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Refine purity check #2837

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Merged
merged 1 commit into from
Jul 10, 2017
Merged

Refine purity check #2837

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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/typer/Typer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1709,7 +1709,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
traverse(stats ++ rest)
case stat :: rest =>
val stat1 = typed(stat)(ctx.exprContext(stat, exprOwner))
if (!ctx.isAfterTyper && isPureExpr(stat1))
if (!ctx.isAfterTyper && isPureExpr(stat1) && !stat1.tpe.isRef(defn.UnitClass))
ctx.warning(em"a pure expression does nothing in statement position", stat.pos)
buf += stat1
traverse(rest)
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6 changes: 5 additions & 1 deletion tests/neg/customArgs/xfatalWarnings.scala
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Expand Up @@ -4,4 +4,8 @@ object xfatalWarnings {
opt match { // error when running with -Xfatal-warnings
case None =>
}
}

object Test {
while (true) {} // should be ok. no "pure expression does nothing in statement position" issued.
}
}