Do not report an excessive number of overflow errors for an ever-growing deref impl

5 files changed, 61 insertions, 3 deletions

diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 6fd509ed32f..c03eeb1790e 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -2942,7 +2942,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Vec<(Vec<&'tcx ty::FieldDef>, GenericArgsRef<'tcx>)> {
         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
 
-        self.autoderef(span, base_ty)
+        let mut autoderef = self.autoderef(span, base_ty).silence_errors();
+        let deref_chain: Vec<_> = autoderef.by_ref().collect();
+
+        // Don't probe if we hit the recursion limit, since it may result in
+        // quadratic blowup if we then try to further deref the results of this
+        // function. This is a best-effort method, after all.
+        if autoderef.reached_recursion_limit() {
+            return vec![];
+        }
+
+        deref_chain
+            .into_iter()
             .filter_map(move |(base_t, _)| {
                 match base_t.kind() {
                     ty::Adt(base_def, args) if !base_def.is_enum() => {
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 3ba3429cbb3..5dc341653e5 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -375,7 +375,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // If our autoderef loop had reached the recursion limit,
         // report an overflow error, but continue going on with
         // the truncated autoderef list.
-        if steps.reached_recursion_limit {
+        if steps.reached_recursion_limit && !is_suggestion.0 {
             self.probe(|_| {
                 let ty = &steps
                     .steps
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index 9ede809ead2..207cf4686b6 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -672,7 +672,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let mut ty_str_reported = ty_str.clone();
         if let ty::Adt(_, generics) = rcvr_ty.kind() {
             if generics.len() > 0 {
-                let mut autoderef = self.autoderef(span, rcvr_ty);
+                let mut autoderef = self.autoderef(span, rcvr_ty).silence_errors();
                 let candidate_found = autoderef.any(|(ty, _)| {
                     if let ty::Adt(adt_def, _) = ty.kind() {
                         self.tcx
diff --git a/tests/ui/methods/probe-error-on-infinite-deref.rs b/tests/ui/methods/probe-error-on-infinite-deref.rs
new file mode 100644
index 00000000000..c671092e6aa
--- /dev/null
+++ b/tests/ui/methods/probe-error-on-infinite-deref.rs
@@ -0,0 +1,17 @@
+use std::ops::Deref;
+
+// Make sure that method probe error reporting doesn't get too tangled up
+// on this infinite deref impl. See #130224.
+
+struct Wrap<T>(T);
+impl<T> Deref for Wrap<T> {
+    type Target = Wrap<Wrap<T>>;
+    fn deref(&self) -> &Wrap<Wrap<T>> { todo!() }
+}
+
+fn main() {
+    Wrap(1).lmao();
+    //~^ ERROR reached the recursion limit
+    //~| ERROR reached the recursion limit
+    //~| ERROR no method named `lmao`
+}
diff --git a/tests/ui/methods/probe-error-on-infinite-deref.stderr b/tests/ui/methods/probe-error-on-infinite-deref.stderr
new file mode 100644
index 00000000000..0d416a71222
--- /dev/null
+++ b/tests/ui/methods/probe-error-on-infinite-deref.stderr
@@ -0,0 +1,30 @@
+error[E0055]: reached the recursion limit while auto-dereferencing `Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<{integer}>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
+  --> $DIR/probe-error-on-infinite-deref.rs:13:13
+   |
+LL |     Wrap(1).lmao();
+   |             ^^^^ deref recursion limit reached
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`probe_error_on_infinite_deref`)
+
+error[E0055]: reached the recursion limit while auto-dereferencing `Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<Wrap<{integer}>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>`
+  --> $DIR/probe-error-on-infinite-deref.rs:13:13
+   |
+LL |     Wrap(1).lmao();
+   |             ^^^^ deref recursion limit reached
+   |
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`probe_error_on_infinite_deref`)
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error[E0599]: no method named `lmao` found for struct `Wrap<{integer}>` in the current scope
+  --> $DIR/probe-error-on-infinite-deref.rs:13:13
+   |
+LL | struct Wrap<T>(T);
+   | -------------- method `lmao` not found for this struct
+...
+LL |     Wrap(1).lmao();
+   |             ^^^^ method not found in `Wrap<{integer}>`
+
+error: aborting due to 3 previous errors
+
+Some errors have detailed explanations: E0055, E0599.
+For more information about an error, try `rustc --explain E0055`.