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Cannot use $this in string interpolation #5856

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scabug opened this issue May 31, 2012 · 9 comments
Closed

Cannot use $this in string interpolation #5856

scabug opened this issue May 31, 2012 · 9 comments

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@scabug
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@scabug scabug commented May 31, 2012

scala> class C { s"$this" }
<console>:7: error: not found: value this
       class C { s"$this" }
                    ^

scala> class C { val q = this; s"$q" }
defined class C
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@scabug scabug commented May 31, 2012

Imported From: https://issues.scala-lang.org/browse/SI-5856?orig=1
Reporter: @xeno-by
Affected Versions: 2.10.0-M3
Other Milestones: 2.10.0-M6

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@scabug scabug commented May 31, 2012

@xeno-by said:
Same for $null, and nonsense like $yield or $extends.

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@scabug scabug commented Jul 10, 2012

@retronym said:
Also works:

class C { s"${this}" }
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@scabug scabug commented Jul 12, 2012

@dgruntz said:
should $yield and $extends not be allowed? Consider

scala> val `yield` = 1
yield: Int = 1

scala> val `extends` = 2
extends: Int = 2

scala> s"$yield / $extends"
res23: String = 1 / 2

Or do you expect that one should have to write

scala> s"$`yield`"
<console>:1: error: invalid string interpolation
       s"$`yield`"

(which currently issues an error message), as in

scala> s"${`yield` + `extends`}"
res24: String = 3

?

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@scabug scabug commented Jul 12, 2012

@retronym said:
Requiring braces for backquoted idents isn't so onerous, IMO.

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@scabug scabug commented Jul 15, 2012

@dgruntz said:
I am about to fix this bug. I have resolved the problem of keywords and literals like null, false and true. After having read the SIP-11 again, I have also decided not to support backquoted identifiers (but they can still be written in a block).

The final question I have is whether to support $this or not. SIP-11 specifies the simpler escape sequence as the $-sign followed by an identifier consisting only of alphanumeric characters, and that $id is equivalent to ${id}. Strictly speaking, this is not an identifier, but probably it might be useful to write $this in an interpolated string. What is your expectation?

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@scabug scabug commented Jul 16, 2012

@retronym said:
Actually, I would just leave it as is and require the use of braces. If I had to allow one, it would be $this.

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@scabug scabug commented Jul 17, 2012

@dgruntz said:
scala/scala#927
I have enabled $this (as a special case).

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@scabug scabug commented Aug 7, 2012

@dgruntz said:
fixed with scala/scala#927.

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