Adopt XStringNode encoding flags

Author: andrykonchin

spec/truffle/parsing/fixtures/strings/encoding_of_backtick_literal/when_non_ascii_characters_only.yaml

@@ -0,0 +1,35 @@
+subject: "String"
+description: "backtick literal / encoding / when there are non-ASCII characters"
+notes: >
+  String may be forced to the BINARY (ASCII-8BIT) encoding sometimes
+focused_on_node: "org.truffleruby.language.dispatch.RubyCallNode"
+ruby: |
+  # encoding: us-ascii
+  `echo \xFF 1`
+ast: |
+  RubyCallNode
+      attributes:
+          descriptor = NoKeywordArgumentsDescriptor
+          dispatchConfig = PRIVATE
+          emptyKeywordsProfile = false
+          flags = 1
+          isAttrAssign = false
+          isSafeNavigation = false
+          isSplatted = false
+          isVCall = false
+          lastArgIsNotHashProfile = false
+          methodName = "`"
+          notEmptyKeywordsProfile = false
+          notRuby2KeywordsHashProfile = false
+      children:
+          arguments = [
+              StringLiteralNode
+                  attributes:
+                      encoding = ASCII-8BIT
+                      flags = 0
+                      tstring = echo \xFF 1
+          ]
+          receiver =
+              SelfNode
+                  attributes:
+                      flags = 0

spec/truffle/parsing/fixtures/strings/encoding_of_backtick_literal/when_utf8_characters.yaml

@@ -0,0 +1,35 @@
+subject: "String"
+description: "backtick literal / encoding / when there are UTF-8 characters in a literal"
+notes: >
+  String may be forced to the UTF-8 encoding sometimes
+focused_on_node: "org.truffleruby.language.dispatch.RubyCallNode"
+ruby: |
+  # encoding: us-ascii
+  `echo \u{A3} 1`
+ast: |
+  RubyCallNode
+      attributes:
+          descriptor = NoKeywordArgumentsDescriptor
+          dispatchConfig = PRIVATE
+          emptyKeywordsProfile = false
+          flags = 1
+          isAttrAssign = false
+          isSafeNavigation = false
+          isSplatted = false
+          isVCall = false
+          lastArgIsNotHashProfile = false
+          methodName = "`"
+          notEmptyKeywordsProfile = false
+          notRuby2KeywordsHashProfile = false
+      children:
+          arguments = [
+              StringLiteralNode
+                  attributes:
+                      encoding = UTF-8
+                      flags = 0
+                      tstring = echo £ 1
+          ]
+          receiver =
+              SelfNode
+                  attributes:
+                      flags = 0

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

@@ -2833,7 +2833,18 @@ public RubyNode visitWhileNode(Nodes.WhileNode node) {
     @Override
     public RubyNode visitXStringNode(Nodes.XStringNode node) {
         // TODO: pass flags, needs https://github.com/ruby/yarp/issues/1567
-        var stringNode = new Nodes.StringNode(NO_FLAGS, node.unescaped, node.startOffset, node.length);
+        // convert EncodingFlags to StringFlags
+        int flags = 0;
+
+        if (node.isForcedBinaryEncoding()) {
+            flags |= Nodes.StringFlags.FORCED_BINARY_ENCODING;
+        }
+
+        if (node.isForcedUtf8Encoding()) {
+            flags |= Nodes.StringFlags.FORCED_UTF8_ENCODING;
+        }
+
+        var stringNode = new Nodes.StringNode((short) flags, node.unescaped, node.startOffset, node.length);
         final RubyNode string = stringNode.accept(this);
 
         final RubyNode rubyNode = createCallNode(new SelfNode(), "`", string);