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Feb 27, 2020
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doc(operators): typo and add import to examples #8367

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doc(operators): typo and add import to examples
robstoll Feb 24, 2020
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doc(operators): wrap one more annotation
robstoll Feb 26, 2020
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14 changes: 10 additions & 4 deletions docs/docs/reference/changed-features/operators.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@ Furthermore, a syntax change allows infix operators to be written on the left in

An `@alpha` annotation on a method definition defines an alternate name for the implementation of that method: Example:
```scala
import scala.annotation.alpha

object VecOps {
@alpha("append") def (xs: Vec[T]) ++= [T] (ys: Vec[T]): Vec[T] = ...
}
Expand Down Expand Up @@ -47,7 +49,7 @@ The `@alpha` annotation serves a dual purpose:
5. Definitions with names in backticks that are not legal host platform names
should have an `@alpha` annotation. Lack of such an annotation will raise a deprecation warning.

6. @alpha annotations must agree: If two definitions are members of an object or class with the same name and matching types, then either none of them has an `@alpha` annotation, or both have `@alpha` annotations with the same name.
6. `@alpha` annotations must agree: If two definitions are members of an object or class with the same name and matching types, then either none of them has an `@alpha` annotation, or both have `@alpha` annotations with the same name.

7. There must be a one-to-one relationship between external and internal names:
If two definitions are members of an object or class with matching types and both have `@alpha` annotations with the same external name, then their internal method names must also be the same.
Expand All @@ -56,6 +58,8 @@ The `@alpha` annotation serves a dual purpose:

An `@infix` annotation on a method definition allows using the method as an infix operation. Example:
```scala
import scala.annotation.alpha

trait MultiSet[T] {

@infix
Expand All @@ -70,13 +74,15 @@ trait MultiSet[T] {
val s1, s2: MultiSet[Int]

s1 union s2 // OK
s1 `union` s2 // also OK but unusual
s1.union(s2) // also OK

s1.difference(s2) // OK
s1 `difference` s2 // OK
s1 difference s2 // gives a deprecation warning

s1 * s2 // OK
s1 `*` s2 // also OK, but unusual
s1.*(s2) // also OK, but unusual
```
Infix operations involving alphanumeric operators are deprecated, unless
Expand All @@ -91,7 +97,7 @@ any unicode character `c` for which `java.lang.Character.isIdentifierPart(c)` re

Infix operations involving symbolic operators are always allowed, so `@infix` is redundant for methods with symbolic names.

The @infix annotation can also be given to a type:
The `@infix` annotation can also be given to a type:
```
@infix type or[X, Y]
val x: String or Int = ...
Expand All @@ -118,15 +124,15 @@ The purpose of the `@infix` annotation is to achieve consistency across a code b
@infix def (x: A) op (y1: B, y2: B): R // error: two parameters
```

4. @infix annotations can also be given to type, trait or class definitions that have exactly two type parameters. An infix type like
4. `@infix` annotations can also be given to type, trait or class definitions that have exactly two type parameters. An infix type like

```scala
@infix type op[X, Y]
```

can be applied using infix syntax, i.e. `A op B`.

5. To smooth migration to Scala 3.0, alphanumeric operations will only be deprecated from Scala 3.1 onwards,
5. To smooth migration to Scala 3.0, alphanumeric operators will only be deprecated from Scala 3.1 onwards,
or if the `-strict` option is given in Dotty/Scala 3.

## Syntax Change
Expand Down