Implement for clauses for implied imports

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

@@ -243,6 +243,8 @@ object Denotations {
      */
     def suchThat(p: Symbol => Boolean)(implicit ctx: Context): SingleDenotation
 
+    override def filterWithPredicate(p: SingleDenotation => Boolean): Denotation
+
     /** If this is a SingleDenotation, return it, otherwise throw a TypeError */
     def checkUnique(implicit ctx: Context): SingleDenotation = suchThat(alwaysTrue)
 
@@ -1253,6 +1255,8 @@ object Denotations {
         else sd1
       else sd2
     }
+    override def filterWithPredicate(p: SingleDenotation => Boolean): Denotation =
+      derivedUnionDenotation(denot1.filterWithPredicate(p), denot2.filterWithPredicate(p))
     def hasAltWith(p: SingleDenotation => Boolean): Boolean =
       denot1.hasAltWith(p) || denot2.hasAltWith(p)
     def accessibleFrom(pre: Type, superAccess: Boolean)(implicit ctx: Context): Denotation = {

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

@@ -592,6 +592,8 @@ object Flags {
   final val ImplicitOrImpliedOrGiven = Implicit | Implied | Given
   final val ImplicitOrGiven = Implicit | Given
 
+  final val ImpliedOrGiven = Implied | Given
+
   final val ImplicitOrImpliedOrGivenTerm = ImplicitOrImpliedOrGiven.toTermFlags
 
   /** Flags retained in export forwarders */

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

@@ -63,6 +63,7 @@ Standard-Section: "ASTs" TopLevelStat*
                                         Modifier*                                  -- modifiers def name [typeparams] paramss : returnType (= rhs)?
   Selector      = IMPORTED              name_NameRef                               -- name
                   RENAMED               to_NameRef                                 -- => name
+                  BOUNDED               type_Term?                                 -- for type
 
   TypeParam     = TYPEPARAM      Length NameRef type_Term Modifier*                -- modifiers name bounds
   Params        = PARAMS         Length Param*
@@ -80,7 +81,7 @@ Standard-Section: "ASTs" TopLevelStat*
                   APPLY          Length fn_Term arg_Term*                          -- fn(args)
                   TYPEAPPLY      Length fn_Term arg_Type*                          -- fn[args]
                   SUPER          Length this_Term mixinTypeIdent_Tree?             -- super[mixin]
-                  TYPED          Length expr_Term ascriptionType_Tern              -- expr: ascription
+                  TYPED          Length expr_Term ascriptionType_Term              -- expr: ascription
                   ASSIGN         Length lhs_Term rhs_Term                          -- lhs = rhs
                   BLOCK          Length expr_Term Stat*                            -- { stats; expr }
                   INLINED        Length expr_Term call_Term? ValOrDefDef*          -- Inlined code from call, with given body `expr` and given bindings
@@ -369,6 +370,7 @@ object TastyFormat {
   final val RECtype = 91
   final val TYPEALIAS = 92
   final val SINGLETONtpt = 93
+  final val BOUNDED = 94
 
   // Cat. 4:    tag Nat AST
 
@@ -461,7 +463,7 @@ object TastyFormat {
   def isLegalTag(tag: Int): Boolean =
     firstSimpleTreeTag <= tag && tag <= EXPORTED ||
     firstNatTreeTag <= tag && tag <= SYMBOLconst ||
-    firstASTTreeTag <= tag && tag <= SINGLETONtpt ||
+    firstASTTreeTag <= tag && tag <= BOUNDED ||
     firstNatASTTreeTag <= tag && tag <= NAMEDARG ||
     firstLengthTreeTag <= tag && tag <= MATCHtpt ||
     tag == HOLE
@@ -601,6 +603,7 @@ object TastyFormat {
     case PARAM => "PARAM"
     case IMPORTED => "IMPORTED"
     case RENAMED => "RENAMED"
+    case BOUNDED => "BOUNDED"
     case APPLY => "APPLY"
     case TYPEAPPLY => "TYPEAPPLY"
     case NEW => "NEW"

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

@@ -606,6 +606,10 @@ class TreePickler(pickler: TastyPickler) {
         pickleSelector(RENAMED, to)
       case id @ Ident(_) =>
         pickleSelector(IMPORTED, id)
+      case bounded @ TypeBoundsTree(untpd.EmptyTree, untpd.TypedSplice(tpt)) =>
+        registerTreeAddr(bounded)
+        writeByte(BOUNDED)
+        pickleTree(tpt)
     }
 
   def pickleSelector(tag: Int, id: untpd.Ident)(implicit ctx: Context): Unit = {

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

@@ -973,6 +973,11 @@ class TreeUnpickler(reader: TastyReader,
           case _ =>
             from :: readSelectors()
         }
+      case BOUNDED =>
+        val start = currentAddr
+        readByte()
+        val bounded = setSpan(start, untpd.TypeBoundsTree(untpd.EmptyTree, untpd.TypedSplice(readTpt())))
+        bounded :: readSelectors()
       case _ =>
         Nil
     }

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -627,9 +627,6 @@ object Parsers {
     def wildcardIdent(): Ident =
       atSpan(accept(USCORE)) { Ident(nme.WILDCARD) }
 
-    def termIdentOrWildcard(): Ident =
-      if (in.token == USCORE) wildcardIdent() else termIdent()
-
     /** Accept identifier acting as a selector on given tree `t`. */
     def selector(t: Tree): Tree =
       atSpan(startOffset(t), in.offset) { Select(t, ident()) }
@@ -2310,8 +2307,50 @@ object Parsers {
      */
     def importExpr(importImplied: Boolean, mkTree: ImportConstr): () => Tree = {
 
+      /** ImportSelectors ::= `{' {ImportSelector `,'} FinalSelector ‘}’
+       *  FinalSelector   ::=  ImportSelector
+       *                    |  ‘_’
+       *                    |  ‘for’ InfixType
+       */
+      def importSelectors(): List[Tree] = in.token match {
+        case USCORE =>
+          wildcardIdent() :: Nil
+        case FOR =>
+          if (!importImplied)
+              syntaxError(em"`for` qualifier only allowed in `import implied`")
+          atSpan(in.skipToken()) { TypeBoundsTree(EmptyTree, infixType()) } :: Nil
+        case _ =>
+          importSelector() :: {
+            if (in.token == COMMA) {
+              in.nextToken()
+              importSelectors()
+            }
+            else Nil
+          }
+      }
+
+      /** ImportSelector ::= id [`=>' id | `=>' `_']
+       */
+      def importSelector(): Tree = {
+        val from = termIdent()
+        if (in.token == ARROW)
+          atSpan(startOffset(from), in.skipToken()) {
+            val start = in.offset
+            val to = if (in.token == USCORE) wildcardIdent() else termIdent()
+            val toWithPos =
+              if (to.name == nme.ERROR)
+                // error identifiers don't consume any characters, so atSpan(start)(id) wouldn't set a span.
+                // Some testcases would then fail in Positioned.checkPos. Set a span anyway!
+                atSpan(start, start, in.lastOffset)(to)
+              else
+                to
+            Thicket(from, toWithPos)
+          }
+        else from
+      }
+
       val handleImport: Tree => Tree = { tree: Tree =>
-        if (in.token == USCORE) mkTree(importImplied, tree, importSelector() :: Nil)
+        if (in.token == USCORE) mkTree(importImplied, tree, wildcardIdent() :: Nil)
         else if (in.token == LBRACE) mkTree(importImplied, tree, inBraces(importSelectors()))
         else tree
       }
@@ -2333,41 +2372,6 @@ object Parsers {
       }
     }
 
-    /** ImportSelectors ::= `{' {ImportSelector `,'} (ImportSelector | `_') `}'
-     */
-    def importSelectors(): List[Tree] = {
-      val sel = importSelector()
-      if (in.token == RBRACE) sel :: Nil
-      else {
-        sel :: {
-          if (!isWildcardArg(sel) && in.token == COMMA) {
-            in.nextToken()
-            importSelectors()
-          }
-          else Nil
-        }
-      }
-    }
-
-    /** ImportSelector ::= id [`=>' id | `=>' `_']
-     */
-    def importSelector(): Tree = {
-      val from = termIdentOrWildcard()
-      if (from.name != nme.WILDCARD && in.token == ARROW)
-        atSpan(startOffset(from), in.skipToken()) {
-          val start = in.offset
-          val to = termIdentOrWildcard()
-          val toWithPos =
-            if (to.name == nme.ERROR)
-              // error identifiers don't consume any characters, so atSpan(start)(id) wouldn't set a span.
-              // Some testcases would then fail in Positioned.checkPos. Set a span anyway!
-              atSpan(start, start, in.lastOffset)(to)
-            else
-              to
-          Thicket(from, toWithPos)
-        }
-      else from
-    }
 
     def posMods(start: Int, mods: Modifiers): Modifiers = {
       in.nextToken()

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

@@ -501,7 +501,8 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
       case Import(importImplied, expr, selectors) =>
         def selectorText(sel: Tree): Text = sel match {
           case Thicket(l :: r :: Nil) => toTextGlobal(l) ~ " => " ~ toTextGlobal(r)
-          case _ => toTextGlobal(sel)
+          case _: Ident => toTextGlobal(sel)
+          case TypeBoundsTree(_, tpt) => "for " ~ toTextGlobal(tpt)
         }
         val selectorsText: Text = selectors match {
           case id :: Nil => toText(id)

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

@@ -1353,7 +1353,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
         }
         def prepare(tp: Type) = tp.stripTypeVar match {
           case tp: NamedType if tp.symbol.is(Module) && tp.symbol.sourceModule.is(Implied) =>
-            flip(tp.widen.widenToParents
+            flip(tp.widen.widenToParents)
           case _ => flip(tp)
         }
         (prepare(tp1) relaxed_<:< prepare(tp2)) || viewExists(tp1, tp2)

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

@@ -10,6 +10,7 @@ import util.SimpleIdentityMap
 import Symbols._, Names._, Types._, Contexts._, StdNames._, Flags._
 import Implicits.RenamedImplicitRef
 import printing.Texts.Text
+import Decorators._
 
 object ImportInfo {
   /** The import info for a root import from given symbol `sym` */
@@ -55,62 +56,86 @@ class ImportInfo(symf: Context => Symbol, val selectors: List[untpd.Tree],
   /** The names that are excluded from any wildcard import */
   def excluded: Set[TermName] = { ensureInitialized(); myExcluded }
 
-  /** A mapping from renamed to original names */
-  def reverseMapping: SimpleIdentityMap[TermName, TermName] = { ensureInitialized(); myMapped }
+  /** A mapping from original to renamed names */
+  def forwardMapping: SimpleIdentityMap[TermName, TermName] = { ensureInitialized(); myForwardMapping }
 
-  /** The original names imported by-name before renaming */
-  def originals: Set[TermName] = { ensureInitialized(); myOriginals }
+  /** A mapping from renamed to original names */
+  def reverseMapping: SimpleIdentityMap[TermName, TermName] = { ensureInitialized(); myReverseMapping }
 
   /** Does the import clause end with wildcard? */
   def isWildcardImport: Boolean = { ensureInitialized(); myWildcardImport }
 
   private[this] var myExcluded: Set[TermName] = null
-  private[this] var myMapped: SimpleIdentityMap[TermName, TermName] = null
-  private[this] var myOriginals: Set[TermName] = null
+  private[this] var myForwardMapping: SimpleIdentityMap[TermName, TermName] = null
+  private[this] var myReverseMapping: SimpleIdentityMap[TermName, TermName] = null
   private[this] var myWildcardImport: Boolean = false
 
   /** Compute info relating to the selector list */
   private def ensureInitialized(): Unit = if (myExcluded == null) {
     myExcluded = Set()
-    myMapped = SimpleIdentityMap.Empty
-    myOriginals = Set()
+    myForwardMapping = SimpleIdentityMap.Empty
+    myReverseMapping = SimpleIdentityMap.Empty
     def recur(sels: List[untpd.Tree]): Unit = sels match {
       case sel :: sels1 =>
         sel match {
           case Thicket(Ident(name: TermName) :: Ident(nme.WILDCARD) :: Nil) =>
             myExcluded += name
           case Thicket(Ident(from: TermName) :: Ident(to: TermName) :: Nil) =>
-            myMapped = myMapped.updated(to, from)
+            myForwardMapping = myForwardMapping.updated(from, to)
+            myReverseMapping = myReverseMapping.updated(to, from)
             myExcluded += from
-            myOriginals += from
           case Ident(nme.WILDCARD) =>
             myWildcardImport = true
           case Ident(name: TermName) =>
-            myMapped = myMapped.updated(name, name)
-            myOriginals += name
+            myForwardMapping = myForwardMapping.updated(name, name)
+            myReverseMapping = myReverseMapping.updated(name, name)
+          case TypeBoundsTree(_, tpt) =>
+            myWildcardImport = true // details are handled separately in impliedBounds
         }
         recur(sels1)
       case nil =>
     }
     recur(selectors)
   }
 
+  private[this] var myImpliedBound: Type = null
+
+  def impliedBound(implicit ctx: Context): Type = {
+    if (myImpliedBound == null)
+      myImpliedBound = selectors.lastOption match {
+        case Some(TypeBoundsTree(_, untpd.TypedSplice(tpt))) => tpt.tpe
+        case Some(TypeBoundsTree(_, tpt)) =>
+          myImpliedBound = NoType
+          ctx.typer.typedAheadType(tpt).tpe
+        case _ => NoType
+      }
+    myImpliedBound
+  }
+
   private def implicitFlag(implicit ctx: Context) =
     if (importImplied || ctx.mode.is(Mode.FindHiddenImplicits)) ImplicitOrImpliedOrGiven
     else Implicit
 
   /** The implicit references imported by this import clause */
   def importedImplicits(implicit ctx: Context): List[ImplicitRef] = {
     val pre = site
-    if (isWildcardImport) {
-      val refs = pre.implicitMembers(implicitFlag)
-      if (excluded.isEmpty) refs
-      else refs filterNot (ref => excluded contains ref.name.toTermName)
-    } else
-      for {
+    if (isWildcardImport)
+      pre.implicitMembers(implicitFlag).flatMap { ref =>
+        val name = ref.name.toTermName
+        if (excluded.contains(name)) Nil
+        else {
+          val renamed = forwardMapping(ref.name)
+          if (renamed == ref.name) ref :: Nil
+          else if (renamed != null) new RenamedImplicitRef(ref, renamed) :: Nil
+          else if (!impliedBound.exists || (ref <:< impliedBound)) ref :: Nil
+          else Nil
+        }
+      }
+    else
+      for
         renamed <- reverseMapping.keys
         denot <- pre.member(reverseMapping(renamed)).altsWith(_ is implicitFlag)
-      } yield {
+      yield {
         val original = reverseMapping(renamed)
         val ref = TermRef(pre, original, denot)
         if (renamed == original) ref
@@ -149,7 +174,7 @@ class ImportInfo(symf: Context => Symbol, val selectors: List[untpd.Tree],
   def featureImported(feature: TermName, owner: Symbol)(implicit ctx: Context): Boolean = {
     def compute = {
       val isImportOwner = site.widen.typeSymbol.eq(owner)
-      if (isImportOwner && originals.contains(feature)) true
+      if (isImportOwner && forwardMapping.contains(feature)) true
       else if (isImportOwner && excluded.contains(feature)) false
       else {
         var c = ctx.outer

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

@@ -177,7 +177,7 @@ class Typer extends Namer
           previous
         }
 
-      def selection(imp: ImportInfo, name: Name) =
+      def selection(imp: ImportInfo, name: Name, checkBounds: Boolean) =
         if (imp.sym.isCompleting) {
           ctx.warning(i"cyclic ${imp.sym}, ignored", posd.sourcePos)
           NoType
@@ -188,7 +188,10 @@ class Typer extends Namer
           var reqd = required
           var excl = EmptyFlags
           if (imp.importImplied) reqd |= Implied else excl |= Implied
-          val denot = pre.memberBasedOnFlags(name, reqd, excl).accessibleFrom(pre)(refctx)
+          var denot = pre.memberBasedOnFlags(name, reqd, excl).accessibleFrom(pre)(refctx)
+          if (checkBounds && imp.impliedBound.exists)
+            denot = denot.filterWithPredicate(_.info <:< imp.impliedBound)
+
             // Pass refctx so that any errors are reported in the context of the
             // reference instead of the
           if (reallyExists(denot)) pre.select(name, denot) else NoType
@@ -209,11 +212,10 @@ class Typer extends Namer
             }
 
             def unambiguousSelection(name: Name) =
-              checkUnambiguous(selection(imp, name))
+              checkUnambiguous(selection(imp, name, checkBounds = false))
 
             selector match {
-              case Thicket(fromId :: Ident(Name) :: _) =>
-                val Ident(from) = fromId
+              case Thicket(Ident(from) :: Ident(Name) :: _) =>
                 unambiguousSelection(if (name.isTypeName) from.toTypeName else from)
               case Ident(Name) =>
                 unambiguousSelection(name)
@@ -231,7 +233,7 @@ class Typer extends Namer
        */
       def wildImportRef(imp: ImportInfo)(implicit ctx: Context): Type =
         if (imp.isWildcardImport && !imp.excluded.contains(name.toTermName) && name != nme.CONSTRUCTOR)
-          selection(imp, name)
+          selection(imp, name, checkBounds = imp.importImplied)
         else NoType
 
       /** Is (some alternative of) the given predenotation `denot`
@@ -1785,7 +1787,12 @@ class Typer extends Namer
   def typedImport(imp: untpd.Import, sym: Symbol)(implicit ctx: Context): Import = track("typedImport") {
     val expr1 = typedExpr(imp.expr, AnySelectionProto)
     checkLegalImportPath(expr1)
-    assignType(cpy.Import(imp)(imp.importImplied, expr1, imp.selectors), sym)
+    val selectors1: List[untpd.Tree] = imp.selectors map {
+      case sel @ TypeBoundsTree(_, tpt) =>
+        untpd.cpy.TypeBoundsTree(sel)(sel.lo, untpd.TypedSplice(typedType(tpt)))
+      case sel => sel
+    }
+    assignType(cpy.Import(imp)(imp.importImplied, expr1, selectors1), sym)
   }
 
   def typedPackageDef(tree: untpd.PackageDef)(implicit ctx: Context): Tree = track("typedPackageDef") {