Add .check file in test

Author: Alex1005a

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

@@ -535,15 +535,13 @@ class PostTyper extends MacroTransform with InfoTransformer { thisPhase =>
             // Make an exception for ChildAnnot, which should really have AnyKind bounds
             Checking.checkBounds(args, fn.tpe.widen.asInstanceOf[PolyType])
           if ctx.settings.Whas.inferUnion then
-            val inferredOrTypes = args.filter(tpt =>
+            val inferredOrTypes = args.find: tpt =>
               tpt.isInstanceOf[InferredTypeTree] && tpt.tpe.stripTypeVar.isInstanceOf[OrType]
-            )
-            inferredOrTypes.headOption.foreach(tpt =>
+            inferredOrTypes.foreach: tpt =>
               report.warning(
                 em"""|A type argument was inferred to be union type ${tpt.tpe.stripTypeVar}
                      |This may indicate a programming error.
                      |""", tpt.srcPos)
-            )
           fn match {
             case sel: Select =>
               val args1 = transform(args)

tests/warn/infer-or-type.check

@@ -0,0 +1,10 @@
+-- Warning: tests/warn/infer-or-type.scala:6:18 ------------------------------------------------------------------------
+6 |  val _ = List(1).contains("") // warn
+  |          ^^^^^^^^^^^^^^^^
+  |          A type argument was inferred to be union type Int | String
+  |          This may indicate a programming error.
+-- Warning: tests/warn/infer-or-type.scala:7:10 ------------------------------------------------------------------------
+7 |  val _ = Pair(1, "") // warn
+  |          ^^^^
+  |          A type argument was inferred to be union type Int | String
+  |          This may indicate a programming error.