[basic.lval] - C++20 → C++23

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@@ -6,18 +6,16 @@ Expressions are categorized according to the taxonomy in Figure
 <a id="fig:basic.lval"></a>
 ![Expression category taxonomy \[fig:basic.lval\]](images/valuecategories.svg)
 - A *glvalue* is an expression whose evaluation determines the identity
-  of an object, bit-field, or function.
 - A *prvalue* is an expression whose evaluation initializes an object or
- a bit-field, or computes the value of an operand of an operator, as
- specified by the context in which it appears, or an expression that
-  has type cv `void`.
-- An *xvalue* is a glvalue that denotes an object or bit-field whose
-  resources can be reused (usually because it is near the end of its
-  lifetime).
 - An *lvalue* is a glvalue that is not an xvalue.
 - An *rvalue* is a prvalue or an xvalue.
 Every expression belongs to exactly one of the fundamental
 classifications in this taxonomy: lvalue, xvalue, or prvalue. This
@@ -41,15 +39,15 @@ values. — *end note*]
 [*Note 3*:
 An expression is an xvalue if it is:
 - the result of calling a function, whether implicitly or explicitly,
   whose return type is an rvalue reference to object type [[expr.call]],
-- a cast to an rvalue reference to object type ([[expr.type.conv]],
-  [[expr.dynamic.cast]], [[expr.static.cast]] [[expr.reinterpret.cast]],
-  [[expr.const.cast]], [[expr.cast]]),
 - a subscripting operation with an xvalue array operand [[expr.sub]],
 - a class member access expression designating a non-static data member
   of non-reference type in which the object expression is an xvalue
   [[expr.ref]], or
 - a `.*` pointer-to-member expression in which the first operand is an
@@ -119,26 +117,26 @@ glvalue for that operand, the temporary materialization conversion
 The discussion of reference initialization in  [[dcl.init.ref]] and of
 temporaries in  [[class.temporary]] indicates the behavior of lvalues
 and rvalues in other significant contexts.
-Unless otherwise indicated [[dcl.type.simple]], a prvalue shall always
 have complete type or the `void` type; if it has a class type or
-(possibly multi-dimensional) array of class type, that class shall not
-be an abstract class [[class.abstract]]. A glvalue shall not have type
 cv `void`.
-[*Note 8*: A glvalue may have complete or incomplete non-`void` type.
 Class and array prvalues can have cv-qualified types; other prvalues
 always have cv-unqualified types. See [[expr.type]]. — *end note*]
 An lvalue is *modifiable* unless its type is const-qualified or is a
 function type.
 [*Note 9*: A program that attempts to modify an object through a
-nonmodifiable lvalue or through an rvalue is ill-formed ([[expr.ass]],
-[[expr.post.incr]], [[expr.pre.incr]]). — *end note*]
 If a program attempts to access [[defns.access]] the stored value of an
 object through a glvalue whose type is not similar [[conv.qual]] to one
 of the following types the behavior is undefined:[^4]
@@ -150,8 +148,9 @@ of the following types the behavior is undefined:[^4]
 If a program invokes a defaulted copy/move constructor or copy/move
 assignment operator for a union of type `U` with a glvalue argument that
 does not denote an object of type cv `U` within its lifetime, the
 behavior is undefined.
-[*Note 10*: Unlike in C, C++ has no accesses of class
-type. — *end note*]

 <a id="fig:basic.lval"></a>
 ![Expression category taxonomy \[fig:basic.lval\]](images/valuecategories.svg)
 - A *glvalue* is an expression whose evaluation determines the identity
+  of an object or function.
 - A *prvalue* is an expression whose evaluation initializes an object or
+  computes the value of an operand of an operator, as specified by the
+  context in which it appears, or an expression that has type cv `void`.
+- An *xvalue* is a glvalue that denotes an object whose resources can be
+  reused (usually because it is near the end of its lifetime).
 - An *lvalue* is a glvalue that is not an xvalue.
 - An *rvalue* is a prvalue or an xvalue.
 Every expression belongs to exactly one of the fundamental
 classifications in this taxonomy: lvalue, xvalue, or prvalue. This
 [*Note 3*:
 An expression is an xvalue if it is:
+- a move-eligible *id-expression* [[expr.prim.id.unqual]],
 - the result of calling a function, whether implicitly or explicitly,
   whose return type is an rvalue reference to object type [[expr.call]],
+- a cast to an rvalue reference to object type
+  [[expr.type.conv]], [[expr.dynamic.cast]], [[expr.static.cast]], [[expr.reinterpret.cast]], [[expr.const.cast]], [[expr.cast]],
 - a subscripting operation with an xvalue array operand [[expr.sub]],
 - a class member access expression designating a non-static data member
   of non-reference type in which the object expression is an xvalue
   [[expr.ref]], or
 - a `.*` pointer-to-member expression in which the first operand is an
 The discussion of reference initialization in  [[dcl.init.ref]] and of
 temporaries in  [[class.temporary]] indicates the behavior of lvalues
 and rvalues in other significant contexts.
+Unless otherwise indicated [[dcl.type.decltype]], a prvalue shall always
 have complete type or the `void` type; if it has a class type or
+(possibly multidimensional) array of class type, that class shall not be
+an abstract class [[class.abstract]]. A glvalue shall not have type
 cv `void`.
+[*Note 8*: A glvalue can have complete or incomplete non-`void` type.
 Class and array prvalues can have cv-qualified types; other prvalues
 always have cv-unqualified types. See [[expr.type]]. — *end note*]
 An lvalue is *modifiable* unless its type is const-qualified or is a
 function type.
 [*Note 9*: A program that attempts to modify an object through a
+nonmodifiable lvalue or through an rvalue is ill-formed
+[[expr.ass]], [[expr.post.incr]], [[expr.pre.incr]]. — *end note*]
 If a program attempts to access [[defns.access]] the stored value of an
 object through a glvalue whose type is not similar [[conv.qual]] to one
 of the following types the behavior is undefined:[^4]
 If a program invokes a defaulted copy/move constructor or copy/move
 assignment operator for a union of type `U` with a glvalue argument that
 does not denote an object of type cv `U` within its lifetime, the
 behavior is undefined.
+[*Note 10*: In C, an entire object of structure type can be accessed,
+e.g., using assignment. By contrast, C++ has no notion of accessing an
+object of class type through an lvalue of class type. — *end note*]

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