This PR cleans up config.Printers imports to make them more grep-able. These changes go in pair with the following updates on https://github.com/lampepfl/dotty/wiki/Workflow:

Compiling files with dotc

From sbt:

run <OPTIONS> <FILE>

From terminal:

$ ./bin/dotc <OPTIONS> <FILE>

Here are some useful debugging :

• -Xprint:PHASE1,PHASE2,... or -Xprint:all: prints the AST after each specified phase. Phase names can be found by searching src/dotty/tools/dotc/transform/ for phaseName.
• -Ylog:PHASE1,PHASE2,... or -Ylog:all: enables ctx.log("") logging for the specified phase.
• -Ycheck:all verifies the consistency of AST nodes between phases, in particular checks that types do not change (option enabled in tests)

Additional logging information can be obtained by changes some noPrinter to new Printer in src/dotty/tools/dotc/config/Printers.scala. This enables the subtyping.println("") and ctx.traceIndented("", subtyping) style logging.

Running tests

From sbt:

partest --show-diff --verbose

Type Stealer

There is no power mode for the repl yet, but you can inspect types with the type stealer:

$ ./bin/dotc -repl
scala> import test.DottyTypeStealer._; import dotty.tools.dotc.core._; import Contexts._,Types._;

Now, you can define types and access their representation. For example:

scala> val s = stealType("class O { type X }", "O#X")
scala> implicit val ctx: Context = s._1
scala> val t = s._2(0)
t: dotty.tools.dotc.core.Types.Type = TypeRef(TypeRef(ThisType(TypeRef(NoPrefix,<empty>)),O),X)
scala> val u = t.asInstanceOf[TypeRef].underlying
u: dotty.tools.dotc.core.Types.Type = TypeBounds(TypeRef(ThisType(TypeRef(NoPrefix,scala)),Nothing), TypeRef(ThisType(TypeRef(NoPrefix,scala)),Any))

Pretty-printing

Many objects in the dotc compiler implement a Showable trait (e.g. Tree, Symbol, Type). These objects may be prettyprinted using the .show method