Why is additional qualification for inline member function definitions prohibited?
If we consider the grammar of a member declaration, it looks like this:
member-declaration:
function-definition;
function-definition:
attribute-specifier-seqopt decl-specifier-seqopt declarator
virt-specifier-seqopt function-body
declarator:
noptr-declarator parameters-and-qualifiers trailing-return-type
This disallows the syntax:
struct B {
A B::*B::read();
};
Why doesn't it allow optional nested-name-specifier ::
before the function name?
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The grammar does not generally prohibit declaring objects named by nested BOM names. In fact, ads friend
should have:
class A
{
friend void OtherNamespace::foo();
};
This is a member declaration with a declaration specifier friend
. It covered (bold emphasis mine):
member-declaration: attribute-specifier-seq opt decl-specifier-seq opt member-declarator-list opt;
and
member-declarator: declarator virt-specifier-seq opt pure-specifier opt
The declarator now has the following grammar:
descriptor:
PTR descriptorPTR descriptor:
noptr descriptornoptr-handle:
a handle-IDdescriptor-id:
...
opt id-expression
Finally, the id expression
id-expression: qualified identifier
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