Check deprecation of inline methods (#19914)

We must check these constraint just before inlining as later on there on
the call might completely disappear. We do the same as we did for
experimental definition checks.

Fixes #19913


### Changes

- Define `CrossVersionChecks.checkRef` that checks both deprecation and
experimental.
- Used in `Inlines` and `PostTyper` to check the deprecation of inlined
calls.
- Rename `checkDeprecated` to `checkDeprecatedRef`
- Move `checkDeprecatedRef` and `skipWarning` to `object
CrossVersionChecks`

compiler/src/dotty/tools/dotc/inlines/Inlines.scala

@@ -100,7 +100,7 @@ object Inlines:
     if ctx.isAfterTyper then
       // During typer we wait with cross version checks until PostTyper, in order
       // not to provoke cyclic references. See i16116 for a test case.
-      CrossVersionChecks.checkExperimentalRef(tree.symbol, tree.srcPos)
+      CrossVersionChecks.checkRef(tree.symbol, tree.srcPos)
 
     if tree.symbol.isConstructor then return tree // error already reported for the inline constructor definition
 

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

@@ -369,7 +369,7 @@ class PostTyper extends MacroTransform with InfoTransformer { thisPhase =>
           }
         case tree @ Inlined(call, bindings, expansion) if !tree.inlinedFromOuterScope =>
           val pos = call.sourcePos
-          CrossVersionChecks.checkExperimentalRef(call.symbol, pos)
+          CrossVersionChecks.checkRef(call.symbol, pos)
           withMode(Mode.NoInline)(transform(call))
           val callTrace = Inlines.inlineCallTrace(call.symbol, pos)(using ctx.withSource(pos.source))
           cpy.Inlined(tree)(callTrace, transformSub(bindings), transform(expansion)(using inlineContext(tree)))

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

@@ -24,54 +24,13 @@ class CrossVersionChecks extends MiniPhase:
   // warnings after the first, but I think it'd be better if we didn't have to
   // arbitrarily choose one as more important than the other.
   private def checkUndesiredProperties(sym: Symbol, pos: SrcPos)(using Context): Unit =
-    checkDeprecated(sym, pos)
-    checkExperimentalRef(sym, pos)
+    checkRef(sym, pos)
 
     val xMigrationValue = ctx.settings.Xmigration.value
     if xMigrationValue != NoScalaVersion then
       checkMigration(sym, pos, xMigrationValue)
   end checkUndesiredProperties
 
-  /**Skip warnings for synthetic members of case classes during declaration and
-    * scan the chain of outer declaring scopes from the current context
-    * a deprecation warning will be skipped if one the following holds
-    * for a given declaring scope:
-    * - the symbol associated with the scope is also deprecated.
-    * - if and only if `sym` is an enum case, the scope is either
-    *   a module that declares `sym`, or the companion class of the
-    *   module that declares `sym`.
-    */
-  def skipWarning(sym: Symbol)(using Context): Boolean =
-
-    /** is the owner an enum or its companion and also the owner of sym */
-    def isEnumOwner(owner: Symbol)(using Context) =
-      // pre: sym is an enumcase
-      if owner.isEnumClass then owner.companionClass eq sym.owner
-      else if owner.is(ModuleClass) && owner.companionClass.isEnumClass then owner eq sym.owner
-      else false
-
-    def isDeprecatedOrEnum(owner: Symbol)(using Context) =
-      // pre: sym is an enumcase
-      owner.isDeprecated || isEnumOwner(owner)
-
-    (ctx.owner.is(Synthetic) && sym.is(CaseClass))
-      || ctx.owner.ownersIterator.exists(if sym.isEnumCase then isDeprecatedOrEnum else _.isDeprecated)
-  end skipWarning
-
-
-  /** If @deprecated is present, and the point of reference is not enclosed
-   * in either a deprecated member or a scala bridge method, issue a warning.
-   */
-  private def checkDeprecated(sym: Symbol, pos: SrcPos)(using Context): Unit =
-
-    // Also check for deprecation of the companion class for synthetic methods
-    val toCheck = sym :: (if sym.isAllOf(SyntheticMethod) then sym.owner.companionClass :: Nil else Nil)
-    for sym <- toCheck; annot <- sym.getAnnotation(defn.DeprecatedAnnot) do
-      if !skipWarning(sym) then
-        val msg = annot.argumentConstant(0).map(": " + _.stringValue).getOrElse("")
-        val since = annot.argumentConstant(1).map(" since " + _.stringValue).getOrElse("")
-        report.deprecationWarning(em"${sym.showLocated} is deprecated${since}${msg}", pos)
-
   private def checkExperimentalAnnots(sym: Symbol)(using Context): Unit =
     if sym.exists && !sym.isInExperimentalScope then
       for annot <- sym.annotations if annot.symbol.isExperimental do
@@ -160,11 +119,11 @@ class CrossVersionChecks extends MiniPhase:
     tpe.foreachPart {
       case TypeRef(_, sym: Symbol)  =>
         if tree.span.isSourceDerived then
-          checkDeprecated(sym, tree.srcPos)
+          checkDeprecatedRef(sym, tree.srcPos)
         checkExperimentalRef(sym, tree.srcPos)
       case TermRef(_, sym: Symbol)  =>
         if tree.span.isSourceDerived then
-          checkDeprecated(sym, tree.srcPos)
+          checkDeprecatedRef(sym, tree.srcPos)
         checkExperimentalRef(sym, tree.srcPos)
       case _ =>
     }
@@ -186,9 +145,55 @@ object CrossVersionChecks:
   val name: String = "crossVersionChecks"
   val description: String = "check issues related to deprecated and experimental"
 
+  /** Check that a reference to an experimental definition with symbol `sym` meets cross-version constraints
+   *  for `@deprecated` and `@experimental`.
+   */
+  def checkRef(sym: Symbol, pos: SrcPos)(using Context): Unit =
+    checkDeprecatedRef(sym, pos)
+    checkExperimentalRef(sym, pos)
+
   /** Check that a reference to an experimental definition with symbol `sym` is only
    *  used in an experimental scope
    */
-  def checkExperimentalRef(sym: Symbol, pos: SrcPos)(using Context): Unit =
+  private[CrossVersionChecks] def checkExperimentalRef(sym: Symbol, pos: SrcPos)(using Context): Unit =
     if sym.isExperimental && !ctx.owner.isInExperimentalScope then
       Feature.checkExperimentalDef(sym, pos)
+
+  /** If @deprecated is present, and the point of reference is not enclosed
+   *  in either a deprecated member or a scala bridge method, issue a warning.
+   */
+  private[CrossVersionChecks] def checkDeprecatedRef(sym: Symbol, pos: SrcPos)(using Context): Unit =
+
+    // Also check for deprecation of the companion class for synthetic methods
+    val toCheck = sym :: (if sym.isAllOf(SyntheticMethod) then sym.owner.companionClass :: Nil else Nil)
+    for sym <- toCheck; annot <- sym.getAnnotation(defn.DeprecatedAnnot) do
+      if !skipWarning(sym) then
+        val msg = annot.argumentConstant(0).map(": " + _.stringValue).getOrElse("")
+        val since = annot.argumentConstant(1).map(" since " + _.stringValue).getOrElse("")
+        report.deprecationWarning(em"${sym.showLocated} is deprecated${since}${msg}", pos)
+
+  /** Skip warnings for synthetic members of case classes during declaration and
+   *  scan the chain of outer declaring scopes from the current context
+   *  a deprecation warning will be skipped if one the following holds
+   *  for a given declaring scope:
+   *  - the symbol associated with the scope is also deprecated.
+   *  - if and only if `sym` is an enum case, the scope is either
+   *    a module that declares `sym`, or the companion class of the
+   *    module that declares `sym`.
+   */
+  private def skipWarning(sym: Symbol)(using Context): Boolean =
+
+    /** is the owner an enum or its companion and also the owner of sym */
+    def isEnumOwner(owner: Symbol)(using Context) =
+      // pre: sym is an enumcase
+      if owner.isEnumClass then owner.companionClass eq sym.owner
+      else if owner.is(ModuleClass) && owner.companionClass.isEnumClass then owner eq sym.owner
+      else false
+
+    def isDeprecatedOrEnum(owner: Symbol)(using Context) =
+      // pre: sym is an enumcase
+      owner.isDeprecated || isEnumOwner(owner)
+
+    (ctx.owner.is(Synthetic) && sym.is(CaseClass))
+      || ctx.owner.ownersIterator.exists(if sym.isEnumCase then isDeprecatedOrEnum else _.isDeprecated)
+  end skipWarning

scaladoc-testcases/src/tests/hugetype.scala

@@ -3,6 +3,7 @@ package tests.hugetype
 import compiletime._
 import compiletime.ops.int._
 import scala.annotation.experimental
+import scala.annotation.nowarn
 
 /**
  * a particular group of people or things that share similar characteristics and form a smaller division of a larger set:
@@ -39,7 +40,7 @@ trait XD extends E:
    */
   @experimental
   @deprecated
-  protected override final implicit transparent inline abstract infix def same[A](a: A): A = a
+  protected override final implicit transparent inline abstract infix def same[A](a: A): A = a: @nowarn
 
 trait Parent[X, A[_], B[_, _]]
 

tests/warn/i19913.check

@@ -0,0 +1,8 @@
+-- Deprecation Warning: tests/warn/i19913.scala:13:25 ------------------------------------------------------------------
+13 |  Deprecated.inlineMethod() // warn
+   |  ^^^^^^^^^^^^^^^^^^^^^^^^^
+   |  method inlineMethod in object Deprecated is deprecated: test
+-- Deprecation Warning: tests/warn/i19913.scala:12:13 ------------------------------------------------------------------
+12 |  Deprecated.method() // warn
+   |  ^^^^^^^^^^^^^^^^^
+   |  method method in object Deprecated is deprecated: test

tests/warn/i19913.scala

@@ -0,0 +1,13 @@
+//> using options -deprecation
+
+object Deprecated:
+
+  @deprecated("test")
+  def method() = ???
+
+  @deprecated("test")
+  inline def inlineMethod() = ???
+
+object Test:
+  Deprecated.method() // warn
+  Deprecated.inlineMethod() // warn