According to [[dcl.type.elab]
p2](http://eel.is/c++draft/dcl.type.elab#2):
> If an
[elaborated-type-specifier](http://eel.is/c++draft/dcl.type.elab#nt:elaborated-type-specifier)
is the sole constituent of a declaration, the declaration is ill-formed
unless it is an explicit specialization, an explicit instantiation or it
has one of the following forms [...]
Consider the following:
```cpp
template<typename T>
struct A
{
template<typename U>
struct B;
};
template<>
template<typename U>
struct A<int>::B; // #1
```
The _elaborated-type-specifier_ at `#1` declares an explicit
specialization (which is itself a template). We currently (incorrectly)
reject this, and this PR fixes that.
I moved the point at which _elaborated-type-specifiers_ with
_nested-name-specifiers_ are diagnosed from `ParsedFreeStandingDeclSpec`
to `ActOnTag` for two reasons: `ActOnTag` isn't called for explicit
instantiations and partial/explicit specializations, and because it's
where we determine if a member specialization is being declared.
With respect to diagnostics, I am currently issuing the diagnostic
without marking the declaration as invalid or returning early, which
results in more diagnostics that I think is necessary. I would like
feedback regarding what the "correct" behavior should be here.
Close https://github.com/llvm/llvm-project/issues/73893
As the issue shows, generally, the diagnose information for
invisible namespace is confusing more than helpful. Also this patch
implements the same solution as suggested in the issue: don't diagnose
on invisible namespace.
It has been reported to that the current clang errors for, specifically,
static_assert in export contexts are a serious blocker to adoption of
modules in some cases.
There is also implementation divergence with GCC and MSVC allowing the
constructs mentioned below where clang currently rejects them with an
error.
The category of errors [for declarations in an exported context] is:
(unnamed, static_assert, empty and asm decls). These are now permitted
after P2615R1 which was approved by WG21 as a DR (and thus should be
applied to C++20 as well).
This patch removes these diagnostics and amends the testsuite accordingly.
Differential Revision: https://reviews.llvm.org/D152946
Currently, the header units are rarely used and it is not well tested.
To avoid further misunderstandings, let's mark it as experimental and
emit a warning when users wants to import it.
This is discussed in modules developers meeting.
A step to address https://github.com/llvm/llvm-project/issues/62707.
It is not user friendly enough to drop the implicitly generated path
directly. Let's emit the warning first and drop it in the next version.
Close https://github.com/llvm/llvm-project/issues/60824
The form -fmodule-file=<path-to-BMI> will load modules eagerly and the
form -fmodule-file=<module-name>=<path-to-BMI> will load modules lazily.
The inconsistency adds many additional burdens to the implementations.
And the inconsistency looks not helpful and necessary neither. So I want
to deprecate the form -fmodule-file=<path-to-BMI> for named modules.
This is pretty helpful for us (the developers).
Does this change make any regression from the perspective of the users?
To be honest, yes. But I think such regression is acceptable. Here is
the example:
```
// M.cppm
export module M;
export int m = 5;
// N.cpp
// import M; // woops, we forgot to import M.
int n = m;
```
In the original version, the compiler can diagnose the users to import
`M` since the compiler have already imported M. But in the later style,
the compiler can only say "unknown identifier `m`".
But I think such regression doesn't make a deal since it only works if
the user put `-fmodule-file=M.pcm` in the command line. But how can the
user put `-fmodule-file=M.pcm` in the command line without `import M;`?
Especially currently such options are generated by build systems. And
the build systems will only generate the command line from the source
file.
So I think this change is pretty pretty helpful for developers and
almost innocent for users and we should accept this one.
I'll add the release notes and edit the document after we land this.
Differential Revision: https://reviews.llvm.org/D144707
Currently there is a -emit-header-module mode, which can combine several
headers together as a module interface. However, this breaks our
assumption (for standard c++ modules) about module interface. The module
interface should come from a module interface unit. And if it is a
header, it should be a header unit. And currently we have no ideas to
combine several headers together.
So I think this mode is an experimental one and it is not maintained and
it is not used. So it will be better to remove them.
Reviewed By: Bigcheese, dblaikie, bruno
Differential Revision: https://reviews.llvm.org/D137609
While working on D53847, I noticed that this test would fail once we
started recognizing the types in the modified `export` statement [0].
The tests would fail because Clang would emit a "declaration does not
declare anything" diagnostic instead of the expected namespace scope
diagnostic.
I believe that the test is currently incorrectly passing because Clang
doesn't parse the type and therefore doesn't treat the statement as a
declaration. My understanding is that the intention of this test case is
that it wants to export a `struct` type, which I believe requires a
`struct` keyword, even for types with template parameters. With this
change, the only error with these two statements should be the
namespace scope issue.
[0]: https://reviews.llvm.org/D53847?id=462032#inline-1297053
Reviewed By: erichkeane
Differential Revision: https://reviews.llvm.org/D134578
This adjusts the handling for:
export module M;
export namespace {};
export namespace N {};
export using namespace N;
In the first case, we were allowing empty anonymous namespaces
as part of an extension allowing empty top-level entities, but that seems
inappropriate in this case, since the linkage would be internal for the
anonymous namespace. We now report an error for this.
The second case was producing a warning diagnostic that this was
accepted as an extension - however the C++20 standard does allow this
as well-formed.
In the third case we keep the current practice that this is accepted with a
warning (as an extension). The C++20 standard says it's an error.
We also ensure that using decls are only applied to items with external linkage.
This adjusts error messages for exports involving redeclarations in modules to
be more specific about the reason that the decl has been rejected.
Differential Revision: https://reviews.llvm.org/D122119
Since only the decls inhabit in a namespace scope could be exported, it
is not meaningful to check it in CheckRedeclarationExported, which
implements [module.interface]/p6.
Reviewed By: urnathan
Differential Revision: https://reviews.llvm.org/D118120
This fixes bug 47716.
According to [module.interface]p2, it is meaningless to export an entity
which is not in namespace scope.
The reason why the compiler crashes is that the compiler missed
ExportDecl when the compiler traverse the subclass of DeclContext. So
here is the crash.
Also, the patch implements [module.interface]p6 in
Sema::CheckRedeclaration* functions.
Reviewed By: aaron.ballman, urnathan
Differential Revision: https://reviews.llvm.org/D112903
const-qualified type is not implicitly given internal linkage. But a
variable template declared 'static' is.
This reinstates part of r359048, reverted in r359076.
llvm-svn: 359260
The change breaks libc++ with the follwing error:
In file included from valarray:4:
.../include/c++/v1/valarray:1062:60: error: explicit instantiation declaration of 'valarray<_Tp>' with internal linkage
_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS valarray<size_t>::valarray(size_t))
^
.../include/c++/v1/valarray:1063:60: error: explicit instantiation declaration of '~valarray<_Tp>' with internal linkage
_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS valarray<size_t>::~valarray())
llvm-svn: 359076
