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TypeScript Academy · Lesson

Compile-Time Input Validation

Reject malformed DSL expressions before runtime.

Compile-Time Input Validation

Type-level DSLs can reject malformed expressions before runtime. Using template literal and conditional types, we validate the structure of a string at the type level and refuse invalid input.

Example: A Tiny Selector Language

Imagine accepting strings like "user.name" or "order.items.length". We want to reject "user." or ".name" at compile time.

All lessons in this course

  1. What Is a Type-Level DSL
  2. Designing a Fluent Query DSL
  3. Compile-Time Input Validation
  4. Error Messages in Type-Level DSLs
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