SI-8030 force symbols on presentation compiler initialization

This commit forces a number of built-in symbols in presentation
compiler to prevent them from being entered during parsing.

The property “parsing doesn’t enter new symbols” is tested on
a rich source file that contains significant number of variations
of Scala syntax.

2 files changed, 14 insertions, 3 deletions

diff --git a/src/interactive/scala/tools/nsc/interactive/Global.scala b/src/interactive/scala/tools/nsc/interactive/Global.scala
index 467a210cab..cab5137a87 100644
--- a/src/interactive/scala/tools/nsc/interactive/Global.scala
+++ b/src/interactive/scala/tools/nsc/interactive/Global.scala
@@ -1234,6 +1234,18 @@ class Global(settings: Settings, _reporter: Reporter, projectName: String = "")
     }
   }
 
+  // We need to force a number of symbols that might be touched by a parser.
+  // Otherwise thread safety property of parseTree method would be violated.
+  protected def forceSymbolsUsedByParser(): Unit = {
+    val symbols =
+      Set(UnitClass, BooleanClass, ByteClass,
+          ShortClass, IntClass, LongClass, FloatClass,
+          DoubleClass, NilModule, ListClass) ++ TupleClass.seq
+    symbols.foreach(_.initialize)
+  }
+
+  forceSymbolsUsedByParser()
+
   /** The compiler has been initialized. Constructors are evaluated in textual order,
    *  so this is set to true only after all super constructors and the primary constructor
    *  have been executed.
diff --git a/src/reflect/scala/reflect/internal/TreeGen.scala b/src/reflect/scala/reflect/internal/TreeGen.scala
index a0bd64f850..6269004298 100644
--- a/src/reflect/scala/reflect/internal/TreeGen.scala
+++ b/src/reflect/scala/reflect/internal/TreeGen.scala
@@ -16,8 +16,7 @@ abstract class TreeGen extends macros.TreeBuilder {
   def rootScalaDot(name: Name)       = Select(rootId(nme.scala_) setSymbol ScalaPackage, name)
   def scalaDot(name: Name)           = Select(Ident(nme.scala_) setSymbol ScalaPackage, name)
   def scalaAnnotationDot(name: Name) = Select(scalaDot(nme.annotation), name)
-  def scalaAnyRefConstrRaw           = scalaDot(tpnme.AnyRef)
-  def scalaAnyRefConstr              = scalaAnyRefConstrRaw setSymbol AnyRefClass // used in ide
+  def scalaAnyRefConstr              = scalaDot(tpnme.AnyRef) // used in ide
 
   def scalaFunctionConstr(argtpes: List[Tree], restpe: Tree, abstractFun: Boolean = false): Tree = {
     val cls = if (abstractFun)
@@ -393,7 +392,7 @@ abstract class TreeGen extends macros.TreeBuilder {
 
   def mkParents(ownerMods: Modifiers, parents: List[Tree], parentPos: Position = NoPosition) =
     if (ownerMods.isCase) parents ::: List(scalaDot(tpnme.Product), scalaDot(tpnme.Serializable))
-    else if (parents.isEmpty) atPos(parentPos)(scalaAnyRefConstrRaw) :: Nil
+    else if (parents.isEmpty) atPos(parentPos)(scalaAnyRefConstr) :: Nil
     else parents
 
   def mkClassDef(mods: Modifiers, name: TypeName, tparams: List[TypeDef], templ: Template): ClassDef = {