Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 669 insertions, 0 deletions

diff --git a/third_party/rust/topological-sort/.cargo-checksum.json b/third_party/rust/topological-sort/.cargo-checksum.json
new file mode 100644
index 0000000000..705676c229
--- /dev/null
+++ b/third_party/rust/topological-sort/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"Cargo.toml":"b4bfbe31191f3e86445d277cf036bc7b2318baf853e8b2b0c7fcca5d61f7a089","LICENSE-APACHE":"c6596eb7be8581c18be736c846fb9173b69eccf6ef94c5135893ec56bd92ba08","LICENSE-MIT":"bf04ecfb8f9aec247301556319593dd528886f67bb9ad81654025d12b20d9e01","README.md":"fb45c72e0317c713589e90b028324c0b7320b6eb7aebbbefd31ade38aaf7e1e2","rustfmt.toml":"785022765c76126d4a9954f880c30cc651b3895857ffcfed55ce8a4f8cf3f61a","src/lib.rs":"aaa8b5ff915f1c6e3132bef12afacede4fc91216fe0711efbd1ead7ab106e82e"},"package":"aa7c7f42dea4b1b99439786f5633aeb9c14c1b53f75e282803c2ec2ad545873c"}
\ No newline at end of file
diff --git a/third_party/rust/topological-sort/Cargo.toml b/third_party/rust/topological-sort/Cargo.toml
new file mode 100644
index 0000000000..1526eb8c66
--- /dev/null
+++ b/third_party/rust/topological-sort/Cargo.toml
@@ -0,0 +1,21 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g. crates.io) dependencies
+#
+# If you believe there's an error in this file please file an
+# issue against the rust-lang/cargo repository. If you're
+# editing this file be aware that the upstream Cargo.toml
+# will likely look very different (and much more reasonable)
+
+[package]
+name = "topological-sort"
+version = "0.1.0"
+authors = ["gifnksm <makoto.nksm+github@gmail.com>"]
+description = "Performs topological sorting."
+documentation = "https://docs.rs/topological-sort/~0.0"
+readme = "README.md"
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/gifnksm/topological-sort-rs"
diff --git a/third_party/rust/topological-sort/LICENSE-APACHE b/third_party/rust/topological-sort/LICENSE-APACHE
new file mode 100644
index 0000000000..8f71f43fee
--- /dev/null
+++ b/third_party/rust/topological-sort/LICENSE-APACHE
@@ -0,0 +1,202 @@
+                                 Apache License
+                           Version 2.0, January 2004
+                        http://www.apache.org/licenses/
+
+   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+   1. Definitions.
+
+      "License" shall mean the terms and conditions for use, reproduction,
+      and distribution as defined by Sections 1 through 9 of this document.
+
+      "Licensor" shall mean the copyright owner or entity authorized by
+      the copyright owner that is granting the License.
+
+      "Legal Entity" shall mean the union of the acting entity and all
+      other entities that control, are controlled by, or are under common
+      control with that entity. For the purposes of this definition,
+      "control" means (i) the power, direct or indirect, to cause the
+      direction or management of such entity, whether by contract or
+      otherwise, or (ii) ownership of fifty percent (50%) or more of the
+      outstanding shares, or (iii) beneficial ownership of such entity.
+
+      "You" (or "Your") shall mean an individual or Legal Entity
+      exercising permissions granted by this License.
+
+      "Source" form shall mean the preferred form for making modifications,
+      including but not limited to software source code, documentation
+      source, and configuration files.
+
+      "Object" form shall mean any form resulting from mechanical
+      transformation or translation of a Source form, including but
+      not limited to compiled object code, generated documentation,
+      and conversions to other media types.
+
+      "Work" shall mean the work of authorship, whether in Source or
+      Object form, made available under the License, as indicated by a
+      copyright notice that is included in or attached to the work
+      (an example is provided in the Appendix below).
+
+      "Derivative Works" shall mean any work, whether in Source or Object
+      form, that is based on (or derived from) the Work and for which the
+      editorial revisions, annotations, elaborations, or other modifications
+      represent, as a whole, an original work of authorship. For the purposes
+      of this License, Derivative Works shall not include works that remain
+      separable from, or merely link (or bind by name) to the interfaces of,
+      the Work and Derivative Works thereof.
+
+      "Contribution" shall mean any work of authorship, including
+      the original version of the Work and any modifications or additions
+      to that Work or Derivative Works thereof, that is intentionally
+      submitted to Licensor for inclusion in the Work by the copyright owner
+      or by an individual or Legal Entity authorized to submit on behalf of
+      the copyright owner. For the purposes of this definition, "submitted"
+      means any form of electronic, verbal, or written communication sent
+      to the Licensor or its representatives, including but not limited to
+      communication on electronic mailing lists, source code control systems,
+      and issue tracking systems that are managed by, or on behalf of, the
+      Licensor for the purpose of discussing and improving the Work, but
+      excluding communication that is conspicuously marked or otherwise
+      designated in writing by the copyright owner as "Not a Contribution."
+
+      "Contributor" shall mean Licensor and any individual or Legal Entity
+      on behalf of whom a Contribution has been received by Licensor and
+      subsequently incorporated within the Work.
+
+   2. Grant of Copyright License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      copyright license to reproduce, prepare Derivative Works of,
+      publicly display, publicly perform, sublicense, and distribute the
+      Work and such Derivative Works in Source or Object form.
+
+   3. Grant of Patent License. Subject to the terms and conditions of
+      this License, each Contributor hereby grants to You a perpetual,
+      worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+      (except as stated in this section) patent license to make, have made,
+      use, offer to sell, sell, import, and otherwise transfer the Work,
+      where such license applies only to those patent claims licensable
+      by such Contributor that are necessarily infringed by their
+      Contribution(s) alone or by combination of their Contribution(s)
+      with the Work to which such Contribution(s) was submitted. If You
+      institute patent litigation against any entity (including a
+      cross-claim or counterclaim in a lawsuit) alleging that the Work
+      or a Contribution incorporated within the Work constitutes direct
+      or contributory patent infringement, then any patent licenses
+      granted to You under this License for that Work shall terminate
+      as of the date such litigation is filed.
+
+   4. Redistribution. You may reproduce and distribute copies of the
+      Work or Derivative Works thereof in any medium, with or without
+      modifications, and in Source or Object form, provided that You
+      meet the following conditions:
+
+      (a) You must give any other recipients of the Work or
+          Derivative Works a copy of this License; and
+
+      (b) You must cause any modified files to carry prominent notices
+          stating that You changed the files; and
+
+      (c) You must retain, in the Source form of any Derivative Works
+          that You distribute, all copyright, patent, trademark, and
+          attribution notices from the Source form of the Work,
+          excluding those notices that do not pertain to any part of
+          the Derivative Works; and
+
+      (d) If the Work includes a "NOTICE" text file as part of its
+          distribution, then any Derivative Works that You distribute must
+          include a readable copy of the attribution notices contained
+          within such NOTICE file, excluding those notices that do not
+          pertain to any part of the Derivative Works, in at least one
+          of the following places: within a NOTICE text file distributed
+          as part of the Derivative Works; within the Source form or
+          documentation, if provided along with the Derivative Works; or,
+          within a display generated by the Derivative Works, if and
+          wherever such third-party notices normally appear. The contents
+          of the NOTICE file are for informational purposes only and
+          do not modify the License. You may add Your own attribution
+          notices within Derivative Works that You distribute, alongside
+          or as an addendum to the NOTICE text from the Work, provided
+          that such additional attribution notices cannot be construed
+          as modifying the License.
+
+      You may add Your own copyright statement to Your modifications and
+      may provide additional or different license terms and conditions
+      for use, reproduction, or distribution of Your modifications, or
+      for any such Derivative Works as a whole, provided Your use,
+      reproduction, and distribution of the Work otherwise complies with
+      the conditions stated in this License.
+
+   5. Submission of Contributions. Unless You explicitly state otherwise,
+      any Contribution intentionally submitted for inclusion in the Work
+      by You to the Licensor shall be under the terms and conditions of
+      this License, without any additional terms or conditions.
+      Notwithstanding the above, nothing herein shall supersede or modify
+      the terms of any separate license agreement you may have executed
+      with Licensor regarding such Contributions.
+
+   6. Trademarks. This License does not grant permission to use the trade
+      names, trademarks, service marks, or product names of the Licensor,
+      except as required for reasonable and customary use in describing the
+      origin of the Work and reproducing the content of the NOTICE file.
+
+   7. Disclaimer of Warranty. Unless required by applicable law or
+      agreed to in writing, Licensor provides the Work (and each
+      Contributor provides its Contributions) on an "AS IS" BASIS,
+      WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+      implied, including, without limitation, any warranties or conditions
+      of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+      PARTICULAR PURPOSE. You are solely responsible for determining the
+      appropriateness of using or redistributing the Work and assume any
+      risks associated with Your exercise of permissions under this License.
+
+   8. Limitation of Liability. In no event and under no legal theory,
+      whether in tort (including negligence), contract, or otherwise,
+      unless required by applicable law (such as deliberate and grossly
+      negligent acts) or agreed to in writing, shall any Contributor be
+      liable to You for damages, including any direct, indirect, special,
+      incidental, or consequential damages of any character arising as a
+      result of this License or out of the use or inability to use the
+      Work (including but not limited to damages for loss of goodwill,
+      work stoppage, computer failure or malfunction, or any and all
+      other commercial damages or losses), even if such Contributor
+      has been advised of the possibility of such damages.
+
+   9. Accepting Warranty or Additional Liability. While redistributing
+      the Work or Derivative Works thereof, You may choose to offer,
+      and charge a fee for, acceptance of support, warranty, indemnity,
+      or other liability obligations and/or rights consistent with this
+      License. However, in accepting such obligations, You may act only
+      on Your own behalf and on Your sole responsibility, not on behalf
+      of any other Contributor, and only if You agree to indemnify,
+      defend, and hold each Contributor harmless for any liability
+      incurred by, or claims asserted against, such Contributor by reason
+      of your accepting any such warranty or additional liability.
+
+   END OF TERMS AND CONDITIONS
+
+   APPENDIX: How to apply the Apache License to your work.
+
+      To apply the Apache License to your work, attach the following
+      boilerplate notice, with the fields enclosed by brackets "{}"
+      replaced with your own identifying information. (Don't include
+      the brackets!)  The text should be enclosed in the appropriate
+      comment syntax for the file format. We also recommend that a
+      file or class name and description of purpose be included on the
+      same "printed page" as the copyright notice for easier
+      identification within third-party archives.
+
+   Copyright {yyyy} {name of copyright owner}
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
diff --git a/third_party/rust/topological-sort/LICENSE-MIT b/third_party/rust/topological-sort/LICENSE-MIT
new file mode 100644
index 0000000000..672d559c7b
--- /dev/null
+++ b/third_party/rust/topological-sort/LICENSE-MIT
@@ -0,0 +1,19 @@
+Copyright (c) 2015 The topological-sort-rs Developers
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/third_party/rust/topological-sort/README.md b/third_party/rust/topological-sort/README.md
new file mode 100644
index 0000000000..87dd7bea59
--- /dev/null
+++ b/third_party/rust/topological-sort/README.md
@@ -0,0 +1,40 @@
+# topological-sort-rs
+
+[![Build Status](https://travis-ci.org/gifnksm/topological-sort-rs.svg)](https://travis-ci.org/gifnksm/topological-sort-rs)
+[![Coverage Status](https://coveralls.io/repos/gifnksm/topological-sort-rs/badge.svg?branch=master&service=github)](https://coveralls.io/github/gifnksm/topological-sort-rs?branch=master)
+[![crates.io](http://meritbadge.herokuapp.com/topological-sort)](https://crates.io/crates/topological-sort)
+
+Performs topological sorting.
+
+[Documentation](https://docs.rs/topological-sort/~0.0)
+
+## How to use?
+
+Add this to your `Cargo.toml`:
+
+```toml
+[dependencies]
+topological-sort = "0.0"
+```
+
+and this to your crate root:
+
+```rust
+extern crate topological_sort;
+```
+
+## License
+
+Licensed under either of
+
+ * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+ * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+
+at your option.
+
+### Contribution
+
+Unless you explicitly state otherwise, any contribution intentionally
+submitted for inclusion in the work by you, as defined in the Apache-2.0
+license, shall be dual licensed as above, without any additional terms or
+conditions.
diff --git a/third_party/rust/topological-sort/rustfmt.toml b/third_party/rust/topological-sort/rustfmt.toml
new file mode 100644
index 0000000000..0468aa5872
--- /dev/null
+++ b/third_party/rust/topological-sort/rustfmt.toml
@@ -0,0 +1,2 @@
+reorder_imports = true
+reorder_imported_names = true
diff --git a/third_party/rust/topological-sort/src/lib.rs b/third_party/rust/topological-sort/src/lib.rs
new file mode 100644
index 0000000000..08b04aab15
--- /dev/null
+++ b/third_party/rust/topological-sort/src/lib.rs
@@ -0,0 +1,384 @@
+// Copyright 2016 oauth-client-rs Developers
+//
+// Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+// http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
+// http://opensource.org/licenses/MIT>, at your option. This file may not be
+// copied, modified, or distributed except according to those terms.
+
+//! Performs topological sorting.
+
+#![warn(bad_style)]
+#![warn(missing_copy_implementations)]
+#![warn(missing_debug_implementations)]
+#![warn(missing_docs)]
+#![warn(trivial_casts)]
+#![warn(trivial_numeric_casts)]
+#![warn(unused)]
+#![warn(unused_extern_crates)]
+#![warn(unused_import_braces)]
+#![warn(unused_qualifications)]
+#![warn(unused_results)]
+#![cfg_attr(feature = "cargo-clippy", warn(if_not_else))]
+#![cfg_attr(feature = "cargo-clippy", warn(invalid_upcast_comparisons))]
+#![cfg_attr(feature = "cargo-clippy", warn(items_after_statements))]
+#![cfg_attr(feature = "cargo-clippy", warn(mut_mut))]
+#![cfg_attr(feature = "cargo-clippy", warn(never_loop))]
+#![cfg_attr(feature = "cargo-clippy", warn(nonminimal_bool))]
+#![cfg_attr(feature = "cargo-clippy", warn(option_map_unwrap_or))]
+#![cfg_attr(feature = "cargo-clippy", warn(option_map_unwrap_or_else))]
+#![cfg_attr(feature = "cargo-clippy", warn(option_unwrap_used))]
+#![cfg_attr(feature = "cargo-clippy", warn(result_unwrap_used))]
+#![cfg_attr(feature = "cargo-clippy", warn(used_underscore_binding))]
+
+use std::cmp::Ordering;
+use std::collections::{HashMap, HashSet};
+use std::collections::hash_map::Entry;
+use std::fmt;
+use std::hash::Hash;
+use std::iter::FromIterator;
+
+#[derive(Clone)]
+struct Dependency<T> {
+    num_prec: usize,
+    succ: HashSet<T>,
+}
+
+impl<T: Hash + Eq> Dependency<T> {
+    fn new() -> Dependency<T> {
+        Dependency {
+            num_prec: 0,
+            succ: HashSet::new(),
+        }
+    }
+}
+
+
+
+/// Performs topological sorting.
+#[derive(Clone)]
+pub struct TopologicalSort<T> {
+    top: HashMap<T, Dependency<T>>,
+}
+
+impl<T: Hash + Eq + Clone> TopologicalSort<T> {
+    /// Creates new empty `TopologicalSort`.
+    ///
+    /// ```rust
+    /// # extern crate topological_sort;
+    /// # fn main() {
+    /// use topological_sort::TopologicalSort;
+    /// let mut ts = TopologicalSort::<&str>::new();
+    /// ts.add_dependency("hello_world.o", "hello_world");
+    /// ts.add_dependency("hello_world.c", "hello_world");
+    /// ts.add_dependency("stdio.h", "hello_world.o");
+    /// ts.add_dependency("glibc.so", "hello_world");
+    /// assert_eq!(vec!["glibc.so", "hello_world.c", "stdio.h"],
+    ///            { let mut v = ts.pop_all(); v.sort(); v });
+    /// assert_eq!(vec!["hello_world.o"],
+    ///            { let mut v = ts.pop_all(); v.sort(); v });
+    /// assert_eq!(vec!["hello_world"],
+    ///            { let mut v = ts.pop_all(); v.sort(); v });
+    /// assert!(ts.pop_all().is_empty());
+    /// # }
+    /// ```
+    #[inline]
+    pub fn new() -> TopologicalSort<T> {
+        TopologicalSort {
+            top: HashMap::new(),
+        }
+    }
+
+    /// Returns the number of elements in the `TopologicalSort`.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.top.len()
+    }
+
+    /// Returns true if the `TopologicalSort` contains no elements.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.top.is_empty()
+    }
+
+    /// Registers the two elements' dependency.
+    ///
+    /// # Arguments
+    ///
+    /// * `prec` - The element appears before `succ`. `prec` is depended on by `succ`.
+    /// * `succ` - The element appears after `prec`. `succ` depends on `prec`.
+    pub fn add_dependency<P, S>(&mut self, prec: P, succ: S)
+    where
+        P: Into<T>,
+        S: Into<T>,
+    {
+        self.add_dependency_impl(prec.into(), succ.into())
+    }
+
+    fn add_dependency_impl(&mut self, prec: T, succ: T) {
+        match self.top.entry(prec) {
+            Entry::Vacant(e) => {
+                let mut dep = Dependency::new();
+                let _ = dep.succ.insert(succ.clone());
+                let _ = e.insert(dep);
+            }
+            Entry::Occupied(e) => {
+                if !e.into_mut().succ.insert(succ.clone()) {
+                    // Already registered
+                    return;
+                }
+            }
+        }
+
+        match self.top.entry(succ) {
+            Entry::Vacant(e) => {
+                let mut dep = Dependency::new();
+                dep.num_prec += 1;
+                let _ = e.insert(dep);
+            }
+            Entry::Occupied(e) => {
+                e.into_mut().num_prec += 1;
+            }
+        }
+    }
+
+    /// Registers a dependency link.
+    pub fn add_link(&mut self, link: DependencyLink<T>) {
+        self.add_dependency(link.prec, link.succ)
+    }
+
+    /// Inserts an element, without adding any dependencies from or to it.
+    ///
+    /// If the `TopologicalSort` did not have this element present, `true` is returned.
+    ///
+    /// If the `TopologicalSort` already had this element present, `false` is returned.
+    pub fn insert<U>(&mut self, elt: U) -> bool
+    where
+        U: Into<T>,
+    {
+        match self.top.entry(elt.into()) {
+            Entry::Vacant(e) => {
+                let dep = Dependency::new();
+                let _ = e.insert(dep);
+                true
+            }
+            Entry::Occupied(_) => false,
+        }
+    }
+
+    /// Removes the item that is not depended on by any other items and returns it, or `None` if
+    /// there is no such item.
+    ///
+    /// If `pop` returns `None` and `len` is not 0, there is cyclic dependencies.
+    pub fn pop(&mut self) -> Option<T> {
+        self.peek().map(T::clone).map(|key| {
+            let _ = self.remove(&key);
+            key
+        })
+    }
+
+
+    /// Removes all items that are not depended on by any other items and returns it, or empty
+    /// vector if there are no such items.
+    ///
+    /// If `pop_all` returns an empty vector and `len` is not 0, there is cyclic dependencies.
+    pub fn pop_all(&mut self) -> Vec<T> {
+        let keys = self.top
+            .iter()
+            .filter(|&(_, v)| v.num_prec == 0)
+            .map(|(k, _)| k.clone())
+            .collect::<Vec<_>>();
+        for k in &keys {
+            let _ = self.remove(k);
+        }
+        keys
+    }
+
+    /// Return a reference to the first item that does not depend on any other items, or `None` if
+    /// there is no such item.
+    pub fn peek(&self) -> Option<&T> {
+        self.top
+            .iter()
+            .filter(|&(_, v)| v.num_prec == 0)
+            .map(|(k, _)| k)
+            .next()
+    }
+
+    /// Return a vector of references to all items that do not depend on any other items, or an
+    /// empty vector if there are no such items.
+    pub fn peek_all(&self) -> Vec<&T> {
+        self.top
+            .iter()
+            .filter(|&(_, v)| v.num_prec == 0)
+            .map(|(k, _)| k)
+            .collect::<Vec<_>>()
+    }
+
+
+    fn remove(&mut self, prec: &T) -> Option<Dependency<T>> {
+        let result = self.top.remove(prec);
+        if let Some(ref p) = result {
+            for s in &p.succ {
+                if let Some(y) = self.top.get_mut(s) {
+                    y.num_prec -= 1;
+                }
+            }
+        }
+        result
+    }
+}
+
+impl<T: PartialOrd + Eq + Hash + Clone> FromIterator<T> for TopologicalSort<T> {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> TopologicalSort<T> {
+        let mut top = TopologicalSort::new();
+        let mut seen = Vec::<T>::default();
+        for item in iter {
+            let _ = top.insert(item.clone());
+            for seen_item in seen.iter().cloned() {
+                match seen_item.partial_cmp(&item) {
+                    Some(Ordering::Less) => {
+                        top.add_dependency(seen_item, item.clone());
+                    }
+                    Some(Ordering::Greater) => {
+                        top.add_dependency(item.clone(), seen_item);
+                    }
+                    _ => (),
+                }
+            }
+            seen.push(item);
+        }
+        top
+    }
+}
+
+/// A link between two items in a sort.
+#[derive(Copy, Clone, Debug)]
+pub struct DependencyLink<T> {
+    /// The element which is depened upon by `succ`.
+    pub prec: T,
+    /// The element which depends on `prec`.
+    pub succ: T,
+}
+
+impl<T> From<(T, T)> for DependencyLink<T> {
+    fn from(tuple: (T, T)) -> Self {
+        DependencyLink {
+            succ: tuple.0,
+            prec: tuple.1,
+        }
+    }
+}
+
+impl<T: Eq + Hash + Clone> FromIterator<DependencyLink<T>> for TopologicalSort<T> {
+    fn from_iter<I: IntoIterator<Item = DependencyLink<T>>>(iter: I) -> TopologicalSort<T> {
+        let mut top = TopologicalSort::new();
+        for link in iter {
+            top.add_link(link);
+        }
+        top
+    }
+}
+
+impl<T: Hash + Eq + Clone> Iterator for TopologicalSort<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<T> {
+        self.pop()
+    }
+}
+
+impl<T: fmt::Debug + Hash + Eq> fmt::Debug for Dependency<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "prec={}, succ={:?}", self.num_prec, self.succ)
+    }
+}
+
+impl<T: fmt::Debug + Hash + Eq + Clone> fmt::Debug for TopologicalSort<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{:?}", self.top)
+    }
+}
+
+
+#[cfg(test)]
+mod test {
+    use super::TopologicalSort;
+    use std::iter::FromIterator;
+
+    #[test]
+    fn from_iter() {
+        let t = vec![4, 3, 3, 5, 7, 6, 8];
+        let mut ts = TopologicalSort::<i32>::from_iter(t);
+        assert_eq!(Some(3), ts.next());
+        assert_eq!(Some(4), ts.next());
+        assert_eq!(Some(5), ts.next());
+        assert_eq!(Some(6), ts.next());
+        assert_eq!(Some(7), ts.next());
+        assert_eq!(Some(8), ts.next());
+        assert_eq!(None, ts.next());
+    }
+
+    #[test]
+    fn iter() {
+        let mut ts = TopologicalSort::<i32>::new();
+        ts.add_dependency(1, 2);
+        ts.add_dependency(2, 3);
+        ts.add_dependency(3, 4);
+        assert_eq!(Some(1), ts.next());
+        assert_eq!(Some(2), ts.next());
+        assert_eq!(Some(3), ts.next());
+        assert_eq!(Some(4), ts.next());
+        assert_eq!(None, ts.next());
+    }
+
+    #[test]
+    fn pop_all() {
+        fn check(result: &[i32], ts: &mut TopologicalSort<i32>) {
+            let l = ts.len();
+            let mut v = ts.pop_all();
+            v.sort();
+            assert_eq!(result, &v[..]);
+            assert_eq!(l - result.len(), ts.len());
+        }
+
+        let mut ts = TopologicalSort::new();
+        ts.add_dependency(7, 11);
+        assert_eq!(2, ts.len());
+        ts.add_dependency(7, 8);
+        assert_eq!(3, ts.len());
+        ts.add_dependency(5, 11);
+        assert_eq!(4, ts.len());
+        ts.add_dependency(3, 8);
+        assert_eq!(5, ts.len());
+        ts.add_dependency(3, 10);
+        assert_eq!(6, ts.len());
+        ts.add_dependency(11, 2);
+        assert_eq!(7, ts.len());
+        ts.add_dependency(11, 9);
+        assert_eq!(8, ts.len());
+        ts.add_dependency(11, 10);
+        assert_eq!(8, ts.len());
+        ts.add_dependency(8, 9);
+        assert_eq!(8, ts.len());
+
+        check(&[3, 5, 7], &mut ts);
+        check(&[8, 11], &mut ts);
+        check(&[2, 9, 10], &mut ts);
+        check(&[], &mut ts);
+    }
+
+    #[test]
+    fn cyclic_deadlock() {
+        let mut ts = TopologicalSort::new();
+        ts.add_dependency("stone", "sharp");
+
+        ts.add_dependency("bucket", "hole");
+        ts.add_dependency("hole", "straw");
+        ts.add_dependency("straw", "axe");
+        ts.add_dependency("axe", "sharp");
+        ts.add_dependency("sharp", "water");
+        ts.add_dependency("water", "bucket");
+        assert_eq!(ts.pop(), Some("stone"));
+        assert!(ts.pop().is_none());
+        println!("{:?}", ts);
+    }
+}