Add an @implicitAmbiguous annotation #32
Conversation
|
This is a fix for SI-6806. My commit raises a question. I've added a class to scala-library.jar - can/should we require users of Typelevel Scala to use a (binary compatible) version of scala-library? Should we instead make them use the standard scala-library.jar and just provide an additional library instead? |
|
Found two failing tests:
|
| @@ -1091,6 +1091,7 @@ trait Definitions extends api.StandardDefinitions { | |||
| lazy val BridgeClass = requiredClass[scala.annotation.bridge] | |||
| lazy val ElidableMethodClass = requiredClass[scala.annotation.elidable] | |||
| lazy val ImplicitNotFoundClass = requiredClass[scala.annotation.implicitNotFound] | |||
| lazy val ImplicitAmbiguousClass = requiredClass[scala.annotation.implicitAmbiguous] | |||
There was a problem hiding this comment.
You probably want to make this getClassIfDefined and handle the missing annotation gracefully (see CompileTimeOnlyAttr, for example).
If you only need additive library changes, consider an extra JAR like scala-library-tlc.jar. You could save (or at least defer) a lot of cost by sticking to compiler only changes in the short term.
There was a problem hiding this comment.
@retronym awesome, thank you!
There was a problem hiding this comment.
If going the extra JAR route, I strongly advocate the use of a new package to avoid the known and hated split package issues, e.g. when working in OSGi or with sealed packages.
|
Seems that to make scala-library-typelevel.jar possible also requires us to fork partest as well as update the build.xml awfulness. What's the possibility of using @paulp's new sbt-based build? |
|
@puffnfresh I can imagine a world where we collaborate on the build infrastructure. This in fact is the main reason I released it now, so as not to miss that opportunity. The code really is not in the state I would have chosen though. What I'm presently in the progress of is extracting most of that code and combining it with a bunch of other sbt code into "libsbt", my attempt at making sbt somewhat usable. You can see the dependency in policy project/plugins.sbt but I haven't published the source yet (except inasmuch as I assume there are source jars alongside the plugin.) Once I complete that process the amount of building-scala-specific code in the policy project will be relatively small. |
|
@paulp so we would just add libsbt as an sbt dep and be pretty much good to go? |
|
@puffnfresh Geez it isn't going to be anywhere near that easy. |
|
Can one of the admins verify this patch? |
puffnfresh
force-pushed
the
feature/implicit-ambiguous-annotation
branch
from
8b730e6
to
4d4f703
Compare
Example usage:
trait =!=[C, D]
implicit def neq[E, F] : E =!= F = null
@annotation.implicitAmbiguous("Could not prove ${J} =!= ${J}")
implicit def neqAmbig1[G, H, J] : J =!= J = null
implicit def neqAmbig2[I] : I =!= I = null
implicitly[Int =!= Int]
Which gives the following error:
implicit-ambiguous.scala:9: error: Could not prove Int =!= Int
implicitly[Int =!= Int]
^
Better than what was previously given:
implicit-ambiguous.scala:9: error: ambiguous implicit values:
both method neqAmbig1 in object Test of type [G, H, J]=> Main.$anon.Test.=!=[J,J]
and method neqAmbig2 in object Test of type [I]=> Main.$anon.Test.=!=[I,I]
match expected type Main.$anon.Test.=!=[Int,Int]
implicitly[Int =!= Int]
^
|
add to whitelist |
|
I know this potentially makes thing much more complex, but I have to say I'm slightly annoyed by the fact we have to provide a dummy body ;-) |
|
@aloiscochard what's much more complex? |
|
Well actually I don't know, just a wild guess than making it work the way I I hope I'm just being pessimistic for no good reason?
|
|
@aloiscochard I'm not sure what you proposed. I think I now understand what you mean by "dummy body" though. If you don't like the fact that it's not total, you could actually provide the same implementation as |
|
As discussed on IRC with @puffnfresh, an other more ad-hoc alternative to achieve the "real" goal (disabling implicits) would be indeed much more complex and take longer. Thanks! 👍 |
This is where our additions to scala-library.jar will go. The current content is the implicitAmbiguous annotation. I seemed to have made the right changes to make the REPL, the test classpath and scala-dist to work. I'm not sure if there's anything else we need but I also inserted references to typelevel where library was also referenced, just in case.
|
@milessabin @non @propensive a review on my last commit here would be useful. Is this the direction we want to go? |
|
I think that's the right thing. We're going to need that jar one way or another. |
|
Yes, I agree. |
…otation Add an @implicitAmbiguous annotation
Non local returns aren't eliminated after inlined in 2.11 or 2.12
```
⚡ scala
Welcome to Scala 2.12.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.
scala> @inlune def foo(a: => Any) = if ("".isEmpty) a else ""
<console>:11: error: not found: type inlune
@inlune def foo(a: => Any) = if ("".isEmpty) a else ""
^
scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any
scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn
scala> :javap -c InlineReturn#test
public java.lang.Object test();
Code:
0: new #4 // class java/lang/Object
3: dup
4: invokespecial #32 // Method java/lang/Object."<init>":()V
7: astore_1
8: getstatic #36 // Field $line4/$read$$iw$$iw$.MODULE$:L$line4/$read$$iw$$iw$;
11: aload_1
12: invokedynamic #59, 0 // InvokeDynamic #0:apply:(Ljava/lang/Object;)Lscala/Function0;
17: invokevirtual #63 // Method $line4/$read$$iw$$iw$.foo:(Lscala/Function0;)Ljava/lang/Object;
20: goto 44
23: astore_2
24: aload_2
25: invokevirtual #66 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
28: aload_1
29: if_acmpne 39
32: aload_2
33: invokevirtual #69 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
36: goto 41
39: aload_2
40: athrow
41: goto 44
44: areturn
Exception table:
from to target type
8 20 23 Class scala/runtime/NonLocalReturnControl
```
```
⚡ ~/scala/2.11.8/bin/scala
Welcome to Scala 2.11.8 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_112).
Type in expressions for evaluation. Or try :help.
scala> @inline def foo(a: => Any) = if ("".isEmpty) a else ""
foo: (a: => Any)Any
scala> class InlineReturn { def test: Any = foo(return "") }
defined class InlineReturn
scala> :javap -c InlineReturn#test
public java.lang.Object test();
Code:
0: new #4 // class java/lang/Object
3: dup
4: invokespecial #13 // Method java/lang/Object."<init>":()V
7: astore_1
8: getstatic #19 // Field .MODULE$:L;
11: new #21 // class InlineReturn$$anonfun$test$1
14: dup
15: aload_0
16: aload_1
17: invokespecial #24 // Method InlineReturn$$anonfun$test$1."<init>":(LInlineReturn;Ljava/lang/Object;)V
20: invokevirtual #28 // Method .foo:(Lscala/Function0;)Ljava/lang/Object;
23: goto 39
26: astore_2
27: aload_2
28: invokevirtual #31 // Method scala/runtime/NonLocalReturnControl.key:()Ljava/lang/Object;
31: aload_1
32: if_acmpne 40
35: aload_2
36: invokevirtual #34 // Method scala/runtime/NonLocalReturnControl.value:()Ljava/lang/Object;
39: areturn
40: aload_2
41: athrow
Exception table:
from to target type
8 26 26 Class scala/runtime/NonLocalReturnControl
scala> :quit
```
Example usage:
Which gives the following error:
Better than what was previously given: