               ++++++++
 
 error: aborting due to previous error
 

src/test/ui/moves/moves-based-on-type-exprs.stderr

@@ -166,6 +166,10 @@ help: consider cloning the value if the performance cost is acceptable
    |
 LL |     let _y = x.clone().into_iter().next().unwrap();
    |               ++++++++
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     let _y = x.clone().into_iter().next().unwrap();
+   |                ++++++++
 
 error[E0382]: borrow of moved value: `x`
   --> $DIR/moves-based-on-type-exprs.rs:83:11
@@ -183,6 +187,10 @@ help: consider cloning the value if the performance cost is acceptable
    |
 LL |     let _y = [x.clone().into_iter().next().unwrap(); 1];
    |                ++++++++
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |     let _y = [x.clone().into_iter().next().unwrap(); 1];
+   |                 ++++++++
 
 error: aborting due to 11 previous errors
 

src/test/ui/suggestions/option-content-move.stderr

@@ -9,6 +9,10 @@ LL |                 if selection.1.unwrap().contains(selection.0) {
    |
 note: `Option::<T>::unwrap` takes ownership of the receiver `self`, which moves `selection.1`
   --> $SRC_DIR/core/src/option.rs:LL:COL
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |                 if selection.1.clone().unwrap().contains(selection.0) {
+   |                                ++++++++
 
 error[E0507]: cannot move out of `selection.1` which is behind a shared reference
   --> $DIR/option-content-move.rs:27:20
@@ -21,6 +25,10 @@ LL |                 if selection.1.unwrap().contains(selection.0) {
    |
 note: `Result::<T, E>::unwrap` takes ownership of the receiver `self`, which moves `selection.1`
   --> $SRC_DIR/core/src/result.rs:LL:COL
+help: you can `clone` the value and consume it, but this might not be your desired behavior
+   |
+LL |                 if selection.1.clone().unwrap().contains(selection.0) {
+   |                                ++++++++
 
 error: aborting due to 2 previous errors