Add high-level support for @cast()ing

This handles all of the parsing, traversal, and optimization.  It
doesn't actually resolve the cast yet though.

* staptree.h (struct cast_op, visitor::visit_cast_op): New.
* staptree.cxx (cast_op::print/visit, various visitor::visit_cast_op's):
Incorporate cast_op into the basic tree operations.
* parse.cxx (parser::parse_symbol): Parse @cast operator with an
expression operand, type string, and optional module string.
* translate.cxx (c_unparser::visit_cast_op): Error out if a @cast
survives to translation.
* elaborate.cxx (typeresolution_info::visit_cast_op): Error out if a
@cast survives to type resolution.
(symbol_fetcher::visit_cast_op): treat @casts as a symbol target
(void_statement_reducer::visit_cast_op): unused @casts can be discarded,
but the operand should still be evaluated.

1 files changed, 1 insertions, 0 deletions

diff --git a/elaborate.h b/elaborate.h
index c8697595..9cc4cbda 100644
--- a/elaborate.h
+++ b/elaborate.h
@@ -95,6 +95,7 @@ struct typeresolution_info: public visitor
   void visit_print_format (print_format* e);
   void visit_stat_op (stat_op* e);
   void visit_hist_op (hist_op* e);
+  void visit_cast_op (cast_op* e);
 };