Test implicitly() too; change err msg

Author: ysthakur

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

@@ -2746,9 +2746,9 @@ class MissingImplicitArgument(
           i"\n\nNote: ${s.ref.symbol.showLocated} was not considered because it was not imported with `import given`."
         def noChainConversionsNote(s: Iterable[TermRef]): Option[String] =
           Option.when(s.nonEmpty)(
-              i"\n\nNote: Chaining implicit conversions is no longer allowed in Scala. " +
-              i"The following conversions were ignored:${s.map(g => s"\n  - ${g.symbol.showDcl}").mkString}" +
-              i"\nIf there is an implicit `Conversion[A, ${pt.show}]` and an implicit `A` in scope, you need to explicitly pass the argument, e.g. `(using summon[A])`"
+              i"\n\nNote: Chaining implicit conversions are not allowed in Scala. " +
+              i"The following conversions are in scope:${s.map(g => s"\n  - ${g.symbol.showDcl}").mkString}" +
+              i"\nIf there is an implicit `Conversion[A, ${pt.show}]` and an implicit `A` in scope, you can explicitly pass the argument, e.g. `(using summon[A])`"
           )
         super.msgPostscript
         ++ ignoredInstanceNormalImport.map(hiddenImplicitNote)

tests/neg/i16453.check

@@ -1,8 +1,18 @@
--- [E172] Type Error: tests/neg/i16453.scala:10:43 ---------------------------------------------------------------------
-10 |  val fails = summon[String => Option[Int]] // error
-   |                                           ^
-   |No given instance of type String => Option[Int] was found for parameter x of method summon in object Predef
+-- [E172] Type Error: tests/neg/i16453.scala:14:21 ---------------------------------------------------------------------
+14 |  summon[Option[Int]] // error
+   |                     ^
+   |No given instance of type Option[Int] was found for parameter x of method summon in object Predef
    |
-   |Note: Chaining implicit conversions is no longer allowed in Scala. The following conversions were ignored:
-   |  - final given def given_Conversion_Function_Function[T]: Conversion[String => T, String => Option[T]]
-   |If there is an implicit `Conversion[A, String => Option[Int]]` and an implicit `A` in scope, you need to explicitly pass the argument, e.g. `(using summon[A])`
+   |Note: Chaining implicit conversions are not allowed in Scala. The following conversions are in scope:
+   |  - final given def given_Conversion_T_Option[T]: Conversion[T, Option[T]]
+   |  - implicit def toOption[T](t: T): Option[T]
+   |If there is an implicit `Conversion[A, Option[Int]]` and an implicit `A` in scope, you can explicitly pass the argument, e.g. `(using summon[A])`
+-- [E172] Type Error: tests/neg/i16453.scala:15:25 ---------------------------------------------------------------------
+15 |  implicitly[Option[Int]] // error
+   |                         ^
+   |No given instance of type Option[Int] was found for parameter e of method implicitly in object Predef
+   |
+   |Note: Chaining implicit conversions are not allowed in Scala. The following conversions are in scope:
+   |  - final given def given_Conversion_T_Option[T]: Conversion[T, Option[T]]
+   |  - implicit def toOption[T](t: T): Option[T]
+   |If there is an implicit `Conversion[A, Option[Int]]` and an implicit `A` in scope, you can explicitly pass the argument, e.g. `(using summon[A])`

tests/neg/i16453.scala

@@ -1,11 +1,16 @@
 import scala.language.implicitConversions
 
-given [T]: Conversion[String => T, String => Option[T]] = ???
+// Scala 3 style conversion
+given [T]: Conversion[T, Option[T]] = ???
+// Scala 2 style conversion
+implicit def toOption[T](t: T): Option[T] = Option(t)
+
 // This one is irrelevant, shouldn't be included in error message
-given irrelevant[T]: Conversion[String => T, String => Byte] = ???
+given irrelevant: Conversion[Int, Option[Long]] = ???
 
 def test() = {
-  given foo: (String => Int) = _ => 42
+  given foo: Int = 0
 
-  val fails = summon[String => Option[Int]] // error
+  summon[Option[Int]] // error
+  implicitly[Option[Int]] // error
 }