Make inline vals effectively erased #8836
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nicolasstucki
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| /** Is this a Scala 2 macro */ | ||
| final def isScala2Macro(implicit ctx: Context): Boolean = is(Macro) && symbol.owner.is(Scala2x) | ||
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| /** An erased value or an inline method. | ||
| */ | ||
| def isEffectivelyErased(implicit ctx: Context): Boolean = | ||
| is(Erased) || isInlineMethod && !isRetainedInlineMethod | ||
| is(Erased) || is(Inline) && !isRetainedInline && !hasAnnotation(defn.ScalaStaticAnnot) |
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What we need the test !hasAnnotation(defn.ScalaStaticAnnot)?
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The @static annotation is supposed to guarantee that the field is emitted in the bytecode with the original signature. Hence we cannot remove the definition. There was one bytecode test with a final val that failed without this test.
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Inline vals are erased unless they implement a non-inline interface. This follows are the same rules used for defs.
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| @@ -34,19 +35,26 @@ class PruneErasedDefs extends MiniPhase with SymTransformer { thisTransform => | |||
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| override def transformApply(tree: Apply)(implicit ctx: Context): Tree = | |||
| if (tree.fun.tpe.widen.isErasedMethod) | |||
| cpy.Apply(tree)(tree.fun, tree.args.map(arg => ref(defn.Predef_undefined))) | |||
| cpy.Apply(tree)(tree.fun, tree.args.map(trivialErasedTree)) | |||
| else tree | |||
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In PostTyper, we also have logic to erase arguments. Is there a duplication of code?
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We keep in TASTy the contents of the erased trees. These are erased here. In PostTyper we only remove contents of erased definitions that were generated by inlining code (i.e. needed for typing). I will recheck what happens if we don't remove them in PostTyper, but fur sure the TASTy will increase.
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This also affects |
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These get erased after pickling. They should be available in the TASTy. |
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I was hoping to be able to constant fold it but it seems scalac doesn't always do that, object HelloWorld {
final val msg = "Hello World"
}
object Test {
def foo = HelloWorld.msg // replaced by `"Hello World"`
def bar = (HelloWorld.msg: "Hello World") // calls HelloWorld$.MODULE$.msg()
def baz(m: HelloWorld.msg.type) = m
def testBaz = baz(HelloWorld.msg) // calls HelloWorld$.MODULE$.msg()
} |
Inline vals are erased unless they implement a non-inline interface.
This follows are the same rules used for defs.