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| author | Paul Phillips <paulp@improving.org> | 2013-08-05 16:41:54 -0700 |
|---|---|---|
| committer | Paul Phillips <paulp@improving.org> | 2013-08-05 18:23:21 -0700 |
| commit | 466b7d29f1c70018aea965961e830f50cf0facd4 (patch) | |
| tree | 70cb04fabc30f4da987c88475172d6acea796792 /src/compiler/scala/tools/nsc/transform/Erasure.scala | |
| parent | 46616ea2e94fa6ac7100b1cde66295f68338e18e (diff) | |
| download | scala-466b7d29f1c70018aea965961e830f50cf0facd4.tar.gz scala-466b7d29f1c70018aea965961e830f50cf0facd4.tar.bz2 scala-466b7d29f1c70018aea965961e830f50cf0facd4.zip | |
Fix N^2 spot in erasure.
An expression containing nested casts would type the same tree 2^N
times where N is the number of nested casts. This was particularly
visible in Vector.scala where one can find a six-cast expression.
It's currently line "why was six afraid of seven", aka line 789.
display5((index >> 25) & 31)
.asInstanceOf[Array[AnyRef]]((index >> 20) & 31)
.asInstanceOf[Array[AnyRef]]((index >> 15) & 31)
.asInstanceOf[Array[AnyRef]]((index >> 10) & 31)
.asInstanceOf[Array[AnyRef]]((index >> 5) & 31)
.asInstanceOf[Array[AnyRef]](index & 31)
.asInstanceOf[T]
Compiling Vector.scala, before/after.
< #unique types : 10805
> #unique types : 9722
< #created tree nodes : 26716
> #created tree nodes : 25647
I found a similar bug about a year ago in 39f01d4f48. It's
interesting to consider how little defense we have against bugs
of this nature - visually non-obvious differences in tree
traversal can have spectacular impact on complexity.
Diffstat (limited to 'src/compiler/scala/tools/nsc/transform/Erasure.scala')
| -rw-r--r-- | src/compiler/scala/tools/nsc/transform/Erasure.scala | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/compiler/scala/tools/nsc/transform/Erasure.scala b/src/compiler/scala/tools/nsc/transform/Erasure.scala index 0f65b11e9b..ee687e56b0 100644 --- a/src/compiler/scala/tools/nsc/transform/Erasure.scala +++ b/src/compiler/scala/tools/nsc/transform/Erasure.scala @@ -706,7 +706,8 @@ abstract class Erasure extends AddInterfaces // } typed(untyped) } - } else tree + } else qual1 + case Apply(TypeApply(sel @ Select(qual, name), List(targ)), List()) if tree.symbol == Any_isInstanceOf => targ.tpe match { |