[C++2b] Implement multidimentional subscript operator

Implement P2128R6 in C++23 mode.

Unlike GCC's implementation, this doesn't try to recover when a user
meant to use a comma expression.

Because the syntax changes meaning in C++23, the patch is *NOT*
implemented as an extension. Instead, declaring an array with not
exactly 1 parameter is an error in older languages modes. There is an
off-by-default extension warning in C++23 mode.

Unlike the standard, we supports default arguments;

Ie, we assume, based on conversations in WG21, that the proposed
resolution to CWG2507 will be accepted.

We allow arrays OpenMP sections and C++23 multidimensional array to
coexist:

[a , b] multi dimensional array
[a : b] open mp section
[a, b: c] // error

The rest of the patch is relatively straight forward: we take care to
support an arbitrary number of arguments everywhere.

1 files changed, 27 insertions, 8 deletions

diff --git a/clang/lib/Sema/SemaAccess.cpp b/clang/lib/Sema/SemaAccess.cpp
index 3f7b387..00d3efd 100644
--- a/clang/lib/Sema/SemaAccess.cpp
+++ b/clang/lib/Sema/SemaAccess.cpp
@@ -1761,14 +1761,11 @@ Sema::CheckStructuredBindingMemberAccess(SourceLocation UseLoc,
   return CheckAccess(*this, UseLoc, Entity);
 }
 
-/// Checks access to an overloaded member operator, including
-/// conversion operators.
 Sema::AccessResult Sema::CheckMemberOperatorAccess(SourceLocation OpLoc,
                                                    Expr *ObjectExpr,
-                                                   Expr *ArgExpr,
+                                                   const SourceRange &Range,
                                                    DeclAccessPair Found) {
-  if (!getLangOpts().AccessControl ||
-      Found.getAccess() == AS_public)
+  if (!getLangOpts().AccessControl || Found.getAccess() == AS_public)
     return AR_accessible;
 
   const RecordType *RT = ObjectExpr->getType()->castAs<RecordType>();
@@ -1776,13 +1773,35 @@ Sema::AccessResult Sema::CheckMemberOperatorAccess(SourceLocation OpLoc,
 
   AccessTarget Entity(Context, AccessTarget::Member, NamingClass, Found,
                       ObjectExpr->getType());
-  Entity.setDiag(diag::err_access)
-    << ObjectExpr->getSourceRange()
-    << (ArgExpr ? ArgExpr->getSourceRange() : SourceRange());
+  Entity.setDiag(diag::err_access) << ObjectExpr->getSourceRange() << Range;
 
   return CheckAccess(*this, OpLoc, Entity);
 }
 
+/// Checks access to an overloaded member operator, including
+/// conversion operators.
+Sema::AccessResult Sema::CheckMemberOperatorAccess(SourceLocation OpLoc,
+                                                   Expr *ObjectExpr,
+                                                   Expr *ArgExpr,
+                                                   DeclAccessPair Found) {
+  return CheckMemberOperatorAccess(
+      OpLoc, ObjectExpr, ArgExpr ? ArgExpr->getSourceRange() : SourceRange(),
+      Found);
+}
+
+Sema::AccessResult Sema::CheckMemberOperatorAccess(SourceLocation OpLoc,
+                                                   Expr *ObjectExpr,
+                                                   ArrayRef<Expr *> ArgExprs,
+                                                   DeclAccessPair FoundDecl) {
+  SourceRange R;
+  if (!ArgExprs.empty()) {
+    R = SourceRange(ArgExprs.front()->getBeginLoc(),
+                    ArgExprs.back()->getEndLoc());
+  }
+
+  return CheckMemberOperatorAccess(OpLoc, ObjectExpr, R, FoundDecl);
+}
+
 /// Checks access to the target of a friend declaration.
 Sema::AccessResult Sema::CheckFriendAccess(NamedDecl *target) {
   assert(isa<CXXMethodDecl>(target->getAsFunction()));