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Avoid infinite looping in `print_def_path`.

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pnkfelix committed Jul 8, 2019
1 parent db592f4 commit 81cc4822653b1f80729e8d50f9527c1fd0e5394f
Showing with 25 additions and 1 deletion.
  1. +25 −1 src/librustc/ty/print/pretty.rs
@@ -228,8 +228,27 @@ pub trait PrettyPrinter<'tcx>:
/// from at least one local module and returns true. If the crate defining `def_id` is
/// declared with an `extern crate`, the path is guaranteed to use the `extern crate`.
fn try_print_visible_def_path(
self,
def_id: DefId,
) -> Result<(Self, bool), Self::Error> {
let mut callers = Vec::new();
self.try_print_visible_def_path_recur(def_id, &mut callers)
}

/// Does the work of `try_print_visible_def_path`, building the
/// full definition path recursively before attempting to
/// post-process it into the valid and visible version that
/// accounts for re-exports.
///
/// This method should only be callled by itself or
/// `try_print_visible_def_path`.
///
/// `callers` is a chain of visible_parent's leading to `def_id`,
/// to support cycle detection during recursion.
fn try_print_visible_def_path_recur(
mut self,
def_id: DefId,
callers: &mut Vec<DefId>,
) -> Result<(Self, bool), Self::Error> {
define_scoped_cx!(self);

@@ -302,14 +321,19 @@ pub trait PrettyPrinter<'tcx>:
Some(parent) => parent,
None => return Ok((self, false)),
};
if callers.contains(&visible_parent) {
return Ok((self, false));
}
callers.push(visible_parent);
// HACK(eddyb) this bypasses `path_append`'s prefix printing to avoid
// knowing ahead of time whether the entire path will succeed or not.
// To support printers that do not implement `PrettyPrinter`, a `Vec` or
// linked list on the stack would need to be built, before any printing.
match self.try_print_visible_def_path(visible_parent)? {
match self.try_print_visible_def_path_recur(visible_parent, callers)? {
(cx, false) => return Ok((cx, false)),
(cx, true) => self = cx,
}
callers.pop();
let actual_parent = self.tcx().parent(def_id);
debug!(
"try_print_visible_def_path: visible_parent={:?} actual_parent={:?}",

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