From Jason Turner

[dcl.type.decltype]

C++20 → C++23 2.2 KB 14 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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  1. tmp/tmpw0c95057/{from.md → to.md} +5 -5
tmp/tmpw0c95057/{from.md → to.md} RENAMED
@@ -12,23 +12,23 @@ follows:
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  [[dcl.struct.bind]], `decltype(E)` is the referenced type as given in
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  the specification of the structured binding declaration;
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  - otherwise, if E is an unparenthesized *id-expression* naming a
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  non-type *template-parameter* [[temp.param]], `decltype(E)` is the
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  type of the *template-parameter* after performing any necessary type
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- deduction ([[dcl.spec.auto]], [[dcl.type.class.deduct]]);
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  - otherwise, if E is an unparenthesized *id-expression* or an
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  unparenthesized class member access [[expr.ref]], `decltype(E)` is the
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- type of the entity named by E. If there is no such entity, or if E
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- names a set of overloaded functions, the program is ill-formed;
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  - otherwise, if E is an xvalue, `decltype(E)` is `T&&`, where `T` is the
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  type of E;
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  - otherwise, if E is an lvalue, `decltype(E)` is `T&`, where `T` is the
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  type of E;
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  - otherwise, `decltype(E)` is the type of E.
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  The operand of the `decltype` specifier is an unevaluated operand
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- [[expr.prop]].
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  [*Example 1*:
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  ``` cpp
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  const int&& foo();
@@ -78,11 +78,11 @@ template<class T> auto f(T) // #1
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  // for the temporary introduced by the use of h().
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  // (A temporary is not introduced as a result of the use of i().)
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  template<class T> auto f(T) // #2
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  -> void;
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  auto g() -> void {
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- f(42); // OK: calls #2. (#1 is not a viable candidate: type deduction
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  // fails[temp.deduct] because A<int>::~A() is implicitly used in its
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  // decltype-specifier)
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  }
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  template<class T> auto q(T)
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  -> decltype((h<T>())); // does not force completion of A<T>; A<T>::~A() is not implicitly
 
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  [[dcl.struct.bind]], `decltype(E)` is the referenced type as given in
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  the specification of the structured binding declaration;
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  - otherwise, if E is an unparenthesized *id-expression* naming a
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  non-type *template-parameter* [[temp.param]], `decltype(E)` is the
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  type of the *template-parameter* after performing any necessary type
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+ deduction [[dcl.spec.auto]], [[dcl.type.class.deduct]];
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  - otherwise, if E is an unparenthesized *id-expression* or an
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  unparenthesized class member access [[expr.ref]], `decltype(E)` is the
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+ type of the entity named by E. If there is no such entity, the program
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+ is ill-formed;
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  - otherwise, if E is an xvalue, `decltype(E)` is `T&&`, where `T` is the
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  type of E;
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  - otherwise, if E is an lvalue, `decltype(E)` is `T&`, where `T` is the
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  type of E;
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  - otherwise, `decltype(E)` is the type of E.
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  The operand of the `decltype` specifier is an unevaluated operand
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+ [[term.unevaluated.operand]].
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  [*Example 1*:
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  ``` cpp
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  const int&& foo();
 
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  // for the temporary introduced by the use of h().
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  // (A temporary is not introduced as a result of the use of i().)
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  template<class T> auto f(T) // #2
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  -> void;
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  auto g() -> void {
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+ f(42); // OK, calls #2. (#1 is not a viable candidate: type deduction
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  // fails[temp.deduct] because A<int>::~A() is implicitly used in its
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  // decltype-specifier)
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  }
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  template<class T> auto q(T)
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  -> decltype((h<T>())); // does not force completion of A<T>; A<T>::~A() is not implicitly