Work towards a non-panicing parser (libsyntax)

- Functions in parser.rs return PResult<> rather than panicing
- Other functions in libsyntax call panic! explicitly for now if they rely on panicing behaviour.
- 'panictry!' macro added as scaffolding while converting panicing functions.
  (This does the same as 'unwrap()' but is easier to grep for and turn into try!())
- Leaves panicing wrappers for the following functions so that the
  quote_* macros behave the same:
  - parse_expr, parse_item, parse_pat, parse_arm, parse_ty, parse_stmt

1 files changed, 4 insertions, 4 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index 71fba789ff8..80ee92608a5 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -652,9 +652,9 @@ impl<'a> ExtCtxt<'a> {
     pub fn bt_push(&mut self, ei: ExpnInfo) {
         self.recursion_count += 1;
         if self.recursion_count > self.ecfg.recursion_limit {
-            self.span_fatal(ei.call_site,
+            panic!(self.span_fatal(ei.call_site,
                             &format!("recursion limit reached while expanding the macro `{}`",
-                                    ei.callee.name));
+                                    ei.callee.name)));
         }
 
         let mut call_site = ei.call_site;
@@ -699,7 +699,7 @@ impl<'a> ExtCtxt<'a> {
     ///   value doesn't have to match anything)
     pub fn span_fatal(&self, sp: Span, msg: &str) -> ! {
         self.print_backtrace();
-        self.parse_sess.span_diagnostic.span_fatal(sp, msg);
+        panic!(self.parse_sess.span_diagnostic.span_fatal(sp, msg));
     }
 
     /// Emit `msg` attached to `sp`, without immediately stopping
@@ -817,7 +817,7 @@ pub fn get_exprs_from_tts(cx: &mut ExtCtxt,
     let mut es = Vec::new();
     while p.token != token::Eof {
         es.push(cx.expander().fold_expr(p.parse_expr()));
-        if p.eat(&token::Comma) {
+        if panictry!(p.eat(&token::Comma)){
             continue;
         }
         if p.token != token::Eof {