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author | Jason Zaugg <jzaugg@gmail.com> | 2015-08-29 21:42:29 +1000 |
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committer | Jason Zaugg <jzaugg@gmail.com> | 2015-09-21 14:00:09 +1000 |
commit | f1e553ecfbea25bcc7e13294f6104d599336f460 (patch) | |
tree | 9720ff6c481398e63700833001e82190c684c097 /src/compiler | |
parent | 0f72dd37f85bbcaa07cfb325685dc019e6bc1c26 (diff) | |
download | scala-f1e553ecfbea25bcc7e13294f6104d599336f460.tar.gz scala-f1e553ecfbea25bcc7e13294f6104d599336f460.tar.bz2 scala-f1e553ecfbea25bcc7e13294f6104d599336f460.zip |
SI-9029 Fix regression in extractor patterns
The unified treatment of classical and named-based pattern matching
does not correctly handle the generalization of "tuple capture".
By "tuple capture", I mean:
```
scala> object Extractor { def unapply(a: Any): Option[(Int, String)] = Some((1, "2")) }
defined object Extractor
scala> "" match { case Extractor(x: Int, y: String) => }
scala> "" match { case Extractor(xy : (Int, String)) => }
warning: there was one deprecation warning; re-run with -deprecation for details
scala> :warnings
<console>:9: warning: object Extractor expects 2 patterns to hold (Int, String) but crushing into 2-tuple to fit single pattern (SI-6675)
"" match { case Extractor(xy : (Int, String)) => }
^
```
Name based pattern matching, new in Scala 2.11, allows one to
deconstruct the elements that structurally resembles `ProductN`:
```
scala> class P2(val _1: Int, val _2: String)
defined class P2
scala> object Extractor { def unapply(a: Any): Option[P2] = Some(new P2(1, "2")) }
defined object Extractor
scala> "" match { case Extractor(x: Int, y: String) => }
```
However, attempting to extract the `P2` in its entirety leads to
an internal error:
```
scala> "" match { case Extractor(p2: P2) => }
<console>:10: warning: fruitless type test: a value of type (Int, String) cannot also be a P2
"" match { case Extractor(p2: P2) => }
^
<console>:10: error: error during expansion of this match (this is a scalac bug).
The underlying error was: type mismatch;
found : P2
required: (Int, String)
"" match { case Extractor(p2: P2) => }
^
```
Note that this match was legal and warning free in 2.10.
This commit avoids the hard-coded assumption that the "tuple capture"
results in a `TupleN`, and instead keeps track of the product-ish
type from which we extracted the element types. I have also opted not
to limit the deprecation warning to `TupleN` extractors.
Diffstat (limited to 'src/compiler')
-rw-r--r-- | src/compiler/scala/tools/nsc/transform/patmat/PatternExpander.scala | 18 | ||||
-rw-r--r-- | src/compiler/scala/tools/nsc/transform/patmat/ScalacPatternExpanders.scala | 34 |
2 files changed, 36 insertions, 16 deletions
diff --git a/src/compiler/scala/tools/nsc/transform/patmat/PatternExpander.scala b/src/compiler/scala/tools/nsc/transform/patmat/PatternExpander.scala index e84ccbf754..1916050dd8 100644 --- a/src/compiler/scala/tools/nsc/transform/patmat/PatternExpander.scala +++ b/src/compiler/scala/tools/nsc/transform/patmat/PatternExpander.scala @@ -86,9 +86,25 @@ trait PatternExpander[Pattern, Type] { * @param fixed The non-sequence types which are extracted * @param repeated The sequence type which is extracted */ - final case class Extractor(whole: Type, fixed: List[Type], repeated: Repeated) { + final case class Extractor(whole: Type, fixed: List[Type], repeated: Repeated, typeOfSinglePattern: Type) { require(whole != NoType, s"expandTypes($whole, $fixed, $repeated)") + /** A pattern with arity-1 that doesn't match the arity of the Product-like result of the `get` method, + * will match that result in its entirety. Example: + * + * {{{ + * warning: there was one deprecation warning; re-run with -deprecation for details + * scala> object Extractor { def unapply(a: Any): Option[(Int, String)] = Some((1, "2")) } + * defined object Extractor + * + * scala> "" match { case Extractor(x: Int, y: String) => } + * + * scala> "" match { case Extractor(xy : (Int, String)) => } + * warning: there was one deprecation warning; re-run with -deprecation for details + * }}} + * */ + def asSinglePattern: Extractor = copy(fixed = List(typeOfSinglePattern)) + def productArity = fixed.length def hasSeq = repeated.exists def elementType = repeated.elementType diff --git a/src/compiler/scala/tools/nsc/transform/patmat/ScalacPatternExpanders.scala b/src/compiler/scala/tools/nsc/transform/patmat/ScalacPatternExpanders.scala index b1783dc81f..55d4366a46 100644 --- a/src/compiler/scala/tools/nsc/transform/patmat/ScalacPatternExpanders.scala +++ b/src/compiler/scala/tools/nsc/transform/patmat/ScalacPatternExpanders.scala @@ -43,8 +43,9 @@ trait ScalacPatternExpanders { orElse definitions.elementType(ArrayClass, seq) ) } - def newExtractor(whole: Type, fixed: List[Type], repeated: Repeated): Extractor = - logResult(s"newExtractor($whole, $fixed, $repeated")(Extractor(whole, fixed, repeated)) + def newExtractor(whole: Type, fixed: List[Type], repeated: Repeated, typeOfSinglePattern: Type): Extractor = + logResult(s"newExtractor($whole, $fixed, $repeated, $typeOfSinglePattern")(Extractor(whole, fixed, repeated, typeOfSinglePattern)) + def newExtractor(whole: Type, fixed: List[Type], repeated: Repeated): Extractor = newExtractor(whole, fixed, repeated, tupleType(fixed)) // Turn Seq[A] into Repeated(Seq[A], A, A*) def repeatedFromSeq(seqType: Type): Repeated = { @@ -74,16 +75,17 @@ trait ScalacPatternExpanders { * it was unapplySeq, so we have to funnel that information in separately. */ def unapplyMethodTypes(whole: Type, result: Type, isSeq: Boolean): Extractor = { - val expanded = ( - if (result =:= BooleanTpe) Nil - else typeOfMemberNamedGet(result) match { + if (result =:= BooleanTpe) newExtractor(whole, Nil, NoRepeated) + else { + val getResult = typeOfMemberNamedGet(result) + val expanded = getResult match { case rawGet if !hasSelectors(rawGet) => rawGet :: Nil case rawGet => typesOfSelectors(rawGet) } - ) - expanded match { - case init :+ last if isSeq => newExtractor(whole, init, repeatedFromSeq(last)) - case tps => newExtractor(whole, tps, NoRepeated) + expanded match { + case init :+ last if isSeq => newExtractor(whole, init, repeatedFromSeq(last), getResult) + case tps => newExtractor(whole, tps, NoRepeated, getResult) + } } } } @@ -142,12 +144,14 @@ trait ScalacPatternExpanders { def acceptMessage = if (extractor.isErroneous) "" else s" to hold ${extractor.offeringString}" val requiresTupling = isUnapply && patterns.totalArity == 1 && productArity > 1 - if (requiresTupling && effectivePatternArity(args) == 1) { - val sym = sel.symbol.owner - currentRun.reporting.deprecationWarning(sel.pos, sym, s"${sym} expects $productArity patterns$acceptMessage but crushing into $productArity-tuple to fit single pattern (SI-6675)") - } - - val normalizedExtractor = if (requiresTupling) tupleExtractor(extractor) else extractor + val normalizedExtractor = if (requiresTupling) { + val tupled = extractor.asSinglePattern + if (effectivePatternArity(args) == 1 && isTupleType(extractor.typeOfSinglePattern)) { + val sym = sel.symbol.owner + currentRun.reporting.deprecationWarning(sel.pos, sym, s"${sym} expects $productArity patterns$acceptMessage but crushing into $productArity-tuple to fit single pattern (SI-6675)") + } + tupled + } else extractor validateAligned(context, fn, Aligned(patterns, normalizedExtractor)) } |