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author | Martin Odersky <odersky@gmail.com> | 2015-10-02 19:02:20 +0200 |
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committer | Martin Odersky <odersky@gmail.com> | 2015-10-06 13:51:39 +0200 |
commit | 0838b81bea4d579f812c02fafdc50e2b1920c059 (patch) | |
tree | 56ca7afdae15fda2ba5dc4b99dd74dd1562fecb5 | |
parent | 6497d02675e651a79383c43f6ef38be918be1867 (diff) | |
download | dotty-0838b81bea4d579f812c02fafdc50e2b1920c059.tar.gz dotty-0838b81bea4d579f812c02fafdc50e2b1920c059.tar.bz2 dotty-0838b81bea4d579f812c02fafdc50e2b1920c059.zip |
Add explanations for rewritings
-rw-r--r-- | src/dotty/tools/dotc/core/TypeComparer.scala | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/src/dotty/tools/dotc/core/TypeComparer.scala b/src/dotty/tools/dotc/core/TypeComparer.scala index 5555d13ba..5fbffe6e9 100644 --- a/src/dotty/tools/dotc/core/TypeComparer.scala +++ b/src/dotty/tools/dotc/core/TypeComparer.scala @@ -347,6 +347,9 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling { case OrType(tp21, tp22) => // Rewrite T1 <: (T211 & T212) | T22 to T1 <: (T211 | T22) and T1 <: (T212 | T22) // and analogously for T1 <: T21 | (T221 & T222) + // `|' types to the right of <: are problematic, because + // we have to choose one constraint set or another, which might cut off + // solutions. The rewriting delays the point where we have to choose. tp21 match { case AndType(tp211, tp212) => return isSubType(tp1, OrType(tp211, tp22)) && isSubType(tp1, OrType(tp212, tp22)) @@ -460,6 +463,9 @@ class TypeComparer(initctx: Context) extends DotClass with ConstraintHandling { case AndType(tp11, tp12) => // Rewrite (T111 | T112) & T12 <: T2 to (T111 & T12) <: T2 and (T112 | T12) <: T2 // and analogously for T11 & (T121 | T122) & T12 <: T2 + // `&' types to the left of <: are problematic, because + // we have to choose one constraint set or another, which might cut off + // solutions. The rewriting delays the point where we have to choose. tp11 match { case OrType(tp111, tp112) => return isSubType(AndType(tp111, tp12), tp2) && isSubType(AndType(tp112, tp12), tp2) |