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Simplify type bounds.

I started out looking to limit the noise from empty type
bounds, i.e. the endless repetition of

  class A[T >: _root_.scala.Nothing <: _root_.scala.Any]

This led me to be reminded of all the unnecessary and
in fact damaging overreaches which are performed during parsing.
Why should a type parameter for which no bounds are
specified be immediately encoded with this giant tree:

  TypeBounds(
    Select(Select(Ident(nme.ROOTPKG), tpnme.scala_), tpnme.Nothing),
    Select(Select(Ident(nme.ROOTPKG), tpnme.scala_), tpnme.Any)
  )

...which must then be manually recognized as empty type bounds?
Truly, this is madness.

 - It deftly eliminates the possibility of recognizing
   whether the user wrote "class A[T]" or "class A[T >: Nothing]"
   or "class A[T <: Any]" or specified both bounds. The fact
   that these work out the same internally does not imply the
   information should be exterminated even before parsing completes.
 - It burdens everyone who must recognize type bounds trees,
   such as this author
 - It is far less efficient than the obvious encoding
 - It offers literally no advantage whatsoever

Encode empty type bounds as

  TypeBounds(EmptyTree, EmptyTree)

What could be simpler.
  • Loading branch information...
commit c29405dfe1a24419ce4ce10500b5e8d05c581bee 1 parent d506bed
Paul Phillips authored
View
18 src/compiler/scala/tools/nsc/ast/parser/Parsers.scala
@@ -2222,16 +2222,18 @@ self =>
* }}}
*/
def typeBounds(): TypeBoundsTree = {
- val t = TypeBoundsTree(
- bound(SUPERTYPE, tpnme.Nothing),
- bound(SUBTYPE, tpnme.Any)
- )
- t setPos wrappingPos(List(t.hi, t.lo))
+ val lo = bound(SUPERTYPE)
+ val hi = bound(SUBTYPE)
+ val t = TypeBoundsTree(lo, hi)
+ val defined = List(t.hi, t.lo) filter (_.pos.isDefined)
+
+ if (defined.nonEmpty)
+ t setPos wrappingPos(defined)
+ else
+ t setPos o2p(in.offset)
}
- def bound(tok: Int, default: TypeName): Tree =
- if (in.token == tok) { in.nextToken(); typ() }
- else atPos(o2p(in.lastOffset)) { rootScalaDot(default) }
+ def bound(tok: Int): Tree = if (in.token == tok) { in.nextToken(); typ() } else EmptyTree
/* -------- DEFS ------------------------------------------- */
View
22 src/compiler/scala/tools/nsc/javac/JavaParsers.scala
@@ -293,15 +293,8 @@ trait JavaParsers extends ast.parser.ParsersCommon with JavaScanners {
if (in.token == QMARK) {
val pos = in.currentPos
in.nextToken()
- var lo: Tree = TypeTree(NothingClass.tpe)
- var hi: Tree = TypeTree(AnyClass.tpe)
- if (in.token == EXTENDS) {
- in.nextToken()
- hi = typ()
- } else if (in.token == SUPER) {
- in.nextToken()
- lo = typ()
- }
+ val hi = if (in.token == EXTENDS) { in.nextToken() ; typ() } else EmptyTree
+ val lo = if (in.token == SUPER) { in.nextToken() ; typ() } else EmptyTree
val tdef = atPos(pos) {
TypeDef(
Modifiers(Flags.JAVA | Flags.DEFERRED),
@@ -408,15 +401,8 @@ trait JavaParsers extends ast.parser.ParsersCommon with JavaScanners {
def typeParam(): TypeDef =
atPos(in.currentPos) {
val name = identForType()
- val hi =
- if (in.token == EXTENDS) {
- in.nextToken()
- bound()
- } else {
- scalaDot(tpnme.Any)
- }
- TypeDef(Modifiers(Flags.JAVA | Flags.DEFERRED | Flags.PARAM), name, List(),
- TypeBoundsTree(scalaDot(tpnme.Nothing), hi))
+ val hi = if (in.token == EXTENDS) { in.nextToken() ; bound() } else EmptyTree
+ TypeDef(Modifiers(Flags.JAVA | Flags.DEFERRED | Flags.PARAM), name, Nil, TypeBoundsTree(EmptyTree, hi))
}
def bound(): Tree =
View
4 src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -5149,8 +5149,8 @@ trait Typers extends Adaptations with Tags {
}
def typedTypeBoundsTree(tree: TypeBoundsTree) = {
- val lo1 = typedType(tree.lo, mode)
- val hi1 = typedType(tree.hi, mode)
+ val lo1 = if (tree.lo.isEmpty) TypeTree(NothingTpe) else typedType(tree.lo, mode)
+ val hi1 = if (tree.hi.isEmpty) TypeTree(AnyTpe) else typedType(tree.hi, mode)
treeCopy.TypeBoundsTree(tree, lo1, hi1) setType TypeBounds(lo1.tpe, hi1.tpe)
}
View
9 src/reflect/scala/reflect/internal/Printers.scala
@@ -421,7 +421,14 @@ trait Printers extends api.Printers { self: SymbolTable =>
print(tp); printRow(args, "[", ", ", "]")
case TypeBoundsTree(lo, hi) =>
- printOpt(" >: ", lo); printOpt(" <: ", hi)
+ // Avoid printing noisy empty typebounds everywhere
+ // Untyped empty bounds are not printed by printOpt,
+ // but after they are typed we have to exclude Nothing/Any.
+ if ((lo.tpe eq null) || !(lo.tpe =:= definitions.NothingTpe))
+ printOpt(" >: ", lo)
+
+ if ((hi.tpe eq null) || !(hi.tpe =:= definitions.AnyTpe))
+ printOpt(" <: ", hi)
case ExistentialTypeTree(tpt, whereClauses) =>
print(tpt)
View
4 test/files/presentation/callcc-interpreter.check
@@ -69,13 +69,13 @@ retrieved 63 members
askType at CallccInterpreter.scala(14,21)
================================================================================
[response] askTypeAt at (14,21)
-def unitM[A >: Nothing <: Any](a: A): callccInterpreter.M[A] = callccInterpreter.this.M.apply[A](((c: A => callccInterpreter.Answer) => c.apply(a)))
+def unitM[A](a: A): callccInterpreter.M[A] = callccInterpreter.this.M.apply[A](((c: A => callccInterpreter.Answer) => c.apply(a)))
================================================================================
askType at CallccInterpreter.scala(16,12)
================================================================================
[response] askTypeAt at (16,12)
-def id[A >: Nothing <: Any]: A => A = ((x: A) => x)
+def id[A]: A => A = ((x: A) => x)
================================================================================
askType at CallccInterpreter.scala(17,25)
View
8 test/files/run/analyzerPlugins.check
@@ -25,13 +25,13 @@ pluginsPt(?, Trees$Assign) [7]
pluginsPt(?, Trees$Block) [4]
pluginsPt(?, Trees$ClassDef) [2]
pluginsPt(?, Trees$DefDef) [14]
-pluginsPt(?, Trees$Ident) [51]
+pluginsPt(?, Trees$Ident) [50]
pluginsPt(?, Trees$If) [2]
pluginsPt(?, Trees$Literal) [16]
pluginsPt(?, Trees$New) [5]
pluginsPt(?, Trees$PackageDef) [1]
pluginsPt(?, Trees$Return) [1]
-pluginsPt(?, Trees$Select) [52]
+pluginsPt(?, Trees$Select) [48]
pluginsPt(?, Trees$Super) [2]
pluginsPt(?, Trees$This) [20]
pluginsPt(?, Trees$TypeApply) [4]
@@ -112,7 +112,6 @@ pluginsTyped(<notype>, Trees$DefDef) [14]
pluginsTyped(<notype>, Trees$PackageDef) [1]
pluginsTyped(<notype>, Trees$TypeDef) [1]
pluginsTyped(<notype>, Trees$ValDef) [21]
-pluginsTyped(<root>, Trees$Ident) [1]
pluginsTyped(=> Boolean @testAnn, Trees$Select) [1]
pluginsTyped(=> Double, Trees$Select) [4]
pluginsTyped(=> Int, Trees$Select) [5]
@@ -151,7 +150,6 @@ pluginsTyped(List[Any], Trees$Apply) [1]
pluginsTyped(List[Any], Trees$Select) [1]
pluginsTyped(List[Any], Trees$TypeTree) [3]
pluginsTyped(Nothing, Trees$Return) [1]
-pluginsTyped(Nothing, Trees$Select) [2]
pluginsTyped(Object, Trees$Apply) [1]
pluginsTyped(String @testAnn, Trees$Ident) [1]
pluginsTyped(String @testAnn, Trees$Select) [1]
@@ -185,8 +183,6 @@ pluginsTyped(scala.annotation.TypeConstraint, Trees$TypeTree) [2]
pluginsTyped(scala.collection.immutable.List.type, Trees$Select) [2]
pluginsTyped(scala.collection.immutable.StringOps, Trees$ApplyImplicitView) [2]
pluginsTyped(scala.collection.mutable.WrappedArray[Any], Trees$Apply) [1]
-pluginsTyped(scala.type, Trees$Ident) [1]
-pluginsTyped(scala.type, Trees$Select) [1]
pluginsTyped(str.type, Trees$Ident) [3]
pluginsTyped(testAnn, Trees$Apply) [5]
pluginsTyped(testAnn, Trees$Ident) [5]
View
4 test/files/run/macro-typecheck-macrosdisabled.check
@@ -7,7 +7,7 @@
$treecreator1.super.<init>();
()
};
- def apply[U >: Nothing <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Tree = {
+ def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Tree = {
val $u: U = $m$untyped.universe;
val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
$u.Literal.apply($u.Constant.apply(2))
@@ -20,7 +20,7 @@
$typecreator2.super.<init>();
()
};
- def apply[U >: Nothing <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
+ def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
val $u: U = $m$untyped.universe;
val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
$u.ConstantType.apply($u.Constant.apply(2))
View
4 test/files/run/macro-typecheck-macrosdisabled2.check
@@ -7,7 +7,7 @@
$treecreator1.super.<init>();
()
};
- def apply[U >: Nothing <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Tree = {
+ def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Tree = {
val $u: U = $m$untyped.universe;
val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
$u.Apply.apply($u.Select.apply($u.build.Ident($m.staticModule("scala.Array")), $u.TermName.apply("apply")), scala.collection.immutable.List.apply[$u.Literal]($u.Literal.apply($u.Constant.apply(2))))
@@ -20,7 +20,7 @@
$typecreator2.super.<init>();
()
};
- def apply[U >: Nothing <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
+ def apply[U <: scala.reflect.api.Universe with Singleton]($m$untyped: scala.reflect.api.Mirror[U]): U#Type = {
val $u: U = $m$untyped.universe;
val $m: $u.Mirror = $m$untyped.asInstanceOf[$u.Mirror];
$u.TypeRef.apply($u.ThisType.apply($m.staticPackage("scala").asModule.moduleClass), $m.staticClass("scala.Array"), scala.collection.immutable.List.apply[$u.Type]($m.staticClass("scala.Int").asType.toTypeConstructor))
View
4 test/files/run/reify-each-node-type.check
@@ -15,7 +15,7 @@
15 { def f(x: Any): Unit = (); () } EmptyTree
16 (null: r.D with r.E) CompoundTypeTree
17 { type T = Int; () } TypeDef
-18 { type CC[T >: Nothing <: r.D] = r.C[T]; () } TypeBoundsTree
+18 { type CC[T <: r.D] = r.C[T]; () } TypeBoundsTree
19 try { 0 } finally Predef.println("") Try
20 ((x: Int) => x) Function
21 { var v = 1; v = 2 } Assign
@@ -24,7 +24,7 @@
24 0: @unchecked Annotated
25 (null: r.Outer#Inner) SelectFromTypeTree
26 (null: Nil.type) SingletonTypeTree
-27 (null: T forSome { type T >: Nothing <: Any }) ExistentialTypeTree
+27 (null: T forSome { type T }) ExistentialTypeTree
28 { import r.{A, B=>C}; () } Import
29 { def f: Int = return 0; () } Return
30 { object x extends AnyRef { def <init>() = { super.<init>(); ModuleDef
View
2  test/files/run/reify_ann1a.check
@@ -1,5 +1,5 @@
{
- @new ann(List.apply("1a")) @new ann(List.apply("1b")) class C[@new ann(List.apply("2a")) @new ann(List.apply("2b")) T >: Nothing <: Any] extends AnyRef {
+ @new ann(List.apply("1a")) @new ann(List.apply("1b")) class C[@new ann(List.apply("2a")) @new ann(List.apply("2b")) T] extends AnyRef {
@new ann(List.apply("3a")) @new ann(List.apply("3b")) <paramaccessor> private[this] val x: T @ann(List.apply("4a")) @ann(List.apply("4b")) = _;
def <init>(@new ann(List.apply("3a")) @new ann(List.apply("3b")) x: T @ann(List.apply("4a")) @ann(List.apply("4b"))) = {
super.<init>();
View
2  test/files/run/reify_ann1b.check
@@ -1,5 +1,5 @@
{
- @new ann(bar = "1a") @new ann(bar = "1b") class C[@new ann(bar = "2a") @new ann(bar = "2b") T >: Nothing <: Any] extends AnyRef {
+ @new ann(bar = "1a") @new ann(bar = "1b") class C[@new ann(bar = "2a") @new ann(bar = "2b") T] extends AnyRef {
@new ann(bar = "3a") @new ann(bar = "3b") <paramaccessor> private[this] val x: T @ann(bar = "4a") @ann(bar = "4b") = _;
def <init>(@new ann(bar = "3a") @new ann(bar = "3b") x: T @ann(bar = "4a") @ann(bar = "4b")) = {
super.<init>();
View
2  test/files/run/reify_ann2a.check
@@ -6,7 +6,7 @@
()
}
};
- @new ann(List.apply("1a")) @new ann(List.apply("1b")) class C[@new ann(List.apply("2a")) @new ann(List.apply("2b")) T >: Nothing <: Any] extends AnyRef {
+ @new ann(List.apply("1a")) @new ann(List.apply("1b")) class C[@new ann(List.apply("2a")) @new ann(List.apply("2b")) T] extends AnyRef {
@new ann(List.apply("3a")) @new ann(List.apply("3b")) <paramaccessor> private[this] val x: T @ann(List.apply("4a")) @ann(List.apply("4b")) = _;
def <init>(@new ann(List.apply("3a")) @new ann(List.apply("3b")) x: T @ann(List.apply("4a")) @ann(List.apply("4b"))) = {
super.<init>();
View
2  test/files/run/reify_ann3.check
@@ -1,5 +1,5 @@
{
- class Tree[A >: Nothing <: Any, B >: Nothing <: Any] extends AnyRef {
+ class Tree[A, B] extends AnyRef {
@new inline @getter() final <paramaccessor> val key: A = _;
def <init>(key: A) = {
super.<init>();
View
2  test/scaladoc/run/t5527.check
@@ -75,7 +75,7 @@ package <empty> {
()
};
/** T */
- type T >: _root_.scala.Nothing <: _root_.scala.Any;
+ type T;
/** f */
def f(i: Int): scala.Unit;
/** v */
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