This repository has been archived by the owner on Sep 1, 2020. It is now read-only.
forked from scala/scala
-
Notifications
You must be signed in to change notification settings - Fork 19
for-comprehensions without _ <- x
and without yield
#21
Labels
Milestone
Comments
👍, somewhat unsurprisingly |
This would also be cool for {
txt = "Hello"
IO.putStrLn(txt)
line <- IO.readLine
IO.putStrLn(line)
} but +1 for everything that's been suggested here! |
You can already drop the yield, unless you're doing something with your bucket of units. |
Without the yield, it shouldn't necessarily map to unit, it could just do the flatMap's without the final map. |
👍 |
milessabin
pushed a commit
that referenced
this issue
Aug 12, 2016
This corrects an error in the change to the trait encoding in scala#5003: getters in traits should have empty bodies and be emitted as abstract. ``` % ~/scala/2.12.0-M4/bin/scalac sandbox/test.scala && javap -c T Compiled from "test.scala" public interface T { public abstract void T$_setter_$x_$eq(int); public int x(); Code: 0: aload_0 1: invokeinterface #15, 1 // InterfaceMethod x:()I 6: ireturn public int y(); Code: 0: aload_0 1: invokeinterface #20, 1 // InterfaceMethod y:()I 6: ireturn public void y_$eq(int); Code: 0: aload_0 1: iload_1 2: invokeinterface #24, 2 // InterfaceMethod y_$eq:(I)V 7: return public void $init$(); Code: 0: aload_0 1: bipush 42 3: invokeinterface #29, 2 // InterfaceMethod T$_setter_$x_$eq:(I)V 8: aload_0 9: bipush 24 11: invokeinterface #24, 2 // InterfaceMethod y_$eq:(I)V 16: return } % qscalac sandbox/test.scala && javap -c T Compiled from "test.scala" public interface T { public abstract void T$_setter_$x_$eq(int); public abstract int x(); public abstract int y(); public abstract void y_$eq(int); public static void $init$(T); Code: 0: aload_0 1: bipush 42 3: invokeinterface #21, 2 // InterfaceMethod T$_setter_$x_$eq:(I)V 8: aload_0 9: bipush 24 11: invokeinterface #23, 2 // InterfaceMethod y_$eq:(I)V 16: return public void $init$(); Code: 0: aload_0 1: invokestatic #27 // Method $init$:(LT;)V 4: return } ```
To resurrect this issue, please rework it as an issue/PR against Lightbend Scala (ie. scala/scala). |
milessabin
pushed a commit
that referenced
this issue
Oct 24, 2016
Top level modules in Scala currently desugar as: ``` class C; object O extends C { toString } ``` ``` public final class O$ extends C { public static final O$ MODULE$; public static {}; Code: 0: new #2 // class O$ 3: invokespecial #12 // Method "<init>":()V 6: return private O$(); Code: 0: aload_0 1: invokespecial #13 // Method C."<init>":()V 4: aload_0 5: putstatic #15 // Field MODULE$:LO$; 8: aload_0 9: invokevirtual #21 // Method java/lang/Object.toString:()Ljava/lang/String; 12: pop 13: return } ``` The static initalizer `<clinit>` calls the constructor `<init>`, which invokes superclass constructor, assigns `MODULE$= this`, and then runs the remainder of the object's constructor (`toString` in the example above.) It turns out that this relies on a bug in the JVM's verifier: assignment to a static final must occur lexically within the <clinit>, not from within `<init>` (even if the latter is happens to be called by the former). I'd like to move the assignment to <clinit> but that would change behaviour of "benign" cyclic references between modules. Example: ``` package p1; class CC { def foo = O.bar}; object O {new CC().foo; def bar = println(1)}; // Exiting paste mode, now interpreting. scala> p1.O 1 ``` This relies on the way that we assign MODULE$ field after the super class constructors are finished, but before the rest of the module constructor is called. Instead, this commit removes the ACC_FINAL bit from the field. It actually wasn't behaving as final at all, precisely the issue that the stricter verifier now alerts us to. ``` scala> :paste -raw // Entering paste mode (ctrl-D to finish) package p1; object O // Exiting paste mode, now interpreting. scala> val O1 = p1.O O1: p1.O.type = p1.O$@ee7d9f1 scala> scala.reflect.ensureAccessible(p1.O.getClass.getDeclaredConstructor()).newInstance() res0: p1.O.type = p1.O$@64cee07 scala> O1 eq p1.O res1: Boolean = false ``` We will still achieve safe publication of the assignment to other threads by virtue of the fact that `<clinit>` is executed within the scope of an initlization lock, as specified by: https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-5.html#jvms-5.5 Fixes scala/scala-dev#SD-194
milessabin
pushed a commit
that referenced
this issue
Jul 31, 2017
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 ```
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
This would be cool:
This would be even cooler:
The text was updated successfully, but these errors were encountered: