/////////////////////////////////////////////////////////////////////////////////
private ExprStatement DispatchStatementList(ExprStatement expr)
{
Debug.Assert(expr != null);
ExprStatement first = expr;
ExprStatement pexpr = first;
while (pexpr != null)
{
// If the processor replaces the statement -- potentially with
// null, another statement, or a list of statements -- then we
// make sure that the statement list is hooked together correctly.
ExprStatement next = pexpr.OptionalNextStatement;
ExprStatement old = pexpr;
// Unhook the next one.
pexpr.OptionalNextStatement = null;
Expr result = Dispatch(pexpr);
Debug.Assert(result == null || result.isSTMT());
if (pexpr == first)
{
first = result?.asSTMT();
}
else
{
pexpr.OptionalNextStatement = result?.asSTMT();
}
// A transformation may return back a list of statements (or
// if the statements have been determined to be unnecessary,
// perhaps it has simply returned null.)
//
// Skip visiting the new list, then hook the tail of the old list
// up to the end of the new list.
while (pexpr.OptionalNextStatement != null)
{
pexpr = pexpr.OptionalNextStatement;
}
// Re-hook the next pointer.
pexpr.OptionalNextStatement = next;
}
return(first);
}
public Expr Visit(Expr pExpr)
{
if (pExpr == null)
{
return(null);
}
Expr pResult;
if (IsCachedExpr(pExpr, out pResult))
{
return(pResult);
}
if (pExpr.isSTMT())
{
return(CacheExprMapping(pExpr, DispatchStatementList(pExpr.asSTMT())));
}
return(CacheExprMapping(pExpr, Dispatch(pExpr)));
}