Fix #4350: Do not check prefix of class type parameters

Author: nicolasstucki

compiler/src/dotty/tools/dotc/transform/ReifyQuotes.scala

@@ -245,7 +245,7 @@ class ReifyQuotes extends MacroTransformWithImplicits with InfoTransformer {
         l == level ||
         sym.is(Inline) && sym.owner.is(Macro) && sym.info.isValueType && l - 1 == level
       case None =>
-        true
+        level == 0
     }
 
     /** Issue a "splice outside quote" error unless we ar in the body of an inline method */
@@ -289,7 +289,7 @@ class ReifyQuotes extends MacroTransformWithImplicits with InfoTransformer {
         if (!isThis) sym.show
         else if (sym.is(ModuleClass)) sym.sourceModule.show
         else i"${sym.name}.this"
-      if (!isThis && sym.maybeOwner.isType)
+      if (!isThis && sym.maybeOwner.isType && !sym.is(Param))
         check(sym.owner, sym.owner.thisType, pos)
       else if (sym.exists && !sym.isStaticOwner && !levelOK(sym))
         for (errMsg <- tryHeal(tp, pos))

tests/neg/i4350.scala

@@ -0,0 +1,5 @@
+import scala.quoted.Type
+
+class Foo[T] {
+  '(null.asInstanceOf[T]) // error
+}

tests/pos/i4350.scala

@@ -0,0 +1,5 @@
+import scala.quoted.Type
+
+class Foo[T: Type] {
+  '(null.asInstanceOf[T])
+}

tests/run-with-compiler/i4350.check

@@ -0,0 +1,6 @@
+{
+  null.asInstanceOf[Object]
+}
+{
+  null.asInstanceOf[String]
+}

tests/run-with-compiler/i4350.scala

@@ -0,0 +1,14 @@
+import dotty.tools.dotc.quoted.Toolbox._
+
+import scala.quoted.Type
+
+class Foo[T: Type] {
+  def q = '(null.asInstanceOf[T])
+}
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    println((new Foo[Object]).q.show)
+    println((new Foo[String]).q.show)
+  }
+}