Implement most of N3638 (return type deduction for normal functions).

Missing (somewhat ironically) is support for the new deduction rules
in lambda functions, plus PCH support for return type patching.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181108 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 20 insertions, 0 deletions

diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 480c4a0d2b..e59c811186 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -5726,6 +5726,14 @@ Sema::AddConversionCandidate(CXXConversionDecl *Conversion,
   if (!CandidateSet.isNewCandidate(Conversion))
     return;
 
+  // If the conversion function has an undeduced return type, trigger its
+  // deduction now.
+  if (getLangOpts().CPlusPlus1y && ConvType->isUndeducedType()) {
+    if (DeduceReturnType(Conversion, From->getExprLoc()))
+      return;
+    ConvType = Conversion->getConversionType().getNonReferenceType();
+  }
+
   // Overload resolution is always an unevaluated context.
   EnterExpressionEvaluationContext Unevaluated(*this, Sema::Unevaluated);
 
@@ -9173,6 +9181,13 @@ private:
           if (S.CheckCUDATarget(Caller, FunDecl))
             return false;
 
+      // If any candidate has a placeholder return type, trigger its deduction
+      // now.
+      if (S.getLangOpts().CPlusPlus1y &&
+          FunDecl->getResultType()->isUndeducedType() &&
+          S.DeduceReturnType(FunDecl, SourceExpr->getLocStart(), Complain))
+        return false;
+
       QualType ResultTy;
       if (Context.hasSameUnqualifiedType(TargetFunctionType, 
                                          FunDecl->getType()) ||
@@ -9439,6 +9454,11 @@ Sema::ResolveSingleFunctionTemplateSpecialization(OverloadExpr *ovl,
     if (FoundResult) *FoundResult = I.getPair();    
   }
 
+  if (Matched && getLangOpts().CPlusPlus1y &&
+      Matched->getResultType()->isUndeducedType() &&
+      DeduceReturnType(Matched, ovl->getExprLoc(), Complain))
+    return 0;
+
   return Matched;
 }