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author | Olivier Blanvillain <olivier.blanvillain@gmail.com> | 2017-04-13 09:18:46 +0200 |
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committer | Olivier Blanvillain <olivier.blanvillain@gmail.com> | 2017-04-13 10:39:29 +0200 |
commit | 3e04b6f3aa4e4088220f199bd6aa5c6644c22354 (patch) | |
tree | c2b1a480a11ea6b23b2bc2f1b322203a8425c4da /compiler | |
parent | 3a9deec8e7a3a093e9b56461650857c4cb7a9d8c (diff) | |
download | dotty-3e04b6f3aa4e4088220f199bd6aa5c6644c22354.tar.gz dotty-3e04b6f3aa4e4088220f199bd6aa5c6644c22354.tar.bz2 dotty-3e04b6f3aa4e4088220f199bd6aa5c6644c22354.zip |
Revert <: Product requierment in pattern matching
The change in question broke the following pattern, commonly used in name based pattern matching:
```scala
object ProdEmpty {
def _1: Int = ???
def _2: String = ???
def isEmpty = true
def get = this
}
```
This type define both `_1` and `get` + `isEmpty` (but is not <: Product). After #1938, `ProdEmpty` became eligibles for both product and name based pattern. Because "in case of ambiguities, *Product Pattern* is preferred over *Name Based Pattern*", isEmpty wouldn't be used, breaking the scalac semantics.
Diffstat (limited to 'compiler')
4 files changed, 7 insertions, 8 deletions
diff --git a/compiler/src/dotty/tools/dotc/core/Definitions.scala b/compiler/src/dotty/tools/dotc/core/Definitions.scala index a97589d73..eee6ba785 100644 --- a/compiler/src/dotty/tools/dotc/core/Definitions.scala +++ b/compiler/src/dotty/tools/dotc/core/Definitions.scala @@ -10,7 +10,6 @@ import scala.collection.{ mutable, immutable } import PartialFunction._ import collection.mutable import util.common.alwaysZero -import typer.Applications object Definitions { @@ -846,6 +845,9 @@ class Definitions { TupleType(elems.size).appliedTo(elems) } + def isProductSubType(tp: Type)(implicit ctx: Context) = + tp.derivesFrom(ProductType.symbol) + /** Is `tp` (an alias) of either a scala.FunctionN or a scala.ImplicitFunctionN? */ def isFunctionType(tp: Type)(implicit ctx: Context) = { val arity = functionArity(tp) diff --git a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala index 41a1218eb..447a003e7 100644 --- a/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala +++ b/compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala @@ -1408,7 +1408,7 @@ class PatternMatcher extends MiniPhaseTransform with DenotTransformer { protected def seqTree(binder: Symbol) = tupleSel(binder)(firstIndexingBinder + 1) protected def tupleSel(binder: Symbol)(i: Int): Tree = { val accessors = - if (Applications.canProductMatch(binder.info)) + if (defn.isProductSubType(binder.info)) productSelectors(binder.info) else binder.caseAccessors val res = diff --git a/compiler/src/dotty/tools/dotc/typer/Applications.scala b/compiler/src/dotty/tools/dotc/typer/Applications.scala index c4d3e2292..7e17abbcd 100644 --- a/compiler/src/dotty/tools/dotc/typer/Applications.scala +++ b/compiler/src/dotty/tools/dotc/typer/Applications.scala @@ -48,9 +48,6 @@ object Applications { ref.info.widenExpr.dealias } - def canProductMatch(tp: Type)(implicit ctx: Context) = - extractorMemberType(tp, nme._1).exists - /** Does `tp` fit the "product match" conditions as an unapply result type * for a pattern with `numArgs` subpatterns? * This is the case of `tp` has members `_1` to `_N` where `N == numArgs`. @@ -72,7 +69,7 @@ object Applications { } def productArity(tp: Type)(implicit ctx: Context) = - if (canProductMatch(tp)) productSelectorTypes(tp).size else -1 + if (defn.isProductSubType(tp)) productSelectorTypes(tp).size else -1 def productSelectors(tp: Type)(implicit ctx: Context): List[Symbol] = { val sels = for (n <- Iterator.from(0)) yield tp.member(nme.selectorName(n)).symbol @@ -114,7 +111,7 @@ object Applications { getUnapplySelectors(getTp, args, pos) else if (unapplyResult isRef defn.BooleanClass) Nil - else if (canProductMatch(unapplyResult)) + else if (defn.isProductSubType(unapplyResult)) productSelectorTypes(unapplyResult) // this will cause a "wrong number of arguments in pattern" error later on, // which is better than the message in `fail`. diff --git a/compiler/src/dotty/tools/dotc/typer/Typer.scala b/compiler/src/dotty/tools/dotc/typer/Typer.scala index 4bf938fd4..02538671e 100644 --- a/compiler/src/dotty/tools/dotc/typer/Typer.scala +++ b/compiler/src/dotty/tools/dotc/typer/Typer.scala @@ -759,7 +759,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit /** Is `formal` a product type which is elementwise compatible with `params`? */ def ptIsCorrectProduct(formal: Type) = { isFullyDefined(formal, ForceDegree.noBottom) && - Applications.canProductMatch(formal) && + defn.isProductSubType(formal) && Applications.productSelectorTypes(formal).corresponds(params) { (argType, param) => param.tpt.isEmpty || argType <:< typedAheadType(param.tpt).tpe |