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Merge pull request #72 from Bekenn/fixes
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More template-parameter substitution
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@cor3ntin
cor3ntin authored Jun 26, 2024
2 parents 10db276 + b9b2f2c commit 1d206a0
Showing 1 changed file with 34 additions and 83 deletions.
117 changes: 34 additions & 83 deletions src/D2841.tex
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Original file line number Diff line number Diff line change
Expand Up @@ -1583,47 +1583,41 @@ \subsection{\textcolor{noteclr}{3. Wording for variable-template and concept tem
int i;

template<class T, T i> void f(T t) {
T t1 = i; // template-parameters \tcode{T} and \tcode{i}
T t1 = i; // \changed{template-parameters}{template parameters} \tcode{T} and \tcode{i}
::T t2 = ::i; // global namespace members \tcode{T} and \tcode{i}
}
\end{codeblock}
Here, the template \tcode{f} has a \grammarterm{type-parameter}
called \tcode{T}, rather than \changed{an unnamed non-type}
\grammarterm{template-parameter} of class \tcode{T}}{a parameter-declaration with no name}.
Here, the template \tcode{f} has a \changed{\grammarterm{type-parameter}}{type template parameter}
called \tcode{T}, rather than an unnamed \changed{non-type
\grammarterm{template-parameter}}{constant template parameter} of class \tcode{T}.
\end{example}
A storage class shall not be specified in a
\grammarterm{template-parameter}
\changed{\grammarterm{template-parameter}}{template parameter}
declaration.
Types shall not be defined in a \grammarterm{template-parameter}
Types shall not be defined in a \changed{\grammarterm{template-parameter}}{template parameter}
declaration.

\pnum
The \grammarterm{identifier} in a \grammarterm{type-parameter} is not looked up.
A \grammarterm{type-parameter}
whose \grammarterm{identifier} does not follow an ellipsis
defines its
\grammarterm{identifier}
The \grammarterm{identifier} in a \changed{\grammarterm{type-parameter}}
{\grammarterm{template-parameter} denoting a type or template} is not looked up.
\changed{A \grammarterm{type-parameter}
whose}{An} \grammarterm{identifier} \added{that} does not follow an ellipsis
\changed{defines its
\grammarterm{identifier}}{is defined}
to be a
\grammarterm{typedef-name}
\removed{(if declared without
\keyword{template})
or
(\changed{if declared without
\keyword{template}}{for a \grammarterm{type-parameter}})\added{,}
\changed{or}{a}
\grammarterm{template-name}
(if declared with
\keyword{template})}
(\changed{if declared with
\keyword{template}}{for a \grammarterm{type-tt-parameter} or \grammarterm{variable-tt-parameter}})\added{,
or a \grammarterm{concept-name} (for a \grammarterm{concept-tt-parameter})}
in the scope of the template declaration.

%TODO
\begin{addedblock}
The \grammarterm{identifier} in a template template parameter is not looked up.
\tcode{P} whose \grammarterm{identifier} does not follow an ellipsis defines its
\grammarterm{identifier} to be a \grammarterm{concept-name} \tcode{T} if \tcode{P} is a \grammarterm{concept-tt-parameter}
or a \grammarterm{template-name} \tcode{T} otherwise.
\tcode{T} is declared in the scope of the template declaration.
\end{addedblock}

\begin{note}
A template argument can be a class template or alias template.
A template argument \added{for a type template template parameter}
can be a class template or alias template.
For example,

\begin{codeblock}
Expand All @@ -1637,11 +1631,10 @@ \subsection{\textcolor{noteclr}{3. Wording for variable-template and concept tem
\end{codeblock}
\end{note}


\textcolor{noteclr}{[...]}

\pnum
A \changed{non-type}{constant} \grammarterm{template-parameter}
A \changed{non-type \grammarterm{template-parameter}}{constant template parameter}
shall have one of the following (possibly cv-qualified) types:
\begin{itemize}
\item a structural type (see below),
Expand All @@ -1654,35 +1647,22 @@ \subsection{\textcolor{noteclr}{3. Wording for variable-template and concept tem
\grammarterm{template-parameter}
are ignored when determining its type.

\pnum
\label{term.structural.type}%
A \defnadj{structural}{type} is one of the following:
\begin{itemize}
\item a scalar type, or
\item an lvalue reference type, or
\item a literal class type with the following properties:
\begin{itemize}
\item
all base classes and non-static data members are public and non-mutable and
\item
the types of all bases classes and non-static data members are
structural types or (possibly multidimensional) array thereof.
\end{itemize}
\end{itemize}
\textcolor{noteclr}{[...]}

\pnum
An \grammarterm{id-expression} naming
a \changed{non-type}{constant} \grammarterm{template-parameter} of class type \tcode{T}
a \changed{non-type \grammarterm{template-parameter}}{constant template parameter}
of class type \tcode{T}
denotes a static storage duration object of type \tcode{const T},
known as a \defn{template parameter object},
which is template-argument-equivalent\iref{temp.type} to
the corresponding template argument
after it has been converted
to the type of the \grammarterm{template-parameter}\iref{temp.arg.nontype}.
to the type of the \changed{\grammarterm{template-parameter}}{template parameter} \iref{temp.arg.nontype}.
No two template parameter objects are template-argument-equivalent.
\begin{note}
If an \grammarterm{id-expression} names
a \removed{non-type} non-reference \added{constant} \grammarterm{template-parameter},
a \removed{non-type} non-reference \added{constant} \changed{\grammarterm{template-parameter}}{template parameter},
then it is a prvalue if it has non-class type.
Otherwise, if it is of class type \tcode{T},
it is an lvalue and has type \tcode{const T} \iref{expr.prim.id.unqual}.
Expand All @@ -1693,10 +1673,10 @@ \subsection{\textcolor{noteclr}{3. Wording for variable-template and concept tem
using X = int;
struct A {};
template<const X& x, int i, A a> void f() {
i++; // error: change of \grammarterm{template-parameter} value
i++; // error: change of \changed{\grammarterm{template-parameter}}{template parameter} value

&x; // OK
&i; // error: address of non-reference template-parameter
&i; // error: address of non-reference \changed{template-parameter}{template parameter}
&a; // OK
int& ri = i; // error: attempt to bind non-const reference to temporary
const int& cri = i; // OK, const reference binds to temporary
Expand All @@ -1707,37 +1687,19 @@ \subsection{\textcolor{noteclr}{3. Wording for variable-template and concept tem

\pnum
\begin{note}
A \changed{non-type}{constant}
\grammarterm{template-parameter}
A \changed{non-type \grammarterm{template-parameter}}{constant template parameter}
cannot be declared to have type \cv{} \keyword{void}.
\begin{example}
\begin{codeblock}
template<void v> class X; // error
template<void* pv> class Y; // OK
\end{codeblock}
\end{example}
\begin{example} \textcolor{noteclr}{[...]} \end{example}
\end{note}

\pnum
A \changed{non-type}{constant}
\grammarterm{template-parameter}
A \changed{non-type \grammarterm{template-parameter}}{constant template parameter}
\indextext{array!template parameter of type}%
of type ``array of \tcode{T}'' or
\indextext{function!template parameter of type}%
of function type \tcode{T}
is adjusted to be of type ``pointer to \tcode{T}''.
\begin{example}
\begin{codeblock}
template<int* a> struct R { };
template<int b[5]> struct S { };
int p;
R<&p> w; // OK
S<&p> x; // OK due to parameter adjustment
int v[5];
R<v> y; // OK due to implicit argument conversion
S<v> z; // OK due to both adjustment and conversion
\end{codeblock}
\end{example}
\begin{example} \textcolor{noteclr}{[...]} \end{example}

\pnum
A \changed{non-type}{constant} template parameter declared with a type that
Expand All @@ -1753,25 +1715,14 @@ \subsection{\textcolor{noteclr}{3. Wording for variable-template and concept tem
A default template argument may be specified for
any kind of \grammarterm{template-parameter} \removed{(type, non-type, template)}
that is not a template parameter pack\iref{temp.variadic}.
A default template argument may be specified in a template declaration.
A default template argument shall not be specified in
the \grammarterm{template-parameter-list}{s}
of the definition of a member of a class template
that appears outside of the member's class.
A default template argument
shall not be specified in a friend class template declaration.
If a friend function template declaration $D$
specifies a default template argument,
that declaration shall be a definition and
there shall be no other declaration of the function template
which is reachable from $D$ or from which $D$ is reachable.
\textcolor{noteclr}{[...]}

\textcolor{noteclr}{[...]}

\indextext{\idxcode{<}!template and}%
\pnum
When parsing a default template argument
for a \changed{non-type}{constant} \grammarterm{template-parameter},
for a \changed{non-type \grammarterm{template-parameter}}{constant template parameter},
the first non-nested \tcode{>} is taken as
the end of the \grammarterm{template-parameter-list}
rather than a greater-than operator.
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