1 files changed, 194 insertions, 0 deletions
diff --git a/compiler/rustc_data_structures/src/vec_map.rs b/compiler/rustc_data_structures/src/vec_map.rs
new file mode 100644
index 000000000..86be0bd87
--- /dev/null
+++ b/compiler/rustc_data_structures/src/vec_map.rs
@@ -0,0 +1,194 @@
+use std::borrow::Borrow;
+use std::fmt::Debug;
+use std::iter::FromIterator;
+use std::slice::Iter;
+use std::vec::IntoIter;
+
+use crate::stable_hasher::{HashStable, StableHasher};
+
+/// A map type implemented as a vector of pairs `K` (key) and `V` (value).
+/// It currently provides a subset of all the map operations, the rest could be added as needed.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub struct VecMap<K, V>(Vec<(K, V)>);
+
+impl<K, V> VecMap<K, V>
+where
+    K: Debug + PartialEq,
+    V: Debug,
+{
+    pub fn new() -> Self {
+        VecMap(Default::default())
+    }
+
+    /// Sets the value of the entry, and returns the entry's old value.
+    pub fn insert(&mut self, k: K, v: V) -> Option<V> {
+        if let Some(elem) = self.0.iter_mut().find(|(key, _)| *key == k) {
+            Some(std::mem::replace(&mut elem.1, v))
+        } else {
+            self.0.push((k, v));
+            None
+        }
+    }
+
+    /// Removes the entry from the map and returns the removed value
+    pub fn remove(&mut self, k: &K) -> Option<V> {
+        self.0.iter().position(|(k2, _)| k2 == k).map(|pos| self.0.remove(pos).1)
+    }
+
+    /// Gets a reference to the value in the entry.
+    pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<&V>
+    where
+        K: Borrow<Q>,
+        Q: Eq,
+    {
+        self.0.iter().find(|(key, _)| k == key.borrow()).map(|elem| &elem.1)
+    }
+
+    /// Gets a mutable reference to the value in the entry.
+    pub fn get_mut<Q: ?Sized>(&mut self, k: &Q) -> Option<&mut V>
+    where
+        K: Borrow<Q>,
+        Q: Eq,
+    {
+        self.0.iter_mut().find(|(key, _)| k == key.borrow()).map(|elem| &mut elem.1)
+    }
+
+    /// Returns the any value corresponding to the supplied predicate filter.
+    ///
+    /// The supplied predicate will be applied to each (key, value) pair and it will return a
+    /// reference to the values where the predicate returns `true`.
+    pub fn any_value_matching(&self, mut predicate: impl FnMut(&(K, V)) -> bool) -> Option<&V> {
+        self.0.iter().find(|kv| predicate(kv)).map(|elem| &elem.1)
+    }
+
+    /// Returns the value corresponding to the supplied predicate filter. It crashes if there's
+    /// more than one matching element.
+    ///
+    /// The supplied predicate will be applied to each (key, value) pair and it will return a
+    /// reference to the value where the predicate returns `true`.
+    pub fn get_value_matching(&self, mut predicate: impl FnMut(&(K, V)) -> bool) -> Option<&V> {
+        let mut filter = self.0.iter().filter(|kv| predicate(kv));
+        let (_, value) = filter.next()?;
+        // This should return just one element, otherwise it's a bug
+        assert!(
+            filter.next().is_none(),
+            "Collection {:#?} should have just one matching element",
+            self
+        );
+        Some(value)
+    }
+
+    /// Returns `true` if the map contains a value for the specified key.
+    ///
+    /// The key may be any borrowed form of the map's key type,
+    /// [`Eq`] on the borrowed form *must* match those for
+    /// the key type.
+    pub fn contains_key<Q: ?Sized>(&self, k: &Q) -> bool
+    where
+        K: Borrow<Q>,
+        Q: Eq,
+    {
+        self.get(k).is_some()
+    }
+
+    /// Returns `true` if the map contains no elements.
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+
+    pub fn iter(&self) -> Iter<'_, (K, V)> {
+        self.into_iter()
+    }
+
+    pub fn iter_mut(&mut self) -> impl Iterator<Item = (&K, &mut V)> {
+        self.into_iter()
+    }
+
+    pub fn retain(&mut self, f: impl Fn(&(K, V)) -> bool) {
+        self.0.retain(f)
+    }
+}
+
+impl<K, V> Default for VecMap<K, V> {
+    #[inline]
+    fn default() -> Self {
+        Self(Default::default())
+    }
+}
+
+impl<K, V> From<Vec<(K, V)>> for VecMap<K, V> {
+    fn from(vec: Vec<(K, V)>) -> Self {
+        Self(vec)
+    }
+}
+
+impl<K, V> Into<Vec<(K, V)>> for VecMap<K, V> {
+    fn into(self) -> Vec<(K, V)> {
+        self.0
+    }
+}
+
+impl<K, V> FromIterator<(K, V)> for VecMap<K, V> {
+    fn from_iter<I: IntoIterator<Item = (K, V)>>(iter: I) -> Self {
+        Self(iter.into_iter().collect())
+    }
+}
+
+impl<'a, K, V> IntoIterator for &'a VecMap<K, V> {
+    type Item = &'a (K, V);
+    type IntoIter = Iter<'a, (K, V)>;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter()
+    }
+}
+
+impl<'a, K: 'a, V: 'a> IntoIterator for &'a mut VecMap<K, V> {
+    type Item = (&'a K, &'a mut V);
+    type IntoIter = impl Iterator<Item = Self::Item>;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.iter_mut().map(|(k, v)| (&*k, v))
+    }
+}
+
+impl<K, V> IntoIterator for VecMap<K, V> {
+    type Item = (K, V);
+    type IntoIter = IntoIter<(K, V)>;
+
+    #[inline]
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+impl<K: PartialEq + Debug, V: Debug> Extend<(K, V)> for VecMap<K, V> {
+    fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, iter: I) {
+        for (k, v) in iter {
+            self.insert(k, v);
+        }
+    }
+
+    fn extend_one(&mut self, (k, v): (K, V)) {
+        self.insert(k, v);
+    }
+
+    fn extend_reserve(&mut self, additional: usize) {
+        self.0.extend_reserve(additional);
+    }
+}
+
+impl<K, V, CTX> HashStable<CTX> for VecMap<K, V>
+where
+    K: HashStable<CTX> + Eq,
+    V: HashStable<CTX>,
+{
+    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
+        self.0.hash_stable(hcx, hasher)
+    }
+}
+
+#[cfg(test)]
+mod tests;