Enforce -new-syntax under -language:future (#23443)

No more Java style conditionals and loops. Always requires then/do.

Also: Enforce latest given syntax, instead of the intermediate one. The
two were rolled into one PR because they require changing the same
submodules.

Author: hamzaremmal

community-build/community-projects/scodec

@@ -31,7 +31,7 @@ enum MigrationVersion(val warnFrom: SourceVersion, val errorFrom: SourceVersion)
   case ImportRename extends MigrationVersion(future, future)
   case ParameterEnclosedByParenthesis extends MigrationVersion(future, future)
   case XmlLiteral extends MigrationVersion(future, future)
-  case GivenSyntax extends MigrationVersion(future, never)
+  case GivenSyntax extends MigrationVersion(future, future)
   case ImplicitParamsWithoutUsing extends MigrationVersion(`3.7`, future)
   case Scala2Implicits extends MigrationVersion(future, future)
 

community-build/community-projects/specs2

@@ -8,7 +8,7 @@ import Feature.isPreviewEnabled
 import util.Property
 
 enum SourceVersion:
-  case `3.0-migration`, `3.0` 
+  case `3.0-migration`, `3.0`
   case `3.1-migration`, `3.1`
   case `3.2-migration`, `3.2`
   case `3.3-migration`, `3.3`
@@ -44,8 +44,10 @@ enum SourceVersion:
   def enablesNamedTuples = isAtLeast(`3.7`)
   def enablesBetterFors(using Context) = isAtLeast(`3.7`) && isPreviewEnabled
 
+  def requiresNewSyntax = isAtLeast(future)
+
 object SourceVersion extends Property.Key[SourceVersion]:
-  
+
   /* The default source version used by the built compiler */
   val defaultSourceVersion = `3.7`
 

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

@@ -196,7 +196,7 @@ class CheckRealizable(using Context) {
         }
       }
     if sourceVersion.isAtLeast(future) then
-      // check fields only from version 3.x.
+      // check fields only from version 3.future.
       // Reason: An embedded field could well be nullable, which means it
       // should not be part of a path and need not be checked; but we cannot recognize
       // this situation until we have a typesystem that tracks nullability.

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

@@ -393,10 +393,9 @@ object Parsers {
       syntaxError(em"""This construct is not allowed under $option.${rewriteNotice(`3.0-migration`, option)}""", span)
 
     def rewriteToNewSyntax(span: Span = Span(in.offset)): Boolean = {
-      if (in.newSyntax) {
-        if (in.rewrite) return true
-        syntaxVersionError("-new-syntax", span)
-      }
+      if in.newSyntax then
+        if in.rewrite then return true
+        syntaxVersionError("-new-syntax or -language:future", span)
       false
     }
 
@@ -2559,7 +2558,7 @@ object Parsers {
       }
     }
 
-    /**    `if' `(' Expr `)' {nl} Expr [[semi] else Expr]
+    /**    `if' `(' Expr `)' {nl} Expr [[semi] else Expr]  -- Scala 2 compat
      *     `if' Expr `then' Expr [[semi] else Expr]
      */
     def ifExpr(start: Offset, mkIf: (Tree, Tree, Tree) => If): If =

compiler/src/dotty/tools/dotc/core/CheckRealizable.scala

@@ -17,7 +17,7 @@ import scala.collection.mutable
 import scala.collection.immutable.SortedMap
 import rewrites.Rewrites.patch
 import config.Feature
-import config.Feature.migrateTo3
+import config.Feature.{migrateTo3, sourceVersion}
 import config.SourceVersion.{`3.0`, `3.0-migration`}
 import config.MigrationVersion
 import reporting.{NoProfile, Profile, Message}
@@ -184,7 +184,7 @@ object Scanners {
 
     val rewrite = ctx.settings.rewrite.value.isDefined
     val oldSyntax = ctx.settings.oldSyntax.value
-    val newSyntax = ctx.settings.newSyntax.value
+    val newSyntax = ctx.settings.newSyntax.value || sourceVersion.requiresNewSyntax
 
     val rewriteToIndent = ctx.settings.indent.value && rewrite
     val rewriteNoIndent = ctx.settings.noindent.value && rewrite

compiler/src/dotty/tools/dotc/parsing/Parsers.scala

@@ -4,7 +4,7 @@ class C:
 
 trait T:
   given Int is C // ok
-  given intC: Int is C // warn
+  given intC: Int is C // error
   given intC2: (Int is C)() // ok
   given intC3: Int is C {} // also ok
 

compiler/src/dotty/tools/dotc/parsing/Scanners.scala

@@ -4,7 +4,3 @@
   |  method foo does not take more parameters
   |
   | longer explanation available when compiling with `-explain`
--- Warning: tests/neg/context-bounds-migration-future.scala:6:6 --------------------------------------------------------
-6 |given [T]: C[T] = C[T]()
-  |      ^
-  |      This old given syntax is no longer supported; use `=>` instead of `:`

tests/warn/abstract-givens-new.scala renamed to tests/neg/abstract-givens-new.scala

@@ -3,7 +3,7 @@
 class C[T]
 def foo[X: C] = ()
 
-given [T]: C[T] = C[T]()
+given [T] => C[T] = C[T]()
 
 def Test =
   foo(C[Int]()) // error