A little tweak to the SFINAE condition reporting. Don't say:

  candidate template ignored: substitution failed [with T = int]: no type named 'type' in 'std::enable_if<false, void>'

Instead, just say:

  candidate template ignored: disabled by 'enable_if' [with T = int]

... and point at the enable_if condition which (we assume) failed.

This is applied to all cases where the user writes 'typename enable_if<...>::type' (optionally prefixed with a nested name specifier), and 'enable_if<...>' names a complete class type which does not have a member named 'type', and this results in a candidate function being ignored in a SFINAE context. Thus it catches 'std::enable_if', 'std::__1::enable_if', 'boost::enable_if' and 'llvm::enable_if'.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@156463 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 2 deletions

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index f065d38d92..b99a638bda 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -8263,13 +8263,23 @@ void DiagnoseBadDeduction(Sema &S, OverloadCandidate *Cand,
           Fn->getDescribedFunctionTemplate()->getTemplateParameters(), *Args);
     }
 
+    // If this candidate was disabled by enable_if, say so.
+    PartialDiagnosticAt *PDiag = Cand->DeductionFailure.getSFINAEDiagnostic();
+    if (PDiag && PDiag->second.getDiagID() ==
+          diag::err_typename_nested_not_found_enable_if) {
+      // FIXME: Use the source range of the condition, and the fully-qualified
+      //        name of the enable_if template. These are both present in PDiag.
+      S.Diag(PDiag->first, diag::note_ovl_candidate_disabled_by_enable_if)
+        << "'enable_if'" << TemplateArgString;
+      return;
+    }
+
     // Format the SFINAE diagnostic into the argument string.
     // FIXME: Add a general mechanism to include a PartialDiagnostic *'s
     //        formatted message in another diagnostic.
     llvm::SmallString<128> SFINAEArgString;
     SourceRange R;
-    if (PartialDiagnosticAt *PDiag =
-          Cand->DeductionFailure.getSFINAEDiagnostic()) {
+    if (PDiag) {
       SFINAEArgString = ": ";
       R = SourceRange(PDiag->first, PDiag->first);
       PDiag->second.EmitToString(S.getDiagnostics(), SFINAEArgString);