TypeScript 5.5新特性：推断类型谓词与独立声明
TypeScript 5.5: Inferred Type Predicates and Isolated Declarations
| iDev Tech | 2026-07-01T10:00:00
详解TypeScript 5.5的重要更新，包括推断类型谓词、独立声明和正则表达式语法检查。
Detailed overview of TypeScript 5.5 updates including inferred type predicates, isolated declarations, and regex syntax checking.
推断类型谓词TypeScript 5.5现在可以自动推断filter回调中的类型守卫。例如[1, null, 2].filter(x => x !== null)的返回类型会被正确推断为number[]，不再需要手动编写类型谓词函数。独立声明新增--isolatedDeclarations选项，要求所有导出的函数和变量都有显式的类型注解。这使得其他工具（如esbuild、swc）可以在不运行完整TypeScript类型检查的情况下生成声明文件，显著加速大型项目的构建。正则表达式语法检查TypeScript 5.5会对正则表达式字面量进行基本的语法检查，在编译时就能发现常见的正则表达式错误。
Inferred Type PredicatesTypeScript 5.5 can now automatically infer type guards in filter callbacks. For example, [1, null, 2].filter(x => x !== null) correctly returns number[] without manual type predicate functions.Isolated DeclarationsThe new --isolatedDeclarations option requires explicit type annotations on all exports. This enables tools like esbuild and swc to generate declaration files without running full TypeScript type checking, significantly accelerating large project builds.Regex Syntax CheckingTypeScript 5.5 performs basic syntax checking on regex literals, catching common regex errors at compile time.