improve error message for rename the same import twice

Author: ingarabr

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

@@ -129,6 +129,7 @@ public enum ErrorMessageID {
     JavaSymbolIsNotAValueID,
     DoubleDeclarationID,
     MatchCaseOnlyNullWarningID,
+    ImportRenamedTwiceID,
     ;
 
     public int errorNumber() {

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

@@ -2105,4 +2105,11 @@ object messages {
     }
     val explanation = ""
   }
+
+  case class ImportRenamedTwice(ident: untpd.Ident)(implicit ctx: Context) extends Message(ImportRenamedTwiceID) {
+    val kind = "Syntax"
+    val msg: String = s"${ident.show} is renamed twice on the same import line."
+    val explanation: String = ""
+  }
+
 }

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

@@ -2,19 +2,14 @@ package dotty.tools.dotc
 package transform
 
 import dotty.tools.dotc.ast.{Trees, tpd, untpd}
-import scala.collection.{ mutable, immutable }
-import ValueClasses._
-import scala.annotation.tailrec
+import scala.collection.mutable
 import core._
-import typer.ErrorReporting._
 import typer.Checking
-import Types._, Contexts._, Constants._, Names._, NameOps._, Flags._, DenotTransformers._
-import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._, Scopes._, Denotations._
-import util.Positions._
+import Types._, Contexts._, Names._, Flags._, DenotTransformers._
+import SymDenotations._, StdNames._, Annotations._, Trees._
 import Decorators._
-import config.Printers.typr
-import Symbols._, TypeUtils._, SymUtils._
-import reporting.diagnostic.messages.{NotAMember, SuperCallsNotAllowedInline}
+import Symbols._, SymUtils._
+import reporting.diagnostic.messages.{ImportRenamedTwice, NotAMember, SuperCallsNotAllowedInline}
 
 object PostTyper {
   val name = "posttyper"
@@ -293,7 +288,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
             if (name != nme.WILDCARD && !exprTpe.member(name).exists && !exprTpe.member(name.toTypeName).exists)
               ctx.error(NotAMember(exprTpe, name, "value"), ident.pos)
             if (seen(ident.name))
-              ctx.error(s"${ident.show} is renamed twice", ident.pos)
+              ctx.error(ImportRenamedTwice(ident), ident.pos)
             seen += ident.name
           }
           selectors.foreach {

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

@@ -6,6 +6,7 @@ import dotty.tools.dotc.core.Contexts.Context
 import dotty.tools.dotc.core.Types.WildcardType
 import dotty.tools.dotc.parsing.Tokens
 import dotty.tools.dotc.reporting.diagnostic.messages._
+import dotty.tools.dotc.transform.PostTyper
 import org.junit.Assert._
 import org.junit.Test
 
@@ -1348,4 +1349,16 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       val (msg @ FunctionTypeNeedsNonEmptyParameterList(_, _)) :: Nil = messages
       assertEquals(msg.mods, "erased implicit")
     }
+
+  @Test def renameImportTwice =
+    checkMessagesAfter(PostTyper.name) {
+      """
+        |import java.lang.{Integer => Foo, Integer => Baz}
+      """.stripMargin
+    }.expect { (ictx, messages) =>
+      implicit val ctx: Context = ictx
+      assertMessageCount(1, messages)
+      val (msg @ ImportRenamedTwice(ident)) :: Nil = messages
+      assertEquals(ident.show, "Integer")
+    }
 }