Great question! Let's break down what's going on with these two Scala Meta versions, why they exist, and how to fix that error you ran into.

Core Differences Between the Two Versions #

Scala Meta's versioning splits sharply based on which Scala language version they target—this is the root of the confusion:

• Target Scala Language

  • 1.8.0: Built exclusively for Scala 2 (supports 2.11, 2.12, 2.13). It relies on Scala 2's traditional macro system and doesn't understand Scala 3's new syntax or meta-programming APIs.
  • 3.7.2: Purpose-built for Scala 3. It's fully adapted to Scala 3's modern features like inline macros, the quotes API, and the revamped meta-programming model, and won't work at all in Scala 2 projects.

• Macro System Model

  • 1.8.0: Uses Scala 2's classic macro system, which requires separate macro implementation classes and relies on scala.reflect.macros. You declare macros with the macro keyword, and the logic lives in a separate class that interacts with Scala 2's reflection ASTs.
  • 3.7.2: Uses Scala 3's new inline macro model. Macros are written directly alongside regular Scala 3 code, using inline def and the quotes context to manipulate syntax trees. No separate macro implementation classes are needed.

• API Design

  • 1.8.0's API is tied to Scala 2's AST structure (e.g., Term, Lit types) and integrates closely with Scala 2's reflection libraries.
  • 3.7.2 has a completely redesigned API that aligns with Scala 3's ASTs, offering cleaner syntax for working with code and types via Expr and Type abstractions.

When to Use Which Version #

• Choose 1.8.0 if:

  • You're working on a Scala 2 project and need meta-programming tools compatible with Scala 2's ecosystem.
  • You're maintaining legacy Scala Meta code written for Scala 2.

• Choose 3.7.2 if:

  • Your project is on Scala 3 and you want to leverage Scala 3's modern meta-programming features (like compile-time computation, inline macros).
  • You're building new meta-programming tools or code generators for Scala 3.

Fixing Your "new-style ('inline') macros require s..." Error #

That error pops up because you're trying to use Scala 3's 3.7.2 version in a Scala 2 project. Scala 2's compiler doesn't recognize Scala 3's inline macro syntax or the underlying model that 3.7.2 relies on.

Here's how to fix it:

1. If you're on Scala 2: Swap your dependency to 1.8.0, and adjust your macro code to follow Scala 2's macro pattern (using macro keyword and separate implementation classes).
2. If you're on Scala 3: Double-check your project configuration:
   • Ensure your scalaVersion in sbt is set to a valid Scala 3 version (e.g., 3.3.1).
   • Use an sbt version of 1.5.0 or higher (Scala 3 requires newer sbt support).
   • Make sure your macro code follows Scala 3's inline macro pattern, like this example:

     import scala.quoted.*
     
     inline def greet: String = ${ greetImpl }
     
     def greetImpl(using Quotes): Expr[String] = Expr("Hello from Scala 3 inline macro!")
     

内容的提问来源于stack exchange，提问作者pme