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Widen type of final vars #1285 #1348

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Widen type of final vars #1285 #1348

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12 changes: 11 additions & 1 deletion src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1008,7 +1008,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
def typedValDef(vdef: untpd.ValDef, sym: Symbol)(implicit ctx: Context) = track("typedValDef") {
val ValDef(name, tpt, _) = vdef
completeAnnotations(vdef, sym)
val tpt1 = checkSimpleKinded(typedType(tpt))
val tpt1 = widenIfFinalMutable(checkSimpleKinded(typedType(tpt)), sym)
val rhs1 = vdef.rhs match {
case rhs @ Ident(nme.WILDCARD) => rhs withType tpt1.tpe
case rhs => typedExpr(rhs, tpt1.tpe)
Expand All @@ -1018,6 +1018,16 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
vdef1
}

/** Widen type if a valDef is both mutable and final, see #1285 */
private def widenIfFinalMutable(vdef: Tree, sym: Symbol)(implicit ctx: Context) = {
if (sym.is(allOf(Mutable, Final))) {
val widened = vdef.tpe.widen
vdef.withType(widened)
sym.info_=(widened)
}
vdef
}

/** Add a @volitile to lazy vals when rewriting from Scala2 */
private def patchIfLazy(vdef: ValDef)(implicit ctx: Context): Unit = {
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There's a simpler way to do it. In Namer.scala

  def isInline = sym.is(Final, butNot = Method)

We just need to exclude Mutable here. E.g.

  def isInline = sym.is(Final, butNot = Method | Mutable)

val sym = vdef.symbol
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5 changes: 5 additions & 0 deletions tests/pos/WidenFinalVars.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
/* For more information, see #1285 */
class Test {
final var x = false
x = true
}
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Missing a new line at the end of the file.