Fix #9246 and #6800: Remove pure statements #9263
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This was
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Jun 30, 2020
smarter
reviewed
Jun 30, 2020
odersky
requested changes
Jul 1, 2020
| case Typed(Block(stats, expr), _) if isPureExpr(expr) => stats | ||
| case stat => if !stat.symbol.isConstructor && isPureExpr(stat) then Nil else List(stat) | ||
| } | ||
| cpy.Block(tree)(stats, tree.expr) |
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This implementation copies all blocks which leads in practice to large scale tree rewriting & allocation even if there are no pure statements. I'd try this instead:
val stats = Trees.flatten(
tree.stats.mapConserve {
case Typed(Block(stats, expr), _) if isPureExpr(expr) => Thicket(stats)
case stat if !stat.symbol.isConstructor && isPureExpr(stat) => EmptyTree
case stat => stat
})(flatten avoids tree copying if possible).
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That variant works well
odersky
approved these changes
Jul 1, 2020
allanrenucci
reviewed
Jul 1, 2020
| case stat if !stat.symbol.isConstructor && isPureExpr(stat) => EmptyTree | ||
| case stat => stat | ||
| }) | ||
| cpy.Block(tree)(stats, tree.expr) |
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Since you're using mapConserve you may not need to call Trees.flatten and cpy.Block:
val stats = tree.stats.mapConserve { ... }
if stats eq tree.stats then tree
else cpy.Block(tree)(Trees.flatten(stats), tree.expr)
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