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author | Paul Phillips <paulp@improving.org> | 2013-08-05 16:41:54 -0700 |
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committer | Paul Phillips <paulp@improving.org> | 2013-08-05 18:23:21 -0700 |
commit | 466b7d29f1c70018aea965961e830f50cf0facd4 (patch) | |
tree | 70cb04fabc30f4da987c88475172d6acea796792 /test/files/pos/erasure-nsquared.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 'test/files/pos/erasure-nsquared.scala')
-rw-r--r-- | test/files/pos/erasure-nsquared.scala | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/test/files/pos/erasure-nsquared.scala b/test/files/pos/erasure-nsquared.scala new file mode 100644 index 0000000000..b0e30ade58 --- /dev/null +++ b/test/files/pos/erasure-nsquared.scala @@ -0,0 +1,35 @@ +trait BigCast { + def bar(x: Int): AnyRef = ( + null + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + .asInstanceOf[List[AnyRef]].head + ) +} |