Remove -Xlink

This mode has not been tested for a while and is not going to be used
in the future. It was the basis on which -from-tasty was created
and tested the loading loading of TASTy trees before -from-tasty existed.

It intended to use the linker call graph to know which classes to reload.
Now that this is not going to be supported this infrastructure is useless.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/Compiler.scala

@@ -52,7 +52,6 @@ class Compiler {
   /** Phases dealing with TASTY tree pickling and unpickling */
   protected def picklerPhases: List[List[Phase]] =
     List(new Pickler) ::            // Generate TASTY info
-    List(new LinkAll) ::            // Reload compilation units from TASTY for library code (if needed)
     List(new ReifyQuotes) ::        // Turn quoted trees into explicit run-time data structures
     Nil
 

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

@@ -144,8 +144,6 @@ class ScalaSettings extends Settings.SettingGroup {
   val YshowVarBounds = BooleanSetting("-Yshow-var-bounds", "Print type variables with their bounds")
   val YshowNoInline = BooleanSetting("-Yshow-no-inline", "Show inlined code without the 'inlined from' info")
 
-  /** Linker specific flags */
-  val Xlink = BooleanSetting("-Xlink", "Recompile library code with the application.")
   val YnoDecodeStacktraces = BooleanSetting("-Yno-decode-stacktraces", "Show raw StackOverflow stacktraces, instead of decoding them into triggering operations.")
 
   /** Dottydoc specific settings */

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

@@ -390,7 +390,7 @@ class ClassfileLoader(val classfile: AbstractFile) extends SymbolLoader {
   }
 
   private def mayLoadTreesFromTasty(implicit ctx: Context): Boolean =
-    ctx.settings.YretainTrees.value || ctx.settings.Xlink.value || ctx.settings.fromTasty.value
+    ctx.settings.YretainTrees.value || ctx.settings.fromTasty.value
 }
 
 class SourcefileLoader(val srcfile: AbstractFile) extends SymbolLoader {

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

@@ -668,10 +668,8 @@ object Symbols {
 
     private[this] var myTree: TreeOrProvider = tpd.EmptyTree
 
-    /** If this is either:
-      *   - a top-level class and `-Yretain-trees` is set
-      *   - a top-level class loaded from TASTY and `-tasty` or `-Xlink` is set
-      * then return the TypeDef tree (possibly wrapped inside PackageDefs) for this class, otherwise EmptyTree.
+    /** If this is a top-level class and `-Yretain-trees` (or `-from-tasty`) is set.
+      * Returns the TypeDef tree (possibly wrapped inside PackageDefs) for this class, otherwise EmptyTree.
       * This will force the info of the class.
       */
     def tree(implicit ctx: Context): Tree = treeContaining("")