Move inline β-reduction out of typer

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -3,12 +3,14 @@ package dotc
 
 import util.SourceFile
 import ast.{tpd, untpd}
-import tpd.{ Tree, TreeTraverser }
+import dotty.tools.dotc.ast.Trees
+import tpd.{Tree, TreeTraverser}
 import typer.PrepareInlineable.InlineAccessors
 import dotty.tools.dotc.core.Contexts.Context
 import dotty.tools.dotc.core.SymDenotations.ClassDenotation
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.transform.SymUtils._
+import dotty.tools.dotc.typer.Inliner
 
 class CompilationUnit(val source: SourceFile) {
 
@@ -23,6 +25,11 @@ class CompilationUnit(val source: SourceFile) {
   /** Pickled TASTY binaries, indexed by class. */
   var pickled: Map[ClassSymbol, Array[Byte]] = Map()
 
+  /** Will be reset to `true` if `tpdTree` contains a call to an inline method. The information
+   *  is used in phase InlineCalls in order to avoid traversing an inline-less tree.
+   */
+  var containsInlineCalls: Boolean = false
+
   /** Will be reset to `true` if `untpdTree` contains `Quote` trees. The information
    *  is used in phase ReifyQuotes in order to avoid traversing a quote-less tree.
    */
@@ -46,17 +53,24 @@ object CompilationUnit {
     if (forceTrees) {
       val force = new Force
       force.traverse(unit1.tpdTree)
+      unit1.containsInlineCalls = force.containsInline
       unit1.containsQuotesOrSplices = force.containsQuotes
     }
     unit1
   }
 
   /** Force the tree to be loaded */
   private class Force extends TreeTraverser {
+    var containsInline = false
     var containsQuotes = false
     def traverse(tree: Tree)(implicit ctx: Context): Unit = {
       if (tree.symbol.isQuote)
         containsQuotes = true
+      tree match {
+        case _: tpd.RefTree | _: Trees.GenericApply[_] if Inliner.isInlineable(tree) =>
+          containsInline = true
+        case _ =>
+      }
       traverseChildren(tree)
     }
   }

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -44,6 +44,7 @@ class Compiler {
   /** Phases dealing with TASTY tree pickling and unpickling */
   protected def picklerPhases: List[List[Phase]] =
     List(new Pickler) ::            // Generate TASTY info
+    List(new InlineCalls) ::        // β-reduce inline calls
     List(new ReifyQuotes) ::        // Turn quoted trees into explicit run-time data structures
     Nil
 

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

@@ -583,9 +583,8 @@ object Trees {
 
   /** A tree representing inlined code.
    *
-   *  @param  call      Info about the original call that was inlined
-   *                    Until PostTyper, this is the full call, afterwards only
-   *                    a reference to the toplevel class from which the call was inlined.
+   *  @param  call      Info about the original call that was inlined.
+   *                    Only a reference to the toplevel class from which the call was inlined.
    *  @param  bindings  Bindings for proxies to be used in the inlined code
    *  @param  expansion The inlined tree, minus bindings.
    *

compiler/src/dotty/tools/dotc/decompiler/TASTYDecompiler.scala

@@ -2,6 +2,7 @@ package dotty.tools.dotc.decompiler
 
 import dotty.tools.dotc.fromtasty._
 import dotty.tools.dotc.core.Phases.Phase
+import dotty.tools.dotc.transform.InlineCalls
 
 /** Compiler from tasty to user readable high text representation
  *  of the compiled scala code.
@@ -14,7 +15,10 @@ class TASTYDecompiler extends TASTYCompiler {
     List(new ReadTastyTreesFromClasses) :: // Load classes from tasty
     Nil
 
-  override protected def picklerPhases: List[List[Phase]] = Nil
+  override protected def picklerPhases: List[List[Phase]] =
+    List(new InlineCalls) :: // TODO should we really inline for the decompiler?
+    Nil
+
   override protected def transformPhases: List[List[Phase]] = Nil
 
   override protected def backendPhases: List[List[Phase]] =

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

@@ -0,0 +1,45 @@
+package dotty.tools.dotc.transform
+
+import dotty.tools.dotc.ast.Trees._
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.core.Phases.Phase
+import dotty.tools.dotc.core.Types.MethodicType
+import dotty.tools.dotc.transform.SymUtils._
+import dotty.tools.dotc.typer.{ConstFold, Inliner}
+
+/** β-reduce all calls to inline methods and preform constant folding */
+class InlineCalls extends MacroTransform { thisPhase =>
+  import tpd._
+
+  override def phaseName: String = InlineCalls.name
+
+  override def run(implicit ctx: Context): Unit =
+    if (ctx.compilationUnit.containsInlineCalls && !ctx.settings.YnoInline.value) super.run
+
+  override def transformPhase(implicit ctx: Context): Phase = thisPhase.next
+
+  protected def newTransformer(implicit ctx: Context): Transformer =
+    new InlineCallsTransformer
+
+  class InlineCallsTransformer extends Transformer {
+    override def transform(tree: Tree)(implicit ctx: Context): Tree = tree match {
+      case _: RefTree | _: GenericApply[_] if !tree.tpe.widenDealias.isInstanceOf[MethodicType] && Inliner.isInlineable(tree) && !ctx.reporter.hasErrors =>
+        val tree2 = super.transform(tree) // transform arguments before inlining (inline arguments and constant fold arguments)
+        transform(Inliner.inlineCall(tree2, tree.tpe.widen))
+      case _: MemberDef =>
+        val newTree = super.transform(tree)
+        newTree.symbol.defTree = newTree // update tree set in PostTyper or set for inlined members
+        newTree
+      case _ =>
+        if (tree.symbol.isQuote || tree.symbol.isSplice)
+          ctx.compilationUnit.containsQuotesOrSplices = true
+        ConstFold(super.transform(tree))
+    }
+  }
+
+}
+
+object InlineCalls {
+  final val name = "inlineCalls"
+}

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

@@ -178,6 +178,11 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
       }
     }
 
+    private def handleInlineCall(sym: Symbol)(implicit ctx: Context): Unit = {
+      if (sym.is(Inline))
+        ctx.compilationUnit.containsInlineCalls = true
+    }
+
     private object dropInlines extends TreeMap {
       override def transform(tree: Tree)(implicit ctx: Context): Tree = tree match {
         case Inlined(call, _, _) =>
@@ -189,12 +194,14 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
     override def transform(tree: Tree)(implicit ctx: Context): Tree =
       try tree match {
         case tree: Ident if !tree.isType =>
+          handleInlineCall(tree.symbol)
           handleMeta(tree.symbol)
           tree.tpe match {
             case tpe: ThisType => This(tpe.cls).withPos(tree.pos)
             case _ => tree
           }
         case tree @ Select(qual, name) =>
+          handleInlineCall(tree.symbol)
           handleMeta(tree.symbol)
           if (name.isTypeName) {
             Checking.checkRealizable(qual.tpe, qual.pos.focus)
@@ -203,6 +210,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
           else
             transformSelect(tree, Nil)
         case tree: Apply =>
+          handleInlineCall(tree.symbol)
           val methType = tree.fun.tpe.widen
           val app =
             if (methType.isErasedMethod)
@@ -223,6 +231,7 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
               super.transform(app)
           }
         case tree: TypeApply =>
+          handleInlineCall(tree.symbol)
           val tree1 @ TypeApply(fn, args) = normalizeTypeArgs(tree)
           if (fn.symbol != defn.ChildAnnot.primaryConstructor) {
             // Make an exception for ChildAnnot, which should really have AnyKind bounds
@@ -236,19 +245,6 @@ class PostTyper extends MacroTransform with IdentityDenotTransformer { thisPhase
             case _ =>
               super.transform(tree1)
           }
-        case Inlined(call, bindings, expansion) if !call.isEmpty =>
-          // Leave only a call trace consisting of
-          //  - a reference to the top-level class from which the call was inlined,
-          //  - the call's position
-          // in the call field of an Inlined node.
-          // The trace has enough info to completely reconstruct positions.
-          // The minimization is done for two reasons:
-          //  1. To save space (calls might contain large inline arguments, which would otherwise
-          //     be duplicated
-          //  2. To enable correct pickling (calls can share symbols with the inlined code, which
-          //     would trigger an assertion when pickling).
-          val callTrace = Ident(call.symbol.topLevelClass.typeRef).withPos(call.pos)
-          cpy.Inlined(tree)(callTrace, transformSub(bindings), transform(expansion)(inlineContext(call)))
         case tree: Template =>
           withNoCheckNews(tree.parents.flatMap(newPart)) {
             val templ1 = paramFwd.forwardParamAccessors(tree)

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

@@ -301,7 +301,10 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
   private def registerType(tpe: Type): Unit = tpe match {
     case tpe: ThisType if !canElideThis(tpe) && !thisProxy.contains(tpe.cls) =>
       val proxyName = s"${tpe.cls.name}_this".toTermName
-      val proxyType = tpe.asSeenFrom(inlineCallPrefix.tpe, inlinedMethod.owner)
+      val proxyType = inlineCallPrefix.tpe.tryNormalize match {
+        case typeMatchResult if typeMatchResult.exists => typeMatchResult
+        case _ => tpe.asSeenFrom(inlineCallPrefix.tpe, inlinedMethod.owner).widenIfUnstable
+      }
       thisProxy(tpe.cls) = newSym(proxyName, InlineProxy, proxyType).termRef
       if (!tpe.cls.isStaticOwner)
         registerType(inlinedMethod.owner.thisType) // make sure we have a base from which to outer-select
@@ -452,9 +455,18 @@ class Inliner(call: tpd.Tree, rhsToInline: tpd.Tree)(implicit ctx: Context) {
 
       if (inlinedMethod == defn.Typelevel_error) issueError()
 
+      // Leave only a call trace consisting of
+      //  - a reference to the top-level class from which the call was inlined,
+      //  - the call's position
+      // in the call field of an Inlined node.
+      // The trace has enough info to completely reconstruct positions.
+      // The minimization is done for the following reason:
+      //   * To save space (calls might contain large inline arguments, which would otherwise be duplicated
+      val callTrace = Ident(call.symbol.topLevelClass.typeRef).withPos(call.pos)
+
       // Take care that only argument bindings go into `bindings`, since positions are
       // different for bindings from arguments and bindings from body.
-      tpd.Inlined(call, finalBindings, finalExpansion)
+      tpd.Inlined(callTrace, finalBindings, finalExpansion)
     }
   }
 

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

@@ -2441,13 +2441,6 @@ class Typer extends Namer
         checkEqualityEvidence(tree, pt)
         tree
       }
-      else if (Inliner.isInlineable(tree) &&
-               !ctx.settings.YnoInline.value &&
-               !ctx.isAfterTyper &&
-               !ctx.reporter.hasErrors &&
-               tree.tpe <:< pt) {
-        readaptSimplified(Inliner.inlineCall(tree, pt))
-      }
       else if (tree.tpe <:< pt) {
         if (pt.hasAnnotation(defn.InlineParamAnnot))
           checkInlineConformant(tree, isFinal = false, "argument to inline parameter")

tests/pos/depfuntype.scala

@@ -16,10 +16,8 @@ object Test {
   val z = depfun3(d)
   val z1: d.M = z
 
-  // Reproduced here because the one from DottyPredef is lacking a Tasty tree and
-  // therefore can't be inlined when testing non-bootstrapped.
-  // But inlining `implicitly` is vital to make the definition of `ifun` below work.
-  inline final def implicitly[T](implicit ev: T): T = ev
+  // Reproduced here because the one from DottyPredef is lacking a parameter dependency of the return type `ev.type`
+  inline final def implicitly[T](implicit ev: T): ev.type = ev
 
   type IDF = implicit (x: C) => x.M
 

tests/run/tuples1a.scala

@@ -0,0 +1,9 @@
+object Test extends App {
+  val t7 = '5' *: 4 *: "C" *: ()
+
+  val t7a = t7.tail
+  val t7b = t7a.tail
+  val t7c: Unit = (t7.tail: (Int, String)).tail
+  val t7d: Unit = (t7.tail: Int *: String *: Unit).tail
+  val t7e: Unit = t7.tail.tail
+}