Add support for Java records in pattern matching #26497
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -185,6 +185,22 @@ object Applications { | |
| (0 until argsNum).map(i => if (i < arity - 1) selectorTypes(i) else elemTp).toList | ||
| end seqSelectors | ||
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| /** The component names of the Java record type `tp`, and whether its last | ||
| * component is a repeated (vararg) parameter, from its | ||
| * `@JavaRecordFields` annotation. The annotation is attached by | ||
| * `JavaParsers.recordDecl` (from the record header) and by the | ||
| * `ClassfileParser` (from the `Record` classfile attribute); since | ||
| * annotations are pickled, it is also available on record symbols | ||
| * unpickled from TASTy in pipelined compilation. | ||
| */ | ||
| def javaRecordFields(tp: Type)(using Context): (Boolean, List[Name]) = | ||
| tp.classSymbol.getAnnotation(defn.JavaRecordFieldsAnnot) match | ||
| case Some(annot) => | ||
| annot.tree match | ||
| case JavaRecordFieldsAnnot(isVararg, names) => (isVararg, names) | ||
| case _ => (false, Nil) | ||
| case None => (false, Nil) | ||
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| /** A utility class that matches results of unapplys with patterns. Two queryable members: | ||
| * val argTypes: List[Type] | ||
| * def typedPatterns(qual: untpd.Tree, typer: Typer): List[Tree] | ||
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@@ -1863,16 +1879,98 @@ trait Applications extends Compatibility { | |
| } | ||
| } | ||
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| // If `qual` denotes a Java record class, its class symbol, otherwise None | ||
| def javaRecordClass(qual: untpd.Tree): Option[ClassSymbol] = qual match | ||
| case qual: untpd.RefTree => | ||
| val nestedCtx = ctx.fresh.setNewTyperState() | ||
| val typeTree = typedType(untpd.rename(qual, qual.name.toTypeName))(using nestedCtx) | ||
| typeTree.tpe.classSymbol match | ||
| case cls: ClassSymbol if cls.isJavaRecord && !nestedCtx.reporter.hasErrors => Some(cls) | ||
| case _ => None | ||
| case _ => None | ||
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| /** For Java record, generate synthetic unapply/unapplySeq: | ||
| * ``` | ||
| * { | ||
| * class $anon: | ||
| * def unapply[...](x: JavaRecord[...]): (T_1, ..., T_n) = (x.f_1(), ..., x.f_n()) | ||
| * new $anon | ||
| * }.unapply | ||
| * ``` | ||
| * For a record with no components the result type is `Boolean` and the body is `true`. | ||
| * | ||
| * For a vararg record - Rec(T_1, ..., T_n, T*) - generate unapplySeq, with return type: | ||
| * - Seq[T] when n = 0 | ||
| * - (T_1, ..., T_n, Seq[T]) when n > 0 | ||
| */ | ||
| def javaRecordUnapply(recCls: ClassSymbol): Tree = | ||
| val recType = recCls.typeRef | ||
| val (isVararg, fields) = javaRecordFields(recType) | ||
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| def methType(recTp: Type) = | ||
| val componentTypes = fields.map: name => | ||
| recTp.member(name).suchThat(_.paramSymss == List(Nil)).info.resultType | ||
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| val resType = | ||
| // For `Rec()` we do `Boolean` | ||
| if componentTypes.isEmpty then defn.BooleanType | ||
| else if isVararg then | ||
| val defn.ArrayOf(elemType) = componentTypes.last.runtimeChecked | ||
| val seqType = defn.SeqType.appliedTo(elemType) | ||
| // For `Rec(T*)` we do `Seq[T]` | ||
| if componentTypes.length == 1 then seqType | ||
| // For `Rec(T1, ..., Tn, T*)` we do `(T1, ..., Tn, Seq[T])` | ||
| else defn.tupleType(componentTypes.init :+ seqType) | ||
| // For `Rec(T1, ..., Tn)` we do `(T1, ..., Tn)` | ||
| else defn.tupleType(componentTypes) | ||
| MethodType(List(nme.x_0), List(recTp), resType) | ||
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| val tparams = recCls.typeParams | ||
| val unapplyInfo = | ||
| if tparams.isEmpty then | ||
| methType(recType) | ||
| else | ||
| PolyType(tparams.map(_.name))( | ||
| pt => tparams.map(_.info.subst(tparams, pt.paramRefs).bounds), | ||
| pt => methType(recType.appliedTo(pt.paramRefs)) | ||
| ) | ||
| val methName = if isVararg then nme.unapplySeq else nme.unapply | ||
| val anon = AnonClass(ctx.owner, List(defn.ObjectType), coord = tree.span) { cls => | ||
| val unapplySym = newSymbol(cls, methName, Synthetic | Method, unapplyInfo, coord = tree.span).entered | ||
| val unapplyDef = DefDef(unapplySym.asTerm, paramss => | ||
| val x0 = paramss.last.last | ||
| def accessor(field: Name) = x0.select(field, _.paramSymss == List(Nil)).appliedToArgs(Nil) | ||
| if fields.isEmpty then Literal(Constant(true)) | ||
| else if isVararg then | ||
| val lastField = accessor(fields.last) | ||
| val defn.ArrayOf(lastElemType) = lastField.tpe.runtimeChecked | ||
| val lastFieldSeq = wrapArray(lastField, lastElemType) | ||
|
Member
There was a problem hiding this comment. This wraps the array in an immutable scala> val a = A("x", "y", "z")
val a: A = A[x=x, xs=[Ljava.lang.String;@2ca50ae3]
scala> val xs = a.xs
val xs: Array[String] = Array("y", "z")
scala> val sq = a match { case A(_, sq*) => sq }
val sq: Seq[String] = ArraySeq("y", "z")
scala> xs(0) = "buh"
scala> sq
val res0: Seq[String] = ArraySeq("buh", "z")I'm not sure if we should keep it this way, or always clone the array. Should I ask in core?
Contributor
Author
There was a problem hiding this comment. Well, it'd be consistent with pattern matching on arrays. scala> val xs = Array("x", "y", "z")
val xs: Array[String] = Array(x, y, z)
scala> val ys = xs match { case Array(r*) => r }
val ys: Seq[String] = ArraySeq(x, y, z)
scala> val zs = xs match { case Array(_, r*) => r }
val zs: Seq[String] = ArraySeq(y, z)
scala> xs(1) = "buh"
scala> ys
val res0: Seq[String] = ArraySeq(x, y, z)
scala> zs
val res1: Seq[String] = ArraySeq(y, z)But I think you can ask
Member
There was a problem hiding this comment. Right, that's implemented in Perhaps we can have a similar wrapper? It would have to accept the initial non-varargs params as well. Or we keep the tuple and use |
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| if fields.length == 1 then lastFieldSeq | ||
| else tupleTree(fields.init.map(accessor) :+ lastFieldSeq) | ||
| else tupleTree(fields.map(accessor)) | ||
| ) | ||
| List(unapplyDef) | ||
| } | ||
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| trySelectUnapply(untpd.TypedSplice(anon)): | ||
| (sel, state) => reportErrors(sel, state) | ||
| end javaRecordUnapply | ||
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| def tryJavaRecordUnapply(qual: untpd.Tree)(fallback: => Tree): Tree = | ||
| javaRecordClass(qual) match | ||
| case Some(recCls) => javaRecordUnapply(recCls) | ||
| case None => fallback | ||
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| /** Produce a typed qual.unapply or qual.unapplySeq tree, or | ||
| * else if this fails follow a type alias and try again. | ||
| */ | ||
| var unapplyFn = | ||
| trySelectUnapply(qual) { | ||
| (sel, state) => | ||
| val qual1 = followTypeAlias(qual) | ||
| if (qual1.isEmpty) tryJavaRecordUnapply(qual)(reportErrors(sel, state)) | ||
| else trySelectUnapply(qual1) { | ||
| (_, state) => tryJavaRecordUnapply(qual)(reportErrors(sel, state)) | ||
| } | ||
| } | ||
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