Update doc pages

Author: odersky

docs/docs/reference/changed-features/operators.md

@@ -92,7 +92,7 @@ The purpose of the `infix` modifier is to achieve consistency across a code base
     can be applied using infix syntax, i.e. `A op B`.
 
  5. To smooth migration to Scala 3.0, alphanumeric operators will only be deprecated from Scala 3.1 onwards,
-or if the `-source 3.1` option is given in Dotty/Scala 3.
+or if the `-source future` option is given in Dotty/Scala 3.
 
 ## The `@targetName` Annotation
 

docs/docs/reference/changed-features/pattern-bindings.md

@@ -15,7 +15,7 @@ val xs: List[Any] = List(1, 2, 3)
 val (x: String) :: _ = xs   // error: pattern's type String is more specialized
                             // than the right-hand side expression's type Any
 ```
-This code gives a compile-time warning in Scala 3.1 (and also in Scala 3.0 under the `-source 3.1` setting) whereas it will fail at runtime with a `ClassCastException` in Scala 2. In Scala 3.1, a pattern binding is only allowed if the pattern is _irrefutable_, that is, if the right-hand side's type conforms to the pattern's type. For instance, the following is OK:
+This code gives a compile-time warning in Scala 3.1 (and also in Scala 3.0 under the `-source future` setting) whereas it will fail at runtime with a `ClassCastException` in Scala 2. In Scala 3.1, a pattern binding is only allowed if the pattern is _irrefutable_, that is, if the right-hand side's type conforms to the pattern's type. For instance, the following is OK:
 ```scala
 val pair = (1, true)
 val (x, y) = pair
@@ -56,4 +56,4 @@ Generator      ::=  [‘case’] Pattern1 ‘<-’ Expr
 
 ## Migration
 
-The new syntax is supported in Scala 3.0. However, to enable smooth cross compilation between Scala 2 and Scala 3, the changed behavior and additional type checks are only enabled under the `-source 3.1` setting. They will be enabled by default in version 3.1 of the language.
+The new syntax is supported in Scala 3.0. However, to enable smooth cross compilation between Scala 2 and Scala 3, the changed behavior and additional type checks are only enabled under the `-source future` setting. They will be enabled by default in version 3.1 of the language.

docs/docs/reference/changed-features/vararg-splices.md

@@ -34,9 +34,9 @@ ParArgumentExprs  ::=  ‘(’ [‘using’] ExprsInParens ‘)’
 ## Compatibility considerations
 
 To enable cross compilation between Scala 2 and Scala 3, the compiler will
-accept both the old and the new syntax. Under the `-source 3.1` setting, an error
+accept both the old and the new syntax. Under the `-source future` setting, an error
 will be emitted when the old syntax is encountered. An automatic rewrite from old
-to new syntax is offered under `-source 3.1-migration`.
+to new syntax is offered under `-source future-migration`.
 
 
 

docs/docs/reference/changed-features/wildcards.md

@@ -31,7 +31,7 @@ A step-by-step migration is made possible with the following measures:
  2. In Scala 3.1, `_` is deprecated in favor of `?` as a name for a wildcard. A `-rewrite` option is
     available to rewrite one to the other.
  3. In Scala 3.2, the meaning of `_` changes from wildcard to placeholder for type parameter.
- 4. The Scala 3.1 behavior is already available today under the `-source 3.1` setting.
+ 4. The Scala 3.1 behavior is already available today under the `-source future` setting.
 
 To smooth the transition for codebases that use kind-projector, we adopt the following measures under the command line
 option `-Ykind-projector`:

docs/docs/reference/contextual/context-bounds.md

@@ -32,7 +32,7 @@ def g[T <: B : C](x: T): R = ...
 To ease migration, context bounds in Dotty map in Scala 3.0 to old-style implicit parameters
 for which arguments can be passed either with a `(using ...)` clause or with a normal application. From Scala 3.1 on, they will map to context parameters instead, as is described above.
 
-If the source version is `3.1` and the `-migration` command-line option is set, any pairing of an evidence
+If the source version is `future` and the `-migration` command-line option is set, any pairing of an evidence
 context parameter stemming from a context bound with a normal argument will give a migration
 warning. The warning indicates that a `(using ...)` clause is needed instead. The rewrite can be
 done automatically under `-rewrite`.

docs/docs/reference/other-new-features/matchable.md

@@ -53,7 +53,7 @@ a type pattern `_: C` it is required that the selector type conforms
 to `Matchable`. If that's not the case a warning is issued. For instance when compiling the example at the start of this section we get:
 
 ```
-> sc ../new/test.scala -source 3.1
+> sc ../new/test.scala -source future
 -- Warning: ../new/test.scala:4:12 ---------------------------------------------
 4 |    case a: Array[Int] => a(0) = 0
   |            ^^^^^^^^^^
@@ -62,7 +62,7 @@ to `Matchable`. If that's not the case a warning is issued. For instance when co
 ```
 
 To allow migration from Scala 2 and cross-compiling
-between Scala 2 and 3 the warning is turned on only for `-source 3.1-migration` or higher.
+between Scala 2 and 3 the warning is turned on only for `-source future-migration` or higher.
 
 `Matchable` is a universal trait with `Any` as its parent class. It is
 extended by both `AnyVal` and `AnyRef`. Since `Matchable` is a supertype of every concrete value or reference class it means that instances of such classes can be matched as before. However, match selectors of the following types will produce a warning:

docs/docs/reference/other-new-features/open-classes.md

@@ -76,4 +76,4 @@ A class that is neither `abstract` nor `open` is similar to a `sealed` class: it
 
 ### Migration
 
-`open` is a new modifier in Scala 3. To allow cross compilation between Scala 2.13 and Scala 3.0 without warnings, the feature warning for ad-hoc extensions is produced only under `-source 3.1`. It will be produced by default from Scala 3.1 on.
+`open` is a new modifier in Scala 3. To allow cross compilation between Scala 2.13 and Scala 3.0 without warnings, the feature warning for ad-hoc extensions is produced only under `-source future`. It will be produced by default from Scala 3.1 on.

docs/docs/usage/language-versions.md

@@ -5,16 +5,18 @@ title: "Language Versions"
 
 The default Scala language version currently supported by the Dotty compiler is `3.0`. There are also other language versions that can be specified instead:
 
- - `3.1`: A preview of changes introduced in the next version after 3.0. Some Scala-2 specific idioms will be dropped in this version. The feature set supported by this version will be refined over time  as we approach its release.
-
  - `3.0-migration`: Same as `3.0` but with a Scala 2 compatibility mode that helps moving Scala 2.13 sources over to Scala 3. In particular, it
 
     - flags some Scala 2 constructs that are disallowed in Scala 3 as migration warnings instead of hard errors,
     - changes some rules to be more lenient and backwards compatible with Scala 2.13
     - gives some additional warnings where the semantics has changed between Scala 2.13 and 3.0
     - in conjunction with `-rewrite`, offer code rewrites from Scala 2.13 to 3.0.
 
- - `3.1-migration`: Same as `3.1` but with additional helpers to migrate from `3.0`. Similarly to the helpers available under `3.0-migration`, these include migration warnings and optional rewrites.
+ - `future`: A preview of changes introduced in the next versions after 3.0. In the doc pages here we refer to the language version with these changes as `3.1`, but it might be that some of these changes will be rolled out in later `3.x` versions.
+
+ Some Scala-2 specific idioms will be dropped in this version. The feature set supported by this version will be refined over time  as we approach its release.
+
+ - `future-migration`: Same as `future` but with additional helpers to migrate from `3.0`. Similarly to the helpers available under `3.0-migration`, these include migration warnings and optional rewrites.
 
 There are two ways to specify a language version.
 
@@ -23,9 +25,10 @@ There are two ways to specify a language version.
 
 ```scala
 package p
-import scala.language.`3.1`
+import scala.language.`future-migration`
 
 class C { ... }
 ```
 
-Language imports supersede command-line settings in the compilation units where they are specified. Only one language import is allowed in a compilation unit, and it must come before any definitions in that unit.
+Language imports supersede command-line settings in the compilation units where they are specified. Only one language import specifying a source version is allowed in a compilation unit, and it must come before any definitions in that unit.
+