Fix thinkos in class type object expression description (#36)

The fields denoting the type of an expression designating an object of class  is _TypeIndex_, not _DeclIndex_.

ltx/exprs.tex

@@ -1296,7 +1296,7 @@ \subsection{\valueTag{ExprSort::ProductTypeValue}}
 	\structure{
 		\DeclareMember{locus}{SourceLocation} \\
 		\DeclareMember{type}{TypeIndex} \\
-		\DeclareMember{class}{DeclIndex} \\
+		\DeclareMember{structure}{TypeIndex} \\
 		\DeclareMember{members}{ExprIndex} \\
 		\DeclareMember{base\_subobjects}{ExprIndex} \\
 	}
@@ -1308,7 +1308,7 @@ \subsection{\valueTag{ExprSort::ProductTypeValue}}
 \begin{itemize}
 	\item \field{locus} denotes the source location of this expression.
 	\item \field{type} denotes the type of this expression.
-	\item \field{class} denotes the declaration of the class type of the object designated by this expression.
+	\item \field{structure} denotes the class type of the object designated by this expression.
 	\item \field{members} denotes the sequence of direct non-base class subobjects of the object.
 	\item \field{base\_subobjects} denotes the sequence of base class subobjects of the object.
 \end{itemize}
@@ -1328,7 +1328,7 @@ \subsection{\valueTag{ExprSort::SumTypeValue}}
 	\structure{
 		\DeclareMember{locus}{SourceLocation} \\
 		\DeclareMember{type}{TypeIndex} \\
-		\DeclareMember{variant}{DeclIndex} \\
+		\DeclareMember{variant}{TypeIndex} \\
 		\DeclareMember{discriminant}{ActiveMember} \\
 		\DeclareMember{value}{ExprIndex} \\
 	}
@@ -1342,7 +1342,7 @@ \subsection{\valueTag{ExprSort::SumTypeValue}}
 \begin{itemize}
 	\item \field{locus} denotes the source location of this expression.
 	\item \field{type} denotes the type of this expression.
-	\item \field{variant} denotes the declaration of the union class type of the object designated by this expression.
+	\item \field{variant} denotes the union class type of the object designated by this expression.
 	\item \field{disciminant} denotes the index of the active member of the union object
 	\item \field{value} denotes the value of the active member.
 \end{itemize}