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Fix #14319: Use correct stat context when transforming Block #14411

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Fix #14319: Use correct stat context when transforming Block #14411

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af31907
Use correct stat context when transforming Block
noti0na1 Feb 4, 2022
c9cad4a
Revert change in MegaPhase
noti0na1 Feb 10, 2022
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8 changes: 1 addition & 7 deletions compiler/src/dotty/tools/dotc/ast/TreeMapWithImplicits.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -48,13 +48,7 @@ class TreeMapWithImplicits extends tpd.TreeMapWithPreciseStatContexts {
override def transform(tree: Tree)(using Context): Tree = {
try tree match {
case Block(stats, expr) =>
inContext(nestedScopeCtx(stats)) {
if stats.exists(_.isInstanceOf[Import]) then
// need to transform stats and expr together to account for import visibility
val stats1 = transformStats(stats :+ expr, ctx.owner)
cpy.Block(tree)(stats1.init, stats1.last)
else super.transform(tree)
}
super.transform(tree)(using nestedScopeCtx(stats))
case tree: DefDef =>
inContext(localCtx(tree)) {
cpy.DefDef(tree)(
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7 changes: 7 additions & 0 deletions compiler/src/dotty/tools/dotc/ast/tpd.scala
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Expand Up @@ -1195,6 +1195,13 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
* - imports are reflected in the contexts of subsequent statements
*/
class TreeMapWithPreciseStatContexts(cpy: TreeCopier = tpd.cpy) extends TreeMap(cpy):
override def transform(tree: Tree)(using Context): Tree = tree match
case Block(stats, expr) =>
val stats1 = transformStats(stats :+ expr, ctx.owner)
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This will lead to great tree node churn. Every block will get new statements on every transform, so everything containing a block will be copied, which means you get a complete copy of the AST for a macro transform. I don't think this is acceptable.

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I think it is better to have an optional expr argument in transformStats. It's more convoluted but I don't see an alternative.

cpy.Block(tree)(stats1.init, stats1.last)
case _ =>
super.transform(tree)

override def transformStats(trees: List[Tree], exprOwner: Symbol)(using Context): List[Tree] =
trees.mapStatements(exprOwner, transform(_))

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10 changes: 10 additions & 0 deletions tests/explicit-nulls/pos/unsafe-chain.scala
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@@ -0,0 +1,10 @@
import java.nio.file.FileSystems
import java.util.ArrayList

def directorySeparator: String =
import scala.language.unsafeNulls
FileSystems.getDefault().getSeparator()

def getFirstOfFirst(xs: ArrayList[ArrayList[ArrayList[String]]]): String =
import scala.language.unsafeNulls
xs.get(0).get(0).get(0)