fix: show implicit param when it is an apply

Author: kasiaMarek

presentation-compiler/src/main/dotty/tools/pc/PcInlayHintsProvider.scala

@@ -3,6 +3,8 @@ package dotty.tools.pc
 
 import java.nio.file.Paths
 
+import scala.annotation.tailrec
+
 import scala.meta.internal.metals.ReportContext
 import dotty.tools.pc.utils.InteractiveEnrichments.*
 import dotty.tools.pc.printer.ShortenedTypePrinter
@@ -194,10 +196,10 @@ object ImplicitConversion:
   def unapply(tree: Tree)(using params: InlayHintsParams, ctx: Context) =
     if (params.implicitConversions()) {
       tree match
-        case Apply(fun: Ident, args) if isSynthetic(fun) =>
+        case Apply(fun: Ident, args) if isSynthetic(fun) && args.exists(!_.span.isZeroExtent) =>
           implicitConversion(fun, args)
         case Apply(Select(fun, name), args)
-            if name == nme.apply && isSynthetic(fun) =>
+            if name == nme.apply && isSynthetic(fun) && args.exists(!_.span.isZeroExtent) =>
           implicitConversion(fun, args)
         case _ => None
     } else None
@@ -218,7 +220,7 @@ object ImplicitParameters:
     if (params.implicitParameters()) {
       tree match
         case Apply(fun, args)
-            if args.exists(isSyntheticArg) && !tree.sourcePos.span.isZeroExtent =>
+            if args.exists(isSyntheticArg) && !tree.sourcePos.span.isZeroExtent && !args.exists(isQuotes(_)) =>
           val (implicitArgs, providedArgs) = args.partition(isSyntheticArg)
           val allImplicit = providedArgs.isEmpty || providedArgs.forall {
             case Ident(name) => name == nme.MISSING
@@ -229,10 +231,12 @@ object ImplicitParameters:
         case _ => None
     } else None
 
-  private def isSyntheticArg(tree: Tree)(using Context) = tree match
+  @tailrec
+  def isSyntheticArg(tree: Tree)(using Context): Boolean = tree match
     case tree: Ident =>
-      tree.span.isSynthetic && tree.symbol.isOneOf(Flags.GivenOrImplicit) &&
-        !isQuotes(tree)
+      tree.span.isSynthetic && tree.symbol.isOneOf(Flags.GivenOrImplicit)
+    case Apply(fun, _ ) if tree.span.isZeroExtent => isSyntheticArg(fun)
+    case TypeApply(fun, _ ) if tree.span.isZeroExtent => isSyntheticArg(fun)
     case _ => false
 
   // Decorations for Quotes are rarely useful

presentation-compiler/test/dotty/tools/pc/tests/inlayHints/InlayHintsSuite.scala

@@ -920,4 +920,24 @@ class InlayHintsSuite extends BaseInlayHintsSuite {
          |      case '[field *: fields] => ???
          |""".stripMargin
    )
+
+  @Test def `arg-apply` =
+    check(
+     """|object Main:
+        |  case class A()
+        |  case class B[T]()
+        |  given A = A()
+        |  implicit def bar(using a: A): B[A] = B[A]()
+        |  def foo(using b: B[A]): String = "aaa"
+        |  val g: String = foo
+        |""".stripMargin,
+     """|object Main:
+        |  case class A()
+        |  case class B[T]()
+        |  given A = A()
+        |  implicit def bar(using a: A): B[A] = B[A]()
+        |  def foo(using b: B[A]): String = "aaa"
+        |  val g: String = foo/*(using bar<<(5:15)>>)*/
+        |""".stripMargin
+    )
 }