This patch addresses a few issues related to 8.5.3 [dcl.init.ref]

It uses a recent API to find inherited conversion functions to do
the initializer to reference lvalue conversion (and removes a FIXME).
It issues the ambiguity diagnostics when multiple conversions are found.
WIP.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@82649 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 63 insertions, 3 deletions

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 2ae2cbe009..cc7bb31638 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -476,6 +476,8 @@ def err_destructor_name : Error<
 
 // C++ initialization
 def err_lvalue_to_rvalue_ref : Error<"rvalue reference cannot bind to lvalue">;
+def err_lvalue_to_rvalue_ambig_ref : Error<"rvalue reference cannot bind to lvalue "
+                                           "due to multiple conversion functions">;
 // FIXME: passing in an English string as %1!
 def err_not_reference_to_const_init : Error<
   "non-const lvalue reference to type %0 cannot be initialized "
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index 875da1a1d9..771af4bf0c 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -3469,6 +3469,11 @@ public:
                                  bool AllowExplicit = false,
                                  bool Elidable = false);
   bool PerformImplicitConversion(Expr *&From, QualType ToType,
+                                 const char *Flavor,
+                                 bool AllowExplicit,
+                                 bool Elidable,
+                                 ImplicitConversionSequence& ICS);
+  bool PerformImplicitConversion(Expr *&From, QualType ToType,
                                  const ImplicitConversionSequence& ICS,
                                  const char *Flavor);
   bool PerformImplicitConversion(Expr *&From, QualType ToType,
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 1896fb0dc3..a4679e0e28 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -3478,7 +3478,7 @@ Sema::CheckReferenceInit(Expr *&Init, QualType DeclType,
 
     OverloadCandidateSet CandidateSet;
     OverloadedFunctionDecl *Conversions
-      = T2RecordDecl->getConversionFunctions();
+      = T2RecordDecl->getVisibleConversionFunctions();
     for (OverloadedFunctionDecl::function_iterator Func
            = Conversions->function_begin();
          Func != Conversions->function_end(); ++Func) {
@@ -3489,7 +3489,7 @@ Sema::CheckReferenceInit(Expr *&Init, QualType DeclType,
         Conv = cast<CXXConversionDecl>(ConvTemplate->getTemplatedDecl());
       else
         Conv = cast<CXXConversionDecl>(*Func);
-
+      
       // If the conversion function doesn't return a reference type,
       // it can't be considered for this conversion.
       if (Conv->getConversionType()->isLValueReferenceType() &&
@@ -3688,7 +3688,27 @@ Sema::CheckReferenceInit(Expr *&Init, QualType DeclType,
     }
     return ICS->ConversionKind == ImplicitConversionSequence::BadConversion;
   } else {
-    return PerformImplicitConversion(Init, T1, "initializing");
+    ImplicitConversionSequence Conversions;
+    bool badConversion = PerformImplicitConversion(Init, T1, "initializing", 
+                                                   false, false, 
+                                                   Conversions);
+    if (badConversion) {
+      if ((Conversions.ConversionKind  == 
+            ImplicitConversionSequence::BadConversion)
+          && Conversions.ConversionFunctionSet.size() > 0) {
+        Diag(Init->getSourceRange().getBegin(), 
+             diag::err_lvalue_to_rvalue_ambig_ref) << Init->getSourceRange();
+        for (int j = Conversions.ConversionFunctionSet.size()-1; 
+             j >= 0; j--) {
+          FunctionDecl *Func = Conversions.ConversionFunctionSet[j];
+          Diag(Func->getLocation(), diag::err_ovl_candidate);
+        }
+      }
+      else
+        Diag(Init->getSourceRange().getBegin(), diag::err_lvalue_to_rvalue_ref)
+              << Init->getSourceRange();
+    }
+    return badConversion;
   }
 }
 
diff --git a/lib/Sema/SemaExprCXX.cpp b/lib/Sema/SemaExprCXX.cpp
index 79909b557d..f500e132de 100644
--- a/lib/Sema/SemaExprCXX.cpp
+++ b/lib/Sema/SemaExprCXX.cpp
@@ -996,6 +996,15 @@ Sema::PerformImplicitConversion(Expr *&From, QualType ToType,
                                 const char *Flavor, bool AllowExplicit,
                                 bool Elidable) {
   ImplicitConversionSequence ICS;
+  return PerformImplicitConversion(From, ToType, Flavor, AllowExplicit, 
+                                   Elidable, ICS);
+}
+
+bool
+Sema::PerformImplicitConversion(Expr *&From, QualType ToType,
+                                const char *Flavor, bool AllowExplicit,
+                                bool Elidable,
+                                ImplicitConversionSequence& ICS) {
   ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
   if (Elidable && getLangOptions().CPlusPlus0x) {
     ICS = TryImplicitConversion(From, ToType,
diff --git a/test/SemaCXX/decl-init-ref.cpp b/test/SemaCXX/decl-init-ref.cpp
new file mode 100644
index 0000000000..a87c0efae2
--- /dev/null
+++ b/test/SemaCXX/decl-init-ref.cpp
@@ -0,0 +1,24 @@
+// RUN: clang-cc -fsyntax-only -verify -std=c++0x %s
+
+struct A {};    // expected-note {{candidate function}}
+
+struct BASE {
+  operator A(); // expected-note {{candidate function}}
+};
+
+struct BASE1 {
+ operator A();  // expected-note {{candidate function}}
+};
+
+class B : public BASE , public BASE1
+{
+  public:
+  B();
+} b;
+
+extern B f();
+
+int main() {
+        const A& rca = f(); // expected-error {{rvalue reference cannot bind to lvalue due to multiple conversion functions}}
+        A& ra = f(); // expected-error {{non-const lvalue reference to type 'struct A' cannot be initialized with a temporary of type 'class B'}}
+}