[expr.const] Factor out some commonality from 'manifestly

constant-evaluated' and 'potentially constant evaluated'.

Author: zygoloid

source/expressions.tex

@@ -6904,8 +6904,8 @@
 \item the initializer of a constexpr variable\iref{dcl.constexpr}, or
 \item an immediate invocation, or
 \item a \grammarterm{constraint-expression}\iref{temp.constr.decl}
-(possibly one formed from the \grammarterm{constraint-logical-or-expression}
-of a \grammarterm{requires-clause}), or
+including one formed from the \grammarterm{constraint-logical-or-expression}
+of a \grammarterm{requires-clause}, or
 \item the initializer of a variable
 that is usable in constant expressions or
 has constant initialization.\footnote{Testing this condition
@@ -6940,15 +6940,10 @@
 
 \begin{itemize}
 \item
-a potentially-evaluated expression\iref{basic.def.odr},
-
-\item
-an immediate invocation,
+a manifestly constant-evaluated expression,
 
 \item
-a \grammarterm{constraint-expression},
-including one formed from the \grammarterm{constraint-logical-or-expression}
-of a \grammarterm{requires-clause},
+a potentially-evaluated expression\iref{basic.def.odr},
 
 \item
 an immediate subexpression of a \grammarterm{braced-init-list},%