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Singleton-type inference in method return type #9023

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scabug opened this issue Dec 1, 2014 · 5 comments
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Singleton-type inference in method return type #9023

scabug opened this issue Dec 1, 2014 · 5 comments
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@adriaanm
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duplicate enhancement infer language spec

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@scabug
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scabug commented Dec 1, 2014

According to SLS, a type in value definition(in method definition, too) is not determined by the local type inference, so

scala> val p = "hello"
p: String = hello

scala> val v = p : p.type
v: p.type = hello

seems ok, but

scala> def v = p : p.type
v: String

. Or SLS is wrong?
@scabug
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scabug commented Dec 1, 2014

Imported From: https://issues.scala-lang.org/browse/SI-9023?orig=1
Reporter: @okomok
Affected Versions: 2.11.4

@scabug
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scabug commented Dec 1, 2014

@retronym said:
Type inference of vals, vars, and defs widen the type of the RHS. The rules are not (yet) specified.

We are reviewing this area in adriaanm/scala#12 and will specify them as part of that SIP.

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scabug commented Dec 3, 2014

@okomok said:
So

scala> val v = p : p.type
v: p.type = hello

will be a bug with the upcoming specifications?

@scabug
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scabug commented Dec 3, 2014

@okomok said:

val p = "hello"
val q = p : p.type
implicitly[q.type =:= p.type]

compiles (wrongly?).

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scabug commented Dec 5, 2014

@okomok said:
After all, this ticket seems a duplicate of #6767.
Thanks.

@scabug scabug closed this as completed Nov 11, 2015
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