Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit73b935c

Browse files
authored
Refine implicit search fallbacks for better ClassTag handling (#23532)
 1. Don't use FullyDefinedType when synthesizing ClassTagsIt's not necessary to instantiate all type variables, deeply, since weare only interested in the outermost shape. Also, that way we do notinstantiate to Nothing, which is something difficult to recover from.This step is necessary to enable (2) 2. Constrain by deepening expected result types in more implicitsearchesWe used to look at the deep expected type when the result of an implicitwas ambiguous. This could add more constraints which could resolve the ambiguity.We now do the same also if the search type has uninstantiated typevariables. In thatcase, consulting more context might further constrain type variables,which might in turn enlarge the implicit scope so that a solution can be found.Fixes#23526
2 parentsfb66af2 +45f7ef6 commit73b935c

File tree

5 files changed

+45
-17
lines changed

5 files changed

+45
-17
lines changed

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

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -445,7 +445,9 @@ object Inferencing {
445445
}
446446

447447
/** The instantiation decision for given poly param computed from the constraint.*/
448-
enumDecision {caseMin;caseMax;caseToMax;caseSkip;caseFail }
448+
enumDecision:
449+
caseMin,Max,ToMax,Skip,Fail
450+
449451
privatedefinstDecision(tvar:TypeVar,v:Int,minimizeSelected:Boolean,ifBottom:IfBottom)(usingContext):Decision=
450452
importDecision.*
451453
valdirection= instDirection(tvar.origin)

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

Lines changed: 12 additions & 8 deletions
Original file line numberDiff line numberDiff line change
@@ -29,17 +29,21 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
2929
privatetypeSpecialHandlers=List[(ClassSymbol,SpecialHandler)]
3030

3131
valsynthesizedClassTag:SpecialHandler= (formal, span)=>
32-
definstArg(tp:Type):Type= tp.stripTypeVarmatch
33-
// Special case to avoid instantiating `Int & S` to `Int & Nothing` in
34-
// i16328.scala. The intersection comes from an earlier instantiation
35-
// to an upper bound.
36-
// The dual situation with unions is harder to trigger because lower
37-
// bounds are usually widened during instantiation.
32+
definstArg(tp:Type):Type= tp.dealiasmatch
3833
casetp:AndOrTypeif tp.tp1=:= tp.tp2=>
34+
// Special case to avoid instantiating `Int & S` to `Int & Nothing` in
35+
// i16328.scala. The intersection comes from an earlier instantiation
36+
// to an upper bound.
37+
// The dual situation with unions is harder to trigger because lower
38+
// bounds are usually widened during instantiation.
3939
instArg(tp.tp1)
40+
casetvar:TypeVarif ctx.typerState.constraint.contains(tvar)=>
41+
instArg(
42+
if tvar.hasLowerBoundthen tvar.instantiate(fromBelow=true)
43+
elseif tvar.hasUpperBoundthen tvar.instantiate(fromBelow=false)
44+
elseNoType)
4045
case _=>
41-
if isFullyDefined(tp,ForceDegree.all)then tp
42-
elseNoType// this happens in tests/neg/i15372.scala
46+
tp
4347

4448
valtag= formal.argInfosmatch
4549
case arg::Nil=>

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

Lines changed: 14 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -4358,12 +4358,23 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
43584358
implicitArgs(formals2, argIndex+1, pt)
43594359

43604360
valarg= inferImplicitArg(formal, tree.span.endPos)
4361+
4362+
defcanProfitFromMoreConstraints=
4363+
arg.tpe.isInstanceOf[AmbiguousImplicits]
4364+
// ambiguity could be decided by more constraints
4365+
||!isFullyDefined(formal,ForceDegree.none)
4366+
// more context might constrain type variables which could make implicit scope larger
4367+
43614368
arg.tpematch
4362-
casefailed:AmbiguousImplicits=>
4369+
casefailed:SearchFailureTypeif canProfitFromMoreConstraints=>
43634370
valpt1= pt.deepenProtoTrans
43644371
if (pt1 `ne` pt)&& (pt1 ne sharpenedPt)&& constrainResult(tree.symbol, wtp, pt1)
4365-
then implicitArgs(formals, argIndex, pt1)
4366-
else arg:: implicitArgs(formals1, argIndex+1, pt1)
4372+
thenreturn implicitArgs(formals, argIndex, pt1)
4373+
case _=>
4374+
4375+
arg.tpematch
4376+
casefailed:AmbiguousImplicits=>
4377+
arg:: implicitArgs(formals1, argIndex+1, pt)
43674378
casefailed:SearchFailureType=>
43684379
lazyvaldefaultArg= findDefaultArgument(argIndex)
43694380
.showing(i"default argument: for$formal,$tree,$argIndex =$result", typr)

‎tests/neg/i9568.check

Lines changed: 2 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -4,13 +4,10 @@
44
| No given instance of type => Monad[F] was found for parameter ev of method blaMonad in object Test.
55
| I found:
66
|
7-
| Test.blaMonad[F², S](Test.blaMonad[F³, S²])
7+
| Test.blaMonad[F², S]
88
|
9-
| But method blaMonad in object Test does not match type => Monad[F²]
9+
| But method blaMonad in object Test does not match type => Monad[F]
1010
|
1111
| where: F is a type variable with constraint <: [_] =>> Any
1212
| F² is a type variable with constraint <: [_] =>> Any
13-
| F³ is a type variable with constraint <: [_] =>> Any
14-
| S is a type variable
15-
| S² is a type variable
1613
| .

‎tests/pos/i23526.scala

Lines changed: 14 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,14 @@
1+
traitB[-A,+To] {
2+
defaddOne(e:A):this.type=this
3+
defres():To
4+
}
5+
6+
classCol[A]
7+
8+
objectFactory {
9+
defnewB[A](using reflect.ClassTag[A])=newB[A,Col[A]] {defres():Col[A]=newCol[A] }
10+
}
11+
12+
deftest=
13+
vala=Factory.newB.addOne(1).res()
14+
valb= collection.immutable.ArraySeq.newBuilder.addOne(1).result()

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp