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Present aligned dependent functions as generic functions
Aligning an expected function type to be dependent gives the false expression that we could have the parameter in a local capture. To avoid that misinterpretation, convert an aligned dependent function as the expected type back to a generic functions before displaying it in the error message.
1 parent 7a3550f commit b2f30a8

20 files changed

+50
-42
lines changed

‎compiler/src/dotty/tools/dotc/cc/CheckCaptures.scala

Lines changed: 12 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1337,6 +1337,7 @@ class CheckCaptures extends Recheck, SymTransformer:
13371337
inline def testAdapted(actual: Type, expected: Type, tree: Tree, addenda: Addenda)
13381338
(fail: (Tree, Type, Addenda) => Unit)(using Context): Type =
13391339
var expected1 = alignDependentFunction(expected, actual.stripCapturing)
1340+
val falseDeps = expected1 ne expected
13401341
val actualBoxed = adapt(actual, expected1, tree)
13411342
//println(i"check conforms $actualBoxed <<< $expected1")
13421343

@@ -1346,6 +1347,7 @@ class CheckCaptures extends Recheck, SymTransformer:
13461347
TypeComparer.compareResult(isCompatible(actualBoxed, expected1)) match
13471348
case TypeComparer.CompareResult.Fail(notes) =>
13481349
capt.println(i"conforms failed for ${tree}: $actual vs $expected")
1350+
if falseDeps then expected1 = unalignFunction(expected1)
13491351
fail(tree.withType(actualBoxed), expected1,
13501352
addApproxAddenda(addenda ++ errorNotes(notes), expected1))
13511353
actual
@@ -1360,10 +1362,8 @@ class CheckCaptures extends Recheck, SymTransformer:
13601362
/** Turn `expected` into a dependent function when `actual` is dependent. */
13611363
private def alignDependentFunction(expected: Type, actual: Type)(using Context): Type =
13621364
def recur(expected: Type): Type = expected.dealias match
1363-
case expected0 @ CapturingType(eparent, refs) =>
1364-
val eparent1 = recur(eparent)
1365-
if eparent1 eq eparent then expected
1366-
else CapturingType(eparent1, refs, boxed = expected0.isBoxed)
1365+
case expected @ CapturingType(eparent, refs) =>
1366+
expected.derivedCapturingType(recur(eparent), refs)
13671367
case expected @ defn.FunctionOf(args, resultType, isContextual)
13681368
if defn.isNonRefinedFunction(expected) =>
13691369
actual match
@@ -1381,6 +1381,14 @@ class CheckCaptures extends Recheck, SymTransformer:
13811381
case _ => expected
13821382
recur(expected)
13831383

1384+
private def unalignFunction(tp: Type)(using Context): Type = tp match
1385+
case tp @ CapturingType(parent, refs) =>
1386+
tp.derivedCapturingType(unalignFunction(parent), refs)
1387+
case defn.RefinedFunctionOf(mt) =>
1388+
mt.toFunctionType(alwaysDependent = false)
1389+
case _ =>
1390+
tp
1391+
13841392
/** For the expected type, implement the rule outlined in #14390:
13851393
* - when checking an expression `a: Ta^Ca` against an expected type `Te^Ce`,
13861394
* - where the capture set `Ce` contains Cls.this,

‎tests/neg-custom-args/captures/box-adapt-cases.check

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
8 | x.value(cap => cap.use()) // error, was OK
33
| ^^^^^^^^^^^^^^^^
44
| Found: (cap: box Cap^?) => Int
5-
| Required: (cap: box Cap^) =>² Int
5+
| Required: box Cap^ =>² Int
66
|
77
| where: => refers to the universal root capability
88
| =>² refers to a fresh root capability created in method test1
@@ -13,13 +13,13 @@
1313
15 | x.value(cap => cap.use()) // error
1414
| ^^^^^^^^^^^^^^^^
1515
| Found: (cap: box Cap^{io}) ->{io} Int
16-
| Required: (cap: box Cap^{io}) -> Int
16+
| Required: box Cap^{io} -> Int
1717
|
1818
| longer explanation available when compiling with `-explain`
1919
-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/box-adapt-cases.scala:29:10 ------------------------------
2020
29 | x.value(cap => cap.use()) // error
2121
| ^^^^^^^^^^^^^^^^
2222
| Found: (cap: box Cap^?) ->{io, fs} Int
23-
| Required: (cap: box Cap^{io, fs}) ->{io} Int
23+
| Required: box Cap^{io, fs} ->{io} Int
2424
|
2525
| longer explanation available when compiling with `-explain`

‎tests/neg-custom-args/captures/depfun-reach.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
12 | List(() => op.foreach((f,g) => { f(); g() })) // error (???)
33
| ^^^^^^^^^^^^^^^^^^^^
44
|Found: (x$1: (box () ->? Unit, box () ->? Unit)^?) ->? Unit
5-
|Required: (x$1: (box () ->{op*} Unit, box () ->{op*} Unit)) => Unit
5+
|Required: ((box () ->{op*} Unit, box () ->{op*} Unit)) => Unit
66
|
77
|where: => refers to a fresh root capability created in anonymous function of type (): Unit when checking argument to parameter op of method foreach
88
|

‎tests/neg-custom-args/captures/effect-swaps-explicit.check

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -19,21 +19,21 @@
1919
| ^
2020
|Found: (contextual$9: boundary.Label[box Result[box Future[box T^?]^?, box E^?]^?]^) ?->{fr, async}
2121
| box Future[box T^?]^{fr, contextual$9}
22-
|Required: (contextual$9: boundary.Label[Result[box Future[box T^?]^?, box E^?]]^) ?=> box Future[box T^?]^?
22+
|Required: (boundary.Label[Result[box Future[box T^?]^{fr, async}, box E^?]]^) ?=> box Future[box T^?]^{fr, async}
2323
|
2424
|where: ?=> refers to a fresh root capability created in method fail4 when checking argument to parameter body of method make
2525
| ^ refers to the universal root capability
2626
|
2727
|Note that reference contextual$9.type
28-
|cannot be included in outer capture set ?
28+
|cannot be included in outer capture set {fr, async}
2929
70 | fr.await.ok
3030
|
3131
| longer explanation available when compiling with `-explain`
3232
-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/effect-swaps-explicit.scala:73:35 ------------------------
3333
73 | Result.make[Future[T], E]: lbl ?=> // error: type mismatch
3434
| ^
3535
|Found: (lbl: boundary.Label[box Result[box Future[box T^?]^?, box E^?]^?]^) ?->{fr, async} Future[box T^?]^{fr, lbl}
36-
|Required: (lbl: boundary.Label[Result[Future[T], E]]^) ?=> Future[T]
36+
|Required: (boundary.Label[Result[Future[T], E]]^) ?=> Future[T]
3737
|
3838
|where: ?=> refers to a fresh root capability created in method fail5 when checking argument to parameter body of method make
3939
| ^ refers to the universal root capability

‎tests/neg-custom-args/captures/effect-swaps.check

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -19,21 +19,21 @@
1919
| ^
2020
|Found: (contextual$9: boundary.Label[box Result[box Future[box T^?]^?, box E^?]^?]^{cap.rd}) ?->{fr, async}
2121
| box Future[box T^?]^{fr, contextual$9}
22-
|Required: (contextual$9: boundary.Label[Result[box Future[box T^?]^?, box E^?]]^{cap.rd}) ?=> box Future[box T^?]^?
22+
|Required: (boundary.Label[Result[box Future[box T^?]^{fr, async}, box E^?]]^{cap.rd}) ?=> box Future[box T^?]^{fr, async}
2323
|
2424
|where: ?=> refers to a fresh root capability created in method fail4 when checking argument to parameter body of method make
2525
| cap is the universal root capability
2626
|
2727
|Note that reference contextual$9.type
28-
|cannot be included in outer capture set ?
28+
|cannot be included in outer capture set {fr, async}
2929
70 | fr.await.ok
3030
|
3131
| longer explanation available when compiling with `-explain`
3232
-- [E007] Type Mismatch Error: tests/neg-custom-args/captures/effect-swaps.scala:73:35 ---------------------------------
3333
73 | Result.make[Future[T], E]: lbl ?=> // error: type mismatch
3434
| ^
3535
|Found: (lbl: boundary.Label[box Result[box Future[box T^?]^?, box E^?]^?]^{cap.rd}) ?->{fr, async} Future[box T^?]^{fr, lbl}
36-
|Required: (lbl: boundary.Label[Result[Future[T], E]]^{cap.rd}) ?=> Future[T]
36+
|Required: (boundary.Label[Result[Future[T], E]]^{cap.rd}) ?=> Future[T]
3737
|
3838
|where: ?=> refers to a fresh root capability created in method fail5 when checking argument to parameter body of method make
3939
| cap is the universal root capability

‎tests/neg-custom-args/captures/heal-tparam-cs.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -50,7 +50,7 @@
5050
44 | io => () => io.use() // error
5151
| ^^^^^^^^^^^^^^^^^^^^
5252
| Found: (io: Capp^) ->? () ->{io} Unit
53-
| Required: (io: Capp^) -> () -> Unit
53+
| Required: Capp^ -> () -> Unit
5454
|
5555
| where: ^ refers to the universal root capability
5656
|

‎tests/neg-custom-args/captures/i16226.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
13 | (ref1, f1) => map[A, B](ref1, f1) // error
33
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
44
|Found: (ref1: LazyRef[box A^?]{val elem: () => A^?}^{io}, f1: A^? => B^?) ->? LazyRef[box B^?]{val elem: () =>² B^?}^{f1, ref1}
5-
|Required: (ref1: LazyRef[A]^{io}, f1: A => B) =>³ LazyRef[B]^
5+
|Required: (LazyRef[A]^{io}, A => B) =>³ LazyRef[B]^
66
|
77
|where: => refers to the universal root capability
88
| =>² refers to a root capability associated with the result type of (ref1: LazyRef[box A^?]{val elem: () => A^?}^{io}, f1: A^? => B^?): LazyRef[box B^?]{val elem: () =>² B^?}^{f1, ref1}

‎tests/neg-custom-args/captures/i21401.check

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@
1616
15 | val a = usingIO[IO^](x => x) // error // error
1717
| ^^^^^^
1818
|Found: (x: IO^) ->? box IO^{x}
19-
|Required: (x: IO^) => box IO^²
19+
|Required: IO^ => box IO^²
2020
|
2121
|where: => refers to a fresh root capability created in value a when checking argument to parameter op of method usingIO
2222
| ^ refers to the universal root capability
@@ -48,7 +48,7 @@
4848
17 | val x: Boxed[IO^] = leaked[Boxed[IO^], Boxed[IO^] -> Boxed[IO^]](x => x) // error // error // error
4949
| ^^^^^^
5050
| Found: (x: Boxed[box IO^]^?) ->? Boxed[box IO^{x*}]^?
51-
| Required: (x: Boxed[box IO^]) -> Boxed[box IO^²]
51+
| Required: Boxed[box IO^] -> Boxed[box IO^²]
5252
|
5353
| where: ^ refers to the universal root capability
5454
| ^² refers to a fresh root capability created in value x²

‎tests/neg-custom-args/captures/i21614.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,7 @@
1111
15 | files.map(new Logger(_)) // error, Q: can we improve the error message?
1212
| ^^^^^^^^^^^^^
1313
|Found: (_$1: box File^{files*}) ->{files*} box Logger{val f: File^{_$1}}^{cap.rd, _$1}
14-
|Required: (_$1: box File^{files*}) => box Logger{val f: File^?}^?
14+
|Required: box File^{files*} => box Logger{val f: File^?}^?
1515
|
1616
|where: => refers to a fresh root capability created in method mkLoggers2 when checking argument to parameter f of method map
1717
| cap is a root capability associated with the result type of (_$1: box File^{files*}): box Logger{val f: File^{_$1}}^{cap.rd, _$1}

‎tests/neg-custom-args/captures/i21920.check

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2,7 +2,7 @@
22
34 | val cell: Cell[File] = File.open(f => Cell(() => Seq(f))) // error
33
| ^^^^^^^^^^^^^^^^^^^^^^^
44
|Found: (f: File^?) ->? box Cell[box File^?]{val head: () ->? IterableOnce[box File^?]^?}^?
5-
|Required: (f: File^) => box Cell[box File^?]{val head: () ->? IterableOnce[box File^?]^?}^?
5+
|Required: File^ => box Cell[box File^?]{val head: () ->? IterableOnce[box File^?]^?}^?
66
|
77
|where: => refers to a fresh root capability created in value cell when checking argument to parameter f of method open
88
| ^ refers to the universal root capability

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