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Liftables: extract nested defs into class scope #2851

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Sep 13, 2022
Merged

Liftables: extract nested defs into class scope #2851

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89 changes: 45 additions & 44 deletions scalameta/common/shared/src/main/scala/scala/meta/internal/trees/Liftables.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -40,37 +40,8 @@ class LiftableMacros(override val c: Context) extends AdtLiftableMacros(c) with
localName: TermName,
body: Tree
): Option[Tree] = {
// NOTE: We have this check as a special case here, in addition to requires in Trees.scala,
// because I think this is going to be a very common mistake that new users are going to make,
// so I'd like that potential mistake to receive extra attention in form of quality error reporting.
def prohibitName(pat: Tree): Tree = {
q"""
def prohibitName(pat: _root_.scala.meta.Tree): _root_.scala.Unit = {
def unquotesName(q: _root_.scala.meta.internal.trees.Quasi): Boolean = {
val tpe = q.hole.arg.tpe // NOTE: no easy way to find this out without holes
tpe != null && tpe <:< typeOf[scala.meta.Term.Name]
}
pat match {
case q: _root_.scala.meta.internal.trees.Quasi if unquotesName(q) =>
val action = if (q.rank == 0) "unquote" else "splice"
c.abort(q.pos, "can't " + action + " a name here, use a pattern instead (e.g. p\"x\")")
case _ =>
}
}
prohibitName($pat)
"""
}
// NOTE: See #277 and #405 to understand why this special-casing is necessary.
def specialcaseTermApply(body: Tree): Tree = {
def liftPath(path: String) = {
val init = q"""c.universe.Ident(c.universe.TermName("_root_"))""": Tree
path
.split('.')
.foldLeft(init)((acc, part) => q"c.universe.Select($acc, c.universe.TermName($part))")
}
def liftField(value: Tree, tpe: Tree) = {
q"_root_.scala.Predef.implicitly[c.universe.Liftable[$tpe]].apply($value)"
}
def specialcaseTermApply: Tree = {
q"""
object ApplyToTripleDots {
def unapply(tree: _root_.scala.meta.Tree): Option[(_root_.scala.meta.Term, _root_.scala.meta.Term.Quasi)] = tree match {
Expand Down Expand Up @@ -100,20 +71,50 @@ class LiftableMacros(override val c: Context) extends AdtLiftableMacros(c) with
}
"""
}
def customize(body: Tree): Option[Tree] = {
if (adt.tpe <:< QuasiSymbol.toType) Some(q"Lifts.liftQuasi($localName)")
else if (adt.tpe <:< TermApplySymbol.toType) Some(specialcaseTermApply(body))
else if (adt.tpe <:< DefnValSymbol.toType)
Some(q"{ $localName.pats.foreach(pat => ${prohibitName(q"pat")}); $body }")
else if (adt.tpe <:< DefnVarSymbol.toType)
Some(q"{ $localName.pats.foreach(pat => ${prohibitName(q"pat")}); $body }")
else if (adt.tpe <:< PatBindSymbol.toType)
Some(q"{ ${prohibitName(q"$localName.lhs")}; $body }")
else if (adt.tpe <:< PatTypedSymbol.toType)
Some(q"{ ${prohibitName(q"$localName.lhs")}; $body }")
else None
}
// NOTE: we ignore tokens here for the time being
customize(body)
if (adt.tpe <:< QuasiSymbol.toType)
Some(q"Lifts.liftQuasi($localName)")
else if (adt.tpe <:< TermApplySymbol.toType)
Some(specialcaseTermApply)
else if (adt.tpe <:< DefnValSymbol.toType)
Some(q"{ $localName.pats.foreach(pat => ${prohibitName(q"pat")}); $body }")
else if (adt.tpe <:< DefnVarSymbol.toType)
Some(q"{ $localName.pats.foreach(pat => ${prohibitName(q"pat")}); $body }")
else if (adt.tpe <:< PatBindSymbol.toType)
Some(q"{ ${prohibitName(q"$localName.lhs")}; $body }")
else if (adt.tpe <:< PatTypedSymbol.toType)
Some(q"{ ${prohibitName(q"$localName.lhs")}; $body }")
else None
}

// NOTE: We have this check as a special case here, in addition to requires in Trees.scala,
// because I think this is going to be a very common mistake that new users are going to make,
// so I'd like that potential mistake to receive extra attention in form of quality error reporting.
private def prohibitName(pat: Tree): Tree = {
q"""
def prohibitName(pat: _root_.scala.meta.Tree): _root_.scala.Unit = {
def unquotesName(q: _root_.scala.meta.internal.trees.Quasi): Boolean = {
val tpe = q.hole.arg.tpe // NOTE: no easy way to find this out without holes
tpe != null && tpe <:< typeOf[scala.meta.Term.Name]
}
pat match {
case q: _root_.scala.meta.internal.trees.Quasi if unquotesName(q) =>
val action = if (q.rank == 0) "unquote" else "splice"
c.abort(q.pos, "can't " + action + " a name here, use a pattern instead (e.g. p\"x\")")
case _ =>
}
}
prohibitName($pat)
"""
}

private def liftPath(path: String): Tree = {
val init = q"""c.universe.Ident(c.universe.TermName("_root_"))""": Tree
path.split('.').foldLeft(init) { (acc, part) =>
q"c.universe.Select($acc, c.universe.TermName($part))"
}
}
private def liftField(value: Tree, tpe: Tree): Tree = {
q"_root_.scala.Predef.implicitly[c.universe.Liftable[$tpe]].apply($value)"
}
}