Add two new AST nodes to represent initialization of an array in terms of
initialization of each array element:

 * ArrayInitLoopExpr is a prvalue of array type with two subexpressions:
   a common expression (an OpaqueValueExpr) that represents the up-front
   computation of the source of the initialization, and a subexpression
   representing a per-element initializer
 * ArrayInitIndexExpr is a prvalue of type size_t representing the current
   position in the loop

This will be used to replace the creation of explicit index variables in lambda
capture of arrays and copy/move construction of classes with array elements,
and also C++17 structured bindings of arrays by value (which inexplicably allow
copying an array by value, unlike all of C++'s other array declarations).

No uses of these nodes are introduced by this change, however.

llvm-svn: 289413
diff --git a/clang/lib/Sema/SemaExceptionSpec.cpp b/clang/lib/Sema/SemaExceptionSpec.cpp
index 3561bd0..781f780 100644
--- a/clang/lib/Sema/SemaExceptionSpec.cpp
+++ b/clang/lib/Sema/SemaExceptionSpec.cpp
@@ -1166,6 +1166,7 @@
   case Expr::ExprWithCleanupsClass:
   case Expr::ExtVectorElementExprClass:
   case Expr::InitListExprClass:
+  case Expr::ArrayInitLoopExprClass:
   case Expr::MemberExprClass:
   case Expr::ObjCIsaExprClass:
   case Expr::ObjCIvarRefExprClass:
@@ -1259,6 +1260,7 @@
   case Expr::ImaginaryLiteralClass:
   case Expr::ImplicitValueInitExprClass:
   case Expr::IntegerLiteralClass:
+  case Expr::ArrayInitIndexExprClass:
   case Expr::NoInitExprClass:
   case Expr::ObjCEncodeExprClass:
   case Expr::ObjCStringLiteralClass: