Don't synthesize context functions with embedded wildcards

Don't synthesize context functions with embedded wildcards in their
parameter types. This leads to a crash later when we typecheck
the closure.

Author: odersky

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

@@ -1203,7 +1203,7 @@ class Typer extends Namer
      *  @post: If result exists, `paramIndex` is defined for the name of
      *         every parameter in `params`.
      */
-    lazy val calleeType: Type = untpd.stripAnnotated(fnBody) match {
+    lazy val calleeType: Type = untpd.stripAnnotated(untpd.unsplice(fnBody)) match {
       case ident: untpd.Ident if isContextual =>
         val ident1 = typedIdent(ident, WildcardType)
         val tp = ident1.tpe.widen
@@ -2700,7 +2700,7 @@ class Typer extends Namer
     // see tests/pos/i7778b.scala
 
     val paramTypes = {
-      val hasWildcard = formals.exists(_.isInstanceOf[WildcardType])
+      val hasWildcard = formals.exists(_.existsPart(_.isInstanceOf[WildcardType], stopAtStatic = true))
       if hasWildcard then formals.map(_ => untpd.TypeTree())
       else formals.map(untpd.TypeTree)
     }

tests/pos/i11350.scala

@@ -0,0 +1,7 @@
+case class A[T](action: A[T] ?=> String) // error
+
+class A1[T](action: A1[T] ?=> String = (_: A1[T]) ?=> "") // works
+case class A2[T](action: A2[?] ?=> String) // works
+case class A3[T](action: A3[T] => String) // works as well
+
+class A4[T](action: A1[T] ?=> String = "")   // error