Move 'Type does not take parameters' to error case class

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

@@ -60,6 +60,7 @@ public enum ErrorMessageID {
     MethodDoesNotTakeParametersId,
     AmbiguousOverloadID,
     ReassignmentToValID,
+    TypeDoesNotTakeParametersID,
     ;
 
     public int errorNumber() {

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

@@ -19,6 +19,7 @@ import printing.Highlighting._
 import printing.Formatting
 import ErrorMessageID._
 import Denotations.SingleDenotation
+import dotty.tools.dotc.ast.Trees
 import dotty.tools.dotc.core.SymDenotations.SymDenotation
 
 object messages {
@@ -1277,7 +1278,7 @@ object messages {
           |$noParameters""".stripMargin
 
   }
-                        
+
   case class AmbiguousOverload(tree: tpd.Tree, alts: List[SingleDenotation], pt: Type)(
     err: typer.ErrorReporting.Errors)(
     implicit ctx: Context)
@@ -1296,7 +1297,7 @@ object messages {
            |- adding a type ascription as in `${"instance.myMethod: String => Int"}`
            |"""
   }
-                        
+
   case class ReassignmentToVal(name: Names.Name)(implicit ctx: Context)
     extends Message(ReassignmentToValID) {
     val kind = "Reference"
@@ -1310,4 +1311,19 @@ object messages {
            |  ${"var"} $name ${"="} ...
            |""".stripMargin
   }
+
+  case class TypeDoesNotTakeParameters(tpe: Types.Type, params: List[Trees.Tree[Trees.Untyped]])(implicit ctx: Context)
+    extends Message(TypeDoesNotTakeParametersID) {
+    val kind = "Reference"
+    val msg = hl"$tpe does not take type parameters"
+
+    private val ps =
+      if (params.size == 1) hl"a type parameter ${params.head}"
+      else hl"type parameters ${params.map(_.show).mkString(", ")}"
+
+    val explanation =
+      i"""You specified $ps for ${hl"$tpe"}, which is not
+         |declared to take any.
+         |"""
+  }
 }

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

@@ -1052,7 +1052,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
     val tpt1 = typed(tree.tpt, AnyTypeConstructorProto)(ctx.retractMode(Mode.Pattern))
     val tparams = tpt1.tpe.typeParams
     if (tparams.isEmpty) {
-      ctx.error(ex"${tpt1.tpe} does not take type parameters", tree.pos)
+      ctx.error(TypeDoesNotTakeParameters(tpt1.tpe, tree.args), tree.pos)
       tpt1
     }
     else {

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

@@ -399,7 +399,7 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       assertEquals("Scope.foo(1)", tree.show)
       assertEquals("((a: Int)Unit)(Scope.foo)", methodPart.show)
     }
-  
+
   @Test def ambiugousOverloadWithWildcard =
     checkMessagesAfter("frontend") {
       """object Context {
@@ -440,4 +440,21 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       val ReassignmentToVal(name) :: Nil = messages
       assertEquals("value", name.show)
     }
+
+  @Test def typeDoesNotTakeParameters =
+    checkMessagesAfter("frontend") {
+      """
+        |trait WithOutParams
+        |class Extending extends WithOutParams[String]
+      """.stripMargin
+    }
+      .expect { (ictx, messages) =>
+        implicit val ctx: Context = ictx
+        val defn = ictx.definitions
+
+        assertMessageCount(1, messages)
+        val TypeDoesNotTakeParameters(tpe, params) :: Nil = messages
+        assertEquals("WithOutParams", tpe.show)
+      }
+
 }