improvement: Add separate option for decorations for evidence params

metals-bench/src/main/scala/bench/InlayHintsBench.scala

@@ -94,6 +94,7 @@ class InlayHintsBench extends PcBenchmark {
         true,
         true,
         true,
+        true,
       )
       pc.inlayHints(pcParams).get().asScala.toList
     }

metals/src/main/scala/scala/meta/internal/metals/Compilers.scala

@@ -616,6 +616,7 @@ class Compilers(
           userConfig().showInferredType.contains("true"),
         implicitParameters = userConfig().showImplicitArguments,
         implicitConversions = userConfig().showImplicitConversionsAndClasses,
+        contextBounds = userConfig().showEvidenceParams,
       )
 
       pc

metals/src/main/scala/scala/meta/internal/metals/UserConfiguration.scala

@@ -44,6 +44,7 @@ case class UserConfiguration(
     showInferredType: Option[String] = None,
     showImplicitArguments: Boolean = false,
     showImplicitConversionsAndClasses: Boolean = false,
+    showEvidenceParams: Boolean = false,
     enableStripMarginOnTypeFormatting: Boolean = true,
     enableIndentOnPaste: Boolean = false,
     enableSemanticHighlighting: Boolean = true,
@@ -260,6 +261,16 @@ object UserConfiguration {
            |shown in the hover.
            |""".stripMargin,
       ),
+      UserConfigurationOption(
+        "show-evidence-params",
+        "false",
+        "false",
+        "Should display context bounds evidence parameters at usage sites",
+        """|When this option is enabled, each place where a context bound is used has it 
+           |displayed either as additional decorations if they are supported by the editor or 
+           |shown in the hover.
+           |""".stripMargin,
+      ),
       UserConfigurationOption(
         "enable-semantic-highlighting",
         "true",
@@ -538,6 +549,8 @@ object UserConfiguration {
       getBooleanKey("show-implicit-arguments").getOrElse(false)
     val showImplicitConversionsAndClasses =
       getBooleanKey("show-implicit-conversions-and-classes").getOrElse(false)
+    val showEvidenceParams =
+      getBooleanKey("show-evidence-params").getOrElse(false)
     val enableStripMarginOnTypeFormatting =
       getBooleanKey("enable-strip-margin-on-type-formatting").getOrElse(true)
     val enableIndentOnPaste =
@@ -609,6 +622,7 @@ object UserConfiguration {
           showInferredType,
           showImplicitArguments,
           showImplicitConversionsAndClasses,
+          showEvidenceParams,
           enableStripMarginOnTypeFormatting,
           enableIndentOnPaste,
           enableSemanticHighlighting,

mtags-interfaces/src/main/java/scala/meta/pc/InlayHintsParams.java

@@ -29,4 +29,8 @@ public interface InlayHintsParams extends RangeParams {
    */
   boolean implicitConversions();
 
+  default boolean contextBounds() {
+    return false;
+  }
+
 }

mtags-shared/src/main/scala/scala/meta/internal/metals/CompilerInlayHintsParams.scala

@@ -10,7 +10,8 @@ case class CompilerInlayHintsParams(
     inferredTypes: Boolean,
     typeParameters: Boolean,
     implicitParameters: Boolean,
-    implicitConversions: Boolean
+    implicitConversions: Boolean,
+    override val contextBounds: Boolean
 ) extends InlayHintsParams {
   override def uri(): URI = rangeParams.uri
   override def text(): String = rangeParams.text

mtags/src/main/scala-2/scala/meta/internal/pc/PcInlayHintsProvider.scala

@@ -57,17 +57,24 @@ final class PcInlayHintsProvider(
             LabelPart(")") :: Nil,
             InlayHintKind.Parameter
           )
-      case ImplicitParameters(symbols, pos, allImplicit)
-          if params.implicitParameters() =>
-        val labelParts = symbols.map(s => List(labelPart(s, s.decodedName)))
-        val label =
-          if (allImplicit) labelParts.separated("(", ", ", ")")
-          else labelParts.separated(", ")
-        inlayHints.add(
-          adjustPos(pos).focusEnd.toLsp,
-          label,
-          InlayHintKind.Parameter
-        )
+      case ImplicitParameters(args, pos, allImplicit)
+          if params.implicitParameters() || params.contextBounds() =>
+        val symbols = args.collect {
+          case Param(sym) if params.implicitParameters() => sym
+          case ContextBound(sym) if params.contextBounds() => sym
+        }
+        if (symbols.isEmpty) inlayHints
+        else {
+          val labelParts = symbols.map(s => List(labelPart(s, s.decodedName)))
+          val label =
+            if (allImplicit) labelParts.separated("(", ", ", ")")
+            else labelParts.separated(", ")
+          inlayHints.add(
+            adjustPos(pos).focusEnd.toLsp,
+            label,
+            InlayHintKind.Parameter
+          )
+        }
       case ValueOf(label, pos) if params.implicitParameters() =>
         inlayHints.add(
           adjustPos(pos).focusEnd.toLsp,
@@ -160,25 +167,43 @@ final class PcInlayHintsProvider(
       fun.pos.isOffset && fun.symbol != null && fun.symbol.isImplicit
   }
   object ImplicitParameters {
-    def unapply(tree: Tree): Option[(List[Symbol], Position, Boolean)] =
+    def unapply(
+        tree: Tree
+    ): Option[(List[ImplicitParamSym], Position, Boolean)] =
       tree match {
-        case Apply(_, args)
+        case Apply(fun, args)
             if args.exists(isSyntheticArg) && !tree.pos.isOffset =>
-          val (implicitArgs, providedArgs) = args.partition(isSyntheticArg)
-          val allImplicit = providedArgs.isEmpty
-          val pos = providedArgs.lastOption.fold(tree.pos)(_.pos)
-          Some(
-            implicitArgs.map(_.symbol),
-            pos,
-            allImplicit
-          )
+          fun.tpe.widen match {
+            case mt: MethodType if mt.params.nonEmpty =>
+              val (implicitArgs0, providedArgs) =
+                args.zip(mt.params).partition { case (arg, _) =>
+                  isSyntheticArg(arg)
+                }
+              val implicitArgs = implicitArgs0.map(ImplicitParamSym(_))
+              val allImplicit = providedArgs.isEmpty
+              val pos = providedArgs.lastOption.fold(tree.pos)(_._1.pos)
+              Some((implicitArgs, pos, allImplicit))
+            case _ => None
+          }
+
         case _ => None
       }
-
     private def isSyntheticArg(arg: Tree): Boolean =
       arg.pos.isOffset && arg.symbol != null && arg.symbol.isImplicit
-  }
 
+  }
+  sealed trait ImplicitParamSym
+  case class Param(sym: Symbol) extends ImplicitParamSym
+  case class ContextBound(sym: Symbol) extends ImplicitParamSym
+  object ImplicitParamSym {
+    def apply(argWithName: (Tree, Symbol)): ImplicitParamSym = {
+      val (arg, name) = argWithName
+      if (isContextBoundParam(name)) ContextBound(arg.symbol)
+      else Param(arg.symbol)
+    }
+    private def isContextBoundParam(sym: Symbol) =
+      sym.name.toString.startsWith(nme.EVIDENCE_PARAM_PREFIX)
+  }
   object ValueOf {
     def unapply(tree: Tree): Option[(String, Position)] = tree match {
       case Apply(ta: TypeApply, Apply(fun, _) :: _)

mtags/src/main/scala-3/scala/meta/internal/pc/PcInlayHintsProvider.scala

@@ -13,6 +13,7 @@ import dotty.tools.dotc.ast.tpd
 import dotty.tools.dotc.ast.tpd.*
 import dotty.tools.dotc.core.Contexts.Context
 import dotty.tools.dotc.core.Flags
+import dotty.tools.dotc.core.Names.Name
 import dotty.tools.dotc.core.StdNames.*
 import dotty.tools.dotc.core.Symbols.*
 import dotty.tools.dotc.core.Types.*
@@ -73,17 +74,23 @@ class PcInlayHintsProvider(
             LabelPart(")") :: Nil,
             InlayHintKind.Parameter,
           )
-      case ImplicitParameters(symbols, pos, allImplicit)
-          if params.implicitParameters() =>
-        val labelParts = symbols.map(s => List(labelPart(s, s.decodedName)))
-        val label =
-          if allImplicit then labelParts.separated("(using ", ", ", ")")
-          else labelParts.separated(", ")
-        inlayHints.add(
-          adjustPos(pos).toLsp,
-          label,
-          InlayHintKind.Parameter,
-        )
+      case ImplicitParameters(args, pos, allImplicit)
+          if params.implicitParameters() || params.contextBounds() =>
+        val symbols = args.collect {
+          case Param(sym) if params.implicitParameters() => sym
+          case ContextBound(sym) if params.contextBounds() => sym
+        }
+        if symbols.isEmpty then inlayHints
+        else
+          val labelParts = symbols.map(s => List(labelPart(s, s.decodedName)))
+          val label =
+            if allImplicit then labelParts.separated("(using ", ", ", ")")
+            else labelParts.separated(", ")
+          inlayHints.add(
+            adjustPos(pos).toLsp,
+            label,
+            InlayHintKind.Parameter,
+          )
       case ValueOf(label, pos) if params.implicitParameters() =>
         inlayHints.add(
           adjustPos(pos).toLsp,
@@ -210,17 +217,20 @@ object ImplicitConversion:
 end ImplicitConversion
 
 object ImplicitParameters:
-  def unapply(tree: Tree)(using Context) =
+  def unapply(tree: Tree)(using Context): Option[(List[ImplicitParamSym], SourcePosition, Boolean)] =
     tree match
       case Apply(fun, args)
           if args.exists(isSyntheticArg) && !tree.sourcePos.span.isZeroExtent =>
-        val (implicitArgs, providedArgs) = args.partition(isSyntheticArg)
-        val allImplicit = providedArgs.isEmpty || providedArgs.forall {
-          case Ident(name) => name == nme.MISSING
-          case _ => false
+        fun.typeOpt.widen.paramNamess.headOption.map {paramNames => 
+          val (implicitArgs0, providedArgs) = args.zip(paramNames).partition((arg, _) => isSyntheticArg(arg))
+          val firstImplicitPos = implicitArgs0.head._1.sourcePos
+          val implicitArgs = implicitArgs0.map(ImplicitParamSym(_))
+          val allImplicit = providedArgs.isEmpty || providedArgs.forall {
+            case (Ident(name), _) => name == nme.MISSING
+            case _ => false
+          }
+          (implicitArgs, firstImplicitPos, allImplicit)
         }
-        val pos = implicitArgs.head.sourcePos
-        Some(implicitArgs.map(_.symbol), pos, allImplicit)
       case _ => None
 
   private def isSyntheticArg(tree: Tree)(using Context) = tree match
@@ -229,6 +239,19 @@ object ImplicitParameters:
     case _ => false
 end ImplicitParameters
 
+sealed trait ImplicitParamSym extends Any
+case class Param(sym: Symbol) extends AnyVal with ImplicitParamSym
+case class ContextBound(sym: Symbol) extends AnyVal with ImplicitParamSym
+
+object ImplicitParamSym:
+  def apply(argWithName: (Tree, Name))(using Context) =
+    val (arg, name) = argWithName
+    if isContextBoundParam(name) then ContextBound(arg.symbol)
+    else Param(arg.symbol)
+  private def isContextBoundParam(name: Name) =
+    // In 3.1.3 NameKinds.ContextBoundParamName.separator is not available
+    name.toString.startsWith("evidence$")
+
 object ValueOf:
   def unapply(tree: Tree)(using Context) =
     tree match

tests/cross/src/main/scala/tests/BaseInlayHintsSuite.scala

@@ -15,7 +15,12 @@ class BaseInlayHintsSuite extends BasePCSuite {
       name: TestOptions,
       base: String,
       expected: String,
-      compat: Map[String, String] = Map.empty
+      compat: Map[String, String] = Map.empty,
+      showInferredType: Boolean = true,
+      showTypeArguments: Boolean = true,
+      showImplicitArguments: Boolean = true,
+      showImplicitConversions: Boolean = true,
+      showContextBounds: Boolean = true
   )(implicit location: Location): Unit =
     test(name) {
       def pkgWrap(text: String) =
@@ -31,10 +36,11 @@ class BaseInlayHintsSuite extends BasePCSuite {
       )
       val pcParams = CompilerInlayHintsParams(
         rangeParams,
-        true,
-        true,
-        true,
-        true
+        showInferredType,
+        showTypeArguments,
+        showImplicitArguments,
+        showImplicitConversions,
+        showContextBounds
       )
 
       val inlayHints = presentationCompiler