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.

1 files changed, 12 insertions, 0 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.