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Fix splice type variable pattern detection #17048

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merged 1 commit into from
Mar 21, 2023
Merged

Fix splice type variable pattern detection #17048

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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/typer/QuotesAndSplices.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -249,7 +249,7 @@ trait QuotesAndSplices {
val pat1 = if (patType eq patType1) pat else pat.withType(patType1)
patBuf += pat1
}
case Select(pat, _) if tree.symbol.isTypeSplice =>
case Select(pat: Bind, _) if tree.symbol.isTypeSplice =>
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  • How are Select where the prefix is not a Bind handled?
  • There are other cases which involve pat like case Apply(fn, pat :: Nil), should those be pat: Bind too?

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How are Select where the prefix is not a Bind handled?

Those just get the default super.transform(tree). The splitter only needs to extract the bindings of the pattern. For types, these are the type variable inline definitions. If there is a t.Underlying that is not a pattern we assume that it is an explicit splice into the pattern. In case, t is not identified as a type variable because t is part of the path of the type.

There are other cases which involve pat like case Apply(fn, pat :: Nil), should those be pat: Bind too?

These are expression splices ${...} in the pattern. There we can have an arbitrary pattern such as ${x} or ${Expr(x)}. Unlike with types, we do not have a notation or notion of inserting an expression is a quoted pattern.

val sym = tree.tpe.dealias.typeSymbol
if sym.exists then
val tdef = TypeDef(sym.asType).withSpan(sym.span)
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7 changes: 7 additions & 0 deletions tests/pos-macros/i17039.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
import scala.quoted.*

def macroImpl(using Quotes) =
val t = summon[Type[Int]]
Type.of[Int] match
case '[t.Underlying] => '{true}
case _ => '{false}