Merge pull request #10234 from dotty-staging/fix-#10062

Fix #10062: Avoid bad case during typing

Author: nicolasstucki

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

@@ -600,8 +600,8 @@ trait Applications extends Compatibility {
             args match {
               case arg :: Nil if isVarArg(arg) =>
                 addTyped(arg, formal)
-              case Typed(Literal(Constant(null)), _) :: Nil =>
-                addTyped(args.head, formal)
+              case (arg as Typed(Literal(Constant(null)), _)) :: Nil if ctx.isAfterTyper =>
+                addTyped(arg, formal)
               case _ =>
                 val elemFormal = formal.widenExpr.argTypesLo.head
                 val typedArgs =

tests/run/i10062.scala

@@ -0,0 +1,9 @@
+class X
+
+object X {
+  extension (x: List[X]) { def isNull = x.head == null }
+}
+
+@main def Test =
+  assert(List(null: X).isNull)
+  assert(List((null: X)).isNull)