Merge pull request #10280 from dotty-staging/fix-#10116

Fix #10116: Fix adaptConstant to that it survives Ycheck

Author: odersky

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

@@ -59,15 +59,6 @@ object ConstFold:
       tree.withFoldedType(Constant(targ.tpe))
     case _ => tree
 
-  /** If tree is a constant value that can be converted to type `pt`, perform
-   *  the conversion.
-   */
-  def apply[T <: Tree](tree: T, pt: Type)(using Context): T =
-    val tree1 = apply(tree)
-    tree.tpe.widenTermRefExpr.normalized match
-      case ConstantType(x) => tree1.withFoldedType(x.convertTo(pt))
-      case _ => tree1
-
   extension [T <: Tree](tree: T)(using Context)
     private def withFoldedType(c: Constant | Null): T =
       if c == null then tree else tree.withType(ConstantType(c)).asInstanceOf[T]

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

@@ -3423,9 +3423,12 @@ class Typer extends Namer
 
     def adaptToSubType(wtp: Type): Tree = {
       // try converting a constant to the target type
-      val folded = ConstFold(tree, pt)
-      if (folded ne tree)
-        return adaptConstant(folded, folded.tpe.asInstanceOf[ConstantType])
+      ConstFold(tree).tpe.widenTermRefExpr.normalized match
+        case ConstantType(x) =>
+          val converted = x.convertTo(pt)
+          if converted != null && (converted ne x) then
+            return adaptConstant(tree, ConstantType(converted))
+        case _ =>
 
       val captured = captureWildcards(wtp)
       if (captured `ne` wtp)

tests/pos/i10116.scala

@@ -0,0 +1,18 @@
+object OverloadedWithLong {
+  def overloaded(x: Long): Any =
+    x
+
+  def overloaded(x: Any): Unit =
+    ???
+}
+
+object Test {
+  def main(args: Array[String]): Unit =
+    import OverloadedWithLong._
+
+    val l: Any = 0 :: Nil
+    val r = overloaded(l match {
+      case x :: xs => 5
+    })
+    assert(r == 5L)
+}