Skip to content

Latest commit

 

History

History
54 lines (41 loc) · 2.96 KB

Scala-Compilers.md

File metadata and controls

54 lines (41 loc) · 2.96 KB
Raw

Scala General View

Soundness

Syntax

Compilers

  • javac 1.3+
  • scalac for 1.x (javac based)
    • written in java-with-patterns/pizza
  • nsc compiler for 2.0-2.10
    • some use of functional capabilities of Scala
  • scalac for 2.11 (ncs-based) (??? and for 2.12 ???)
    • REPL
    • presentation compiler for IDE (Eclipse, Ensime)
    • run-time metaprogramming with toolboxes

Dotty Architecture

dsc = Dotty scala Compiler

ER diagram of core compiler architecture

Dotty treats positions a bit differently from scalac. The architecture is as follows:

  1. There are untyped and typed trees. Both kinds of trees are immutable. The job of the typer is to map one to the other.
  2. Untyped trees are very close to source and have precise range positions. For instance, for-expression generators and filters are expressed as particular untyped trees.
  3. Typed trees are a desugared subset of untyped trees. An untyped tree may map to several typed trees (example: an untyped case class def maps into a class def and a module def of the companion object).
  4. Typed trees also have range positions which are copied from the positions of the untyped trees from which they are generated.
  5. There is a navigation API which works with the positions in order to:
  • map a typed tree to the untyped tree from which it is derived,
  • map an untyped tree to the set of typed trees that derive from it.

Language Server Protocol

Dictionary

The Scala IDE for Eclipse uses the Scala Presentation Compiler, a faster asynchronous version of the Scala Compiler. The presentation compiler only runs the phases up until and including the typer phase, that is, the first 4 of the 27 scala compilation phases. The IDE uses the presentation compiler to provide semantic features such as live error markers, inferred type hovers, and semantic highlighting.

The presentation compiler was introduced so that external tools could get access to the compiler's internal model.

The source for the presentation compiler can be found in the Scala repository in the package scala.tools.nsc.interactive. The most important file for this discussion is Global.scala. If you open Global.scala, you'll see that it extends the standard Scala compiler, scala.tools.nsc.Global, and mixes in several helpers.

Compiler tricks

You can get a list of all the phases of the compiler by passing the -Yshow-phases option to scalac.

Links