[c++20] Add support for explicit(bool), as described in P0892R2.

Patch by Tyker!

Differential Revision: https://reviews.llvm.org/D60934

llvm-svn: 360311
diff --git a/clang/lib/Sema/SemaCodeComplete.cpp b/clang/lib/Sema/SemaCodeComplete.cpp
index 4d23bf6..2a62eca 100644
--- a/clang/lib/Sema/SemaCodeComplete.cpp
+++ b/clang/lib/Sema/SemaCodeComplete.cpp
@@ -4970,7 +4970,8 @@
       AddOverloadCandidate(FD, DeclAccessPair::make(FD, C->getAccess()), Args,
                            CandidateSet,
                            /*SuppressUsedConversions=*/false,
-                           /*PartialOverloading=*/true);
+                           /*PartialOverloading=*/true,
+                           /*AllowExplicit*/ true);
     } else if (auto *FTD = dyn_cast<FunctionTemplateDecl>(C)) {
       AddTemplateOverloadCandidate(
           FTD, DeclAccessPair::make(FTD, C->getAccess()),