Migrating Code from Scalac - smarter/dotty GitHub Wiki

Minor tweaks

sym.linkedClassOfClass => sym.linkedClass
definitions => ctx.definitions

Member Lookup

tpe.member(name) and tpe.decl(name) now return a Denotation, not a Symbol. If no definition is found they return NoDenotation (instead of NoSymbol).

Symbol Properties

Most sym.isProperty methods don't exist in dotc, test for flags instead. See dotc vs scalac: Trees, Symbols, Types & Denotations.

Logging, Error Reporting, Failures

There are various kinds of logging

Errors, warnings, etc: ctx.inform, ctx.warning, ctx.error, ...
Log messages displayed under -Ylog:phase: log(msg) in scalac => ctx.log(msg) in dotc
Debug-Log messages displayed under -Ydebug -Ylog:<phase>: debuglog(msg) in scalac => ctx.debuglog(msg) in dotc
Assertions: assert(invariant)
Fatal errors: abort(msg) in scalac => throw new dotty.tools.dotc.FatalError(msg) in dotc

During development / debugging

Instead of Predef.println, use dotc.config.Printers.somePrinter.println Printers.scala. Printers can be easily added, enabled and disabled without changing command line arguments.

  val default: Printer           = new Printer   // new Printer => print
  val core: Printer              = noPrinter     // noPrinter   => shut up
  ...