Add support for @deprecatedName

Author: hamzaremmal

compiler/src/dotty/tools/dotc/core/Definitions.scala

@@ -1011,6 +1011,7 @@ class Definitions {
   @tu lazy val DeprecatedAnnot: ClassSymbol = requiredClass("scala.deprecated")
   @tu lazy val DeprecatedOverridingAnnot: ClassSymbol = requiredClass("scala.deprecatedOverriding")
   @tu lazy val DeprecatedInheritanceAnnot: ClassSymbol = requiredClass("scala.deprecatedInheritance")
+  @tu lazy val DeprecatedNameAnnot: ClassSymbol = requiredClass("scala.deprecatedName")
   @tu lazy val ImplicitAmbiguousAnnot: ClassSymbol = requiredClass("scala.annotation.implicitAmbiguous")
   @tu lazy val ImplicitNotFoundAnnot: ClassSymbol = requiredClass("scala.annotation.implicitNotFound")
   @tu lazy val InlineParamAnnot: ClassSymbol = requiredClass("scala.annotation.internal.InlineParam")

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

@@ -5,6 +5,7 @@ import core.*
 import Names.*
 import dotty.tools.dotc.transform.MegaPhase.*
 import ast.untpd
+import ast.tpd
 import Flags.*
 import Types.*
 import Constants.Constant
@@ -174,6 +175,17 @@ class FirstTransform extends MiniPhase with InfoTransformer { thisPhase =>
   override def transformTypeApply(tree: TypeApply)(using Context): Tree =
     constToLiteral(tree)
 
+  override def prepareForApply(tree: tpd.Apply)(using Context): Context =
+    val paramSymss = tree.symbol.paramSymss.flatten
+    for namedArg <- tree.args.filterConserve(isNamedArg).asInstanceOf[List[NamedArg]]
+        name = namedArg.name
+        // We will have at most one parameter (we have 0 if the parameter name changed with a refined type)
+        sym <- paramSymss.filter(_.name == name)
+        annot <- sym.getAnnotation(defn.DeprecatedNameAnnot)
+    do
+      report.deprecationWarning(em"naming parameter $name is deprecated", namedArg.srcPos)
+    ctx
+
   override def transformApply(tree: Apply)(using Context): Tree =
     constToLiteral(foldCondition(tree))
 

tests/warn/i19077.check

@@ -0,0 +1,4 @@
+-- Deprecation Warning: tests/warn/i19077.scala:6:6 --------------------------------------------------------------------
+6 |  f(x = 2) // warn
+  |    ^^^^^
+  |    naming parameter x is deprecated

tests/warn/i19077.scala

@@ -0,0 +1,6 @@
+//> using options -deprecation
+
+def f(@deprecatedName x: Int) = x * 2
+
+@main def Test =
+  f(x = 2) // warn