[PATCH] D157708: [Sema] Suppress lookup diagnostics when checking reversed operators

[Ilya Biryukov via Phabricator via cfe-commits]

ilya-biryukov created this revision.
ilya-biryukov added reviewers: shafik, rsmith.
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The standard specified that Clang should 'search' for members in this
case, which does not involve full lookup and the corresponding checks.

See `[over.match.oper]p4` and `[basic.lookup.general]p3`.

The added test has an example code that breaks.
The change that exposed this behavior is cc1b6668c57170cd440d321037ced89d6a61a9cb <https://reviews.llvm.org/rGcc1b6668c57170cd440d321037ced89d6a61a9cb>.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D157708

Files:
  clang/lib/Sema/SemaOverload.cpp
  clang/test/SemaCXX/cxx20-reversed-operators-search.cpp


Index: clang/test/SemaCXX/cxx20-reversed-operators-search.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/cxx20-reversed-operators-search.cpp
@@ -0,0 +1,30 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify %s
+// expected-no-diagnostics
+
+
+namespace members {
+
+struct X {
+  virtual ~X();
+  virtual bool operator ==(X);
+  bool operator !=(X);
+};
+
+struct Y {
+  virtual ~Y();
+  virtual bool operator ==(Y);
+  bool operator !=(Y);
+};
+
+struct Z : X, Y {
+  virtual bool operator==(Z);
+  bool operator==(X) override;
+  bool operator==(Y) override;
+};
+
+void test() {
+  bool b = Z() == Z();
+}
+
+} // namespace members
+
Index: clang/lib/Sema/SemaOverload.cpp
===================================================================
--- clang/lib/Sema/SemaOverload.cpp
+++ clang/lib/Sema/SemaOverload.cpp
@@ -950,7 +950,10 @@
     LookupResult Members(S, NotEqOp, OpLoc,
                          Sema::LookupNameKind::LookupMemberName);
     S.LookupQualifiedName(Members, RHSRec->getDecl());
-    Members.suppressAccessDiagnostics();
+    // According to [over.match.oper]p4 we should run "search" and not "lookup"
+    // for reversed operators, so suppress diagnostics.
+    Members.suppressDiagnostics();
+
     for (NamedDecl *Op : Members)
       if (FunctionsCorrespond(S.Context, EqFD, Op->getAsFunction()))
         return false;


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