Add message CheckStatic for member with same name as @static one

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

@@ -134,7 +134,8 @@ public enum ErrorMessageID {
     TermMemberNeedsNeedsResultTypeForImplicitSearchID,
     CaseClassCannotExtendEnumID,
     ValueClassParameterMayNotBeCallByNameID,
-    NotAnExtractorID
+    NotAnExtractorID,
+    MemberWithSameNameAsStaticID
     ;
 
     public int errorNumber() {

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

@@ -2131,4 +2131,12 @@ object messages {
            |For this reason, you can also define patterns through `unapplySeq` which returns `Option[Seq[T]]`.
            |This mechanism is used for instance in pattern `case List(x1, ..., xn)`""".stripMargin
   }
+
+  case class MemberWithSameNameAsStatic()(implicit val ctx: Context)
+    extends Message(MemberWithSameNameAsStaticID) {
+
+    override def msg: String = hl"Companion classes cannot define members with same name as a @static member"
+    override def kind: String = "Syntax"
+    override def explanation: String = ""
+  }
 }

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

@@ -8,7 +8,7 @@ import Contexts.Context
 import Symbols._
 import dotty.tools.dotc.ast.tpd
 import Decorators._
-import reporting.diagnostic.messages.{MissingCompanionForStatic, StaticFieldsOnlyAllowedInObjects}
+import reporting.diagnostic.messages.{MemberWithSameNameAsStatic, MissingCompanionForStatic, StaticFieldsOnlyAllowedInObjects}
 
 /** A transformer that check that requirements of Static fields\methods are implemented:
   *  1. Only objects can have members annotated with `@static`
@@ -46,7 +46,7 @@ class CheckStatic extends MiniPhase {
         if (!companion.exists) {
           ctx.error(MissingCompanionForStatic(defn.symbol), defn.pos)
         } else if (clashes.exists) {
-          ctx.error("companion classes cannot define members with same name as @static member", defn.pos)
+          ctx.error(MemberWithSameNameAsStatic(), defn.pos)
          } else if (defn.symbol.is(Flags.Mutable) && companion.is(Flags.Trait)) {
           ctx.error("Companions of traits cannot define mutable @static fields", defn.pos)
         } else if (defn.symbol.is(Flags.Lazy)) {

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

@@ -1527,4 +1527,22 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       val NotAnExtractor(tree) = messages.head
       assertEquals("Foo", tree.show)
     }
+
+  @Test def memberWithSameNameAsStatic() =
+    checkMessagesAfter(CheckStatic.name) {
+      """
+        |import scala.annotation.static
+        |class Camp {
+        |  val name = ""
+        |}
+        |object Camp {
+        |  @static val name = ""
+        |}
+      """.stripMargin
+    }.expect { (_, messages) =>
+      assertMessageCount(1, messages)
+      val message = messages.head
+      assertTrue(message.isInstanceOf[MemberWithSameNameAsStatic])
+      assertEquals(message.msg, "Companion classes cannot define members with same name as a @static member")
+    }
 }