Remove NamedArg from inlined arguments (#17228)

Fixes #17227

Author: nicolasstucki

compiler/src/dotty/tools/dotc/inlines/Inliner.scala

@@ -207,11 +207,18 @@ class Inliner(val call: tpd.Tree)(using Context):
   private[inlines] def paramBindingDef(name: Name, formal: Type, arg0: Tree,
                               buf: DefBuffer)(using Context): ValOrDefDef = {
     val isByName = formal.dealias.isInstanceOf[ExprType]
-    val arg = arg0 match {
-      case Typed(arg1, tpt) if tpt.tpe.isRepeatedParam && arg1.tpe.derivesFrom(defn.ArrayClass) =>
-        wrapArray(arg1, arg0.tpe.elemType)
-      case _ => arg0
-    }
+    val arg =
+      def dropNameArg(arg: Tree): Tree = arg match
+        case NamedArg(_, arg1) => arg1
+        case SeqLiteral(elems, tpt) =>
+          cpy.SeqLiteral(arg)(elems.mapConserve(dropNameArg), tpt)
+        case _ => arg
+      arg0 match
+        case Typed(seq, tpt) if tpt.tpe.isRepeatedParam =>
+          if seq.tpe.derivesFrom(defn.ArrayClass) then wrapArray(dropNameArg(seq), arg0.tpe.elemType)
+          else cpy.Typed(arg0)(dropNameArg(seq), tpt)
+        case arg0 =>
+          dropNameArg(arg0)
     val argtpe = arg.tpe.dealiasKeepAnnots.translateFromRepeated(toArray = false)
     val argIsBottom = argtpe.isBottomTypeAfterErasure
     val bindingType =

tests/pos-macros/i17227/Macro_1.scala

@@ -0,0 +1,22 @@
+import scala.quoted.*
+
+inline def foo(f: Int => Int): Int => Int = ${impl('f)}
+inline def bar(inline f: Int => Int): Int => Int = ${impl('f)}
+inline def baz(inline f: (Int => Int)*): Int => Int = ${impl2('f)}
+
+def impl(f: Expr[Int => Int])(using Quotes): Expr[Int => Int] =
+  assertNoNamedArgs(f)
+  '{identity}
+
+def impl2(f: Expr[Seq[Int => Int]])(using Quotes): Expr[Int => Int] =
+  assertNoNamedArgs(f)
+  '{identity}
+
+def assertNoNamedArgs(expr: Expr[Any])(using Quotes): Unit =
+  import quotes.reflect.*
+  new TreeTraverser {
+    override def traverseTree(tree: Tree)(owner: Symbol): Unit = tree match
+      case _: NamedArg =>
+        report.throwError(s"Unexpected NamedArg after inlining: ${tree}", tree.pos)
+      case _ => traverseTreeChildren(tree)(owner)
+  }.traverseTree(expr.asTerm)(Symbol.spliceOwner)

tests/pos-macros/i17227/Test_2.scala

@@ -0,0 +1,6 @@
+def g(i: Int): Int = i
+
+def test =
+  foo(f = g)
+  bar(f = g)
+  baz(f = g)

tests/pos/i17227.scala

@@ -0,0 +1,10 @@
+inline def foo(f: Int => Int): Int => Int = f
+inline def bar(inline f: Int => Int): Int => Int = f
+inline def baz(f: (Int => Int)*): Int => Int = f.head
+
+def g(i: Int): Int = i
+
+def test =
+  foo(f = g)
+  bar(f = g)
+  baz(f = g)