**從Haxe 3.1.0以后** > **Since Haxe 3.1.0** 通過下面的語法，可以使用編譯時類型檢查： > It is possible to employ compile-time type checks using the following syntax: ~~~ (expr : type) ~~~ 括號是強制性的。不想安全轉換（第5.23.2），這個結構沒有運行時的影響。它有兩個編譯時的影響： > The parentheses are mandatory. Unlike safe casts (5.23.2) this construct has no run-time impact. It has two compile-time implications: * 從上至下的推斷（第3.6.1節）用于類型化 expr 為 type 類型 * 結果的類型化的表達式統一（第3.5節）為type 類型 > * Top-down inference (3.6.1) is used to type expr with type type. > * The resulting typed expression is uni?ed (3.5) with type type. 這通常影響兩個操作，如當執行絕對的標識符解析（第3.7.3節）時給定類型被用為預期的類型，和抽象類型的轉換的合一檢查。 > This has the usual effect of both operations such as the given type being used as expected type when performing unquali?ed identi?er resolution (3.7.3) and the uni?cation checking for abstract casts (2.8.1).