Interactive suggestion on fields precedence added

Author: youroff

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

@@ -1936,20 +1936,24 @@ object messages {
       hl"${"@static"} members are only allowed inside objects."
   }
 
-  case class StaticFieldsShouldPrecedeNonStatic(member: Symbol)(implicit ctx: Context) extends Message(StaticFieldsShouldPrecedeNonStaticID) {
+  case class StaticFieldsShouldPrecedeNonStatic(member: Symbol, defns: List[tpd.Tree])(implicit ctx: Context) extends Message(StaticFieldsShouldPrecedeNonStaticID) {
     val msg: String = hl"${"@static"} $member in ${member.owner} must be defined before non-static fields."
     val kind: String = "Syntax"
+
     val explanation: String = {
-      val codeExample = """object Foo {
-                        |  @static val foo = 1
-                        |  val bar = 2
+      val nonStatics = defns.takeWhile(_.symbol != member).take(3).filter(_.isInstanceOf[tpd.ValDef])
+      val codeExample = s"""object ${member.owner.name.firstPart} {
+                        |  @static ${member} = ...
+                        |  ${nonStatics.map(m => s"${m.symbol} = ...").mkString("\n  ")}
+                        |  ...
                         |}"""
-      hl"""The fields annotated with @static should precede any non-@static fields.
+      hl"""The fields annotated with @static should precede any non @static fields.
         |This ensures that we do not introduce surprises for users in initialization order of this class.
-        |$codeExample
-        |
         |Static field are initialized when class loading the code of Foo.
         |Non static fields are only initialized the first  time that Foo is accessed.
+        |
+        |The definition of ${member.name} should have been before the non ${"@static val"}s:
+        |$codeExample
         |"""
     }
   }

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

@@ -37,7 +37,7 @@ class CheckStatic extends MiniPhase {
         }
 
         if (defn.isInstanceOf[ValDef] && hadNonStaticField) {
-          ctx.error(StaticFieldsShouldPrecedeNonStatic(defn.symbol), defn.pos)
+          ctx.error(StaticFieldsShouldPrecedeNonStatic(defn.symbol, defns), defn.pos)
         }
 
         val companion = ctx.owner.companionClass