Member `operator new` and `operator delete` should reject explicit object parameters

[Rajveer100]

These functions are members, but they are implicitly static members as in this draft, which means they shouldn't be allowed to have explicit object parameters.

Snippet:

#include <new>
#include <memory>

struct S {
    void *operator new(this unsigned long);
    void operator delete(this void*);
    void operator delete(this S*, std::destroying_delete_t);
};

GodBolt

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Rajveer Singh Bharadwaj (Rajveer100)

These functions are members, but they are implicitly static members as in this [draft](https://eel.is/c++draft/class#free-3), which means they shouldn't be allowed to have explicit object parameters.

Snippet:

#include <new>
#include <memory>

struct S {
    void *operator new(this unsigned long);
    void operator delete(this void*);
    void operator delete(this S*, std::destroying_delete_t);
};

GodBolt

[shafik]

The fix for this may be similar to: #80327

but where err_explicit_object_parameter_nonmember diagnostic is handled.

[shafik]

I used a slightly reduced version to test: https://godbolt.org/z/z7jd8nnh7

I am surprised only MSVC diagnoses this.

The fix would be to modify:

llvm-project/clang/lib/Sema/SemaDeclCXX.cpp

Lines 11398 to 11402 in 54b014b

	if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static) {
	Diag(ExplicitObjectParam->getBeginLoc(),
	diag::err_explicit_object_parameter_nonmember)
	<< D.getSourceRange() << /*static=*/0 << IsLambda;
	D.setInvalidType();

as follows:

if (D.getDeclSpec().getStorageClassSpec() == DeclSpec::SCS_static ||
      (D.getContext() == clang::DeclaratorContext::Member &&
          D.isStaticMember())) {

This change diagnoses and passes check-clang I am bit surprised we don't obtain more diagnostics though.

CC @cor3ntin

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. In the comments of the issue, request for it to be assigned to you.
2. Fix the issue locally.
3. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
4. Create a Git commit.
5. Run git clang-format HEAD~1 to format your changes.
6. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Rajveer Singh Bharadwaj (Rajveer100)

These functions are members, but they are implicitly static members as in this [draft](https://eel.is/c++draft/class#free-3), which means they shouldn't be allowed to have explicit object parameters.

Snippet:

#include <new>
#include <memory>

struct S {
    void *operator new(this unsigned long);
    void operator delete(this void*);
    void operator delete(this S*, std::destroying_delete_t);
};

GodBolt

[shafik]

Apologies, when I first opened this issue there was not a PR against it and I just realized there is a PR now with the exact solution I was proposing.