New phase for entering annotations

If we want to do annotation macros right, we need to add
annotations before completing definitions. This commit achieves
that by adding a new "phase" between index and typecheck.

Author: odersky

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

@@ -650,6 +650,13 @@ class Definitions {
   def isTupleClass(cls: Symbol) = isVarArityClass(cls, tpnme.Tuple)
   def isProductClass(cls: Symbol) = isVarArityClass(cls, tpnme.Product)
 
+  val predefClassNames: Set[Name] =
+    Set("Predef$", "DeprecatedPredef", "LowPriorityImplicits").map(_.toTypeName)
+
+  /** Is `cls` the predef module class, or a class inherited by Predef? */
+  def isPredefClass(cls: Symbol) =
+    (cls.owner eq ScalaPackageClass) && predefClassNames.contains(cls.name)
+
   val StaticRootImportFns = List[() => TermRef](
     () => JavaLangPackageVal.termRef,
     () => ScalaPackageVal.termRef

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

@@ -44,6 +44,12 @@ class FrontEnd extends Phase {
     typr.println("entered: " + unit.source)
   }
 
+  def enterAnnotations(implicit ctx: Context) = monitor("annotating") {
+    val unit = ctx.compilationUnit
+    ctx.typer.annotate(unit.untpdTree :: Nil)
+    typr.println("annotated: " + unit.source)
+  }
+
   def typeCheck(implicit ctx: Context) = monitor("typechecking") {
     val unit = ctx.compilationUnit
     unit.tpdTree = ctx.typer.typedExpr(unit.untpdTree)
@@ -69,8 +75,9 @@ class FrontEnd extends Phase {
     }
     unitContexts foreach (parse(_))
     record("parsedTrees", ast.Trees.ntrees)
-    unitContexts foreach (enterSyms(_))
-    unitContexts foreach (typeCheck(_))
+    unitContexts.foreach(enterSyms(_))
+    unitContexts.foreach(enterAnnotations(_))
+    unitContexts.foreach(typeCheck(_))
     record("total trees after typer", ast.Trees.ntrees)
     unitContexts.map(_.compilationUnit).filterNot(discardAfterTyper)
   }

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

@@ -528,18 +528,96 @@ class Namer { typer: Typer =>
       }
     }
 
-    stats foreach expand
+    stats.foreach(expand)
     mergeCompanionDefs()
     val ctxWithStats = (ctx /: stats) ((ctx, stat) => indexExpanded(stat)(ctx))
     createCompanionLinks(ctxWithStats)
     ctxWithStats
   }
 
+  /** Add all annotations of definitions in `stats` to the defined symbols */
+  def annotate(stats: List[Tree])(implicit ctx: Context): Unit = {
+    def recur(stat: Tree): Unit = stat match {
+      case pcl: PackageDef =>
+        annotate(pcl.stats)
+      case stat: untpd.MemberDef =>
+        stat.getAttachment(SymOfTree) match {
+          case Some(sym) =>
+            sym.infoOrCompleter match {
+              case info: Completer if !defn.isPredefClass(sym.owner) =>
+                // Annotate Predef methods only when they are completed;
+                // This is necessary to break a cyclic dependence between `Predef`
+                // and `deprecated` in test `compileStdLib`.
+                addAnnotations(sym, stat)(info.creationContext)
+              case _ =>
+                // Annotations were already added as part of the symbol's completion
+            }
+          case none =>
+            assert(stat.typeOpt.exists, i"no symbol for $stat")
+        }
+      case stat: untpd.Thicket =>
+        stat.trees.foreach(recur)
+      case _ =>
+    }
+
+    for (stat <- stats) recur(expanded(stat))
+  }
+
+  /** Add annotations of `stat` to `sym`.
+   *  This method can be called twice on a symbol (e.g. once
+   *  during the `annotate` phase and then again during completion).
+   *  Therefore, care needs to be taken not to add annotations again
+   *  that are already added to the symbol.
+   */
+  def addAnnotations(sym: Symbol, stat: MemberDef)(implicit ctx: Context) = {
+    // (1) The context in which an annotation of a top-evel class or module is evaluated
+    // is the closest enclosing context which has the enclosing package as owner.
+    // (2) The context in which an annotation for any other symbol is evaluated is the
+    // closest enclosing context which has the owner of the class enclpsing the symbol as owner.
+    // E.g in
+    //
+    //     package p
+    //     import a.b
+    //     class C {
+    //       import d.e
+    //       @ann m() ...
+    //     }
+    //
+    // `@ann` is evaluated in the context just outside `C`, where the `a.b`
+    // import is visible but the `d.e` import is forgotten. This measure is necessary
+    // in order to avoid cycles.
+    lazy val annotCtx = {
+      var target = sym.owner.lexicallyEnclosingClass
+      if (!target.is(PackageClass)) target = target.owner
+      var c = ctx
+      while (c.owner != target) c = c.outer
+      c
+    }
+    for (annotTree <- untpd.modsDeco(stat).mods.annotations) {
+      val cls = typedAheadAnnotation(annotTree)(annotCtx)
+      if (sym.unforcedAnnotation(cls).isEmpty) {
+        val ann = Annotation.deferred(cls, implicit ctx => typedAnnotation(annotTree))
+        sym.addAnnotation(ann)
+        if (cls == defn.InlineAnnot && sym.is(Method, butNot = Accessor))
+          sym.setFlag(Inline)
+      }
+    }
+  }
+
+  def indexAndAnnotate(stats: List[Tree])(implicit ctx: Context): Context = {
+    val localCtx = index(stats)
+    annotate(stats)
+    localCtx
+  }
+
   /** The completer of a symbol defined by a member def or import (except ClassSymbols) */
   class Completer(val original: Tree)(implicit ctx: Context) extends LazyType {
 
     protected def localContext(owner: Symbol) = ctx.fresh.setOwner(owner).setTree(original)
 
+    /** The context with which this completer was created */
+    def creationContext = ctx
+
     protected def typeSig(sym: Symbol): Type = original match {
       case original: ValDef =>
         if (sym is Module) moduleValSig(sym)
@@ -572,19 +650,6 @@ class Namer { typer: Typer =>
       completeInCreationContext(denot)
     }
 
-    protected def addAnnotations(denot: SymDenotation): Unit = original match {
-      case original: untpd.MemberDef =>
-        var hasInlineAnnot = false
-        for (annotTree <- untpd.modsDeco(original).mods.annotations) {
-          val cls = typedAheadAnnotation(annotTree)
-          val ann = Annotation.deferred(cls, implicit ctx => typedAnnotation(annotTree))
-          denot.addAnnotation(ann)
-          if (cls == defn.InlineAnnot && denot.is(Method, butNot = Accessor))
-            denot.setFlag(Inline)
-        }
-      case _ =>
-    }
-
     private def addInlineInfo(denot: SymDenotation) = original match {
       case original: untpd.DefDef if denot.isInlineMethod =>
         Inliner.registerInlineInfo(
@@ -598,7 +663,10 @@ class Namer { typer: Typer =>
      *  to pick up the context at the point where the completer was created.
      */
     def completeInCreationContext(denot: SymDenotation): Unit = {
-      addAnnotations(denot)
+      original match {
+        case original: MemberDef => addAnnotations(denot.symbol, original)
+        case _ =>
+      }
       addInlineInfo(denot)
       denot.info = typeSig(denot.symbol)
       Checking.checkWellFormed(denot.symbol)
@@ -742,7 +810,7 @@ class Namer { typer: Typer =>
         ok
       }
 
-      addAnnotations(denot)
+      addAnnotations(denot.symbol, original)
 
       val selfInfo =
         if (self.isEmpty) NoType
@@ -765,9 +833,10 @@ class Namer { typer: Typer =>
       // accessors, that's why the constructor needs to be completed before
       // the parent types are elaborated.
       index(constr)
+      annotate(constr :: params)
       symbolOfTree(constr).ensureCompleted()
 
-      index(rest)(inClassContext(selfInfo))
+      indexAndAnnotate(rest)(inClassContext(selfInfo))
 
       val tparamAccessors = decls.filter(_ is TypeParamAccessor).toList
       val parentTypes = ensureFirstIsClass(parents.map(checkedParentType(_, tparamAccessors)))
@@ -790,7 +859,7 @@ class Namer { typer: Typer =>
       case Some(ttree) => ttree
       case none =>
         val ttree = typer.typed(tree, pt)
-        xtree.pushAttachment(TypedAhead, ttree)
+        xtree.putAttachment(TypedAhead, ttree)
         ttree
     }
   }
@@ -810,7 +879,7 @@ class Namer { typer: Typer =>
 
   /** Enter and typecheck parameter list */
   def completeParams(params: List[MemberDef])(implicit ctx: Context) = {
-    index(params)
+    indexAndAnnotate(params)
     for (param <- params) typedAheadExpr(param)
   }
 
@@ -990,7 +1059,7 @@ class Namer { typer: Typer =>
     //   3. Info of CP is computed (to be copied to DP).
     //   4. CP is completed.
     //   5. Info of CP is copied to DP and DP is completed.
-    index(tparams)
+    indexAndAnnotate(tparams)
     if (isConstructor) sym.owner.typeParams.foreach(_.ensureCompleted())
     for (tparam <- tparams) typedAheadExpr(tparam)
 

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

@@ -72,6 +72,7 @@ class ReTyper extends Typer {
   override def localTyper(sym: Symbol) = this
 
   override def index(trees: List[untpd.Tree])(implicit ctx: Context) = ctx
+  override def annotate(trees: List[untpd.Tree])(implicit ctx: Context) = ()
 
   override def tryInsertApplyOrImplicit(tree: Tree, pt: ProtoType)(fallBack: (Tree, TyperState) => Tree)(implicit ctx: Context): Tree =
     fallBack(tree, ctx.typerState)

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

@@ -192,12 +192,12 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
             }
 
             def selection(name: Name) =
-              if (unimported.contains(imp.site.termSymbol))
-                NoType
-              else if (imp.sym.isCompleting) {
+              if (imp.sym.isCompleting) {
                 ctx.warning(i"cyclic ${imp.sym}, ignored", tree.pos)
                 NoType
               }
+              else if (unimported.nonEmpty && unimported.contains(imp.site.termSymbol))
+                NoType
               else {
                 // Pass refctx so that any errors are reported in the context of the
                 // reference instead of the
@@ -588,7 +588,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
   }
 
   def typedBlockStats(stats: List[untpd.Tree])(implicit ctx: Context): (Context, List[tpd.Tree]) =
-    (index(stats), typedStats(stats, ctx.owner))
+    (indexAndAnnotate(stats), typedStats(stats, ctx.owner))
 
   def typedBlock(tree: untpd.Block, pt: Type)(implicit ctx: Context) = track("typedBlock") {
     val (exprCtx, stats1) = typedBlockStats(tree.stats)
@@ -1070,7 +1070,7 @@ class Typer extends Namer with TypeAssigner with Applications with Implicits wit
 
   def typedPolyTypeTree(tree: untpd.PolyTypeTree)(implicit ctx: Context): Tree = track("typedPolyTypeTree") {
     val PolyTypeTree(tparams, body) = tree
-    index(tparams)
+    indexAndAnnotate(tparams)
     val tparams1 = tparams.mapconserve(typed(_).asInstanceOf[TypeDef])
     val body1 = typedType(tree.body)
     assignType(cpy.PolyTypeTree(tree)(tparams1, body1), tparams1, body1)

tests/neg/nopredef.scala

@@ -0,0 +1,5 @@
+import Predef.{assert => _}
+
+object Test {
+  assert("asdf" == "asdf") // error: not found assert
+}