Merge pull request #3516 from esarbe/staticOnly

#1589: add dedicated error message for @static annotation not inside object

Author: allanrenucci

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

@@ -115,6 +115,7 @@ public enum ErrorMessageID {
     TraitRedefinedFinalMethodFromAnyRefID,
     PackageNameAlreadyDefinedID,
     UnapplyInvalidNumberOfArgumentsID,
+    StaticFieldsOnlyAllowedInObjectsID,
     ;
 
     public int errorNumber() {

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

@@ -1942,4 +1942,11 @@ object messages {
         |where subsequent arguments would have following types: ($argTypes%, %).
         |""".stripMargin
   }
+
+  case class StaticFieldsOnlyAllowedInObjects(member: Symbol)(implicit ctx: Context) extends Message(StaticFieldsOnlyAllowedInObjectsID) {
+    val msg = hl"${"@static"} $member in ${member.owner} must be defined inside an ${"object"}."
+    val kind = "Syntax"
+    val explanation =
+      hl"${"@static"} members are only allowed inside objects."
+  }
 }

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

@@ -21,6 +21,7 @@ import Names.Name
 import NameOps._
 import Decorators._
 import TypeUtils._
+import reporting.diagnostic.messages.StaticFieldsOnlyAllowedInObjects
 
 /** A transformer that check that requirements of Static fields\methods are implemented:
   *  1. Only objects can have members annotated with `@static`
@@ -45,7 +46,7 @@ class CheckStatic extends MiniPhase {
     for(defn <- defns) {
       if (defn.symbol.hasAnnotation(ctx.definitions.ScalaStaticAnnot)) {
         if(!ctx.owner.is(Module)) {
-          ctx.error("@static fields are only allowed inside objects", defn.pos)
+          ctx.error(StaticFieldsOnlyAllowedInObjects(defn.symbol), defn.pos)
         }
 
         if (defn.isInstanceOf[ValDef] && hadNonStaticField) {

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

@@ -1224,4 +1224,18 @@ class ErrorMessagesTests extends ErrorMessagesTest {
         assertEquals("Boo", qual.show)
         assertEquals("(class Int, class String)", argTypes.map(_.typeSymbol).mkString("(", ", ", ")"))
       }
+
+
+  @Test def staticOnlyAllowedInsideObjects =
+    checkMessagesAfter("checkStatic") {
+      """
+        |class Foo {
+        |  @annotation.static def bar(): Unit = bar()
+        |}
+      """.stripMargin
+    }.expect { (ictx, messages) =>
+      implicit val ctx: Context = ictx
+      val StaticFieldsOnlyAllowedInObjects(field) = messages.head
+      assertEquals(field.show, "method bar")
+    }
 }