Merge pull request #2368 from retronym/ticket/7335

SI-7335 Simpler bootstrapping the standard library

2 files changed, 20 insertions, 23 deletions

diff --git a/src/reflect/scala/reflect/internal/Symbols.scala b/src/reflect/scala/reflect/internal/Symbols.scala
index 76ed9b8af7..a87d002f25 100644
--- a/src/reflect/scala/reflect/internal/Symbols.scala
+++ b/src/reflect/scala/reflect/internal/Symbols.scala
@@ -887,9 +887,23 @@ trait Symbols extends api.Symbols { self: SymbolTable =>
         supersym == NoSymbol || supersym.isIncompleteIn(base)
       }
 
-    // Does not always work if the rawInfo is a SourcefileLoader, see comment
-    // in "def coreClassesFirst" in Global.
-    def exists = !isTopLevel || { rawInfo.load(this); rawInfo != NoType }
+    def exists: Boolean = !isTopLevel || {
+      val isSourceLoader = rawInfo match {
+        case sl: SymLoader => sl.fromSource
+        case _             => false
+      }
+      def warnIfSourceLoader() {
+        if (isSourceLoader)
+          // Predef is completed early due to its autoimport; we used to get here when type checking its
+          // parent LowPriorityImplicits. See comment in c5441dc for more elaboration.
+          // Since the fix for SI-7335 Predef parents must be defined in Predef.scala, and we should not
+          // get here anymore.
+          devWarning(s"calling Symbol#exists with sourcefile based symbol loader may give incorrect results.");
+      }
+
+      rawInfo load this
+      rawInfo != NoType || { warnIfSourceLoader(); false }
+    }
 
     final def isInitialized: Boolean =
       validTo != NoPeriod
diff --git a/src/reflect/scala/reflect/internal/TreeInfo.scala b/src/reflect/scala/reflect/internal/TreeInfo.scala
index b1f58814c7..3296353b6b 100644
--- a/src/reflect/scala/reflect/internal/TreeInfo.scala
+++ b/src/reflect/scala/reflect/internal/TreeInfo.scala
@@ -663,20 +663,9 @@ abstract class TreeInfo {
       unapply(dissectApplied(tree))
   }
 
-  /** Does list of trees start with a definition of
-   *  a class of module with given name (ignoring imports)
-   */
-  def firstDefinesClassOrObject(trees: List[Tree], name: Name): Boolean = trees match {
-      case Import(_, _) :: xs               => firstDefinesClassOrObject(xs, name)
-      case Annotated(_, tree1) :: Nil       => firstDefinesClassOrObject(List(tree1), name)
-      case ModuleDef(_, `name`, _) :: Nil   => true
-      case ClassDef(_, `name`, _, _) :: Nil => true
-      case _                                => false
-    }
-
-
   /** Is this file the body of a compilation unit which should not
-   *  have Predef imported?
+   *  have Predef imported? This is the case iff the first import in the
+   *  unit explicitly refers to Predef.
    */
   def noPredefImportForUnit(body: Tree) = {
     // Top-level definition whose leading imports include Predef.
@@ -685,13 +674,7 @@ abstract class TreeInfo {
       case Import(expr, _)      => isReferenceToPredef(expr)
       case _                    => false
     }
-    // Compilation unit is class or object 'name' in package 'scala'
-    def isUnitInScala(tree: Tree, name: Name) = tree match {
-      case PackageDef(Ident(nme.scala_), defs) => firstDefinesClassOrObject(defs, name)
-      case _                                   => false
-    }
-
-    isUnitInScala(body, nme.Predef) || isLeadingPredefImport(body)
+    isLeadingPredefImport(body)
   }
 
   def isAbsTypeDef(tree: Tree) = tree match {