Backport "Improve when deprecation warnings are emitted" to LTS

compiler/src/dotty/tools/dotc/typer/CrossVersionChecks.scala

@@ -159,10 +159,12 @@ class CrossVersionChecks extends MiniPhase:
     val tpe = tree.tpe
     tpe.foreachPart {
       case TypeRef(_, sym: Symbol)  =>
-        checkDeprecated(sym, tree.srcPos)
+        if tree.span.isSourceDerived then
+          checkDeprecated(sym, tree.srcPos)
         checkExperimentalRef(sym, tree.srcPos)
       case TermRef(_, sym: Symbol)  =>
-        checkDeprecated(sym, tree.srcPos)
+        if tree.span.isSourceDerived then
+          checkDeprecated(sym, tree.srcPos)
         checkExperimentalRef(sym, tree.srcPos)
       case _ =>
     }

tests/warn/i19302.check

@@ -0,0 +1,20 @@
+-- Deprecation Warning: tests/warn/i19302.scala:8:20 -------------------------------------------------------------------
+8 |  def doo(): Option[Thing] = // warn
+  |                    ^^^^^
+  |                    class Thing is deprecated since n/a: is deprecated
+-- Deprecation Warning: tests/warn/i19302.scala:9:13 -------------------------------------------------------------------
+9 |    Some(new Thing(1)) // warn
+  |             ^^^^^
+  |             class Thing is deprecated since n/a: is deprecated
+-- Deprecation Warning: tests/warn/i19302.scala:10:23 ------------------------------------------------------------------
+10 |  def wop(x: => Option[Thing]) = println(x) // warn
+   |                       ^^^^^
+   |                       class Thing is deprecated since n/a: is deprecated
+-- Deprecation Warning: tests/warn/i19302.scala:13:16 ------------------------------------------------------------------
+13 |  doo().map((t: Thing) => println(t)) // warn
+   |                ^^^^^
+   |                class Thing is deprecated since n/a: is deprecated
+-- Deprecation Warning: tests/warn/i19302.scala:18:18 ------------------------------------------------------------------
+18 |  val thing = new Thing(42) // warn
+   |                  ^^^^^
+   |                  class Thing is deprecated since n/a: is deprecated

tests/warn/i19302.scala

@@ -0,0 +1,23 @@
+//> using options -deprecation
+
+@deprecated("is deprecated", "n/a")
+class Thing(val value: Int)
+
+object Main extends App {
+
+  def doo(): Option[Thing] = // warn
+    Some(new Thing(1)) // warn
+  def wop(x: => Option[Thing]) = println(x) // warn
+
+  doo().map(t => println(t))
+  doo().map((t: Thing) => println(t)) // warn
+  doo().map(println)
+  doo().foreach(println)
+  for (x <- doo()) println(x)
+
+  val thing = new Thing(42) // warn
+  println(thing)
+
+  val something = Some(thing)
+  wop(something)
+}