Fix #8843: Normalize type when constant folding

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -510,7 +510,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
    */
   def constToLiteral(tree: Tree)(implicit ctx: Context): Tree = {
     val tree1 = ConstFold(tree)
-    tree1.tpe.widenTermRefExpr.dealias match {
+    tree1.tpe.widenTermRefExpr.dealias.normalized match {
       case ConstantType(value) =>
         if (isIdempotentExpr(tree1)) Literal(value).withSpan(tree.span)
         else tree1 match {

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

@@ -1002,14 +1002,9 @@ object SymDenotations {
     /** Is this a Scala 2 macro */
     final def isScala2Macro(implicit ctx: Context): Boolean = is(Macro) && symbol.owner.is(Scala2x)
 
-    /** An erased value or an inline method.
-     */
+    /** An erased value or an erased inline method or field */
     def isEffectivelyErased(implicit ctx: Context): Boolean =
       is(Erased) || is(Inline) && !isRetainedInline && !hasAnnotation(defn.ScalaStaticAnnot)
-      // Do not mark local inline vals as erased. Currently some inline val references do not get
-      // fully inlined and then would fail the erased check.
-      // TODO: remove this condition when #8842 and #8843 are fixed
-      && (owner.isClass || is(Method))
 
     /** ()T and => T types should be treated as equivalent for this symbol.
      *  Note: For the moment, we treat Scala-2 compiled symbols as loose matching,

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

@@ -49,7 +49,7 @@ class PruneErasedDefs extends MiniPhase with SymTransformer { thisTransform =>
     else tree
 
   private def trivialErasedTree(tree: Tree)(using Context): Tree =
-    tree.tpe.widenTermRefExpr.dealias match
+    tree.tpe.widenTermRefExpr.dealias.normalized match
       case ConstantType(c) => Literal(c)
       case _ => ref(defn.Predef_undefined)
 

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

@@ -887,7 +887,7 @@ trait Checking {
     if sym.is(Inline, butNot = DeferredOrTermParamOrAccessor) && !ctx.erasedTypes && !ctx.inInlineMethod then
       // final vals can be marked inline even if they're not pure, see Typer#patchFinalVals
       val purityLevel = if (sym.is(Final)) Idempotent else Pure
-      tpt.tpe.widenTermRefExpr.dealias match
+      tpt.tpe.widenTermRefExpr.dealias.normalized match
         case tp: ConstantType =>
           if !(exprPurity(tree) >= purityLevel) then
             ctx.error(em"inline value must be pure", tree.sourcePos)

tests/pos/i8843.scala

@@ -0,0 +1,11 @@
+class C:
+  type X <: Tuple
+
+inline def f(c: C): Unit = {
+  inline val size = compiletime.constValue[Tuple.Size[c.X]]
+  val n = size
+  val m: Int = n
+  ???
+}
+
+def test: Unit = f(??? : C { type X = Tuple1[Any] })