Refs #1589 Move "wrong number of parameters" error to a new errors fo…

compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java

@@ -93,6 +93,7 @@ public enum ErrorMessageID {
     ModifiersNotAllowedID,
     WildcardOnTypeArgumentNotAllowedOnNewID,
     ImplicitFunctionTypeNeedsNonEmptyParameterListID,
+    WrongNumberOfParametersID
     ;
 
     public int errorNumber() {

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -1687,4 +1687,11 @@ object messages {
     }
   }
 
+  case class WrongNumberOfParameters(expected: Int)(implicit ctx: Context)
+    extends Message(WrongNumberOfParametersID) {
+    val kind = "Syntax"
+    val msg = s"wrong number of parameters, expected: $expected"
+    val explanation = ""
+  }
+
 }

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

@@ -798,7 +798,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
 
       def protoFormal(i: Int): Type =
         if (protoFormals.length == params.length) protoFormals(i)
-        else errorType(i"wrong number of parameters, expected: ${protoFormals.length}", tree.pos)
+        else errorType(WrongNumberOfParameters(protoFormals.length), tree.pos)
 
       /** Is `formal` a product type which is elementwise compatible with `params`? */
       def ptIsCorrectProduct(formal: Type) = {

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -893,4 +893,21 @@ class ErrorMessagesTests extends ErrorMessagesTest {
         messages.foreach(assertEquals(_, ImplicitFunctionTypeNeedsNonEmptyParameterList()))
       }
 
+  @Test def wrongNumberOfParameters =
+    checkMessagesAfter("refchecks") {
+      """object NumberOfParams {
+        |  def unary[T](x: T => Unit) = ()
+        |  unary((x, y) => ())
+        |} """.stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        val defn = ictx.definitions
+
+        assertMessageCount(1, messages)
+        val err :: Nil = messages
+
+        assertEquals(err, WrongNumberOfParameters(1))
+      }
+
 }