cache types during normalization

compiler/rustc_infer/src/infer/combine.rs

@@ -31,13 +31,11 @@ use super::unify_key::replace_if_possible;
 use super::unify_key::{ConstVarValue, ConstVariableValue};
 use super::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
 use super::{InferCtxt, MiscVariable, TypeTrace};
-use arrayvec::ArrayVec;
-use rustc_data_structures::fx::FxHashMap;
-use std::hash::Hash;
 
 use crate::traits::{Obligation, PredicateObligations};
 
 use rustc_ast as ast;
+use rustc_data_structures::mini_map::MiniMap;
 use rustc_hir::def_id::DefId;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::error::TypeError;
@@ -47,63 +45,6 @@ use rustc_middle::ty::{self, InferConst, ToPredicate, Ty, TyCtxt, TypeFoldable};
 use rustc_middle::ty::{IntType, UintType};
 use rustc_span::DUMMY_SP;
 
-/// Small-storage-optimized implementation of a map
-/// made specifically for caching results.
-///
-/// Stores elements in a small array up to a certain length
-/// and switches to `HashMap` when that length is exceeded.
-enum MiniMap<K, V> {
-    Array(ArrayVec<[(K, V); 8]>),
-    Map(FxHashMap<K, V>),
-}
-
-impl<K: Eq + Hash, V> MiniMap<K, V> {
-    /// Creates an empty `MiniMap`.
-    pub fn new() -> Self {
-        MiniMap::Array(ArrayVec::new())
-    }
-
-    /// Inserts or updates value in the map.
-    pub fn insert(&mut self, key: K, value: V) {
-        match self {
-            MiniMap::Array(array) => {
-                for pair in array.iter_mut() {
-                    if pair.0 == key {
-                        pair.1 = value;
-                        return;
-                    }
-                }
-                if let Err(error) = array.try_push((key, value)) {
-                    let mut map: FxHashMap<K, V> = array.drain(..).collect();
-                    let (key, value) = error.element();
-                    map.insert(key, value);
-                    *self = MiniMap::Map(map);
-                }
-            }
-            MiniMap::Map(map) => {
-                map.insert(key, value);
-            }
-        }
-    }
-
-    /// Return value by key if any.
-    pub fn get(&self, key: &K) -> Option<&V> {
-        match self {
-            MiniMap::Array(array) => {
-                for pair in array {
-                    if pair.0 == *key {
-                        return Some(&pair.1);
-                    }
-                }
-                return None;
-            }
-            MiniMap::Map(map) => {
-                return map.get(key);
-            }
-        }
-    }
-}
-
 #[derive(Clone)]
 pub struct CombineFields<'infcx, 'tcx> {
     pub infcx: &'infcx InferCtxt<'infcx, 'tcx>,