Handle default arguments in later parameter sections.

Default arguments in later parameter sections are functions that take
ealier arguments as parameters. When we just want to test whether a method
is applicable, we don't keep track of these earlier arguments. Therefore,
we always assume in this case that a default getter matches, if one was found.

Author: odersky

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

@@ -589,6 +589,7 @@ trait Applications extends Compatibility {
 
           def tryDefault(n: Int, args1: List[Arg]): Unit = {
             val sym = methRef.symbol
+            val testOnly = this.isInstanceOf[TestApplication[?]]
 
             val defaultArg =
               if (isJavaAnnotConstr(sym)) {
@@ -604,12 +605,14 @@ trait Applications extends Compatibility {
                 else
                   EmptyTree
               }
-              else defaultArgument(normalizedFun, n, this.isInstanceOf[TestApplication[?]])
+              else defaultArgument(normalizedFun, n, testOnly)
 
             def implicitArg = implicitArgTree(formal, appPos.span)
 
             if !defaultArg.isEmpty then
-              matchArgs(args1, addTyped(treeToArg(defaultArg)), n + 1)
+              defaultArg.tpe.widen match
+                case _: MethodOrPoly if testOnly => matchArgs(args1, formals1, n + 1)
+                case _ => matchArgs(args1, addTyped(treeToArg(defaultArg)), n + 1)
             else if methodType.isContextualMethod && ctx.mode.is(Mode.ImplicitsEnabled) then
               matchArgs(args1, addTyped(treeToArg(implicitArg)), n + 1)
             else

project/MiMaFilters.scala

@@ -3,5 +3,6 @@ import com.typesafe.tools.mima.core._
 
 object MiMaFilters {
   val Library: Seq[ProblemFilter] = Seq(
+    ProblemFilters.exclude[MissingClassProblem]("scala.annotation.internal.MappedAlternative"),
   )
 }

tests/run/i15287.scala

@@ -0,0 +1,4 @@
+def f(x: Char)(someParam: String): String = "a"
+def f(x: Char)(min: Boolean, max: Int = 4): String = "b"
+
+@main def Test() = f('c')(false)