diff --git a/src/hash_map.hpp b/src/hash_map.hpp
index 69e5568093..45440d61e7 100644
--- a/src/hash_map.hpp
+++ b/src/hash_map.hpp
@@ -19,45 +19,64 @@ public:
         init_capacity(capacity);
     }
     void deinit(void) {
-        heap::c_allocator.deallocate(_entries, _capacity);
+        _entries.deinit();
+        heap::c_allocator.deallocate(_index_bytes,
+                _indexes_len * capacity_index_size(_indexes_len));
     }
 
     struct Entry {
         K key;
         V value;
-        bool used;
-        int distance_from_start_index;
     };
 
     void clear() {
-        for (int i = 0; i < _capacity; i += 1) {
-            _entries[i].used = false;
-        }
-        _size = 0;
+        _entries.clear();
+        memset(_index_bytes, 0, _indexes_len * capacity_index_size(_indexes_len));
         _max_distance_from_start_index = 0;
         _modification_count += 1;
     }
 
-    int size() const {
-        return _size;
+    size_t size() const {
+        return _entries.length;
     }
 
     void put(const K &key, const V &value) {
         _modification_count += 1;
-        internal_put(key, value);
 
-        // if we get too full (60%), double the capacity
-        if (_size * 5 >= _capacity * 3) {
-            Entry *old_entries = _entries;
-            int old_capacity = _capacity;
-            init_capacity(_capacity * 2);
-            // dump all of the old elements into the new table
-            for (int i = 0; i < old_capacity; i += 1) {
-                Entry *old_entry = &old_entries[i];
-                if (old_entry->used)
-                    internal_put(old_entry->key, old_entry->value);
+        // if we would get too full (60%), double the indexes size
+        if ((_entries.length + 1) * 5 >= _indexes_len * 3) {
+            heap::c_allocator.deallocate(_index_bytes,
+                    _indexes_len * capacity_index_size(_indexes_len));
+            _indexes_len *= 2;
+            size_t sz = capacity_index_size(_indexes_len);
+            // This zero initializes the bytes, setting them all empty.
+            _index_bytes = heap::c_allocator.allocate<uint8_t>(_indexes_len * sz);
+            _max_distance_from_start_index = 0;
+            for (size_t i = 0; i < _entries.length; i += 1) {
+                Entry *entry = &_entries.items[i];
+                switch (sz) {
+                    case 1:
+                        put_index(key_to_index(entry->key), i, (uint8_t*)_index_bytes);
+                        continue;
+                    case 2:
+                        put_index(key_to_index(entry->key), i, (uint16_t*)_index_bytes);
+                        continue;
+                    case 4:
+                        put_index(key_to_index(entry->key), i, (uint32_t*)_index_bytes);
+                        continue;
+                    default:
+                        put_index(key_to_index(entry->key), i, (size_t*)_index_bytes);
+                        continue;
+                }
             }
-            heap::c_allocator.deallocate(old_entries, old_capacity);
+        }
+
+
+        switch (capacity_index_size(_indexes_len)) {
+            case 1: return internal_put(key, value, (uint8_t*)_index_bytes);
+            case 2: return internal_put(key, value, (uint16_t*)_index_bytes);
+            case 4: return internal_put(key, value, (uint32_t*)_index_bytes);
+            default: return internal_put(key, value, (size_t*)_index_bytes);
         }
     }
 
@@ -81,40 +100,21 @@ public:
         return internal_get(key);
     }
 
-    void maybe_remove(const K &key) {
-        if (maybe_get(key)) {
-            remove(key);
-        }
+    bool remove(const K &key) {
+        bool deleted_something = maybe_remove(key);
+        if (!deleted_something)
+            zig_panic("key not found");
+        return deleted_something;
     }
 
-    void remove(const K &key) {
+    bool maybe_remove(const K &key) {
         _modification_count += 1;
-        int start_index = key_to_index(key);
-        for (int roll_over = 0; roll_over <= _max_distance_from_start_index; roll_over += 1) {
-            int index = (start_index + roll_over) % _capacity;
-            Entry *entry = &_entries[index];
-
-            if (!entry->used)
-                zig_panic("key not found");
-
-            if (!EqualFn(entry->key, key))
-                continue;
-
-            for (; roll_over < _capacity; roll_over += 1) {
-                int next_index = (start_index + roll_over + 1) % _capacity;
-                Entry *next_entry = &_entries[next_index];
-                if (!next_entry->used || next_entry->distance_from_start_index == 0) {
-                    entry->used = false;
-                    _size -= 1;
-                    return;
-                }
-                *entry = *next_entry;
-                entry->distance_from_start_index -= 1;
-                entry = next_entry;
-            }
-            zig_panic("shifting everything in the table");
+        switch (capacity_index_size(_indexes_len)) {
+            case 1: return internal_remove(key, (uint8_t*)_index_bytes);
+            case 2: return internal_remove(key, (uint16_t*)_index_bytes);
+            case 4: return internal_remove(key, (uint32_t*)_index_bytes);
+            default: return internal_remove(key, (size_t*)_index_bytes);
         }
-        zig_panic("key not found");
     }
 
     class Iterator {
@@ -122,24 +122,16 @@ public:
         Entry *next() {
             if (_inital_modification_count != _table->_modification_count)
                 zig_panic("concurrent modification");
-            if (_count >= _table->size())
-                return NULL;
-            for (; _index < _table->_capacity; _index += 1) {
-                Entry *entry = &_table->_entries[_index];
-                if (entry->used) {
-                    _index += 1;
-                    _count += 1;
-                    return entry;
-                }
-            }
-            zig_panic("no next item");
+            if (_index >= _table->_entries.length)
+                return nullptr;
+            Entry *entry = &_table->_entries.items[_index];
+            _index += 1;
+            return entry;
         }
     private:
         const HashMap * _table;
-        // how many items have we returned
-        int _count = 0;
         // iterator through the entry array
-        int _index = 0;
+        size_t _index = 0;
         // used to detect concurrent modification
         uint32_t _inital_modification_count;
         Iterator(const HashMap * table) :
@@ -154,89 +146,166 @@ public:
     }
 
 private:
+    // Maintains insertion order.
+    ZigList<Entry> _entries;
+    // If _indexes_len is less than 2**8, this is an array of uint8_t.
+    // If _indexes_len is less than 2**16, it is an array of uint16_t.
+    // If _indexes_len is less than 2**32, it is an array of uint32_t.
+    // Otherwise it is size_t.
+    // It's off by 1. 0 means empty slot, 1 means index 0, etc.
+    uint8_t *_index_bytes;
+    // This is the number of indexes. When indexes are bytes, it equals number of bytes.
+    // When indexes are uint16_t, _indexes_len is half the number of bytes.
+    size_t _indexes_len;
 
-    Entry *_entries;
-    int _capacity;
-    int _size;
-    int _max_distance_from_start_index;
-    // this is used to detect bugs where a hashtable is edited while an iterator is running.
+    size_t _max_distance_from_start_index;
+    // This is used to detect bugs where a hashtable is edited while an iterator is running.
     uint32_t _modification_count;
 
-    void init_capacity(int capacity) {
-        _capacity = capacity;
-        _entries = heap::c_allocator.allocate<Entry>(_capacity);
-        _size = 0;
+    void init_capacity(size_t capacity) {
+        _entries = {};
+        _entries.ensure_capacity(capacity);
+        // So that at capacity it will only be 60% full.
+        _indexes_len = capacity * 5 / 3;
+        size_t sz = capacity_index_size(_indexes_len);
+        // This zero initializes _index_bytes which sets them all to empty.
+        _index_bytes = heap::c_allocator.allocate<uint8_t>(_indexes_len * sz);
+
         _max_distance_from_start_index = 0;
-        for (int i = 0; i < _capacity; i += 1) {
-            _entries[i].used = false;
-        }
+        _modification_count = 0;
     }
 
-    void internal_put(K key, V value) {
-        int start_index = key_to_index(key);
-        for (int roll_over = 0, distance_from_start_index = 0;
-                roll_over < _capacity; roll_over += 1, distance_from_start_index += 1)
+    static size_t capacity_index_size(size_t len) {
+        if (len < UINT8_MAX)
+            return 1;
+        if (len < UINT16_MAX)
+            return 2;
+        if (len < UINT32_MAX)
+            return 4;
+        return sizeof(size_t);
+    }
+
+    template <typename I>
+    void internal_put(const K &key, const V &value, I *indexes) {
+        size_t start_index = key_to_index(key);
+        for (size_t roll_over = 0, distance_from_start_index = 0;
+                roll_over < _indexes_len; roll_over += 1, distance_from_start_index += 1)
         {
-            int index = (start_index + roll_over) % _capacity;
-            Entry *entry = &_entries[index];
-
-            if (entry->used && !EqualFn(entry->key, key)) {
-                if (entry->distance_from_start_index < distance_from_start_index) {
-                    // robin hood to the rescue
-                    Entry tmp = *entry;
-                    if (distance_from_start_index > _max_distance_from_start_index)
-                        _max_distance_from_start_index = distance_from_start_index;
-                    *entry = {
-                        key,
-                        value,
-                        true,
-                        distance_from_start_index,
-                    };
-                    key = tmp.key;
-                    value = tmp.value;
-                    distance_from_start_index = tmp.distance_from_start_index;
-                }
-                continue;
+            size_t index_index = (start_index + roll_over) % _indexes_len;
+            I index_data = indexes[index_index];
+            if (index_data == 0) {
+                _entries.append({key, value});
+                indexes[index_index] = _entries.length;
+                if (distance_from_start_index > _max_distance_from_start_index)
+                    _max_distance_from_start_index = distance_from_start_index;
+                return;
             }
-
-            if (!entry->used) {
-                // adding an entry. otherwise overwriting old value with
-                // same key
-                _size += 1;
+            Entry *entry = &_entries.items[index_data - 1];
+            if (EqualFn(entry->key, key)) {
+                *entry = {key, value};
+                if (distance_from_start_index > _max_distance_from_start_index)
+                    _max_distance_from_start_index = distance_from_start_index;
+                return;
             }
-
-            if (distance_from_start_index > _max_distance_from_start_index)
-                _max_distance_from_start_index = distance_from_start_index;
-            *entry = {
-                key,
-                value,
-                true,
-                distance_from_start_index,
-            };
-            return;
         }
-        zig_panic("put into a full HashMap");
+        zig_unreachable();
     }
 
+    template <typename I>
+    void put_index(size_t start_index, size_t entry_index, I *indexes) {
+        for (size_t roll_over = 0, distance_from_start_index = 0;
+                roll_over < _indexes_len; roll_over += 1, distance_from_start_index += 1)
+        {
+            size_t index_index = (start_index + roll_over) % _indexes_len;
+            if (indexes[index_index] == 0) {
+                indexes[index_index] = entry_index + 1;
+                if (distance_from_start_index > _max_distance_from_start_index)
+                    _max_distance_from_start_index = distance_from_start_index;
+                return;
+            }
+        }
+        zig_unreachable();
+    }
 
     Entry *internal_get(const K &key) const {
-        int start_index = key_to_index(key);
-        for (int roll_over = 0; roll_over <= _max_distance_from_start_index; roll_over += 1) {
-            int index = (start_index + roll_over) % _capacity;
-            Entry *entry = &_entries[index];
+        switch (capacity_index_size(_indexes_len)) {
+            case 1: return internal_get2(key, (uint8_t*)_index_bytes);
+            case 2: return internal_get2(key, (uint16_t*)_index_bytes);
+            case 4: return internal_get2(key, (uint32_t*)_index_bytes);
+            default: return internal_get2(key, (size_t*)_index_bytes);
+        }
+    }
 
-            if (!entry->used)
-                return NULL;
+    template <typename I>
+    Entry *internal_get2(const K &key, I *indexes) const {
+        size_t start_index = key_to_index(key);
+        for (size_t roll_over = 0; roll_over <= _max_distance_from_start_index; roll_over += 1) {
+            size_t index_index = (start_index + roll_over) % _indexes_len;
+            size_t index_data = indexes[index_index];
+            if (index_data == 0)
+                return nullptr;
 
+            Entry *entry = &_entries.items[index_data - 1];
             if (EqualFn(entry->key, key))
                 return entry;
         }
-        return NULL;
+        return nullptr;
     }
 
-    int key_to_index(const K &key) const {
-        return (int)(HashFunction(key) % ((uint32_t)_capacity));
+    size_t key_to_index(const K &key) const {
+        return ((size_t)HashFunction(key)) % _indexes_len;
+    }
+
+    template <typename I>
+    bool internal_remove(const K &key, I *indexes) {
+        size_t start_index = key_to_index(key);
+        for (size_t roll_over = 0; roll_over <= _max_distance_from_start_index; roll_over += 1) {
+            size_t index_index = (start_index + roll_over) % _indexes_len;
+            size_t index_data = indexes[index_index];
+            if (index_data == 0)
+                return false;
+
+            size_t index = index_data - 1;
+            Entry *entry = &_entries.items[index];
+            if (!EqualFn(entry->key, key))
+                continue;
+
+            indexes[index_index] = 0;
+            _entries.swap_remove(index);
+            if (_entries.length > 0 && _entries.length != index) {
+                // Because of the swap remove, now we need to update the index that was
+                // pointing to the last entry and is now pointing to this removed item slot.
+                update_entry_index(_entries.length, index, indexes);
+            }
+
+            // Now we have to shift over the following indexes.
+            roll_over += 1;
+            for (; roll_over <= _max_distance_from_start_index; roll_over += 1) {
+                size_t next_index = (start_index + roll_over) % _indexes_len;
+                if (indexes[next_index] == 0)
+                    break;
+                size_t next_start_index = key_to_index(_entries.items[indexes[next_index]].key);
+                if (next_start_index != start_index)
+                    break;
+                indexes[next_index - 1] = indexes[next_index];
+            }
+
+            return true;
+        }
+        return false;
+    }
+
+    template <typename I>
+    void update_entry_index(size_t old_entry_index, size_t new_entry_index, I *indexes) {
+        size_t start_index = key_to_index(_entries.items[new_entry_index].key);
+        for (size_t roll_over = 0; roll_over <= _max_distance_from_start_index; roll_over += 1) {
+            size_t index_index = (start_index + roll_over) % _indexes_len;
+            if (indexes[index_index] == old_entry_index + 1) {
+                indexes[index_index] = new_entry_index + 1;
+                return;
+            }
+        }
+        zig_unreachable();
     }
 };
-
 #endif
diff --git a/test/stage1/behavior/type_info.zig b/test/stage1/behavior/type_info.zig
index 68ff3aa310..2685a3552e 100644
--- a/test/stage1/behavior/type_info.zig
+++ b/test/stage1/behavior/type_info.zig
@@ -251,14 +251,13 @@ fn testStruct() void {
 }
 
 const TestStruct = packed struct {
-    const Self = @This();
-
     fieldA: usize,
     fieldB: void,
     fieldC: *Self,
     fieldD: u32 = 4,
 
     pub fn foo(self: *const Self) void {}
+    const Self = @This();
 };
 
 test "type info: function type info" {