@@ -96,7 +96,7 @@ occurrence typing approach will refine not only the types of variables

but also the types of generic expressions (bypassing usual type

inference). Second, the result of our analysis can be used to infer

intersection types for functions, even in the absence of precise type

annotations such as the one in the definition of \code{foo} in~\eqref{foo2}: in practice, we are able to

annotations such as the one in the definition of \code{foo} in~\eqref{foo2}: to put it simply, we are able to

infer the type~\eqref{eq:inter} for the unannotated pure JavaScript code of \code{foo}. Third, we

show how to combine occurrence typing with gradual typing, and in

particular how the former can be used to optimize the compilation of

...

...

@@ -118,7 +118,7 @@ Depending on the actual $t$ and on the static types of $x_1$ and $x_2$, we

can make type assumptions for $x_1$, for $x_2$, \emph{and} for the application $x_1x_2$

when typing $e_1$ that are different from those we can make when typing

$e_2$. For instance, suppose $x_1$ is bound to the function \code{foo} defined in \eqref{foo2}. Thus $x_1$ has type $(\Int\to\Int)\wedge(\String\to\String)$ (we used the syntax of the types of Section~\ref{sec:language} where unions and intersections are denoted by $\vee$ and $\wedge$ and have priority over $\to$ and $\times$, but not over $\neg$).

Then it is not hard to see that if $x_2:\Int{\vee}\String$, then the expression\footnote{This and most of the following expressions are just given for the sake of example. Determining the type \emph{in each branch} of expressions other than variables is interesting for constructors but less so for destructors such as applications, projections, and selections: any reasonable programmer would not repeat the same application twice, (s)he would store its result in a variable. This becomes meaningful with constructor such as pairs, as we do for instance in the expression in~\eqref{pair}.}

Then, it is not hard to see that if $x_2:\Int{\vee}\String$, then the expression\footnote{This and most of the following expressions are just given for the sake of example. Determining the type \emph{in each branch} of expressions other than variables is interesting for constructors but less so for destructors such as applications, projections, and selections: any reasonable programmer would not repeat the same application twice, (s)he would store its result in a variable. This becomes meaningful with constructor such as pairs, as we do for instance in the expression in~\eqref{pair}.}

%

\begin{equation}\label{mezzo}

\texttt{let }x_1 \texttt{\,=\,}\code{foo}\texttt{ in }\ifty{x_1x_2}{\Int}{((x_1x_2)+x_2)}{\texttt{42}}

...

...

@@ -239,7 +239,7 @@ largest subtype of $\dom{t_1}$ such that\vspace{-1.29mm}

\begin{equation}\label{eq1}

t_1\circ s\leq\neg t

\end{equation}

In other terms, $s$ contains all the arguments that make any function

In other terms, $s$ contains all the legal arguments that make any function

in $t_1$ return a result not in $t$. Then we can safely remove from

$t_2$ all the values in $s$ or, equivalently, keep in $t_2$ all the

values of $\dom{t_1}$ that are not in $s$. Let us implement the second