Add early check that the source encoding is ASCII compatible

* The check in RubyLexer is too late, at that point the TruffleString is
  already in a non-ASCII compatible encoding and the check does not work.

Author: eregon

src/main/java/org/truffleruby/parser/TranslatorDriver.java

@@ -114,6 +114,11 @@ public RootCallTarget parse(RubySource rubySource, ParserContext parserContext,
                     "A frame should be given iff the context is not toplevel: " + parserContext + " " + parentFrame);
         }
 
+        if (!rubySource.getEncoding().isAsciiCompatible) {
+            throw new RaiseException(context, context.getCoreExceptions()
+                    .argumentError(rubySource.getEncoding() + " is not ASCII compatible", currentNode));
+        }
+
         final Source source = rubySource.getSource();
 
         final StaticScope staticScope = new StaticScope(StaticScope.Type.LOCAL, null);

src/main/java/org/truffleruby/parser/YARPTranslatorDriver.java

@@ -117,6 +117,11 @@ public RootCallTarget parse(RubySource rubySource, ParserContext parserContext,
                     "A frame should be given iff the context is not toplevel: " + parserContext + " " + parentFrame);
         }
 
+        if (!rubySource.getEncoding().isAsciiCompatible) {
+            throw new RaiseException(context, context.getCoreExceptions()
+                    .argumentError(rubySource.getEncoding() + " is not ASCII compatible", currentNode));
+        }
+
         final Source source = rubySource.getSource();
 
         final StaticScope staticScope = new StaticScope(StaticScope.Type.LOCAL, null);