[Sema] Compare canonical conversion function

clang/lib/Sema/SemaOverload.cpp

@@ -4404,14 +4404,23 @@ CompareImplicitConversionSequences(Sema &S, SourceLocation Loc,
     Result = CompareStandardConversionSequences(S, Loc,
                                                 ICS1.Standard, ICS2.Standard);
   else if (ICS1.isUserDefined()) {
+    // With lazy template loading, it is possible to find non-canonical
+    // FunctionDecls, depending on when redecl chains are completed. Make sure
+    // to compare the canonical decls of conversion functions. This avoids
+    // ambiguity problems for templated conversion operators.
+    const FunctionDecl *ConvFunc1 = ICS1.UserDefined.ConversionFunction;
+    if (ConvFunc1)
+      ConvFunc1 = ConvFunc1->getCanonicalDecl();
+    const FunctionDecl *ConvFunc2 = ICS2.UserDefined.ConversionFunction;
+    if (ConvFunc2)
+      ConvFunc2 = ConvFunc2->getCanonicalDecl();
     // User-defined conversion sequence U1 is a better conversion
     // sequence than another user-defined conversion sequence U2 if
     // they contain the same user-defined conversion function or
     // constructor and if the second standard conversion sequence of
     // U1 is better than the second standard conversion sequence of
     // U2 (C++ 13.3.3.2p3).
-    if (ICS1.UserDefined.ConversionFunction ==
-          ICS2.UserDefined.ConversionFunction)
+    if (ConvFunc1 == ConvFunc2)
       Result = CompareStandardConversionSequences(S, Loc,
                                                   ICS1.UserDefined.After,
                                                   ICS2.UserDefined.After);

clang/test/Modules/pr133057.cpp

@@ -0,0 +1,143 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+//
+// RUN: %clang_cc1 -xc++ -std=c++20 -emit-module -fmodule-name=hf -fno-cxx-modules -fmodules -fno-implicit-modules %t/CMO.cppmap -o %t/WI9.pcm
+// RUN: %clang_cc1 -xc++ -std=c++20 -emit-module -fmodule-name=g -fno-cxx-modules -fmodules -fno-implicit-modules -fmodule-file=%t/WI9.pcm %t/E6H.cppmap -o %t/4BK.pcm
+// RUN: %clang_cc1 -xc++ -std=c++20 -emit-module -fmodule-name=r -fno-cxx-modules -fmodules -fno-implicit-modules -fmodule-file=%t/WI9.pcm %t/HMT.cppmap -o %t/LUM.pcm
+// RUN: %clang_cc1 -xc++ -std=c++20 -emit-module -fmodule-name=q -fno-cxx-modules -fmodules -fno-implicit-modules -fmodule-file=%t/LUM.pcm -fmodule-file=%t/4BK.pcm %t/JOV.cppmap -o %t/9VX.pcm
+// RUN: %clang_cc1 -xc++ -std=c++20 -verify -fsyntax-only -fno-cxx-modules -fmodules -fno-implicit-modules -fmodule-file=%t/9VX.pcm %t/XFD.cc
+
+//--- 2OT.h
+#include "LQ1.h"
+
+namespace ciy {
+namespace xqk {
+template <typename>
+class vum {
+ public:
+  using sc = std::C::wmd;
+  friend bool operator==(vum, vum);
+};
+template <typename>
+class me {
+ public:
+  using vbh = vum<me>;
+  using sc = std::C::vy<vbh>::sc;
+  template <typename db>
+  operator db() { return {}; }
+};
+}  // namespace xqk
+template <typename vus>
+xqk::me<vus> uvo(std::C::wmd, vus);
+}  // namespace ciy
+
+class ua {
+  std::C::wmd kij() {
+    ciy::uvo(kij(), '-');
+    return {};
+  }
+};
+
+//--- 9KF.h
+#include "LQ1.h"
+#include "2OT.h"
+namespace {
+void al(std::C::wmd lou) { std::C::jv<std::C::wmd> yt = ciy::uvo(lou, '/'); }
+}  // namespace
+
+//--- CMO.cppmap
+module "hf" {
+header "LQ1.h"
+}
+
+
+//--- E6H.cppmap
+module "g" {
+export *
+header "2OT.h"
+}
+
+
+//--- HMT.cppmap
+module "r" {
+header "2OT.h"
+}
+
+
+//--- JOV.cppmap
+module "q" {
+header "9KF.h"
+}
+
+
+//--- LQ1.h
+namespace std {
+namespace C {
+template <class zd>
+struct vy : zd {};
+template <class ub>
+struct vy<ub*> {
+  typedef ub jz;
+};
+struct wmd {};
+template <class uo, class zt>
+void sk(uo k, zt gf) {
+  (void)(k != gf);
+}
+template <class uo>
+class fm {
+ public:
+  fm(uo);
+};
+template <class kj, class kju>
+bool operator==(kj, kju);
+template <class epn>
+void afm(epn) {
+  using yp = vy<epn>;
+  if (__is_trivially_copyable(yp)) {
+    sk(fm(epn()), nullptr);
+  }
+}
+template <class ub>
+class jv {
+ public:
+  constexpr void gq();
+  ub *nef;
+};
+template <class ub>
+constexpr void jv<ub>::gq() {
+    afm(nef);
+}
+}  // namespace C
+}  // namespace std
+namespace ciy {
+}  // namespace ciy
+
+//--- XFD.cc
+// expected-no-diagnostics
+#include "LQ1.h"
+#include "2OT.h"
+class wiy {
+ public:
+  std::C::wmd eyb();
+};
+template <typename wpa>
+void i(wpa fg) {
+  std::C::jv<std::C::wmd> zs;
+  zs = ciy::uvo(fg.eyb(), '\n');
+}
+namespace ciy {
+namespace xqk {
+struct sbv;
+std::C::jv<sbv> ns() {
+  std::C::jv<sbv> ubs;
+  ubs.gq();
+  return ubs;
+}
+}  // namespace xqk
+}  // namespace ciy
+void s() {
+  wiy fg;
+  i(fg);
+}