Fix opaque types leaking rhs when inlined and found in type params (and a related stale symbol issue) (#22655)

This PR fixes the 2 issues found in
#20449, split into 2 commits.

The first commit fixes the stale symbol related issue found if the files
from the issue minimization are compiled together. After suspending and
retrying compilation, the classDefs that are defined directly in
packages previously would sometimes not have companion objects
regenerated, instead relying on the stale symbols from the previous run,
causing them not to to pass the reallyExists check when looking for a
specific ref. Now we make sure to go through lastKnwonDenotation, since
the current one may not exists and may not point us to a Module flag
when checking if to regenerate it.

The second commit fixes the opaque type alias rhs leaking in a macro.
That was caused by building proxies for all parts of the type, including
type arguments to opaque types - from the perspective of a type like
Object[OpaqueType], the opaque type rhs should not be visible.

Author: dwijnand

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

@@ -399,7 +399,17 @@ class Inliner(val call: tpd.Tree)(using Context):
    *  type aliases, add proxy definitions to `opaqueProxies` that expose these aliases.
    */
   private def addOpaqueProxies(tp: Type, span: Span, forThisProxy: Boolean)(using Context): Unit =
-    tp.foreachPart {
+    val foreachTpPart =
+      (p: Type => Unit) =>
+        if forThisProxy then
+          // Performs operations on all parts of this type, outside of the applied type arguments
+          new ForeachAccumulator(p, StopAt.None) {
+            override def apply(x: Unit, tp: Type) = tp match
+              case AppliedType(tycon, _) => super.apply(x, tycon)
+              case other => super.apply(x, other)
+          }.apply((), tp)
+        else tp.foreachPart(p)
+    foreachTpPart {
       case ref: TermRef =>
         for cls <- ref.widen.baseClasses do
           if cls.containsOpaques

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

@@ -712,7 +712,13 @@ class Namer { typer: Typer =>
               enterSymbol(classConstructorCompanion(classSym.asClass))
             else
               for moduleSym <- companionVals do
-                if moduleSym.is(Module) && !moduleSym.isDefinedInCurrentRun then
+                // by not going through `.lastKnownDenotation` (instead using `.current`),
+                // we guarantee that the `moduleSym` will be brought forward to the current run,
+                // rendering `moduleSym.isDefinedInCurrentRun` as always true.
+                // We want to regenerate the companion instead of bringing it forward,
+                // as even if we are able to bring forward the object symbol,
+                // we might not be able to do the same with its stale module class symbol (see `tests/pos/i20449`)
+                if moduleSym.lastKnownDenotation.is(Module) && !moduleSym.isDefinedInCurrentRun then
                   val companion =
                     if needsConstructorProxies(classSym) then
                       classConstructorCompanion(classSym.asClass)

tests/pos-macros/i20449/Macro.scala

@@ -0,0 +1,3 @@
+import scala.quoted.*
+transparent inline def getTypeInfo[T]() = ${ getTypeInfoImpl[T] }
+def getTypeInfoImpl[T: Type](using ctx: Quotes): Expr[Unit] = '{ () }

tests/pos-macros/i20449/Main.scala

@@ -0,0 +1,6 @@
+
+class Wrapper1[A]
+val a = {
+  getTypeInfo[Any]()
+  val wrapper2 = Wrapper1[Any]()
+}

tests/run-macros/i20449.check

@@ -0,0 +1,50 @@
+------ UserName.T - Directly -------
+Original: Main_2$package.UserName.T
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ UserName.T - Directly -------
+Original: Main_2$package.UserName
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ ForeignWrapper1[UserName.T] -------
+Original: Main_2$package.UserName.T
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ ForeignWrapper2[UserName.T] -------
+Original: Main_2$package.UserName.T
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ ForeignWrapper1[UserName] -------
+Original: Main_2$package.UserName
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ ForeignWrapper2[UserName] -------
+Original: Main_2$package.UserName
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ Wrapper1[UserName.T] -------
+Original: Main_2$package.UserName.T
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ Wrapper2[UserName.T] -------
+Original: Main_2$package.UserName.T
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ Wrapper1[UserName] -------
+Original: Main_2$package.UserName
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    
+------ Wrapper2[UserName] -------
+Original: Main_2$package.UserName
+Dealias: Main_2$package.UserName.T
+Dealias dealias: Main_2$package.UserName.T
+    

tests/run-macros/i20449/Macro_1.scala

@@ -0,0 +1,29 @@
+import scala.quoted.*
+
+class ForeignWrapper1[-A] {
+  inline def getTypeInfo(inline source: String): String =
+    ${ getTypeInfoImpl[A]('source) }
+  def createWrapper2 = ForeignWrapper2(this)
+}
+
+class ForeignWrapper2[-A](val self: ForeignWrapper1[A]) {
+  inline def getTypeInfo(inline source: String): String =
+    ${getTypeInfoImpl[A]('source)}
+}
+
+transparent inline def getTypeInfo[T](inline source: String) =
+  ${ getTypeInfoImpl[T]('source) }
+
+def getTypeInfoImpl[T: Type](source: Expr[String])(using ctx: Quotes) : Expr[String] = {
+  import ctx.reflect.*
+
+  val tpe = TypeRepr.of[T]
+  val str =
+    s"""|------ ${source.valueOrAbort} -------
+       |Original: ${tpe.show}
+       |Dealias: ${tpe.dealias.show}
+       |Dealias dealias: ${tpe.dealias.dealias.show}
+    """.stripMargin
+
+  Expr(str)
+}

tests/run-macros/i20449/Main_2.scala

@@ -0,0 +1,41 @@
+object UserName {
+  opaque type T = String
+
+  def apply(s: String): T = s
+}
+
+type UserName = UserName.T
+
+class Wrapper1[-A] {
+  inline def getTypeInfo(inline source: String): String =
+    ${ getTypeInfoImpl[A]('source) }
+  def createWrapper2 = Wrapper2(this)
+}
+
+class Wrapper2[-A](val self: Wrapper1[A]) {
+  inline def getTypeInfo(inline source: String): String =
+    ${getTypeInfoImpl[A]('source)}
+}
+
+
+@main def Test() = {
+  println(getTypeInfo[UserName.T]("UserName.T - Directly"))
+  println(getTypeInfo[UserName]("UserName.T - Directly"))
+
+  val foreignWrapper = ForeignWrapper1[UserName.T]()
+  println(foreignWrapper.getTypeInfo("ForeignWrapper1[UserName.T]"))
+  println(foreignWrapper.createWrapper2.getTypeInfo("ForeignWrapper2[UserName.T]"))
+
+  val foreignWrapper2 = ForeignWrapper1[UserName]()
+  println(foreignWrapper2.getTypeInfo("ForeignWrapper1[UserName]"))
+  println(foreignWrapper2.createWrapper2.getTypeInfo("ForeignWrapper2[UserName]"))
+
+  val wrapper = Wrapper1[UserName.T]()
+  println(wrapper.getTypeInfo("Wrapper1[UserName.T]"))
+  println(wrapper.createWrapper2.getTypeInfo("Wrapper2[UserName.T]"))
+
+  val wrapper2 = Wrapper1[UserName]()
+  println(wrapper2.getTypeInfo("Wrapper1[UserName]"))
+  println(wrapper2.createWrapper2.getTypeInfo("Wrapper2[UserName]"))
+
+}