When instantiating a class template, we would lose track of function
template explicit specializations, marking them with the wrong
specialization kind.
This would lead to improperly using the explcit specialization arguments
to instantiate the function body.
This also better matches MSVC on the behaviour of explicitly vs
implicitly instantiating these.
Fixes#111266
According to [expr.prim.id.general] p2:
> If an _id-expression_ `E` denotes a non-static non-type member of some
class `C` at a point where the current class is `X` and
> - `E` is potentially evaluated or `C` is `X` or a base class of `X`,
and
> - `E` is not the _id-expression_ of a class member access expression,
and
> - if `E` is a _qualified-id_, `E` is not the un-parenthesized operand
of the unary `&` operator,
>
> the _id-expression_ is transformed into a class member access
expression using `(*this)` as the object expression.
Consider the following:
```
struct A
{
void f0();
template<typename T>
void f1();
};
template<typename T>
struct B : T
{
auto g0() -> decltype(T::f0()); // ok
auto g1() -> decltype(T::template f1<int>()); // error: call to non-static member function without an object argument
};
template struct B<A>;
```
Clang incorrectly rejects the call to `f1` in the _trailing-return-type_
of `g1`. Furthermore, the following snippet results in a crash during
codegen:
```
struct A
{
void f();
};
template<typename T>
struct B : T
{
template<typename U>
static void g();
template<>
void g<int>()
{
return T::f(); // crash here
}
};
template struct B<A>;
```
This happens because we unconditionally build a
`CXXDependentScopeMemberExpr` (with an implicit object expression) for
`T::f` when parsing the template definition, even though we don't know
whether `g` is an implicit object member function yet.
This patch fixes these issues by instead building
`DependentScopeDeclRefExpr`s for such expressions, and only transforming
them into implicit class member access expressions during instantiation.
Since we implemented the MS "unqualified lookup into dependent bases"
extension by building an implicit class member access (and relying on
the first component name of the _nested-name-specifier_ to be looked up
in the context of the object expression during instantiation), we
instead pre-append a fake _nested-name-specifier_ that refers to the
injected-class-name of the enclosing class. This patch also refactors
`Sema::BuildQualifiedDeclarationNameExpr` and
`Sema::BuildQualifiedTemplateIdExpr`, streamlining their implementation
and removing any redundant checks.
Reapplies #87541 and #88311 (again) addressing the bug which caused
expressions naming overload sets to be incorrectly rebuilt, as well as
the bug which caused base class members to always be treated as overload
sets.
The primary change since #88311 is `UnresolvedLookupExpr::Create` is called directly in `BuildPossibleImplicitMemberExpr` with `KnownDependent` as `true` (which causes the expression type to be set to `ASTContext::DependentTy`). This ensures that any further semantic analysis involving the type of the potentially implicit class member access expression is deferred until instantiation.
This patch fixes a crash that happens when '`this`' is referenced
(implicitly or explicitly) in a dependent class scope function template
specialization that instantiates to a static member function. For
example:
```
template<typename T>
struct A
{
template<typename U>
static void f();
template<>
void f<int>()
{
this; // causes crash during instantiation
}
};
template struct A<int>;
```
This happens because during instantiation of the function body,
`Sema::getCurrentThisType` will return a null `QualType` which we
rebuild the `CXXThisExpr` with. A similar problem exists for implicit
class member access expressions in such contexts (which shouldn't really
happen within templates anyways per [class.mfct.non.static]
p2, but changing that is non-trivial). This patch fixes the crash by building
`UnresolvedLookupExpr`s instead of `MemberExpr`s for these implicit
member accesses, which will then be correctly rebuilt as `MemberExpr`s
during instantiation.
More generally, this permits a template to be specialized in any scope in which
it could be defined, so this also supersedes DR44 and DR374 (the latter of
which we previously only implemented in C++11 mode onwards due to unclarity as
to whether it was a DR).
llvm-svn: 327705
The code had a typo it was doing:
Param->setUninstantiatedDefaultArg(Param->getUninstantiatedDefaultArg());
This is a no-op but may assert, we wanted to do:
Param->setUninstantiatedDefaultArg(OldParam->getUninstantiatedDefaultArg());
This fixes PR28082.
llvm-svn: 272425
Example:
template <class T>
class A {
public:
template <class U> void f(U p) { }
template <> void f(int p) { } // <== class scope specialization
};
This extension is necessary to parse MSVC standard C++ headers, MFC and ATL code.
BTW, with this feature in, clang can parse (-fsyntax-only) all the MSVC 2010 standard header files without any error.
llvm-svn: 137573
