[Sema][SVE] Reject "delete" with sizeless types

[rsandifo-arm]

Summary

Sizeless types can't be used with "new", so it doesn't make sense
to use them with "delete" either. The SVE ACLE therefore doesn't
allow that.

This is slightly stronger than for normal incomplete types, since:

struct S;
void f(S *s) { delete s; }

is (by necessity) just a default-on warning rather than an error.

[efriedma]

LGTM

clang/lib/Sema/SemaExprCXX.cpp

if (!Ex.get()->isTypeDependent()) {
 
     CXXRecordDecl *PointeeRD = nullptr;
     if (Pointee->isVoidType() && !isSFINAEContext()) {
       // The C++ standard bans deleting a pointer to a non-object type, which
       // effectively bans deletion of "void*". However, most compilers support
       // this, so we treat it as a warning unless we're in a SFINAE context.
       Diag(StartLoc, diag::ext_delete_void_ptr_operand)
         << Type << Ex.get()->getSourceRange();
-    } else if (Pointee->isFunctionType() || Pointee->isVoidType()) {
+    } else if (Pointee->isFunctionType() || Pointee->isVoidType() ||
+               Pointee->isSizelessType()) {
       return ExprError(Diag(StartLoc, diag::err_delete_operand)
         << Type << Ex.get()->getSourceRange());
     } else if (!Pointee->isDependentType()) {
       // FIXME: This can result in errors if the definition was imported from a
       // module but is hidden.
       if (!RequireCompleteType(StartLoc, Pointee,
                                diag::warn_delete_incomplete, Ex.get())) {
         if (const RecordType *RT = PointeeElem->getAs<RecordType>())

clang/test/SemaCXX/sizeless-1.cpp

#endif
   new svint8_t();   // expected-error {{allocation of sizeless type 'svint8_t'}}
   new svint8_t[10]; // expected-error {{allocation of sizeless type 'svint8_t'}}
   new svint8_t *;
 
   new (global_int8_ptr) svint8_t;     // expected-error {{allocation of sizeless type 'svint8_t'}}
   new (global_int8_ptr) svint8_t();   // expected-error {{allocation of sizeless type 'svint8_t'}}
   new (global_int8_ptr) svint8_t[10]; // expected-error {{allocation of sizeless type 'svint8_t'}}
 
+  delete global_int8_ptr;   // expected-error {{cannot delete expression of type 'svint8_t *'}}
+  delete[] global_int8_ptr; // expected-error {{cannot delete expression of type 'svint8_t *'}}
+
   local_int8.~__SVInt8_t(); // expected-error {{object expression of non-scalar type 'svint8_t' (aka '__SVInt8_t') cannot be used in a pseudo-destructor expression}}
 
   (void)svint8_t();
 
   local_int8 = svint8_t();
   local_int8 = svint16_t(); // expected-error {{assigning to 'svint8_t' (aka '__SVInt8_t') from incompatible type 'svint16_t'}}
 
   s_template<int> st_int;