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Add compiletime.ops.string.CharAt #14431

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merged 2 commits into from
May 20, 2022
Merged

Add compiletime.ops.string.CharAt #14431

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d8e6355
Add compiletime.ops.string.CharAt
OlivierBlanvillain Feb 8, 2022
96a4c1b
Update annotations
OlivierBlanvillain May 17, 2022
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/core/Definitions.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1168,7 +1168,7 @@ class Definitions {
)
private val compiletimePackageBooleanTypes: Set[Name] = Set(tpnme.Not, tpnme.Xor, tpnme.And, tpnme.Or)
private val compiletimePackageStringTypes: Set[Name] = Set(
tpnme.Plus, tpnme.Length, tpnme.Substring, tpnme.Matches
tpnme.Plus, tpnme.Length, tpnme.Substring, tpnme.Matches, tpnme.CharAt
)
private val compiletimePackageOpTypes: Set[Name] =
Set(tpnme.S)
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1 change: 1 addition & 0 deletions compiler/src/dotty/tools/dotc/core/StdNames.scala
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Expand Up @@ -234,6 +234,7 @@ object StdNames {
final val Plus: N = "+"
final val S: N = "S"
final val Substring: N = "Substring"
final val CharAt: N = "CharAt"
final val Times: N = "*"
final val ToInt: N = "ToInt"
final val ToLong: N = "ToLong"
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2 changes: 2 additions & 0 deletions compiler/src/dotty/tools/dotc/core/Types.scala
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Expand Up @@ -4439,6 +4439,8 @@ object Types {
case tpnme.Matches => constantFold2(stringValue, _ matches _)
case tpnme.Substring =>
constantFold3(stringValue, intValue, intValue, (s, b, e) => s.substring(b, e))
case tpnme.CharAt =>
constantFold2AB(stringValue, intValue, _ charAt _)
case _ => None
} else if (owner == defn.CompiletimeOpsBooleanModuleClass) name match {
case tpnme.Not => constantFold1(boolValue, x => !x)
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4 changes: 0 additions & 4 deletions library/src/scala/compiletime/ops/any.scala
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@@ -1,8 +1,6 @@
package scala.compiletime
package ops

import annotation.experimental

object any:
/** Equality comparison of two singleton types.
* ```scala
Expand Down Expand Up @@ -41,7 +39,6 @@ object any:
* ```
* @syntax markdown
*/
@experimental
type IsConst[X] <: Boolean

/** String conversion of a constant singleton type.
Expand All @@ -51,5 +48,4 @@ object any:
* ```
* @syntax markdown
*/
@experimental
type ToString[+X] <: String
3 changes: 0 additions & 3 deletions library/src/scala/compiletime/ops/double.scala
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@@ -1,9 +1,6 @@
package scala.compiletime
package ops

import scala.annotation.experimental

@experimental
object double:
/** Addition of two `Double` singleton types.
* ```scala
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3 changes: 0 additions & 3 deletions library/src/scala/compiletime/ops/float.scala
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@@ -1,9 +1,6 @@
package scala.compiletime
package ops

import scala.annotation.experimental

@experimental
object float:
/** Addition of two `Float` singleton types.
* ```scala
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6 changes: 0 additions & 6 deletions library/src/scala/compiletime/ops/int.scala
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@@ -1,8 +1,6 @@
package scala.compiletime
package ops

import annotation.experimental

object int:
/** Successor of a natural number where zero is the type 0 and successors are reduced as if the definition was:
*
Expand Down Expand Up @@ -192,7 +190,6 @@ object int:
* ```
* @syntax markdown
*/
@experimental
type ToLong[+X <: Int] <: Long

/** Float conversion of an `Int` singleton type.
Expand All @@ -201,7 +198,6 @@ object int:
* ```
* @syntax markdown
*/
@experimental
type ToFloat[+X <: Int] <: Float

/** Double conversion of an `Int` singleton type.
Expand All @@ -210,7 +206,6 @@ object int:
* ```
* @syntax markdown
*/
@experimental
type ToDouble[+X <: Int] <: Double

/** Number of zero bits preceding the highest-order ("leftmost")
Expand All @@ -225,5 +220,4 @@ object int:
* ```
* @syntax markdown
*/
@experimental
type NumberOfLeadingZeros[+X <: Int] <: Int
3 changes: 0 additions & 3 deletions library/src/scala/compiletime/ops/long.scala
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Original file line number Diff line number Diff line change
@@ -1,9 +1,6 @@
package scala.compiletime
package ops

import scala.annotation.experimental

@experimental
object long:
/** Successor of a natural number where zero is the type 0 and successors are reduced as if the definition was:
*
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15 changes: 10 additions & 5 deletions library/src/scala/compiletime/ops/string.scala
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Original file line number Diff line number Diff line change
@@ -1,8 +1,6 @@
package scala.compiletime
package ops

import scala.annotation.experimental

object string:
/** Concatenation of two `String` singleton types.
* ```scala
Expand All @@ -18,7 +16,6 @@ object string:
* ```
* @syntax markdown
*/
@experimental
type Length[+X <: String] <: Int

/** Substring of a `String` singleton type, with a singleton type
Expand All @@ -31,7 +28,6 @@ object string:
* ```
* @syntax markdown
*/
@experimental
type Substring[+S <: String, +IBeg <: Int, +IEnd <: Int] <: String

/** Tests if this `String` singleton type matches the given
Expand All @@ -41,5 +37,14 @@ object string:
* ```
* @syntax markdown
*/
@experimental
type Matches[+S <: String, +Regex <: String] <: Boolean

/** Returns the Char type at the specified index.
* An index ranges from 0 to Length[S] - 1. The first Char of
* the sequence is at index 0, the next at index 1, and so on.
* ```scala
* val c: CharAt["hello", 0] = 'h'
* ```
* @syntax markdown
*/
type CharAt[+S <: String, +Idx <: Int] <: Char
19 changes: 19 additions & 0 deletions tests/neg/singleton-ops-string.scala
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Expand Up @@ -15,4 +15,23 @@ object Test {

val t9: Matches["hamburger", "ham.*"] = true
val t10: Matches["hamburger", "ham.*"] = false // error

val t11: CharAt["String", 0] = 'S'
val t12: CharAt["String", 1] = 't'
val t13: CharAt["String", 2] = '!' // error
// ^^^
// Found: ('!' : Char)
// Required: ('r' : Char)
val t14: CharAt["String", 3] = '!' // error
// ^^^
// Found: ('!' : Char)
// Required: ('i' : Char)
val t15: CharAt["String", 4] = 'n'
val t16: CharAt["String", 5] = 'g'
val t17: CharAt["String", 6] = '!' // error
// ^
// String index out of range: 6
val t18: CharAt["String", -1] = '?' // error
// ^
// String index out of range: -1
}
17 changes: 0 additions & 17 deletions tests/run-custom-args/tasty-inspector/stdlibExperimentalDefinitions.scala
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Expand Up @@ -32,23 +32,6 @@ val experimentalDefinitionInLibrary = Set(
"scala.annotation.MainAnnotation",
"scala.annotation.MainAnnotation$",

//// New APIs: compiletime.ops
// Can be stabilized in 3.3.0 or later.
// Needs user feedback
"scala.compiletime.ops.any$.IsConst",
"scala.compiletime.ops.any$.ToString",
"scala.compiletime.ops.double", "scala.compiletime.ops.double$",
"scala.compiletime.ops.float",
"scala.compiletime.ops.float$",
"scala.compiletime.ops.int$.NumberOfLeadingZeros",
"scala.compiletime.ops.int$.ToDouble",
"scala.compiletime.ops.int$.ToFloat",
"scala.compiletime.ops.int$.ToLong",
"scala.compiletime.ops.long", "scala.compiletime.ops.long$",
"scala.compiletime.ops.string$.Length",
"scala.compiletime.ops.string$.Matches",
"scala.compiletime.ops.string$.Substring",
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@mbovel didn't we say that these operations would stay experimental?

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See #14431 (comment); when we first discussed it, I hadn't realized that some compile-time operations were already stable. Given this, I re-discussed it with Martin and he agreed to make these operations stable as well.

The argument is that operations on long, float and double are exactly the same as the ones on int which are already stable, so it makes sense to make them stable as well. In term of maintenance, this doesn't change much.

Including operations on strings as well makes sense are they are important building blocks to do anything useful with strings at the type-level (Olivier used them for his work on regular expressions for example).


//// New APIs: Mirror
// Can be stabilized in 3.2.0 or later.
"scala.deriving.Mirror$.fromTuple", // Probably for 3.2.0
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