bugfix: Extension completions in interpolated strings

Author: kasiaMarek

presentation-compiler/src/main/dotty/tools/pc/completions/CompletionProvider.scala

@@ -243,21 +243,29 @@ class CompletionProvider(
               r match
                 case IndexedContext.Result.InScope =>
                   mkItem(
-                    ident.backticked(backtickSoftKeyword) + completionTextSuffix
+                    v.insertText.getOrElse(
+                      ident.backticked(
+                        backtickSoftKeyword
+                      ) + completionTextSuffix
+                    ),
+                    range = v.range,
                   )
                 case _ if isInStringInterpolation =>
                   mkItem(
-                    "{" + sym.fullNameBackticked + completionTextSuffix + "}"
+                    "{" + sym.fullNameBackticked + completionTextSuffix + "}",
+                    range = v.range
                   )
                 case _ if v.isExtensionMethod =>
                   mkItem(
-                    ident.backticked(backtickSoftKeyword) + completionTextSuffix
+                    ident.backticked(backtickSoftKeyword) + completionTextSuffix,
+                    range = v.range
                   )
                 case _ =>
                   mkItem(
                     sym.fullNameBackticked(
                       backtickSoftKeyword
-                    ) + completionTextSuffix
+                    ) + completionTextSuffix,
+                    range = v.range
                   )
               end match
           end match

presentation-compiler/src/main/dotty/tools/pc/completions/CompletionValue.scala

@@ -268,6 +268,7 @@ object CompletionValue:
     )(using Context): String =
       if isExtension then s"${printer.completionSymbol(symbol)} (extension)"
       else super.description(printer)
+    override def isExtensionMethod: Boolean = isExtension
   end Interpolator
 
   case class MatchCompletion(

presentation-compiler/test/dotty/tools/pc/tests/completion/CompletionInterpolatorSuite.scala

@@ -635,7 +635,7 @@ class CompletionInterpolatorSuite extends BaseCompletionSuite:
          |""".stripMargin,
       """|class Paths
          |object Main {
-         |  s"this is an interesting {java.nio.file.Paths}"
+         |  s"this is an interesting ${java.nio.file.Paths}"
          |}
          |""".stripMargin,
       assertSingleItem = false,
@@ -710,6 +710,26 @@ class CompletionInterpolatorSuite extends BaseCompletionSuite:
       filterText = "aaa.plus"
     )
 
+
+  @Test def `extension3` =
+    checkEdit(
+      """|trait Cursor
+         |
+         |extension (c: Cursor) def spelling: String = "hello"
+         |object Main {
+         |  val c = new Cursor {}
+         |  val x = s"$c.spelli@@"
+         |}
+         |""".stripMargin,
+      """|trait Cursor
+         |
+         |extension (c: Cursor) def spelling: String = "hello"
+         |object Main {
+         |  val c = new Cursor {}
+         |  val x = s"${c.spelling$0}"
+         |}""".stripMargin
+    )
+
   @Test def `filter-by-type` =
     check(
       """|package example