address review comment

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -313,6 +313,18 @@ pub trait TypeErrCtxtExt<'tcx> {
         predicate: ty::Predicate<'tcx>,
         call_hir_id: HirId,
     );
+
+    fn look_for_iterator_item_mistakes(
+        &self,
+        assocs_in_this_method: &[Option<(Span, (DefId, Ty<'tcx>))>],
+        typeck_results: &TypeckResults<'tcx>,
+        type_diffs: &[TypeError<'tcx>],
+        param_env: ty::ParamEnv<'tcx>,
+        path_segment: &hir::PathSegment<'_>,
+        args: &[hir::Expr<'_>],
+        err: &mut Diagnostic,
+    );
+
     fn point_at_chain(
         &self,
         expr: &hir::Expr<'_>,
@@ -321,6 +333,7 @@ pub trait TypeErrCtxtExt<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         err: &mut Diagnostic,
     );
+
     fn probe_assoc_types_at_expr(
         &self,
         type_diffs: &[TypeError<'tcx>],
@@ -3592,39 +3605,24 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         }
     }
 
-    fn point_at_chain(
+    fn look_for_iterator_item_mistakes(
         &self,
-        expr: &hir::Expr<'_>,
+        assocs_in_this_method: &[Option<(Span, (DefId, Ty<'tcx>))>],
         typeck_results: &TypeckResults<'tcx>,
-        type_diffs: Vec<TypeError<'tcx>>,
+        type_diffs: &[TypeError<'tcx>],
         param_env: ty::ParamEnv<'tcx>,
+        path_segment: &hir::PathSegment<'_>,
+        args: &[hir::Expr<'_>],
         err: &mut Diagnostic,
     ) {
-        let mut primary_spans = vec![];
-        let mut span_labels = vec![];
-
         let tcx = self.tcx;
-
-        let mut print_root_expr = true;
-        let mut assocs = vec![];
-        let mut expr = expr;
-        let mut prev_ty = self.resolve_vars_if_possible(
-            typeck_results.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(tcx)),
-        );
-        while let hir::ExprKind::MethodCall(path_segment, rcvr_expr, args, span) = expr.kind {
-            // Point at every method call in the chain with the resulting type.
-            // vec![1, 2, 3].iter().map(mapper).sum<i32>()
-            //               ^^^^^^ ^^^^^^^^^^^
-            expr = rcvr_expr;
-            let assocs_in_this_method =
-                self.probe_assoc_types_at_expr(&type_diffs, span, prev_ty, expr.hir_id, param_env);
         // Special case for iterator chains, we look at potential failures of `Iterator::Item`
         // not being `: Clone` and `Iterator::map` calls with spurious trailing `;`.
-            for entry in &assocs_in_this_method {
+        for entry in assocs_in_this_method {
             let Some((_span, (def_id, ty))) = entry else {
                 continue;
             };
-                for diff in &type_diffs {
+            for diff in type_diffs {
                 let Sorts(expected_found) = diff else {
                     continue;
                 };
@@ -3708,6 +3706,43 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 }
             }
         }
+    }
+
+    fn point_at_chain(
+        &self,
+        expr: &hir::Expr<'_>,
+        typeck_results: &TypeckResults<'tcx>,
+        type_diffs: Vec<TypeError<'tcx>>,
+        param_env: ty::ParamEnv<'tcx>,
+        err: &mut Diagnostic,
+    ) {
+        let mut primary_spans = vec![];
+        let mut span_labels = vec![];
+
+        let tcx = self.tcx;
+
+        let mut print_root_expr = true;
+        let mut assocs = vec![];
+        let mut expr = expr;
+        let mut prev_ty = self.resolve_vars_if_possible(
+            typeck_results.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(tcx)),
+        );
+        while let hir::ExprKind::MethodCall(path_segment, rcvr_expr, args, span) = expr.kind {
+            // Point at every method call in the chain with the resulting type.
+            // vec![1, 2, 3].iter().map(mapper).sum<i32>()
+            //               ^^^^^^ ^^^^^^^^^^^
+            expr = rcvr_expr;
+            let assocs_in_this_method =
+                self.probe_assoc_types_at_expr(&type_diffs, span, prev_ty, expr.hir_id, param_env);
+            self.look_for_iterator_item_mistakes(
+                &assocs_in_this_method,
+                typeck_results,
+                &type_diffs,
+                param_env,
+                path_segment,
+                args,
+                err,
+            );
             assocs.push(assocs_in_this_method);
             prev_ty = self.resolve_vars_if_possible(
                 typeck_results.expr_ty_adjusted_opt(expr).unwrap_or(Ty::new_misc_error(tcx)),