shrinkAndFree

        pub fn shrinkAndFree(self: *Self, gpa: Allocator, new_len: usize) void {
            if (new_len == 0) return clearAndFree(self, gpa);

            assert(new_len <= self.capacity);
            assert(new_len <= self.len);

            const other_bytes = gpa.alignedAlloc(u8, sizes.big_align, capacityInBytes(new_len)) catch {
                const self_slice = self.slice();
                inline for (field_types, 0..) |field_type, i| {
                    if (@sizeOf(field_type) != 0) {
                        const field = @as(Field, @fromBackingInt(@intCast(i)));
                        const dest_slice = self_slice.items(field)[new_len..];
                        // We use memset here for more efficient codegen in safety-checked,
                        // valgrind-enabled builds. Otherwise the valgrind client request
                        // will be repeated for every element.
                        @memset(dest_slice, undefined);
                    }
                }
                self.len = new_len;
                return;
            };
            var other = Self{
                .bytes = other_bytes.ptr,
                .capacity = new_len,
                .len = new_len,
            };
            self.len = new_len;
            const self_slice = self.slice();
            const other_slice = other.slice();
            inline for (field_types, 0..) |field_type, i| {
                if (@sizeOf(field_type) != 0) {
                    const field = @as(Field, @fromBackingInt(@intCast(i)));
                    @memcpy(other_slice.items(field), self_slice.items(field));
                }
            }
            gpa.free(self.allocatedBytes());
            self.* = other;
        }