Replace ShortcutImplicits

[odersky]

Don't duplicate methods in ShortcutImplicits. Instead, always merge
context function result parameters with normal parameters in one erased
method, as long as the context functions were expanded as closures
in the method's rhs.

In some cases (notably, but not exclusively, for bridges) this needs
an eta expansion step at erasure.

[odersky]

@nicolasstucki @anatoliykmetyuk Could you investigate why the test disabled in 41cd7d1 fails? It seems to have nothing to do with the changes in this PR.

[odersky]

Here's the failing test:

echo "testing sbt dotc with suspension"
clear_out "$OUT"
"$SBT" "dotc -d $OUT tests/pos-macros/macros-in-same-project-1/Bar.scala tests/pos-macros/macros-in-same-project-1/Foo.scala"

The test does not fail locally on my machine (either running sbt test) or executing the command by hand.

[odersky]

I think I know what goes on. The command test dotc has the following classpath

[info] running (fork) dotty.tools.dotc.Main -classpath /Users/odersky/.coursier/cache/v1/https/repo1.maven.org/maven2/org/scala-lang/scala-library/2.13.1/scala-library-2.13.1.jar:/Users/odersky/workspace/dotty/library/../out/bootstrap/dotty-library-bootstrapped/scala-0.23/dotty-library_0.23-0.23.0-bin-SNAPSHOT.jar -d /Users/odersky/classes tests/pos-macros/macros-in-same-project-1/Bar.scala tests/pos-macros/macros-in-same-project-1/Foo.scala

It looks for scala.internal.quoted.Unpickler$.unpickleExpr in workspace/dotty/library/../out/bootstrap/dotty-library-bootstrapped/scala-0.23/dotty-library_0.23-0.23.0-bin-SNAPSHOT.jar. But since unpickleExpr returns a CFT, its type has changed in this PR. So it does not find the method under the correct type and gives the error message

java.lang.NoSuchMethodError: scala.internal.quoted.Unpickler$.unpickleExpr(Lscala/collection/immutable/List;Lscala/collection/immutable/Seq;Lscala/quoted/QuoteContext;)Lscala/quoted/Expr;

So the correct way to set up the test is to use the output directory instead of SNAPSHOT-jar when searching for unpickleExpr.

Alternatively, we could leave the test disabled and revive it again once unpickleExpr with the new type signature is in SNAPSHOT.jar. That's easier. And the type of this method should not change that often.

[That also explains why the test worked locally: I have the output directory on the classpath, so it found the right unpickleExpr.]

[odersky]

So, this is ready for review now.

[smarter]

OK, so this should work fine if dotc is replaced by dotty-compiler-bootstrapped/dotc in the command (the non-bootstrapped compiler should never be used to run macro code to avoid this exact sort of problem).

[odersky]

@smarter That seems to work, yes. At least locally it worked. Let's see what the CI says.

[anatoliykmetyuk]

Otherwise LGTM

[anatoliykmetyuk]

I think this object belongs at Types.scala.

[odersky]

One can debate this. I put it next to isContextFunctionType and asContextFunctionType, since it is related.