Avoid printing root capture set

odersky · odersky · commit 8aa41030067d · 2023-05-04T17:57:42.000+02:00
Use ^ and =&gt; shorthands instead.
diff --git a/compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala b/compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala
@@ -155,8 +155,15 @@ class PlainPrinter(_ctx: Context) extends Printer {
     else if !cs.isConst && cs.elems.isEmpty then "?"
     else "{" ~ Text(cs.elems.toList.map(toTextCaptureRef), ", ") ~ "}"
 
+  /** Print capturing type, overridden in RefinedPrinter to account for
+   *  capturing function types.
+   */
   protected def toTextCapturing(parent: Type, refsText: Text, boxText: Text): Text =
-    changePrec(InfixPrec)(boxText ~ toTextLocal(parent) ~ "^" ~ refsText)
+    changePrec(InfixPrec):
+      boxText ~ toTextLocal(parent) ~ "^"
+      ~ (refsText provided refsText != rootSetText)
+
+  final protected def rootSetText = Str("{*}")
 
   def toText(tp: Type): Text = controlled {
     homogenize(tp) match {
@@ -214,7 +221,8 @@ class PlainPrinter(_ctx: Context) extends Printer {
         }.close
       case tp @ EventuallyCapturingType(parent, refs) =>
         val boxText: Text = Str("box ") provided tp.isBoxed //&& ctx.settings.YccDebug.value
-        toTextCapturing(parent, toTextCaptureSet(refs), boxText)
+        val refsText = if refs.isUniversal then rootSetText else toTextCaptureSet(refs)
+        toTextCapturing(parent, refsText, boxText)
       case tp: PreviousErrorType if ctx.settings.XprintTypes.value =>
         "<error>" // do not print previously reported error message because they may try to print this error type again recuresevely
       case tp: ErrorType =>
diff --git a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
@@ -148,7 +148,9 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
     val AppliedType(tycon, args) = (tp: @unchecked)
     val tsym = tycon.typeSymbol
     val isGiven = tsym.name.isContextFunction
-    val isPure = Feature.pureFunsEnabled && !tsym.name.isImpureFunction
+    val capturesRoot = refs == rootSetText
+    val isPure =
+      Feature.pureFunsEnabled && !tsym.name.isImpureFunction && !capturesRoot
     changePrec(GlobalPrec) {
       val argStr: Text =
         if args.length == 2
@@ -160,17 +162,21 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
           "("
           ~ argsText(args.init)
           ~ ")"
-      argStr ~ " " ~ arrow(isGiven, isPure) ~ refs  ~ " " ~ argText(args.last)
+      argStr
+      ~ " " ~ arrow(isGiven, isPure)
+      ~ (refs provided !capturesRoot)
+      ~ " " ~ argText(args.last)
     }
 
   private def toTextMethodAsFunction(info: Type, isPure: Boolean, refs: Text = Str("")): Text = info match
     case info: MethodType =>
+      val capturesRoot = refs == rootSetText
       changePrec(GlobalPrec) {
         "("
         ~ paramsText(info)
         ~ ") "
-        ~ arrow(info.isImplicitMethod, isPure)
-        ~ refs
+        ~ arrow(info.isImplicitMethod, isPure && !capturesRoot)
+        ~ (refs provided !capturesRoot)
         ~ " "
         ~ toTextMethodAsFunction(info.resultType, isPure)
       }
diff --git a/tests/neg-custom-args/captures/capt1.check b/tests/neg-custom-args/captures/capt1.check
@@ -41,13 +41,13 @@
 32 |  val z2 = h[() -> Cap](() => x) // error
    |                        ^^^^^^^
    |                        Found:    () ->{x} Cap
-   |                        Required: () -> box C^{*}
+   |                        Required: () -> box C^
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/capt1.scala:33:5 -----------------------------------------
 33 |    (() => C())  // error
    |     ^^^^^^^^^
    |     Found:    () ->? Cap
-   |     Required: () -> box C^{*}
+   |     Required: () -> box C^
    |
    | longer explanation available when compiling with `-explain`
diff --git a/tests/neg-custom-args/captures/cc-this3.check b/tests/neg-custom-args/captures/cc-this3.check
@@ -1,7 +1,7 @@
 -- [E058] Type Mismatch Error: tests/neg-custom-args/captures/cc-this3.scala:8:6 ---------------------------------------
 8 |class B extends A: // error
   |      ^
-  |      illegal inheritance: self type B^{*} of class B does not conform to self type A^{}
+  |      illegal inheritance: self type B^ of class B does not conform to self type A^{}
   |      of parent class A
   |
   | longer explanation available when compiling with `-explain`
diff --git a/tests/neg-custom-args/captures/cc-this3.scala b/tests/neg-custom-args/captures/cc-this3.scala
@@ -6,13 +6,13 @@ class A:
   val x: A = this
 
 class B extends A: // error
-  this: B^{*} =>
+  this: B^ =>
 
 class C(val f: () => Int) extends A // error
 
 class A2
 
 class B2 extends A2:  // ok
-  this: B2^{*} =>
+  this: B2^ =>
 
 class C2(val f: () => Int) extends A2 // ok
diff --git a/tests/neg-custom-args/captures/curried-simplified.check b/tests/neg-custom-args/captures/curried-simplified.check
@@ -8,7 +8,7 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/curried-simplified.scala:9:28 ----------------------------
 9 |  def y2: () -> () => Int = x2 // error
   |                            ^^
-  |                            Found:    () ->{x} () ->{*} Int
+  |                            Found:    () ->{x} () => Int
   |                            Required: () -> () => Int
   |
   | longer explanation available when compiling with `-explain`
diff --git a/tests/neg-custom-args/captures/exception-definitions.check b/tests/neg-custom-args/captures/exception-definitions.check
@@ -2,16 +2,16 @@
 2 |class Err extends Exception: // error
   |^
   |reference (scala.caps.* : Any) is not included in allowed capture set {} of pure base class class Throwable
-3 |  self: Err^{*} =>
+3 |  self: Err^ =>
 -- Error: tests/neg-custom-args/captures/exception-definitions.scala:10:6 ----------------------------------------------
-10 |class Err4(c: Any^{*}) extends AnyVal // error
-   |^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |reference (Err4.this.c : Any^{*}) is not included in allowed capture set {} of pure base class class AnyVal
+10 |class Err4(c: Any^) extends AnyVal // error
+   |^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |reference (Err4.this.c : Any^) is not included in allowed capture set {} of pure base class class AnyVal
 -- Error: tests/neg-custom-args/captures/exception-definitions.scala:7:12 ----------------------------------------------
 7 |    val x = c  // error
   |            ^
-  |(c : Any^{*}) cannot be referenced here; it is not included in the allowed capture set {} of pure base class class Throwable
+  |(c : Any^) cannot be referenced here; it is not included in the allowed capture set {} of pure base class class Throwable
 -- Error: tests/neg-custom-args/captures/exception-definitions.scala:8:8 -----------------------------------------------
-8 |  class Err3(c: Any^{*}) extends Exception // error
-  |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-  |  reference (Err3.this.c : Any^{*}) is not included in allowed capture set {} of pure base class class Throwable
+8 |  class Err3(c: Any^) extends Exception // error
+  |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |  reference (Err3.this.c : Any^) is not included in allowed capture set {} of pure base class class Throwable
diff --git a/tests/neg-custom-args/captures/exception-definitions.scala b/tests/neg-custom-args/captures/exception-definitions.scala
@@ -1,12 +1,12 @@
 
 class Err extends Exception: // error
-  self: Err^{*} =>
+  self: Err^ =>
 
-def test(c: Any^{*}) =
+def test(c: Any^) =
   class Err2 extends Exception:
     val x = c  // error
-  class Err3(c: Any^{*}) extends Exception // error
+  class Err3(c: Any^) extends Exception // error
 
-class Err4(c: Any^{*}) extends AnyVal // error
+class Err4(c: Any^) extends AnyVal // error
 
 
diff --git a/tests/neg-custom-args/captures/i15116.check b/tests/neg-custom-args/captures/i15116.check
@@ -9,7 +9,7 @@
 5 |  val x = Foo(m)   // error
   |  ^^^^^^^^^^^^^^
   |  Non-local value x cannot have an inferred type
-  |  Foo{val m: String^{*}}^{Baz.this}
+  |  Foo{val m: String^}^{Baz.this}
   |  with non-empty capture set {Baz.this}.
   |  The type needs to be declared explicitly.
 -- Error: tests/neg-custom-args/captures/i15116.scala:7:6 --------------------------------------------------------------
@@ -23,6 +23,6 @@
 9 |  val x = Foo(m)   // error
   |  ^^^^^^^^^^^^^^
   |  Non-local value x cannot have an inferred type
-  |  Foo{val m: String^{*}}^{Baz2.this}
+  |  Foo{val m: String^}^{Baz2.this}
   |  with non-empty capture set {Baz2.this}.
   |  The type needs to be declared explicitly.
diff --git a/tests/neg-custom-args/captures/i15116.scala b/tests/neg-custom-args/captures/i15116.scala
@@ -1,9 +1,9 @@
-class Foo(m: String^{*})
-class Bar(val m: String^{*}):
+class Foo(m: String^)
+class Bar(val m: String^):
   val x = Foo(m)   // error
-trait Baz(val m: String^{*}):
+trait Baz(val m: String^):
   val x = Foo(m)   // error
-class Bar1(m: String^{*}):
+class Bar1(m: String^):
   val x = Foo(m)   // error
-trait Baz2(m: String^{*}):
+trait Baz2(m: String^):
   val x = Foo(m)   // error
diff --git a/tests/neg-custom-args/captures/i15772.check b/tests/neg-custom-args/captures/i15772.check
@@ -1,22 +1,22 @@
--- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:20:49 ---------------------------------------
-20 |    val boxed1 : ((C^{*}) => Unit) -> Unit = box1(c)  // error
-   |                                             ^^^^^^^
-   |                                             Found:    (C{val arg: C^{*}}^{c} ->{*} Unit) ->{c} Unit
-   |                                             Required: (C^{*} => Unit) -> Unit
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:20:46 ---------------------------------------
+20 |    val boxed1 : ((C^) => Unit) -> Unit = box1(c)  // error
+   |                                          ^^^^^^^
+   |                                          Found:    (C{val arg: C^}^{c} => Unit) ->{c} Unit
+   |                                          Required: (C^ => Unit) -> Unit
    |
    | longer explanation available when compiling with `-explain`
--- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:27:38 ---------------------------------------
-27 |    val boxed2 : Observe[C^{*}] = box2(c)  // error
-   |                                  ^^^^^^^
-   |                                  Found:    (C{val arg: C^{*}}^{c} ->{*} Unit) ->{c} Unit
-   |                                  Required: Observe[C^{*}]
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:27:35 ---------------------------------------
+27 |    val boxed2 : Observe[C^] = box2(c)  // error
+   |                               ^^^^^^^
+   |                               Found:    (C{val arg: C^}^{c} => Unit) ->{c} Unit
+   |                               Required: Observe[C^]
    |
    | longer explanation available when compiling with `-explain`
--- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:33:37 ---------------------------------------
-33 |  val boxed2 : Observe[C]^{*} = box2(c) // error
-   |                                     ^
-   |                                     Found:    C^{*}
-   |                                     Required: box C{val arg: C^?}^{*}
+-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:33:34 ---------------------------------------
+33 |  val boxed2 : Observe[C]^ = box2(c) // error
+   |                                  ^
+   |                                  Found:    C^
+   |                                  Required: box C{val arg: C^?}^
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i15772.scala:44:2 ----------------------------------------
diff --git a/tests/neg-custom-args/captures/i15772.scala b/tests/neg-custom-args/captures/i15772.scala
@@ -1,6 +1,6 @@
 type Observe[T] = (T => Unit) -> Unit
 
-def unsafe(cap: C^{*}) = cap.bad()
+def unsafe(cap: C^) = cap.bad()
 
 def box1[T](v: T) : (T => Unit) -> Unit = {
   (fn: T => Unit) => fn(v)
@@ -10,34 +10,34 @@ def box2[T](v: T) : Observe[T] = {
   (fn: T => Unit) => fn(v)
 }
 
-class C(val arg: C^{*}) {
+class C(val arg: C^) {
   def bad() = println("I've gone bad!")
 }
 
-def main1(x: C^{*}) : () -> Int =
+def main1(x: C^) : () -> Int =
   () =>
     val c : C^{x} = new C(x)
-    val boxed1 : ((C^{*}) => Unit) -> Unit = box1(c)  // error
-    boxed1((cap: C^{*}) => unsafe(c))
+    val boxed1 : ((C^) => Unit) -> Unit = box1(c)  // error
+    boxed1((cap: C^) => unsafe(c))
     0
 
-def main2(x: C^{*}) : () -> Int =
+def main2(x: C^) : () -> Int =
   () =>
     val c : C^{x} = new C(x)
-    val boxed2 : Observe[C^{*}] = box2(c)  // error
-    boxed2((cap: C^{*}) => unsafe(c))
+    val boxed2 : Observe[C^] = box2(c)  // error
+    boxed2((cap: C^) => unsafe(c))
     0
 
-def main3(x: C^{*}) =
-  def c : C^{*} = new C(x)
-  val boxed2 : Observe[C]^{*} = box2(c) // error
-  boxed2((cap: C^{*}) => unsafe(c))
+def main3(x: C^) =
+  def c : C^ = new C(x)
+  val boxed2 : Observe[C]^ = box2(c) // error
+  boxed2((cap: C^) => unsafe(c))
   0
 
 trait File:
   def write(s: String): Unit
 
-def main(io: Any^{*}) =
+def main(io: Any^) =
   val sayHello: ((File^{io}) => Unit) = (file: File^{io}) => file.write("Hello World!\r\n")
   val filesList : List[File]^{io} = ???
   val x = () => filesList.foreach(sayHello)
diff --git a/tests/neg-custom-args/captures/lazylist.check b/tests/neg-custom-args/captures/lazylist.check
@@ -8,8 +8,8 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylist.scala:35:29 -------------------------------------
 35 |  val ref1c: LazyList[Int] = ref1 // error
    |                             ^^^^
-   |              Found:    (ref1 : lazylists.LazyCons[Int]{val xs: () ->{cap1} lazylists.LazyList[Int]^{*}}^{cap1})
-   |              Required: lazylists.LazyList[Int]
+   |                 Found:    (ref1 : lazylists.LazyCons[Int]{val xs: () ->{cap1} lazylists.LazyList[Int]^}^{cap1})
+   |                 Required: lazylists.LazyList[Int]
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazylist.scala:37:36 -------------------------------------
@@ -34,9 +34,9 @@
    |
    | longer explanation available when compiling with `-explain`
 -- [E164] Declaration Error: tests/neg-custom-args/captures/lazylist.scala:22:6 ----------------------------------------
-22 |  def tail: LazyList[Nothing]^{*} = ???  // error overriding
+22 |  def tail: LazyList[Nothing]^ = ???  // error overriding
    |      ^
    |      error overriding method tail in class LazyList of type -> lazylists.LazyList[Nothing];
-   |        method tail of type -> lazylists.LazyList[Nothing]^{*} has incompatible type
+   |        method tail of type -> lazylists.LazyList[Nothing]^ has incompatible type
    |
    | longer explanation available when compiling with `-explain`
diff --git a/tests/neg-custom-args/captures/lazylist.scala b/tests/neg-custom-args/captures/lazylist.scala
@@ -1,7 +1,7 @@
 package lazylists
 
 abstract class LazyList[+T]:
-  this: LazyList[T]^{*} =>
+  this: LazyList[T]^ =>
 
   def isEmpty: Boolean
   def head: T
@@ -11,21 +11,21 @@ abstract class LazyList[+T]:
     if isEmpty then LazyNil
     else LazyCons(f(head), () => tail.map(f))
 
-class LazyCons[+T](val x: T, val xs: () => LazyList[T]^{*}) extends LazyList[T]:
+class LazyCons[+T](val x: T, val xs: () => LazyList[T]^) extends LazyList[T]:
   def isEmpty = false
   def head = x
   def tail = xs() // error
 
 object LazyNil extends LazyList[Nothing]:
   def isEmpty = true
   def head = ???
-  def tail: LazyList[Nothing]^{*} = ???  // error overriding
+  def tail: LazyList[Nothing]^ = ???  // error overriding
 
-def map[A, B](xs: LazyList[A]^{*}, f: A => B): LazyList[B]^{f, xs} =
+def map[A, B](xs: LazyList[A]^, f: A => B): LazyList[B]^{f, xs} =
   xs.map(f)
 
 class CC
-type Cap = CC^{*}
+type Cap = CC^
 
 def test(cap1: Cap, cap2: Cap, cap3: Cap) =
   def f[T](x: LazyList[T]): LazyList[T] = if cap1 == cap1 then x else LazyNil
diff --git a/tests/neg-custom-args/captures/lazylists-exceptions.check b/tests/neg-custom-args/captures/lazylists-exceptions.check
@@ -1,7 +1,7 @@
 -- Error: tests/neg-custom-args/captures/lazylists-exceptions.scala:36:2 -----------------------------------------------
 36 |  try  // error
    |  ^
-   |  The expression's type LazyList[Int]^{*} is not allowed to capture the root capability `*`.
+   |  The expression's type LazyList[Int]^ is not allowed to capture the root capability `*`.
    |  This usually means that a capability persists longer than its allowed lifetime.
 37 |    tabulate(10) { i =>
 38 |      if i > 9 then throw Ex1()
diff --git a/tests/neg-custom-args/captures/lazylists-exceptions.scala b/tests/neg-custom-args/captures/lazylists-exceptions.scala
@@ -12,16 +12,16 @@ object LazyNil extends LazyList[Nothing]:
   def head = ???
   def tail = ???
 
-final class LazyCons[+T](val x: T, val xs: () => LazyList[T]^{*}) extends LazyList[T]:
-  this: LazyList[T]^{*} =>
+final class LazyCons[+T](val x: T, val xs: () => LazyList[T]^) extends LazyList[T]:
+  this: LazyList[T]^ =>
 
   def isEmpty = false
   def head = x
   def tail: LazyList[T]^{this} = xs()
 end LazyCons
 
 extension [A](x: A)
-  def #:(xs1: => LazyList[A]^{*}): LazyList[A]^{xs1} =
+  def #:(xs1: => LazyList[A]^): LazyList[A]^{xs1} =
     LazyCons(x, () => xs1)
 
 def tabulate[A](n: Int)(gen: Int => A): LazyList[A]^{gen} =
diff --git a/tests/neg-custom-args/captures/lazyref.check b/tests/neg-custom-args/captures/lazyref.check
@@ -8,21 +8,21 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazyref.scala:21:35 --------------------------------------
 21 |  val ref2c: LazyRef[Int]^{cap2} = ref2 // error
    |                                   ^^^^
-   |                                   Found:    (ref2 : LazyRef[Int]{val elem: () ->{*} Int}^{cap2, ref1})
+   |                                   Found:    (ref2 : LazyRef[Int]{val elem: () => Int}^{cap2, ref1})
    |                                   Required: LazyRef[Int]^{cap2}
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazyref.scala:23:35 --------------------------------------
 23 |  val ref3c: LazyRef[Int]^{ref1} = ref3 // error
    |                                   ^^^^
-   |                                   Found:    (ref3 : LazyRef[Int]{val elem: () ->{*} Int}^{cap2, ref1})
+   |                                   Found:    (ref3 : LazyRef[Int]{val elem: () => Int}^{cap2, ref1})
    |                                   Required: LazyRef[Int]^{ref1}
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/lazyref.scala:25:35 --------------------------------------
 25 |  val ref4c: LazyRef[Int]^{cap1} = ref4 // error
    |                                   ^^^^
-   |                                   Found:    (ref4 : LazyRef[Int]{val elem: () ->{*} Int}^{cap2, cap1})
+   |                                   Found:    (ref4 : LazyRef[Int]{val elem: () => Int}^{cap2, cap1})
    |                                   Required: LazyRef[Int]^{cap1}
    |
    | longer explanation available when compiling with `-explain`
diff --git a/tests/neg-custom-args/captures/lazyref.scala b/tests/neg-custom-args/captures/lazyref.scala
diff --git a/tests/neg-custom-args/captures/nestedclass.scala b/tests/neg-custom-args/captures/nestedclass.scala
diff --git a/tests/neg-custom-args/captures/real-try.check b/tests/neg-custom-args/captures/real-try.check
diff --git a/tests/neg-custom-args/captures/try.check b/tests/neg-custom-args/captures/try.check
diff --git a/tests/neg-custom-args/captures/usingLogFile.check b/tests/neg-custom-args/captures/usingLogFile.check
diff --git a/tests/neg-custom-args/captures/usingLogFile.scala b/tests/neg-custom-args/captures/usingLogFile.scala
diff --git a/tests/neg-custom-args/captures/vars.check b/tests/neg-custom-args/captures/vars.check

Original file line number	Diff line number	Diff line change
`@@ -1,7 +1,7 @@`
`1`	`1`	`-- [E058] Type Mismatch Error: tests/neg-custom-args/captures/cc-this3.scala:8:6 ---------------------------------------`
`2`	`2`	`8 \|class B extends A: // error`
`3`	`3`	`\| ^`
`4`		`- \| illegal inheritance: self type B^{*} of class B does not conform to self type A^{}`
	`4`	`+ \| illegal inheritance: self type B^ of class B does not conform to self type A^{}`
`5`	`5`	`\| of parent class A`
`6`	`6`	`\|`
`7`	`7`	\| longer explanation available when compiling with `-explain`
Original file line number	Diff line number	Diff line change
`@@ -8,7 +8,7 @@`
`8`	`8`	`-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/curried-simplified.scala:9:28 ----------------------------`
`9`	`9`	`9 \| def y2: () -> () => Int = x2 // error`
`10`	`10`	`\| ^^`
`11`		`- \| Found: () ->{x} () ->{*} Int`
	`11`	`+ \| Found: () ->{x} () => Int`
`12`	`12`	`\| Required: () -> () => Int`
`13`	`13`	`\|`
`14`	`14`	\| longer explanation available when compiling with `-explain`