Refine deref suggestions

Author: nataliakokoromyti

compiler/rustc_borrowck/src/diagnostics/move_errors.rs

@@ -800,7 +800,10 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 let mut is_raw_ptr = false;
                 let mut is_ref = false;
                 let mut is_destructuring_assignment = false;
+                let mut is_nested_deref = false;
                 if let Some(inner) = inner {
+                    is_nested_deref =
+                        matches!(inner.kind, hir::ExprKind::Unary(hir::UnOp::Deref, _));
                     let typck_result = self.infcx.tcx.typeck(self.mir_def_id());
                     if let Some(inner_type) = typck_result.node_type_opt(inner.hir_id) {
                         if matches!(inner_type.kind(), ty::RawPtr(..)) {
@@ -822,21 +825,25 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 }
                 // If the `inner` is a raw pointer, do not suggest removing the "*", see #126863
                 // FIXME: need to check whether the assigned object can be a raw pointer, see `tests/ui/borrowck/issue-20801.rs`.
-                if !is_raw_ptr && (!is_destructuring_pattern_move || is_ref) {
+                if is_raw_ptr {
+                    return;
+                }
+
+                if !is_destructuring_pattern_move || is_ref {
                     err.span_suggestion_verbose(
                         span.with_hi(span.lo() + BytePos(1)),
                         "consider removing the dereference here",
                         String::new(),
                         Applicability::MaybeIncorrect,
                     );
-                } else if !is_raw_ptr && !is_destructuring_assignment {
+                } else if !is_destructuring_assignment && !is_nested_deref {
                     err.span_suggestion_verbose(
                         span.shrink_to_lo(),
                         "consider borrowing here",
                         '&',
                         Applicability::MaybeIncorrect,
                     );
-                } else if !is_raw_ptr {
+                } else {
                     err.span_help(
                         span,
                         "destructuring assignment cannot borrow from this expression; consider using a `let` binding instead",

tests/ui/suggestions/issue-102892.stderr

@@ -61,12 +61,12 @@ LL |     let (a, b) = **arc; // suggests putting `&**arc` here; with that, fixed
    |          |  ...and here
    |          data moved here
    |
-   = note: move occurs because these variables have types that don't implement the `Copy` trait
-help: consider removing the dereference here
-   |
-LL -     let (a, b) = **arc; // suggests putting `&**arc` here; with that, fixed!
-LL +     let (a, b) = *arc; // suggests putting `&**arc` here; with that, fixed!
+help: destructuring assignment cannot borrow from this expression; consider using a `let` binding instead
+  --> $DIR/issue-102892.rs:11:18
    |
+LL |     let (a, b) = **arc; // suggests putting `&**arc` here; with that, fixed!
+   |                  ^^^^^
+   = note: move occurs because these variables have types that don't implement the `Copy` trait
 
 error: aborting due to 4 previous errors