Address review comment

Author: smoelius

compiler/rustc_lint/src/internal.rs

@@ -84,10 +84,10 @@ declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY, UNTRACKED_QUE
 
 impl<'tcx> LateLintPass<'tcx> for QueryStability {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
-        if let Some((def_id, span, generic_args, _recv, _args)) =
+        if let Some((callee_def_id, span, generic_args, _recv, _args)) =
             get_callee_span_generic_args_and_args(cx, expr)
             && let Ok(Some(instance)) =
-                ty::Instance::try_resolve(cx.tcx, cx.typing_env(), def_id, generic_args)
+                ty::Instance::try_resolve(cx.tcx, cx.typing_env(), callee_def_id, generic_args)
         {
             let def_id = instance.def_id();
             if cx.tcx.has_attr(def_id, sym::rustc_lint_query_instability) {
@@ -96,6 +96,13 @@ impl<'tcx> LateLintPass<'tcx> for QueryStability {
                     span,
                     QueryInstability { query: cx.tcx.item_name(def_id) },
                 );
+            } else if has_unstable_into_iter_predicate(cx, callee_def_id, generic_args) {
+                let call_span = span.with_hi(expr.span.hi());
+                cx.emit_span_lint(
+                    POTENTIAL_QUERY_INSTABILITY,
+                    call_span,
+                    QueryInstability { query: sym::into_iter },
+                );
             }
             if cx.tcx.has_attr(def_id, sym::rustc_lint_untracked_query_information) {
                 cx.emit_span_lint(
@@ -105,25 +112,19 @@ impl<'tcx> LateLintPass<'tcx> for QueryStability {
                 );
             }
         }
-        check_into_iter_stability(cx, expr);
     }
 }
 
-fn check_into_iter_stability<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+fn has_unstable_into_iter_predicate<'tcx>(
+    cx: &LateContext<'tcx>,
+    callee_def_id: DefId,
+    generic_args: GenericArgsRef<'tcx>,
+) -> bool {
     let Some(into_iterator_def_id) = cx.tcx.get_diagnostic_item(sym::IntoIterator) else {
-        return;
+        return false;
     };
     let Some(into_iter_fn_def_id) = cx.tcx.lang_items().into_iter_fn() else {
-        return;
-    };
-    if expr.span.from_expansion() {
-        return;
-    };
-    // Is `expr` a function or method call?
-    let Some((callee_def_id, span, generic_args, _recv, _args)) =
-        get_callee_span_generic_args_and_args(cx, expr)
-    else {
-        return;
+        return false;
     };
     let predicates = cx.tcx.predicates_of(callee_def_id).instantiate(cx.tcx, generic_args);
     for (predicate, _) in predicates {
@@ -143,16 +144,11 @@ fn check_into_iter_stability<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx
         };
         // Does the input type's `IntoIterator` implementation have the
         // `rustc_lint_query_instability` attribute on its `into_iter` method?
-        if !cx.tcx.has_attr(instance.def_id(), sym::rustc_lint_query_instability) {
-            return;
+        if cx.tcx.has_attr(instance.def_id(), sym::rustc_lint_query_instability) {
+            return true;
         }
-        let span = span.with_hi(expr.span.hi());
-        cx.emit_span_lint(
-            POTENTIAL_QUERY_INSTABILITY,
-            span,
-            QueryInstability { query: cx.tcx.item_name(instance.def_id()) },
-        );
     }
+    false
 }
 
 /// Checks whether an expression is a function or method call and, if so, returns its `DefId`,