Rollup merge of #75304 - Aaron1011:feature/diag-deref-move-out, r=estebank

Note when a a move/borrow error is caused by a deref coercion

Fixes #73268

When a deref coercion occurs, we may end up with a move error if the
base value has been partially moved out of. However, we do not indicate
anywhere that a deref coercion is occuring, resulting in an error
message with a confusing span.

This PR adds an explicit note to move errors when a deref coercion is
involved. We mention the name of the type that the deref-coercion
resolved to, as well as the `Deref::Target` associated type being used.

2 files changed, 8 insertions, 1 deletions

diff --git a/compiler/rustc_trait_selection/src/autoderef.rs b/compiler/rustc_trait_selection/src/autoderef.rs
index 02eefe56223..b9c5123e49a 100644
--- a/compiler/rustc_trait_selection/src/autoderef.rs
+++ b/compiler/rustc_trait_selection/src/autoderef.rs
@@ -27,6 +27,7 @@ pub struct Autoderef<'a, 'tcx> {
     // Meta infos:
     infcx: &'a InferCtxt<'a, 'tcx>,
     span: Span,
+    overloaded_span: Span,
     body_id: hir::HirId,
     param_env: ty::ParamEnv<'tcx>,
 
@@ -98,10 +99,12 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
         body_id: hir::HirId,
         span: Span,
         base_ty: Ty<'tcx>,
+        overloaded_span: Span,
     ) -> Autoderef<'a, 'tcx> {
         Autoderef {
             infcx,
             span,
+            overloaded_span,
             body_id,
             param_env,
             state: AutoderefSnapshot {
@@ -190,6 +193,10 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
         self.span
     }
 
+    pub fn overloaded_span(&self) -> Span {
+        self.overloaded_span
+    }
+
     pub fn reached_recursion_limit(&self) -> bool {
         self.state.reached_recursion_limit
     }
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 82e809d014d..90a8d9634ae 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -483,7 +483,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         };
 
         if let ty::Ref(region, base_ty, mutbl) = *real_ty.kind() {
-            let mut autoderef = Autoderef::new(self, param_env, body_id, span, base_ty);
+            let mut autoderef = Autoderef::new(self, param_env, body_id, span, base_ty, span);
             if let Some(steps) = autoderef.find_map(|(ty, steps)| {
                 // Re-add the `&`
                 let ty = self.tcx.mk_ref(region, TypeAndMut { ty, mutbl });