Add Inlined.inlinedFromOuterScope and refactor inline context (#18236)

This is the first step towards supporting `Inlined` trees after lambda
lift (see
#18230 (comment)).

We decouple the way we compute if a call was inlined from an outer scope
from the inlined call.

Author: smarter

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

@@ -673,6 +673,9 @@ object Trees {
    */
   case class Inlined[+T <: Untyped] private[ast] (call: tpd.Tree, bindings: List[MemberDef[T]], expansion: Tree[T])(implicit @constructorOnly src: SourceFile)
     extends Tree[T] {
+
+    def inlinedFromOuterScope: Boolean = call.isEmpty
+
     type ThisTree[+T <: Untyped] = Inlined[T]
     override def isTerm = expansion.isTerm
     override def isType = expansion.isType
@@ -1479,7 +1482,7 @@ object Trees {
      *  innermost enclosing call for which the inlined version is currently
      *  processed.
      */
-    protected def inlineContext(call: tpd.Tree)(using Context): Context = ctx
+    protected def inlineContext(tree: Inlined)(using Context): Context = ctx
 
     /** The context to use when mapping or accumulating over a tree */
     def localCtx(tree: Tree)(using Context): Context
@@ -1549,8 +1552,8 @@ object Trees {
               cpy.Try(tree)(transform(block), transformSub(cases), transform(finalizer))
             case SeqLiteral(elems, elemtpt) =>
               cpy.SeqLiteral(tree)(transform(elems), transform(elemtpt))
-            case Inlined(call, bindings, expansion) =>
-              cpy.Inlined(tree)(call, transformSub(bindings), transform(expansion)(using inlineContext(call)))
+            case tree @ Inlined(call, bindings, expansion) =>
+              cpy.Inlined(tree)(call, transformSub(bindings), transform(expansion)(using inlineContext(tree)))
             case TypeTree() =>
               tree
             case SingletonTypeTree(ref) =>
@@ -1693,8 +1696,8 @@ object Trees {
               this(this(this(x, block), handler), finalizer)
             case SeqLiteral(elems, elemtpt) =>
               this(this(x, elems), elemtpt)
-            case Inlined(call, bindings, expansion) =>
-              this(this(x, bindings), expansion)(using inlineContext(call))
+            case tree @ Inlined(call, bindings, expansion) =>
+              this(this(x, bindings), expansion)(using inlineContext(tree))
             case TypeTree() =>
               x
             case SingletonTypeTree(ref) =>

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

@@ -1392,17 +1392,17 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
    *  EmptyTree calls (for parameters) cancel the next-enclosing call in the list instead of being added to it.
    *  We assume parameters are never nested inside parameters.
    */
-  override def inlineContext(call: Tree)(using Context): Context = {
+  override def inlineContext(tree: Inlined)(using Context): Context = {
     // We assume enclosingInlineds is already normalized, and only process the new call with the head.
     val oldIC = enclosingInlineds
 
     val newIC =
-      if call.isEmpty then
+      if tree.inlinedFromOuterScope then
         oldIC match
           case t1 :: ts2 => ts2
           case _ => oldIC
       else
-        call :: oldIC
+        tree.call :: oldIC
 
     val ctx1 = ctx.fresh.setProperty(InlinedCalls, newIC)
     if oldIC.isEmpty then ctx1.setProperty(InlinedTrees, new Counter) else ctx1

compiler/src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -528,12 +528,12 @@ class TreePickler(pickler: TastyPickler) {
         case SeqLiteral(elems, elemtpt) =>
           writeByte(REPEATED)
           withLength { pickleTree(elemtpt); elems.foreach(pickleTree) }
-        case Inlined(call, bindings, expansion) =>
+        case tree @ Inlined(call, bindings, expansion) =>
           writeByte(INLINED)
           bindings.foreach(preRegister)
           withLength {
             pickleTree(expansion)
-            if (!call.isEmpty) pickleTree(call)
+            if (!tree.inlinedFromOuterScope) pickleTree(call)
             bindings.foreach { b =>
               assert(b.isInstanceOf[DefDef] || b.isInstanceOf[ValDef])
               pickleTree(b)

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

@@ -342,8 +342,8 @@ class InlineReducer(inliner: Inliner)(using Context):
           }
         case Alternative(pats) =>
           pats.exists(reducePattern(caseBindingMap, scrut, _))
-        case Inlined(EmptyTree, Nil, ipat) =>
-          reducePattern(caseBindingMap, scrut, ipat)
+        case tree: Inlined if tree.inlinedFromOuterScope =>
+          reducePattern(caseBindingMap, scrut, tree.expansion)
         case _ => false
       }
     }

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

@@ -129,7 +129,7 @@ object Inliner:
       new InlinerMap(typeMap, treeMap, oldOwners, newOwners, substFrom, substTo)
 
     override def transformInlined(tree: Inlined)(using Context) =
-      if tree.call.isEmpty then
+      if tree.inlinedFromOuterScope then
         tree.expansion match
           case expansion: TypeTree => expansion
           case _ => tree
@@ -549,7 +549,7 @@ class Inliner(val call: tpd.Tree)(using Context):
 
     val inlineTyper = new InlineTyper(ctx.reporter.errorCount)
 
-    val inlineCtx = inlineContext(call).fresh.setTyper(inlineTyper).setNewScope
+    val inlineCtx = inlineContext(Inlined(call, Nil, ref(defn.Predef_undefined))).fresh.setTyper(inlineTyper).setNewScope
 
     def inlinedFromOutside(tree: Tree)(span: Span): Tree =
       Inlined(EmptyTree, Nil, tree)(using ctx.withSource(inlinedMethod.topLevelClass.source)).withSpan(span)
@@ -1049,7 +1049,7 @@ class Inliner(val call: tpd.Tree)(using Context):
     }
     val inlinedNormalizer = new TreeMap {
       override def transform(tree: tpd.Tree)(using Context): tpd.Tree = tree match {
-        case Inlined(EmptyTree, Nil, expr) if enclosingInlineds.isEmpty => transform(expr)
+        case tree @ Inlined(_, Nil, expr) if tree.inlinedFromOuterScope && enclosingInlineds.isEmpty => transform(expr)
         case _ => super.transform(tree)
       }
     }

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

@@ -101,7 +101,7 @@ object Inlines:
       override def transform(t: Tree)(using Context) =
         if call.span.exists then
           t match
-            case Inlined(t, Nil, expr) if t.isEmpty => expr
+            case t @ Inlined(_, Nil, expr) if t.inlinedFromOuterScope => expr
             case _ if t.isEmpty => t
             case _ => super.transform(t.withSpan(call.span))
         else t

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -535,7 +535,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case tree @ Inlined(call, bindings, body) =>
         val bodyText = if bindings.isEmpty then toText(body) else blockText(bindings :+ body)
         if homogenizedView || !ctx.settings.XprintInline.value then bodyText
-        else if call.isEmpty then stringText("{{") ~ stringText("/* inlined from outside */") ~ bodyText ~ stringText("}}")
+        else if tree.inlinedFromOuterScope then stringText("{{") ~ stringText("/* inlined from outside */") ~ bodyText ~ stringText("}}")
         else keywordText("{{") ~ keywordText("/* inlined from ") ~ toText(call) ~ keywordText(" */") ~ bodyText ~ keywordText("}}")
       case tpt: untpd.DerivedTypeTree =>
         "<derived typetree watching " ~ tpt.watched.showSummary() ~ ">"

compiler/src/dotty/tools/dotc/quoted/PickledQuotes.scala

@@ -81,12 +81,12 @@ object PickledQuotes {
 
   /** Unpickle the tree contained in the TastyExpr */
   def unpickleTerm(pickled: String | List[String], typeHole: TypeHole, termHole: ExprHole)(using Context): Tree = {
-    val unpickled = withMode(Mode.ReadPositions)(unpickle(pickled, isType = false))
-    val Inlined(call, Nil, expansion) = unpickled: @unchecked
-    val inlineCtx = inlineContext(call)
-    val expansion1 = spliceTypes(expansion, typeHole)(using inlineCtx)
-    val expansion2 = spliceTerms(expansion1, typeHole, termHole)(using inlineCtx)
-    cpy.Inlined(unpickled)(call, Nil, expansion2)
+    withMode(Mode.ReadPositions)(unpickle(pickled, isType = false)) match
+      case tree @ Inlined(call, Nil, expansion) =>
+        val inlineCtx = inlineContext(tree)
+        val expansion1 = spliceTypes(expansion, typeHole)(using inlineCtx)
+        val expansion2 = spliceTerms(expansion1, typeHole, termHole)(using inlineCtx)
+        cpy.Inlined(tree)(call, Nil, expansion2)
   }
 
 

compiler/src/dotty/tools/dotc/sbt/ExtractDependencies.scala

@@ -388,10 +388,10 @@ private class ExtractDependenciesCollector extends tpd.TreeTraverser { thisTreeT
     }
 
     tree match {
-      case Inlined(call, _, _) if !call.isEmpty =>
+      case tree: Inlined if !tree.inlinedFromOuterScope =>
         // The inlined call is normally ignored by TreeTraverser but we need to
         // record it as a dependency
-        traverse(call)
+        traverse(tree.call)
       case vd: ValDef if vd.symbol.is(ModuleVal) =>
         // Don't visit module val
       case t: Template if t.symbol.owner.is(ModuleClass) =>

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

@@ -396,7 +396,7 @@ class MegaPhase(val miniPhases: Array[MiniPhase]) extends Phase {
       case tree: Inlined =>
         inContext(prepInlined(tree, start)(using outerCtx)) {
           val bindings = transformSpecificTrees(tree.bindings, start)
-          val expansion = transformTree(tree.expansion, start)(using inlineContext(tree.call))
+          val expansion = transformTree(tree.expansion, start)(using inlineContext(tree))
           goInlined(cpy.Inlined(tree)(tree.call, bindings, expansion), start)
         }
       case tree: Quote =>