Sync language.scala with main and backport "Add tests for context bounds migration" (#19515)

Backports #19510

Author: Kordyjan

compiler/src/dotty/tools/dotc/config/MigrationVersion.scala

@@ -33,7 +33,7 @@ object MigrationVersion:
 
   val AscriptionAfterPattern = MigrationVersion(`3.3`, future)
 
-  val ExplicitContextBoundArgument = MigrationVersion(`3.4`, future)
+  val ExplicitContextBoundArgument = MigrationVersion(`3.4`, `3.5`)
 
   val AlphanumericInfix = MigrationVersion(`3.4`, future)
   val RemoveThisQualifier = MigrationVersion(`3.4`, future)

library/src/scala/runtime/stdLibPatches/language.scala

@@ -246,6 +246,20 @@ object language:
   @compileTimeOnly("`3.4` can only be used at compile time in import statements")
   object `3.4`
 
+  /** Set source version to 3.5-migration.
+    *
+    * @see [[https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html]]
+    */
+  @compileTimeOnly("`3.5-migration` can only be used at compile time in import statements")
+  object `3.5-migration`
+
+  /** Set source version to 3.5
+    *
+    * @see [[https://docs.scala-lang.org/scala3/guides/migration/compatibility-intro.html]]
+    */
+  @compileTimeOnly("`3.5` can only be used at compile time in import statements")
+  object `3.5`
+
   // !!! Keep in sync with dotty.tools.dotc.config.SourceVersion !!!
   // Also add tests in `tests/pos/source-import-3-x.scala` and `tests/pos/source-import-3-x-migration.scala`
 

tests/neg/context-bounds-migration-3.5.check

@@ -0,0 +1,6 @@
+-- Error: tests/neg/context-bounds-migration-3.5.scala:9:2 -------------------------------------------------------------
+9 |  foo(C[Int]()) // error
+  |  ^^^
+  |  Context bounds will map to context parameters.
+  |  A `using` clause is needed to pass explicit arguments to them.
+  |  This code can be rewritten automatically under -rewrite -source 3.4-migration.

tests/neg/context-bounds-migration-3.5.scala

@@ -0,0 +1,10 @@
+//> using options -source 3.5
+
+class C[T]
+def foo[X: C] = ()
+
+given [T]: C[T] = C[T]()
+
+def Test =
+  foo(C[Int]()) // error
+  foo(using C[Int]()) // ok

tests/neg/context-bounds-migration-future.check

@@ -0,0 +1,6 @@
+-- [E050] Type Error: tests/neg/context-bounds-migration-future.scala:9:2 ----------------------------------------------
+9 |  foo(C[Int]()) // error
+  |  ^^^
+  |  method foo does not take more parameters
+  |
+  | longer explanation available when compiling with `-explain`

tests/neg/context-bounds-migration-future.scala

@@ -0,0 +1,10 @@
+//> using options -source future
+
+class C[T]
+def foo[X: C] = ()
+
+given [T]: C[T] = C[T]()
+
+def Test =
+  foo(C[Int]()) // error
+  foo(using C[Int]()) // ok

tests/warn/context-bounds-migration-3.4.check

@@ -0,0 +1,6 @@
+-- Warning: tests/warn/context-bounds-migration-3.4.scala:9:2 ----------------------------------------------------------
+9 |  foo(C[Int]())  // warn
+  |  ^^^
+  |  Context bounds will map to context parameters.
+  |  A `using` clause is needed to pass explicit arguments to them.
+  |  This code can be rewritten automatically under -rewrite -source 3.4-migration.