CWG2618 Substitution during deduction should exclude exception specifications

Author: burblebee

source/templates.tex

@@ -7130,8 +7130,16 @@
 obtained from default arguments are substituted.
 
 \pnum
-The substitution occurs in all types and expressions that are used in the function
-type and in template parameter declarations. The expressions include not only
+\indextext{deduction!deduction substitution loci}%
+The \defn{deduction substitution loci} are
+\begin{itemize}
+\item the function type outside of the \grammarterm{noexcept-specifier},
+\item the \grammarterm{explicit-specifier}, and
+\item the template parameter declarations.
+\end{itemize}
+The substitution occurs in all types and expressions that are used
+in the deduction substitution loci.
+The expressions include not only
 constant expressions such as those that appear in array bounds or as nontype
 template arguments but also general expressions (i.e., non-constant expressions)
 inside \tcode{sizeof}, \keyword{decltype}, and other contexts that allow non-constant
@@ -7175,11 +7183,8 @@
 as part of the substitution
 process.
 \end{note}
-Only invalid types and expressions in the immediate context of
-the function type,
-its template parameter types,
-and its \grammarterm{explicit-specifier}
-can result in a deduction failure.
+Invalid types and expressions can result in a deduction failure
+only in the immediate context of the deduction substitution loci.
 \begin{note}
 The substitution into types and expressions can result
 in effects such as the instantiation of class template specializations and/or