[clang] 18a0313 - [Sema] Fix strict ordering in overload candidate comparisons

[Ilya Biryukov via cfe-commits]

Author: Ilya Biryukov
Date: 2023-11-10T17:12:24+01:00
New Revision: 18a0313149ea2d6134e566d9190ecede96e77afb

URL: https://github.com/llvm/llvm-project/commit/18a0313149ea2d6134e566d9190ecede96e77afb
DIFF: https://github.com/llvm/llvm-project/commit/18a0313149ea2d6134e566d9190ecede96e77afb.diff

LOG: [Sema] Fix strict ordering in overload candidate comparisons

This is a follow-up to febf5c97bba7910e796041c9518fce01f31ae826 and
another instance of #64121.

The added test only fails if Clang is built with libc++ and a enabled
debug check for strict weak ordering.

Added: 
    

Modified: 
    clang/lib/Sema/SemaOverload.cpp
    clang/test/SemaCXX/overloaded-operators-display-order-crash.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index f97e244120612e3..858654e35cbb6bd 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -12107,9 +12107,12 @@ struct CompareOverloadCandidatesForDisplay {
         if (RFailureKind != ovl_fail_bad_deduction)
           return true;
 
-        if (L->DeductionFailure.Result != R->DeductionFailure.Result)
-          return RankDeductionFailure(L->DeductionFailure)
-               < RankDeductionFailure(R->DeductionFailure);
+        if (L->DeductionFailure.Result != R->DeductionFailure.Result) {
+          unsigned LRank = RankDeductionFailure(L->DeductionFailure);
+          unsigned RRank = RankDeductionFailure(R->DeductionFailure);
+          if (LRank != RRank)
+            return LRank < RRank;
+        }
       } else if (RFailureKind == ovl_fail_bad_deduction)
         return false;
 

diff  --git a/clang/test/SemaCXX/overloaded-operators-display-order-crash.cpp b/clang/test/SemaCXX/overloaded-operators-display-order-crash.cpp
index 5abd048f1d136e5..79e2840583b5d65 100644
--- a/clang/test/SemaCXX/overloaded-operators-display-order-crash.cpp
+++ b/clang/test/SemaCXX/overloaded-operators-display-order-crash.cpp
@@ -52,3 +52,17 @@ namespace bad_conversion {
     // CHECK-NEXT: void func(double*, int, int)
   }
 }
+
+namespace bad_deduction {
+  template <class> struct templ {};
+  template <class T> void func(templ<T>);
+  template <class T> void func(T*);
+  template <class T> auto func(T&) -> decltype(T().begin());
+  template <class T> auto func(const T&) -> decltype(T().begin());
+
+  bool doit() {
+    struct record {} r;
+    func(r); // expected-error {{no matching function for call to 'func'}}
+             // expected-note@* 4{{candidate}}
+  }
+}