From 4216caed31b56d1980812960b740af5d93de36b9 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Sat, 22 Oct 2022 20:34:37 +0000
Subject: [PATCH] filter candidates in pick probe for diagnostics

---
 compiler/rustc_hir_typeck/src/demand.rs       | 41 +++++++++++--------
 compiler/rustc_hir_typeck/src/method/probe.rs | 13 ++++--
 2 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index 2974ac97f2368..7c74ac6f17037 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -530,24 +530,29 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         checked_ty: Ty<'tcx>,
         hir_id: hir::HirId,
     ) -> Vec<AssocItem> {
-        let mut methods =
-            self.probe_for_return_type(span, probe::Mode::MethodCall, expected, checked_ty, hir_id);
-        methods.retain(|m| {
-            self.has_only_self_parameter(m)
-                && self
-                    .tcx
-                    // This special internal attribute is used to permit
-                    // "identity-like" conversion methods to be suggested here.
-                    //
-                    // FIXME (#46459 and #46460): ideally
-                    // `std::convert::Into::into` and `std::borrow:ToOwned` would
-                    // also be `#[rustc_conversion_suggestion]`, if not for
-                    // method-probing false-positives and -negatives (respectively).
-                    //
-                    // FIXME? Other potential candidate methods: `as_ref` and
-                    // `as_mut`?
-                    .has_attr(m.def_id, sym::rustc_conversion_suggestion)
-        });
+        let methods = self.probe_for_return_type(
+            span,
+            probe::Mode::MethodCall,
+            expected,
+            checked_ty,
+            hir_id,
+            |m| {
+                self.has_only_self_parameter(m)
+                    && self
+                        .tcx
+                        // This special internal attribute is used to permit
+                        // "identity-like" conversion methods to be suggested here.
+                        //
+                        // FIXME (#46459 and #46460): ideally
+                        // `std::convert::Into::into` and `std::borrow:ToOwned` would
+                        // also be `#[rustc_conversion_suggestion]`, if not for
+                        // method-probing false-positives and -negatives (respectively).
+                        //
+                        // FIXME? Other potential candidate methods: `as_ref` and
+                        // `as_mut`?
+                        .has_attr(m.def_id, sym::rustc_conversion_suggestion)
+            },
+        );
 
         methods
     }
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 74cf2ac32aab2..28aa2302f882f 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -252,7 +252,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// would result in an error (basically, the same criteria we
     /// would use to decide if a method is a plausible fit for
     /// ambiguity purposes).
-    #[instrument(level = "debug", skip(self))]
+    #[instrument(level = "debug", skip(self, candidate_filter))]
     pub fn probe_for_return_type(
         &self,
         span: Span,
@@ -260,6 +260,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         return_type: Ty<'tcx>,
         self_ty: Ty<'tcx>,
         scope_expr_id: hir::HirId,
+        candidate_filter: impl Fn(&ty::AssocItem) -> bool,
     ) -> Vec<ty::AssocItem> {
         let method_names = self
             .probe_op(
@@ -271,7 +272,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self_ty,
                 scope_expr_id,
                 ProbeScope::AllTraits,
-                |probe_cx| Ok(probe_cx.candidate_method_names()),
+                |probe_cx| Ok(probe_cx.candidate_method_names(candidate_filter)),
             )
             .unwrap_or_default();
         method_names
@@ -966,12 +967,16 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         }
     }
 
-    fn candidate_method_names(&self) -> Vec<Ident> {
+    fn candidate_method_names(
+        &self,
+        candidate_filter: impl Fn(&ty::AssocItem) -> bool,
+    ) -> Vec<Ident> {
         let mut set = FxHashSet::default();
         let mut names: Vec<_> = self
             .inherent_candidates
             .iter()
             .chain(&self.extension_candidates)
+            .filter(|candidate| candidate_filter(&candidate.item))
             .filter(|candidate| {
                 if let Some(return_ty) = self.return_type {
                     self.matches_return_type(&candidate.item, None, return_ty)
@@ -1689,7 +1694,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             pcx.allow_similar_names = true;
             pcx.assemble_inherent_candidates();
 
-            let method_names = pcx.candidate_method_names();
+            let method_names = pcx.candidate_method_names(|_| true);
             pcx.allow_similar_names = false;
             let applicable_close_candidates: Vec<ty::AssocItem> = method_names
                 .iter()