Dotty Documentation

0.18.0-bin-SNAPSHOT

Dropped: Scala 2 Macros

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The previous, experimental macro system has been dropped. Instead, there is a cleaner, more restricted system based on two complementary concepts: inline and '{ ... }/${ ... } code generation. '{ ... } delays the compilation of the code and produces an object containing the code, dually ${ ... } evaluates an expression which produces code and inserts it in the surrounding ${ ... }. In this setting, a definition marked as inlined containing a ${ ... } is a macro, the code inside the ${ ... } is executed at compile-time and produces code in the form of '{ ... }. Additionally, the contents of code can be inspected and created with a more complex reflection API (TASTy Reflect) as an extension of '{ ... }/${ ... } framework.

  • inline has been implemented in Dotty.
  • Quotes '{ ... } and splices ${ ... } has been implemented in Dotty.
    • TASTy reflect provides more complex tree based APIs to inspect or create quoted code.