Simplify Existential.mapCapInResults

odersky · odersky · commit 3ad3660b471a · 2025-02-27T16:29:22.000+01:00
diff --git a/compiler/src/dotty/tools/dotc/cc/Existential.scala b/compiler/src/dotty/tools/dotc/cc/Existential.scala
@@ -372,28 +372,23 @@ object Existential:
   end mapCap
 
   /** Map `cap` in function results to fresh existentials */
-  def mapCapInResults(fail: Message => Unit)(using Context): TypeMap = new:
-
-    def mapFunOrMethod(tp: Type, args: List[Type], res: Type): Type =
-      val args1 = atVariance(-variance)(args.map(this))
-      val res1 = res match
-        case res: MethodType => mapFunOrMethod(res, res.paramInfos, res.resType)
-        case res: PolyType => mapFunOrMethod(res, Nil, res.resType) // TODO: Also map bounds of PolyTypes
-        case _ => mapCap(apply(res), fail)
-          //.showing(i"map cap res $res / ${apply(res)} of $tp = $result")
-      tp.derivedFunctionOrMethod(args1, res1)
-
+  def mapCapInResults(fail: Message => Unit)(using Context): TypeMap = new TypeMap with FollowAliasesMap:
     def apply(t: Type): Type = t match
-      case FunctionOrMethod(args, res) if variance > 0 && !isAliasFun(t) =>
-        mapFunOrMethod(t, args, res)
+      case defn.RefinedFunctionOf(mt) =>
+        val mt1 = apply(mt)
+        if mt1 ne mt then mt1.toFunctionType(alwaysDependent = true)
+        else t
+      case t: MethodType if variance > 0 && !t.resType.isInstanceOf[MethodOrPoly] =>
+        val t1 = mapOver(t).asInstanceOf[MethodType]
+        t1.derivedLambdaType(resType = mapCap(t1.resType, fail))
       case CapturingType(parent, refs) =>
         t.derivedCapturingType(this(parent), refs)
       case Existential(_, _) =>
         t
       case t: (LazyRef | TypeVar) =>
         mapConserveSuper(t)
       case _ =>
-        mapOver(t)
+        mapFollowingAliases(t)
   end mapCapInResults
 
   /** Is `mt` a method represnting an existential type when used in a refinement? */
diff --git a/tests/neg-custom-args/captures/capt1.check b/tests/neg-custom-args/captures/capt1.check
@@ -36,33 +36,33 @@
 -- Error: tests/neg-custom-args/captures/capt1.scala:36:16 -------------------------------------------------------------
 36 |  val z2 = h[() -> Cap](() => x) // error // error
    |             ^^^^^^^^^
-   |             Type variable X of method h cannot be instantiated to () -> (ex$18: caps.Exists) -> C^{ex$18} since
-   |             the part C^{ex$18} of that type captures the root capability `cap`.
+   |             Type variable X of method h cannot be instantiated to () -> (ex$14: caps.Exists) -> C^{ex$14} since
+   |             the part C^{ex$14} of that type captures the root capability `cap`.
 -- Error: tests/neg-custom-args/captures/capt1.scala:36:30 -------------------------------------------------------------
 36 |  val z2 = h[() -> Cap](() => x) // error // error
    |                              ^
    |                     reference (x : C^) is not included in the allowed capture set {}
-   |                     of an enclosing function literal with expected type () -> (ex$18: caps.Exists) -> C^{ex$18}
+   |                     of an enclosing function literal with expected type () -> (ex$14: caps.Exists) -> C^{ex$14}
 -- Error: tests/neg-custom-args/captures/capt1.scala:38:13 -------------------------------------------------------------
 38 |  val z3 = h[(() -> Cap) @retains(x)](() => x)(() => C())  // error
    |             ^^^^^^^^^^^^^^^^^^^^^^^
-   |      Type variable X of method h cannot be instantiated to box () ->{x} (ex$23: caps.Exists) -> C^{ex$23} since
-   |      the part C^{ex$23} of that type captures the root capability `cap`.
+   |      Type variable X of method h cannot be instantiated to box () ->{x} (ex$19: caps.Exists) -> C^{ex$19} since
+   |      the part C^{ex$19} of that type captures the root capability `cap`.
 -- Error: tests/neg-custom-args/captures/capt1.scala:43:7 --------------------------------------------------------------
 43 |    if x == null then  // error: separation
    |       ^
    |       Separation failure: Illegal access to {x} which is hidden by the previous definition
-   |       of value z1 with type () => (ex$27: caps.Exists) -> C^{ex$27}.
+   |       of value z1 with type () => (ex$23: caps.Exists) -> C^{ex$23}.
    |       This type hides capabilities  {x}
 -- Error: tests/neg-custom-args/captures/capt1.scala:44:12 -------------------------------------------------------------
 44 |      () => x  // error: separation
    |            ^
    |            Separation failure: Illegal access to {x} which is hidden by the previous definition
-   |            of value z1 with type () => (ex$27: caps.Exists) -> C^{ex$27}.
+   |            of value z1 with type () => (ex$23: caps.Exists) -> C^{ex$23}.
    |            This type hides capabilities  {x}
 -- Error: tests/neg-custom-args/captures/capt1.scala:47:2 --------------------------------------------------------------
 47 |  x // error: separation
    |  ^
    |  Separation failure: Illegal access to {x} which is hidden by the previous definition
-   |  of value z1 with type () => (ex$27: caps.Exists) -> C^{ex$27}.
+   |  of value z1 with type () => (ex$23: caps.Exists) -> C^{ex$23}.
    |  This type hides capabilities  {x}
diff --git a/tests/neg-custom-args/captures/depfun-reach.check b/tests/neg-custom-args/captures/depfun-reach.check
@@ -2,14 +2,14 @@
 13 |    op // error
    |    ^^
    |    Found:    (xs: List[(X, box () ->{io} Unit)]) ->{op} List[box () ->{xs*} Unit]
-   |    Required: (xs: List[(X, box () ->{io} Unit)]) ->{fresh} List[() -> Unit]
+   |    Required: (xs: List[(X, box () ->{io} Unit)]) => List[() -> Unit]
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/depfun-reach.scala:20:60 ---------------------------------
 20 |  val b: (xs: List[() ->{io} Unit]) => List[() ->{} Unit] = a // error
    |                                                            ^
    |                                        Found:    (xs: List[box () ->{io} Unit]) ->{a} List[box () ->{xs*} Unit]
-   |                                        Required: (xs: List[box () ->{io} Unit]) ->{fresh} List[() -> Unit]
+   |                                        Required: (xs: List[box () ->{io} Unit]) => List[() -> Unit]
    |
    | longer explanation available when compiling with `-explain`
 -- Error: tests/neg-custom-args/captures/depfun-reach.scala:12:17 ------------------------------------------------------
diff --git a/tests/neg-custom-args/captures/existential-mapping.check b/tests/neg-custom-args/captures/existential-mapping.check
@@ -19,70 +19,70 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:15:30 --------------------------
 15 |  val _: A^ -> (x: C^) -> C = x3 // error
    |                              ^^
-   |                              Found:    (x3 : A^ -> (x: C^) -> (ex$11: caps.Exists) -> C^{ex$11})
+   |                              Found:    (x3 : A^ -> (x: C^) -> (ex$9: caps.Exists) -> C^{ex$9})
    |                              Required: A^ -> (x: C^) -> C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:18:25 --------------------------
 18 |  val _: A^ -> C^ -> C = x4 // error
    |                         ^^
-   |                         Found:    (x4 : A^ -> C^ -> (ex$19: caps.Exists) -> C^{ex$19})
+   |                         Found:    (x4 : A^ -> C^ -> (ex$17: caps.Exists) -> C^{ex$17})
    |                         Required: A^ -> C^ -> C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:21:30 --------------------------
 21 |  val _: A^ -> (x: C^) -> C = x5 // error
    |                              ^^
-   |                              Found:    (x5 : A^ -> (x: C^) -> (ex$27: caps.Exists) -> C^{ex$27})
+   |                              Found:    (x5 : A^ -> (x: C^) -> (ex$23: caps.Exists) -> C^{ex$23})
    |                              Required: A^ -> (x: C^) -> C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:24:30 --------------------------
 24 |  val _: A^ -> (x: C^) => C = x6 // error
    |                              ^^
-   |              Found:    (x6 : A^ -> (ex$36: caps.Exists) -> (x: C^) ->{ex$36} (ex$35: caps.Exists) -> C^{ex$35})
-   |              Required: A^ -> (ex$39: caps.Exists) -> (x: C^) ->{ex$39} C
+   |              Found:    (x6 : A^ -> (ex$32: caps.Exists) -> (x: C^) ->{ex$32} (ex$31: caps.Exists) -> C^{ex$31})
+   |              Required: A^ -> (ex$35: caps.Exists) -> (x: C^) ->{ex$35} C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:27:25 --------------------------
 27 |  val _:  (x: C^) => C = y1 // error
    |                         ^^
-   |                         Found:    (y1 : (x: C^) ->{fresh} (ex$41: caps.Exists) -> C^{ex$41})
+   |                         Found:    (y1 : (x: C^) ->{fresh} (ex$37: caps.Exists) -> C^{ex$37})
    |                         Required: (x: C^) ->{fresh} C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:30:20 --------------------------
 30 |  val _:  C^ => C = y2 // error
    |                    ^^
-   |                    Found:    (y2 : C^ ->{fresh} (ex$45: caps.Exists) -> C^{ex$45})
+   |                    Found:    (y2 : C^ ->{fresh} (ex$41: caps.Exists) -> C^{ex$41})
    |                    Required: C^ ->{fresh} C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:33:30 --------------------------
 33 |  val _: A^ => (x: C^) => C = y3 // error
    |                              ^^
-   |       Found:    (y3 : A^ ->{fresh} (ex$50: caps.Exists) -> (x: C^) ->{ex$50} (ex$49: caps.Exists) -> C^{ex$49})
-   |       Required: A^ ->{fresh} (ex$53: caps.Exists) -> (x: C^) ->{ex$53} C
+   |       Found:    (y3 : A^ ->{fresh} (ex$44: caps.Exists) -> (x: C^) ->{ex$44} (ex$43: caps.Exists) -> C^{ex$43})
+   |       Required: A^ ->{fresh} (ex$47: caps.Exists) -> (x: C^) ->{ex$47} C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:36:25 --------------------------
 36 |  val _: A^ => C^ => C = y4 // error
    |                         ^^
-   |            Found:    (y4 : A^ ->{fresh} (ex$56: caps.Exists) -> C^ ->{ex$56} (ex$55: caps.Exists) -> C^{ex$55})
-   |            Required: A^ ->{fresh} (ex$59: caps.Exists) -> C^ ->{ex$59} C
+   |            Found:    (y4 : A^ ->{fresh} (ex$50: caps.Exists) -> C^ ->{ex$50} (ex$49: caps.Exists) -> C^{ex$49})
+   |            Required: A^ ->{fresh} (ex$52: caps.Exists) -> C^ ->{ex$52} C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:39:30 --------------------------
 39 |  val _: A^ => (x: C^) -> C = y5 // error
    |                              ^^
-   |                              Found:    (y5 : A^ ->{fresh} (x: C^) -> (ex$61: caps.Exists) -> C^{ex$61})
+   |                              Found:    (y5 : A^ ->{fresh} (x: C^) -> (ex$54: caps.Exists) -> C^{ex$54})
    |                              Required: A^ ->{fresh} (x: C^) -> C
    |
    | longer explanation available when compiling with `-explain`
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/existential-mapping.scala:42:30 --------------------------
 42 |  val _: A^ => (x: C^) => C = y6 // error
    |                              ^^
-   |       Found:    (y6 : A^ ->{fresh} (ex$70: caps.Exists) -> (x: C^) ->{ex$70} (ex$69: caps.Exists) -> C^{ex$69})
-   |       Required: A^ ->{fresh} (ex$73: caps.Exists) -> (x: C^) ->{ex$73} C
+   |       Found:    (y6 : A^ ->{fresh} (ex$63: caps.Exists) -> (x: C^) ->{ex$63} (ex$62: caps.Exists) -> C^{ex$62})
+   |       Required: A^ ->{fresh} (ex$66: caps.Exists) -> (x: C^) ->{ex$66} C
    |
    | longer explanation available when compiling with `-explain`
diff --git a/tests/neg-custom-args/captures/i19330.check b/tests/neg-custom-args/captures/i19330.check
@@ -7,11 +7,11 @@
 22 |  val bad: bar.T = foo(bar) // error
    |                   ^^^^^^^^
    |                   Found:    () => Logger^
-   |                   Required: () ->{fresh} (ex$9: caps.Exists) -> Logger^{ex$9}
+   |                   Required: () ->{fresh} (ex$7: caps.Exists) -> Logger^{ex$7}
    |
    | longer explanation available when compiling with `-explain`
 -- Error: tests/neg-custom-args/captures/i19330.scala:16:14 ------------------------------------------------------------
 16 |    val t: () => Logger^ = () => l // error
    |           ^^^^^^^^^^^^^
-   |           Separation failure: value t's type () => (ex$5: caps.Exists) -> Logger^{ex$5} hides parameter l.
+   |           Separation failure: value t's type () => (ex$3: caps.Exists) -> Logger^{ex$3} hides parameter l.
    |           The parameter needs to be annotated with @consume to allow this.
diff --git a/tests/neg-custom-args/captures/i21401.check b/tests/neg-custom-args/captures/i21401.check
@@ -21,5 +21,5 @@
 -- Error: tests/neg-custom-args/captures/i21401.scala:17:52 ------------------------------------------------------------
 17 |  val x: Boxed[IO^] = leaked[Boxed[IO^], Boxed[IO^] -> Boxed[IO^]](x => x) // error // error
    |                                         ^^^^^^^^^^^^^^^^^^^^^^^^
-   |Type variable X of value leaked cannot be instantiated to Boxed[box IO^] -> (ex$20: caps.Exists) -> Boxed[box IO^{ex$20}] since
-   |the part box IO^{ex$20} of that type captures the root capability `cap`.
+   |Type variable X of value leaked cannot be instantiated to Boxed[box IO^] -> (ex$14: caps.Exists) -> Boxed[box IO^{ex$14}] since
+   |the part box IO^{ex$14} of that type captures the root capability `cap`.
diff --git a/tests/neg-custom-args/captures/i21614.check b/tests/neg-custom-args/captures/i21614.check
@@ -8,7 +8,7 @@
 -- [E007] Type Mismatch Error: tests/neg-custom-args/captures/i21614.scala:15:12 ---------------------------------------
 15 |  files.map(new Logger(_)) // error, Q: can we improve the error message?
    |            ^^^^^^^^^^^^^
-   |Found:    (_$1: box File^{files*}) ->{files*} (ex$16: caps.Exists) -> box Logger{val f: File^{_$1}}^{ex$16.rd, _$1}
+   |Found:    (_$1: box File^{files*}) ->{files*} (ex$14: caps.Exists) -> box Logger{val f: File^{_$1}}^{ex$14.rd, _$1}
    |Required: (_$1: box File^{files*}) => box Logger{val f: File^?}^?
    |
    |Note that the universal capability `cap.rd`

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/i21614.scala:15:12 ---------------------------------------`
`9`	`9`	`15 \| files.map(new Logger(_)) // error, Q: can we improve the error message?`
`10`	`10`	`\| ^^^^^^^^^^^^^`
`11`		`- \|Found: (_$1: box File^{files}) ->{files} (ex$16: caps.Exists) -> box Logger{val f: File^{_$1}}^{ex$16.rd, _$1}`
	`11`	`+ \|Found: (_$1: box File^{files}) ->{files} (ex$14: caps.Exists) -> box Logger{val f: File^{_$1}}^{ex$14.rd, _$1}`
`12`	`12`	`\|Required: (_$1: box File^{files*}) => box Logger{val f: File^?}^?`
`13`	`13`	`\|`
`14`	`14`	\|Note that the universal capability `cap.rd`