Merge pull request #15073 from dotty-staging/fix-14696

Detect quoted pattern variables in alternatives

compiler/src/dotty/tools/dotc/core/Mode.scala

@@ -89,7 +89,7 @@ object Mode {
   /** Don't suppress exceptions thrown during show */
   val PrintShowExceptions: Mode = newMode(18, "PrintShowExceptions")
 
-  val PatternOrTypeBits: Mode = Pattern | Type | InPatternAlternative
+  val PatternOrTypeBits: Mode = Pattern | Type
 
   /** We are elaborating the fully qualified name of a package clause.
    *  In this case, identifiers should never be imported.

compiler/src/dotty/tools/dotc/typer/QuotesAndSplices.scala

@@ -20,7 +20,7 @@ import dotty.tools.dotc.typer.Implicits._
 import dotty.tools.dotc.typer.Inferencing._
 import dotty.tools.dotc.util.Spans._
 import dotty.tools.dotc.util.Stats.record
-
+import dotty.tools.dotc.reporting.IllegalVariableInPatternAlternative
 import scala.collection.mutable
 
 
@@ -321,7 +321,9 @@ trait QuotesAndSplices {
       }
 
       private def transformTypeBindingTypeDef(nameOfSyntheticGiven: TermName, tdef: TypeDef, buff: mutable.Builder[Tree, List[Tree]])(using Context): Tree = {
-        if (variance == -1)
+        if ctx.mode.is(Mode.InPatternAlternative) then
+          report.error(IllegalVariableInPatternAlternative(tdef.symbol.name), tdef.srcPos)
+        if variance == -1 then
           tdef.symbol.addAnnotation(Annotation(New(ref(defn.QuotedRuntimePatterns_fromAboveAnnot.typeRef)).withSpan(tdef.span)))
         val bindingType = getBinding(tdef.symbol).symbol.typeRef
         val bindingTypeTpe = AppliedType(defn.QuotedTypeClass.typeRef, bindingType :: Nil)

tests/neg-macros/i14696.scala

@@ -0,0 +1,27 @@
+import scala.quoted.*
+
+def test(a: Expr[Any])(using Quotes): Unit = a match
+  case '{ ${_}: String } | '{ ${_}: Int } =>
+  case '{ $x1: String } | '{ ${_}: Int } => // error
+  case '{ $x: String } | '{ $x: Int } => // error // error
+  case '{ $x1: String } | '{ ${x2: Expr[Int]} } => // error // error
+  case '{ ${Str(x)}: String } | '{ ${y @ Str(z)}: Int } => // error // error
+  case '{ val x: Int = ???; ${_}(x): String } | '{ '{ val x: String = ???; ${_}(x): String }} =>
+  case '{ val x: Int = ???; $f(x): String } | '{ val x: String = ???; ${_}(x): String } => // error
+  case '{ val x: Int = ???; $f(x): String } | '{ val x: String = ???; $f(x): String } => // error // error
+  case '{ val x: Int = ???; $f(x): String } | '{ val x: String = ???; $g(x): String } => // error // error
+  case '{ varargs(${_}*) } | '{  varargs(${_}*) } =>
+  case '{ varargs($args*) } | '{  varargs(${_}*) } => // error
+  case '{ varargs($args*) } | '{  varargs($args*) } => // error // error
+  case '{ varargs($args1*) } | '{  varargs($args2*) } => // error // error
+  case '{ ${_}: t } | '{ ${_}: Int } => // error
+  case '{ ${_}: t } | '{ ${_}: t } => // error // error
+  case '{ ${_}: t } | '{ ${_}: u } => // error // error
+  case '{ type t; () } | '{ 1 } => // error
+  case '{ type t; () } | '{ type t; () } => // error // error
+  case '{ type t; () } | '{ type u; () } => // error // error
+
+def varargs(x: Any*): Unit = ()
+
+object Str:
+  def unapply(x: Any): Option[String] = ???