Rollup merge of rust-lang#56843 - csmoe:non-copy, r=davidtwco

Add a note describing the type of the non-Copy moved variable

Closes rust-lang#56654
r?@davidtwco

Author: pietroalbini

src/librustc_mir/borrow_check/error_reporting.rs

@@ -191,38 +191,36 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                 );
             }
 
-            if let Some(ty) = self.retrieve_type_for_place(used_place) {
-                let needs_note = match ty.sty {
-                    ty::Closure(id, _) => {
-                        let tables = self.infcx.tcx.typeck_tables_of(id);
-                        let node_id = self.infcx.tcx.hir().as_local_node_id(id).unwrap();
-                        let hir_id = self.infcx.tcx.hir().node_to_hir_id(node_id);
-
-                        tables.closure_kind_origins().get(hir_id).is_none()
-                    }
-                    _ => true,
-                };
+            let ty = used_place.ty(self.mir, self.infcx.tcx).to_ty(self.infcx.tcx);
+            let needs_note = match ty.sty {
+                ty::Closure(id, _) => {
+                    let tables = self.infcx.tcx.typeck_tables_of(id);
+                    let node_id = self.infcx.tcx.hir().as_local_node_id(id).unwrap();
+                    let hir_id = self.infcx.tcx.hir().node_to_hir_id(node_id);
 
-                if needs_note {
-                    let mpi = self.move_data.moves[move_out_indices[0]].path;
-                    let place = &self.move_data.move_paths[mpi].place;
-
-                    if let Some(ty) = self.retrieve_type_for_place(place) {
-                        let note_msg = match self.describe_place_with_options(
-                            place,
-                            IncludingDowncast(true),
-                        ) {
-                            Some(name) => format!("`{}`", name),
-                            None => "value".to_owned(),
-                        };
-
-                        err.note(&format!(
-                            "move occurs because {} has type `{}`, \
-                             which does not implement the `Copy` trait",
-                            note_msg, ty
-                        ));
-                    }
+                    tables.closure_kind_origins().get(hir_id).is_none()
                 }
+                _ => true,
+            };
+
+            if needs_note {
+                let mpi = self.move_data.moves[move_out_indices[0]].path;
+                let place = &self.move_data.move_paths[mpi].place;
+
+                let ty = place.ty(self.mir, self.infcx.tcx).to_ty(self.infcx.tcx);
+                let note_msg = match self.describe_place_with_options(
+                    place,
+                    IncludingDowncast(true),
+                ) {
+                    Some(name) => format!("`{}`", name),
+                    None => "value".to_owned(),
+                };
+
+                err.note(&format!(
+                    "move occurs because {} has type `{}`, \
+                     which does not implement the `Copy` trait",
+                    note_msg, ty
+                ));
             }
 
             if let Some((_, mut old_err)) = self.move_error_reported
@@ -1568,7 +1566,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
                         )?;
                         buf.push_str("[");
                         if self.append_local_to_string(index, buf).is_err() {
-                            buf.push_str("..");
+                            buf.push_str("_");
                         }
                         buf.push_str("]");
                     }
@@ -1673,22 +1671,6 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
         }
     }
 
-    /// Retrieve type of a place for the current MIR representation
-    fn retrieve_type_for_place(&self, place: &Place<'tcx>) -> Option<ty::Ty> {
-        match place {
-            Place::Local(local) => {
-                let local = &self.mir.local_decls[*local];
-                Some(local.ty)
-            }
-            Place::Promoted(ref prom) => Some(prom.1),
-            Place::Static(ref st) => Some(st.ty),
-            Place::Projection(ref proj) => match proj.elem {
-                ProjectionElem::Field(_, ty) => Some(ty),
-                _ => None,
-            },
-        }
-    }
-
     /// Check if a place is a thread-local static.
     pub fn is_place_thread_local(&self, place: &Place<'tcx>) -> bool {
         if let Place::Static(statik) = place {

src/test/ui/borrowck/borrowck-describe-lvalue.mir.stderr

@@ -316,7 +316,7 @@ LL |         v[0].y;
 LL |         drop(x);
    |              - borrow later used here
 
-error[E0503]: cannot use `v[..].y` because it was mutably borrowed
+error[E0503]: cannot use `v[_].y` because it was mutably borrowed
   --> $DIR/borrowck-describe-lvalue.rs:271:9
    |
 LL |         let x = &mut v;

src/test/ui/borrowck/borrowck-describe-lvalue.rs

@@ -270,7 +270,7 @@ fn main() {
         let x = &mut v;
         v[0].y;
         //[ast]~^ ERROR cannot use `v[..].y` because it was mutably borrowed
-        //[mir]~^^ ERROR cannot use `v[..].y` because it was mutably borrowed
+        //[mir]~^^ ERROR cannot use `v[_].y` because it was mutably borrowed
         //[mir]~| ERROR cannot use `*v` because it was mutably borrowed
         drop(x);
     }

src/test/ui/borrowck/borrowck-move-out-from-array.mir.stderr

@@ -5,6 +5,8 @@ LL |     let [_, _x] = a;
    |             -- value moved here
 LL |     let [.., _y] = a; //[ast]~ ERROR [E0382]
    |              ^^ value used here after move
+   |
+   = note: move occurs because `a[..]` has type `std::boxed::Box<i32>`, which does not implement the `Copy` trait
 
 error[E0382]: use of moved value: `a[..]`
   --> $DIR/borrowck-move-out-from-array.rs:27:10
@@ -13,6 +15,8 @@ LL |     let [_x, _] = a;
    |          -- value moved here
 LL |     let [_y..] = a; //[ast]~ ERROR [E0382]
    |          ^^ value used here after move
+   |
+   = note: move occurs because `a[..]` has type `std::boxed::Box<i32>`, which does not implement the `Copy` trait
 
 error: aborting due to 2 previous errors
 

src/test/ui/borrowck/borrowck-vec-pattern-move-tail.cmp.stderr

@@ -7,14 +7,14 @@ LL |         [1, 2, ref tail..] => tail,
 LL |     a[2] = 0; //[ast]~ ERROR cannot assign to `a[..]` because it is borrowed
    |     ^^^^^^^^ assignment to borrowed `a[..]` occurs here
 
-error[E0506]: cannot assign to `a[..]` because it is borrowed (Mir)
+error[E0506]: cannot assign to `a[_]` because it is borrowed (Mir)
   --> $DIR/borrowck-vec-pattern-move-tail.rs:24:5
    |
 LL |         [1, 2, ref tail..] => tail,
-   |                -------- borrow of `a[..]` occurs here
+   |                -------- borrow of `a[_]` occurs here
 ...
 LL |     a[2] = 0; //[ast]~ ERROR cannot assign to `a[..]` because it is borrowed
-   |     ^^^^^^^^ assignment to borrowed `a[..]` occurs here
+   |     ^^^^^^^^ assignment to borrowed `a[_]` occurs here
 ...
 LL |     println!("t[0]: {}", t[0]);
    |                          ---- borrow later used here

src/test/ui/borrowck/borrowck-vec-pattern-move-tail.rs

@@ -23,7 +23,7 @@ fn main() {
     println!("t[0]: {}", t[0]);
     a[2] = 0; //[ast]~ ERROR cannot assign to `a[..]` because it is borrowed
               //[cmp]~^ ERROR cannot assign to `a[..]` because it is borrowed (Ast)
-              //[cmp]~| ERROR cannot assign to `a[..]` because it is borrowed (Mir)
+              //[cmp]~| ERROR cannot assign to `a[_]` because it is borrowed (Mir)
     println!("t[0]: {}", t[0]);
     t[0];
 }

src/test/ui/borrowck/two-phase-nonrecv-autoref.nll.stderr

@@ -14,6 +14,8 @@ LL |         f(f(10));
    |         - ^ value used here after move
    |         |
    |         value moved here
+   |
+   = note: move occurs because `*f` has type `F`, which does not implement the `Copy` trait
 
 error[E0499]: cannot borrow `*f` as mutable more than once at a time
   --> $DIR/two-phase-nonrecv-autoref.rs:86:11
@@ -43,6 +45,8 @@ LL |         f(f(10));
    |         - ^ value used here after move
    |         |
    |         value moved here
+   |
+   = note: move occurs because `*f` has type `dyn std::ops::FnOnce(i32) -> i32`, which does not implement the `Copy` trait
 
 error[E0502]: cannot borrow `a` as immutable because it is also borrowed as mutable
   --> $DIR/two-phase-nonrecv-autoref.rs:139:27

src/test/ui/issues/issue-27282-move-match-input-into-guard.stderr

@@ -8,6 +8,8 @@ LL |         _ if { (|| { let bar = b; *bar = false; })();
 LL |                      false } => { },
 LL |         &mut true => { println!("You might think we should get here"); },
    |              ^^^^ value used here after move
+   |
+   = note: move occurs because `b` has type `&mut bool`, which does not implement the `Copy` trait
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-46604.mir.stderr

@@ -4,7 +4,7 @@ error[E0017]: references in statics may only refer to immutable values
 LL | static buf: &mut [u8] = &mut [1u8,2,3,4,5,7];   //[ast]~ ERROR E0017
    |                         ^^^^^^^^^^^^^^^^^^^^ statics require immutable values
 
-error[E0594]: cannot assign to `buf[..]`, as `buf` is an immutable static item
+error[E0594]: cannot assign to `buf[_]`, as `buf` is an immutable static item
   --> $DIR/issue-46604.rs:20:5
    |
 LL |     buf[0]=2;                                   //[ast]~ ERROR E0389

src/test/ui/nll/drop-no-may-dangle.rs

@@ -27,10 +27,10 @@ fn main() {
         use_x(*p.value);
     } else {
         use_x(22);
-        v[0] += 1; //~ ERROR cannot assign to `v[..]` because it is borrowed
+        v[0] += 1; //~ ERROR cannot assign to `v[_]` because it is borrowed
     }
 
-    v[0] += 1; //~ ERROR cannot assign to `v[..]` because it is borrowed
+    v[0] += 1; //~ ERROR cannot assign to `v[_]` because it is borrowed
 }
 
 struct WrapMayNotDangle<T> {