[Concepts] Function trailing requires clauses

Function trailing requires clauses now parsed, supported in overload resolution and when calling, referencing and taking the address of functions or function templates.

Differential Revision: https://reviews.llvm.org/D43357

1 files changed, 18 insertions, 6 deletions

diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 521160d1ad2..d267ae8572e 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3389,11 +3389,6 @@ Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
           PartialOverloading))
     return Result;
 
-  if (TemplateDeductionResult Result
-        = CheckDeducedArgumentConstraints(*this, FunctionTemplate, Builder,
-                                          Info))
-    return Result;
-
   // C++ [temp.deduct.call]p10: [DR1391]
   //   If deduction succeeds for all parameters that contain
   //   template-parameters that participate in template argument deduction,
@@ -3439,6 +3434,23 @@ Sema::TemplateDeductionResult Sema::FinishTemplateArgumentDeduction(
     return TDK_SubstitutionFailure;
   }
 
+  // C++2a [temp.deduct]p5
+  //   [...] When all template arguments have been deduced [...] all uses of
+  //   template parameters [...] are replaced with the corresponding deduced
+  //   or default argument values.
+  //   [...] If the function template has associated constraints
+  //   ([temp.constr.decl]), those constraints are checked for satisfaction
+  //   ([temp.constr.constr]). If the constraints are not satisfied, type
+  //   deduction fails.
+  if (CheckInstantiatedFunctionTemplateConstraints(Info.getLocation(),
+          Specialization, Builder, Info.AssociatedConstraintsSatisfaction))
+    return TDK_MiscellaneousDeductionFailure;
+
+  if (!Info.AssociatedConstraintsSatisfaction.IsSatisfied) {
+    Info.reset(TemplateArgumentList::CreateCopy(Context, Builder));
+    return TDK_ConstraintsNotSatisfied;
+  }
+
   if (OriginalCallArgs) {
     // C++ [temp.deduct.call]p4:
     //   In general, the deduction process attempts to find template argument
@@ -3559,7 +3571,7 @@ ResolveOverloadForDeduction(Sema &S, TemplateParameterList *TemplateParams,
 
     DeclAccessPair DAP;
     if (FunctionDecl *Viable =
-            S.resolveAddressOfOnlyViableOverloadCandidate(Arg, DAP))
+            S.resolveAddressOfSingleOverloadCandidate(Arg, DAP))
       return GetTypeOfFunction(S, R, Viable);
 
     return {};