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Clarify implicit in class params #9494

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scabug opened this issue Sep 29, 2015 · 4 comments · Fixed by scala/scala#10568
Closed

Clarify implicit in class params #9494

scabug opened this issue Sep 29, 2015 · 4 comments · Fixed by scala/scala#10568
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@scabug
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scabug commented Sep 29, 2015

It's not obvious that keyword implicit means "implicit parameter list" when it is not the first token in a parameter list.

This matters for class parameters, which may have other modifiers.

scala> class C(protected implicit val s: String, i: Int)
defined class C

scala> implicit val z = "hello"
z: String = hello

scala> new C()
<console>:13: error: could not find implicit value for parameter i: Int
       new C()
       ^

"What does 'override implicit' mean?" is a good ice breaker for a job interview.
@scabug
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scabug commented Sep 29, 2015

Imported From: https://issues.scala-lang.org/browse/SI-9494?orig=1
Reporter: @som-snytt
Affected Versions: 2.11.7

@scabug
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scabug commented Feb 14, 2017

@som-snytt said (edited on Feb 14, 2017 8:31:39 PM UTC):
I'd prefer leading leading implicit to mean implicit param section.

For def f(implicit x: X) to mean locally implicit, just

def f(x: X) { implicit val xx = x }

Somewhere, in the distant past, retronym said this was too finicky, but maybe the discussion is worth taking up again.

@scabug
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scabug commented Feb 15, 2017

Stu Hood (stuhood) said:
Highly relevant as well: scala/scala3#1260

This was referenced Apr 7, 2017
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@scala scala deleted a comment from scabug Oct 10, 2017
@som-snytt som-snytt self-assigned this Sep 15, 2023
@som-snytt som-snytt removed their assignment Oct 16, 2023
@som-snytt som-snytt mentioned this issue Oct 16, 2023
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@som-snytt
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It's a beloved wart.

Recent discussion of implicit + default had me rereading the section.

@SethTisue SethTisue added this to the Backlog milestone Oct 16, 2023
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Clarify implicit params som-snytt/scala
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@SethTisue @som-snytt @scabug