pack expansion.
Previously, if all parameter / argument pairs for a pack expansion
deduction were non-deduced contexts, we would not deduce the arity of
the pack, and could end up deducing a different arity (leading to
failures during substitution) or defaulting to an arity of 0 (leading to
bad diagnostics about passing the wrong number of arguments to a
variadic function). Instead, we now always deduce the arity for all
involved packs any time we deduce a pack expansion.
This will result in less substitution happening in some cases, which
could avoid non-SFINAEable errors, and should generally improve the
quality of diagnostics when passing initializer lists to variadic
functions.
destructors.
We previously tried to patch up the exception specification after
completing the class, which went wrong when the exception specification
was needed within the class body (in particular, by a friend
redeclaration of the destructor in a nested class). We now mark the
destructor as having a not-yet-computed exception specification
immediately after creating it.
This requires delaying various checks against the exception
specification (where we'd previously have just got the wrong exception
specification, and now find we have an exception specification that we
can't compute yet) when those checks fire while the class is being
defined.
This also exposed an issue that we were missing a CodeSynthesisContext
for computation of exception specifications (otherwise we'd fail to make
the module containing the definition of the class visible when computing
its members' exception specs). Adding that incidentally also gives us a
diagnostic quality improvement.
This has also exposed an pre-existing problem: making the exception
specification evaluation context a non-SFINAE context (as it should be)
results in a bootstrap failure; PR38850 filed for this.
llvm-svn: 341499
This is not required by the standard (yet), but there seems to be reasonable
support for this being a defect according to CWG discussion, and libstdc++ 7.1
relies on it working.
llvm-svn: 304946
Under this defect resolution, the injected-class-name of a class or class
template cannot be used except in very limited circumstances (when declaring a
constructor, in a nested-name-specifier, in a base-specifier, or in an
elaborated-type-specifier). This is apparently done to make parsing easier, but
it's a pain for us since we don't know whether a template-id using the
injected-class-name is valid at the point when we annotate it (we don't yet
know whether the template-id will become part of an elaborated-type-specifier).
As a tentative resolution to a perceived language defect, mem-initializer-ids
are added to the list of exceptions here (they generally follow the same rules
as base-specifiers).
When the reference to the injected-class-name uses the 'typename' or 'template'
keywords, we permit it to be used to name a type or template as an extension;
other compilers also accept some cases in this area. There are also a couple of
corner cases with dependent template names that we do not yet diagnose, but
which will also get this treatment.
llvm-svn: 292518
Diasllow a declaration using the 'auto' type specifier from using two different
meanings of it at once, or from declaring multiple functions with deduced
return types or introducing multiple trailing return types.
The standard does not technically disallow the multiple trailing return types
case if all the declarators declare variables (such as function pointers with
trailing return types), but we disallow that too, following the clear intent.
llvm-svn: 291880
* Update version number in DR tests from 4.0 to 4
* Teach make_cxx_dr_status script about version numbers that don't contain a
period.
* Update cxx_status.html and cxx_dr_status.html to list Clang 4 features as
"Clang 4" rather than "SVN"
Clang 4 features are still listed in yellow rather than green until release.
llvm-svn: 291871
Check for implicit conversion sequences for non-dependent function
template parameters between deduction and substitution. The idea is to accept
as many cases as possible, on the basis that substitution failure outside the
immediate context is much more common during substitution than during implicit
conversion sequence formation.
This re-commits r290808, reverted in r290811 and r291412, with a couple of
fixes for handling of explicitly-specified non-trailing template argument
packs.
llvm-svn: 291427
This issue clarifies how deduction proceeds past a non-trailing function
parameter pack. Essentially, the pack itself is skipped and consumes no
arguments (except for those implied by an explicitly-specified template
arguments), and nothing is deduced from it. As a small fix to the standard's
rule, we do not allow subsequent deduction to change the length of the function
parameter pack (by preventing extension of the explicitly-specified pack if
present, and otherwise deducing all contained packs to empty packs).
llvm-svn: 291425
Check for implicit conversion sequences for non-dependent function
template parameters between deduction and substitution. The idea is to accept
as many cases as possible, on the basis that substitution failure outside the
immediate context is much more common during substitution than during implicit
conversion sequence formation.
This re-commits r290808, reverted in r290811, with a fix for handling of
explicitly-specified template argument packs.
llvm-svn: 291410
This reverts commit r290808, as it broken all ARM and AArch64 test-suite
test: MultiSource/UnitTests/C++11/frame_layout
Also, please, next time, try to write a commit message in according to
our guidelines:
http://llvm.org/docs/DeveloperPolicy.html#commit-messages
llvm-svn: 290811
template parameters between deduction and substitution. The idea is to accept
as many cases as possible, on the basis that substitution failure outside
the immediate context is much more common during substitution than during
implicit conversion sequence formation.
This does not implement the partial ordering portion of DR1391, which so
far appears to be misguided.
llvm-svn: 290808
to make reference to template parameters. This is only a partial
implementation; we retain the restriction that the argument must not be
type-dependent, since it's unclear how that would work given the existence of
other language rules requiring an exact type match in this context, even for
type-dependent cases (a question has been raised on the core reflector).
llvm-svn: 290647
We continue to support dynamic exception specifications in C++1z as an
extension, but produce an error-by-default warning when we encounter one. This
allows users to opt back into the feature with a warning flag, and implicitly
opts system headers back into the feature should they happen to use it.
There is one semantic change implied by P0003R5 but not implemented here:
violating a throw() exception specification should now call std::terminate
directly instead of calling std::unexpected(), but since P0003R5 also removes
std::unexpected() and std::set_unexpected, and the default unexpected handler
calls std::terminate(), a conforming C++1z program cannot tell that we are
still calling it. The upside of this strategy is perfect backwards
compatibility; the downside is that we don't get the more efficient 'noexcept'
codegen for 'throw()'.
llvm-svn: 289019
mismatched dynamic exception specifications in expressions from an error to a
warning, since this is no longer ill-formed in C++1z.
Allow reference binding of a reference-to-non-noexcept function to a noexcept
function lvalue. As defect resolutions, also allow a conditional between
noexcept and non-noexcept function lvalues to produce a non-noexcept function
lvalue (rather than decaying to a function pointer), and allow function
template argument deduction to deduce a reference to non-noexcept function when
binding to a noexcept function type.
llvm-svn: 284905
not instantiate exception specifications of functions if they were only used in
unevaluated contexts (other than 'noexcept' expressions).
In C++17 onwards, this becomes essential since the exception specification is
now part of the function's type.
Note that this means that constructs like the following no longer work:
struct A {
static T f() noexcept(...);
decltype(f()) *p;
};
... because the decltype expression now needs the exception specification of
'f', which has not yet been parsed.
llvm-svn: 284549
std::initializer_list<T> type. Instead, the list must contain a single element
and the type is deduced from that.
In Clang 3.7, we warned by default on all the cases that would change meaning
due to this change. In Clang 3.8, we will support only the new rules -- per
the request in N3922, this change is applied as a Defect Report against earlier
versions of the C++ standard.
This change is not entirely trivial, because for lambda init-captures we
previously did not track the difference between direct-list-initialization and
copy-list-initialization. The difference was not previously observable, because
the two forms of initialization always did the same thing (the elements of the
initializer list were always copy-initialized regardless of the initialization
style used for the init-capture).
llvm-svn: 252688
Richard Smith