tmp/tmplj4ptu27/{from.md → to.md}
RENAMED
|
@@ -1,14 +1,22 @@
|
|
| 1 |
### Relationships between types <a id="meta.rel">[[meta.rel]]</a>
|
| 2 |
|
| 3 |
-
|
| 4 |
relationships between types at compile time.
|
| 5 |
|
| 6 |
Each of these templates shall be a *Cpp17BinaryTypeTrait* [[meta.rqmts]]
|
| 7 |
with a base characteristic of `true_type` if the corresponding condition
|
| 8 |
is true, otherwise `false_type`.
|
| 9 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| 10 |
For the purpose of defining the templates in this subclause, a function
|
| 11 |
call expression `declval<T>()` for any type `T` is considered to be a
|
| 12 |
trivial [[term.trivial.type]], [[special]] function call that is not an
|
| 13 |
odr-use [[term.odr.use]] of `declval` in the context of the
|
| 14 |
corresponding definition notwithstanding the restrictions of
|
|
@@ -43,19 +51,19 @@ implicit conversions to the return type of the function:
|
|
| 43 |
To test() {
|
| 44 |
return declval<From>();
|
| 45 |
}
|
| 46 |
```
|
| 47 |
|
| 48 |
-
[*Note
|
| 49 |
types, array types, function types, and cv `void`. — *end note*]
|
| 50 |
|
| 51 |
Access checking is performed in a context unrelated to `To` and `From`.
|
| 52 |
Only the validity of the immediate context of the *expression* of the
|
| 53 |
`return` statement [[stmt.return]] (including initialization of the
|
| 54 |
returned object or reference) is considered.
|
| 55 |
|
| 56 |
-
[*Note
|
| 57 |
instantiation of class template specializations and function template
|
| 58 |
specializations, the generation of implicitly-defined functions, and so
|
| 59 |
on. Such side effects are not in the “immediate context” and can result
|
| 60 |
in the program being ill-formed. — *end note*]
|
| 61 |
|
|
|
|
| 1 |
### Relationships between types <a id="meta.rel">[[meta.rel]]</a>
|
| 2 |
|
| 3 |
+
The templates specified in [[meta.rel]] may be used to query
|
| 4 |
relationships between types at compile time.
|
| 5 |
|
| 6 |
Each of these templates shall be a *Cpp17BinaryTypeTrait* [[meta.rqmts]]
|
| 7 |
with a base characteristic of `true_type` if the corresponding condition
|
| 8 |
is true, otherwise `false_type`.
|
| 9 |
|
| 10 |
+
Let `ELEMS-OF(T)` be the parameter pack `get<N>(declval<T>())`, where
|
| 11 |
+
*`N`* is the pack of `size_t` template arguments of the specialization
|
| 12 |
+
of `index_sequence` denoted by
|
| 13 |
+
`make_index_sequence<tuple_size_v<remove_reference_t<T>>>`.
|
| 14 |
+
|
| 15 |
+
[*Note 1*: Virtual base classes that are private, protected, or
|
| 16 |
+
ambiguous are, nonetheless, virtual base classes. — *end note*]
|
| 17 |
+
|
| 18 |
For the purpose of defining the templates in this subclause, a function
|
| 19 |
call expression `declval<T>()` for any type `T` is considered to be a
|
| 20 |
trivial [[term.trivial.type]], [[special]] function call that is not an
|
| 21 |
odr-use [[term.odr.use]] of `declval` in the context of the
|
| 22 |
corresponding definition notwithstanding the restrictions of
|
|
|
|
| 51 |
To test() {
|
| 52 |
return declval<From>();
|
| 53 |
}
|
| 54 |
```
|
| 55 |
|
| 56 |
+
[*Note 2*: This requirement gives well-defined results for reference
|
| 57 |
types, array types, function types, and cv `void`. — *end note*]
|
| 58 |
|
| 59 |
Access checking is performed in a context unrelated to `To` and `From`.
|
| 60 |
Only the validity of the immediate context of the *expression* of the
|
| 61 |
`return` statement [[stmt.return]] (including initialization of the
|
| 62 |
returned object or reference) is considered.
|
| 63 |
|
| 64 |
+
[*Note 3*: The initialization can result in side effects such as the
|
| 65 |
instantiation of class template specializations and function template
|
| 66 |
specializations, the generation of implicitly-defined functions, and so
|
| 67 |
on. Such side effects are not in the “immediate context” and can result
|
| 68 |
in the program being ill-formed. — *end note*]
|
| 69 |
|