[Sema] List conversion validate character array.

The function `TryListConversion` didn't properly validate the following
part of the standard:

    Otherwise, if the parameter type is a character array [... ]
    and the initializer list has a single element that is an
    appropriately-typed string literal (8.5.2 [dcl.init.string]), the
    implicit conversion sequence is the identity conversion.

This caused the following call to `f()` to be ambiguous.
    void f(int(&&)[1]);
    void f(unsigned(&&)[1]);

    void g(unsigned i) {
      f({i});
    }

This issue only occurs when the initializer list had one element.

Differential Revision: https://reviews.llvm.org/D87561

1 files changed, 4 insertions, 0 deletions

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index a9f707b..751b785 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -141,6 +141,10 @@ static StringInitFailureKind IsStringInit(Expr *init, QualType declType,
   return IsStringInit(init, arrayType, Context);
 }
 
+bool Sema::IsStringInit(Expr *Init, const ArrayType *AT) {
+  return ::IsStringInit(Init, AT, Context) == SIF_None;
+}
+
 /// Update the type of a string literal, including any surrounding parentheses,
 /// to match the type of the object which it is initializing.
 static void updateStringLiteralType(Expr *E, QualType Ty) {