Improve our handling of user-defined conversions as part of overload

resolution. There are two sources of problems involving user-defined
conversions that this change eliminates, along with providing simpler
interfaces for checking implicit conversions:

  - It eliminates a case of infinite recursion found in Boost.

  - It eliminates the search for the constructor needed to copy a temporary
    generated by an implicit conversion from overload
    resolution. Overload resolution assumes that, if it gets a value
    of the parameter's class type (or a derived class thereof), there
    is a way to copy if... even if there isn't. We now model this
    properly.

llvm-svn: 101680

1 files changed, 27 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaOverload.h b/clang/lib/Sema/SemaOverload.h
index 2b9604ac146..5e611113083 100644
--- a/clang/lib/Sema/SemaOverload.h
+++ b/clang/lib/Sema/SemaOverload.h
@@ -381,6 +381,33 @@ namespace clang {
       assert(isInitialized() && "querying uninitialized conversion");
       return Kind(ConversionKind);
     }
+    
+    /// \brief Return a ranking of the implicit conversion sequence
+    /// kind, where smaller ranks represent better conversion
+    /// sequences.
+    ///
+    /// In particular, this routine gives user-defined conversion
+    /// sequences and ambiguous conversion sequences the same rank,
+    /// per C++ [over.best.ics]p10.
+    unsigned getKindRank() const {
+      switch (getKind()) {
+      case StandardConversion: 
+        return 0;
+
+      case UserDefinedConversion:
+      case AmbiguousConversion: 
+        return 1;
+
+      case EllipsisConversion:
+        return 2;
+
+      case BadConversion:
+        return 3;
+      }
+
+      return 3;
+    }
+
     bool isBad() const { return getKind() == BadConversion; }
     bool isStandard() const { return getKind() == StandardConversion; }
     bool isEllipsis() const { return getKind() == EllipsisConversion; }