Crate ruby_prism

ruby-prism

Rustified version of Ruby’s prism parser.

Structs

• AliasGlobalVariableNode
  Represents the use of the alias keyword to alias a global variable.
• AliasMethodNode
  Represents the use of the alias keyword to alias a method.
• AlternationPatternNode
  Represents an alternation pattern in pattern matching.
• AndNode
  Represents the use of the && operator or the and keyword.
• ArgumentsNode
  Represents a set of arguments to a method or a keyword.
• ArrayNode
  Represents an array literal. This can be a regular array using brackets or a special array using % like %w or %i.
• ArrayPatternNode
  Represents an array pattern in pattern matching.
• AssocNode
  Represents a hash key/value pair.
• AssocSplatNode
  Represents a splat in a hash literal.
• BackReferenceReadNode
  Represents reading a reference to a field in the previous match.
• BeginNode
  Represents a begin statement.
• BlockArgumentNode
  Represents a block argument using &.
• BlockLocalVariableNode
  Represents a block local variable.
• BlockNode
  Represents a block of ruby code.
• BlockParameterNode
  Represents a block parameter of a method, block, or lambda definition.
• BlockParametersNode
  Represents a block’s parameters declaration.
• BreakNode
  Represents the use of the break keyword.
• CallAndWriteNode
  Represents the use of the &&= operator on a call.
• CallNode
  Represents a method call, in all of the various forms that can take.
• CallOperatorWriteNode
  Represents the use of an assignment operator on a call.
• CallOrWriteNode
  Represents the use of the ||= operator on a call.
• CallTargetNode
  Represents assigning to a method call.
• CapturePatternNode
  Represents assigning to a local variable in pattern matching.
• CaseMatchNode
  Represents the use of a case statement for pattern matching.
• CaseNode
  Represents the use of a case statement.
• ClassNode
  Represents a class declaration involving the class keyword.
• ClassVariableAndWriteNode
  Represents the use of the &&= operator for assignment to a class variable.
• ClassVariableOperatorWriteNode
  Represents assigning to a class variable using an operator that isn’t =.
• ClassVariableOrWriteNode
  Represents the use of the ||= operator for assignment to a class variable.
• ClassVariableReadNode
  Represents referencing a class variable.
• ClassVariableTargetNode
  Represents writing to a class variable in a context that doesn’t have an explicit value.
• ClassVariableWriteNode
  Represents writing to a class variable.
• Comment
  A comment that was found during parsing.
• Comments
  A struct created by the comments method on ParseResult. It can be used to iterate over the comments in the parse result.
• ConstantAndWriteNode
  Represents the use of the &&= operator for assignment to a constant.
• ConstantId
  A handle for a constant ID.
• ConstantList
  A list of constants.
• ConstantListIter
  An iterator over the constants in a list.
• ConstantOperatorWriteNode
  Represents assigning to a constant using an operator that isn’t =.
• ConstantOrWriteNode
  Represents the use of the ||= operator for assignment to a constant.
• ConstantPathAndWriteNode
  Represents the use of the &&= operator for assignment to a constant path.
• ConstantPathNode
  Represents accessing a constant through a path of :: operators.
• ConstantPathOperatorWriteNode
  Represents assigning to a constant path using an operator that isn’t =.
• ConstantPathOrWriteNode
  Represents the use of the ||= operator for assignment to a constant path.
• ConstantPathTargetNode
  Represents writing to a constant path in a context that doesn’t have an explicit value.
• ConstantPathWriteNode
  Represents writing to a constant path.
• ConstantReadNode
  Represents referencing a constant.
• ConstantTargetNode
  Represents writing to a constant in a context that doesn’t have an explicit value.
• ConstantWriteNode
  Represents writing to a constant.
• DefNode
  Represents a method definition.
• DefinedNode
  Represents the use of the defined? keyword.
• Diagnostic
  A diagnostic message that came back from the parser.
• Diagnostics
  A struct created by the errors or warnings methods on ParseResult. It can be used to iterate over the diagnostics in the parse result.
• ElseNode
  Represents an else clause in a case, if, or unless statement.
• EmbeddedStatementsNode
  Represents an interpolated set of statements.
• EmbeddedVariableNode
  Represents an interpolated variable.
• EnsureNode
  Represents an ensure clause in a begin statement.
• FalseNode
  Represents the use of the literal false keyword.
• FindPatternNode
  Represents a find pattern in pattern matching.
• FlipFlopNode
  Represents the use of the .. or ... operators to create flip flops.
• FloatNode
  Represents a floating point number literal.
• ForNode
  Represents the use of the for keyword.
• ForwardingArgumentsNode
  Represents forwarding all arguments to this method to another method.
• ForwardingParameterNode
  Represents the use of the forwarding parameter in a method, block, or lambda declaration.
• ForwardingSuperNode
  Represents the use of the super keyword without parentheses or arguments.
• GlobalVariableAndWriteNode
  Represents the use of the &&= operator for assignment to a global variable.
• GlobalVariableOperatorWriteNode
  Represents assigning to a global variable using an operator that isn’t =.
• GlobalVariableOrWriteNode
  Represents the use of the ||= operator for assignment to a global variable.
• GlobalVariableReadNode
  Represents referencing a global variable.
• GlobalVariableTargetNode
  Represents writing to a global variable in a context that doesn’t have an explicit value.
• GlobalVariableWriteNode
  Represents writing to a global variable.
• HashNode
  Represents a hash literal.
• HashPatternNode
  Represents a hash pattern in pattern matching.
• IfNode
  Represents the use of the if keyword, either in the block form or the modifier form, or a ternary expression.
• ImaginaryNode
  Represents an imaginary number literal.
• ImplicitNode
  Represents a node that is implicitly being added to the tree but doesn’t correspond directly to a node in the source.
• ImplicitRestNode
  Represents using a trailing comma to indicate an implicit rest parameter.
• InNode
  Represents the use of the in keyword in a case statement.
• IndexAndWriteNode
  Represents the use of the &&= operator on a call to the [] method.
• IndexOperatorWriteNode
  Represents the use of an assignment operator on a call to [].
• IndexOrWriteNode
  Represents the use of the ||= operator on a call to [].
• IndexTargetNode
  Represents assigning to an index.
• InstanceVariableAndWriteNode
  Represents the use of the &&= operator for assignment to an instance variable.
• InstanceVariableOperatorWriteNode
  Represents assigning to an instance variable using an operator that isn’t =.
• InstanceVariableOrWriteNode
  Represents the use of the ||= operator for assignment to an instance variable.
• InstanceVariableReadNode
  Represents referencing an instance variable.
• InstanceVariableTargetNode
  Represents writing to an instance variable in a context that doesn’t have an explicit value.
• InstanceVariableWriteNode
  Represents writing to an instance variable.
• Integer
  A handle for an arbitarily-sized integer.
• IntegerNode
  Represents an integer number literal.
• InterpolatedMatchLastLineNode
  Represents a regular expression literal that contains interpolation that is being used in the predicate of a conditional to implicitly match against the last line read by an IO object.
• InterpolatedRegularExpressionNode
  Represents a regular expression literal that contains interpolation.
• InterpolatedStringNode
  Represents a string literal that contains interpolation.
• InterpolatedSymbolNode
  Represents a symbol literal that contains interpolation.
• InterpolatedXStringNode
  Represents an xstring literal that contains interpolation.
• ItLocalVariableReadNode
  Represents reading from the implicit it local variable.
• ItParametersNode
  Represents an implicit set of parameters through the use of the it keyword within a block or lambda.
• KeywordHashNode
  Represents a hash literal without opening and closing braces.
• KeywordRestParameterNode
  Represents a keyword rest parameter to a method, block, or lambda definition.
• LambdaNode
  Represents using a lambda literal (not the lambda method call).
• LocalVariableAndWriteNode
  Represents the use of the &&= operator for assignment to a local variable.
• LocalVariableOperatorWriteNode
  Represents assigning to a local variable using an operator that isn’t =.
• LocalVariableOrWriteNode
  Represents the use of the ||= operator for assignment to a local variable.
• LocalVariableReadNode
  Represents reading a local variable. Note that this requires that a local variable of the same name has already been written to in the same scope, otherwise it is parsed as a method call.
• LocalVariableTargetNode
  Represents writing to a local variable in a context that doesn’t have an explicit value.
• LocalVariableWriteNode
  Represents writing to a local variable.
• Location
  A range in the source file.
• MatchLastLineNode
  Represents a regular expression literal used in the predicate of a conditional to implicitly match against the last line read by an IO object.
• MatchPredicateNode
  Represents the use of the modifier in operator.
• MatchRequiredNode
  Represents the use of the => operator.
• MatchWriteNode
  Represents writing local variables using a regular expression match with named capture groups.
• MissingNode
  Represents a node that is missing from the source and results in a syntax error.
• ModuleNode
  Represents a module declaration involving the module keyword.
• MultiTargetNode
  Represents a multi-target expression.
• MultiWriteNode
  Represents a write to a multi-target expression.
• NextNode
  Represents the use of the next keyword.
• NilNode
  Represents the use of the nil keyword.
• NoKeywordsParameterNode
  Represents the use of **nil inside method arguments.
• NodeList
  A list of nodes.
• NodeListIter
  An iterator over the nodes in a list.
• NumberedParametersNode
  Represents an implicit set of parameters through the use of numbered parameters within a block or lambda.
• NumberedReferenceReadNode
  Represents reading a numbered reference to a capture in the previous match.
• OptionalKeywordParameterNode
  Represents an optional keyword parameter to a method, block, or lambda definition.
• OptionalParameterNode
  Represents an optional parameter to a method, block, or lambda definition.
• OrNode
  Represents the use of the || operator or the or keyword.
• ParametersNode
  Represents the list of parameters on a method, block, or lambda definition.
• ParenthesesNode
  Represents a parenthesized expression
• ParseResult
  The result of parsing a source string.
• PinnedExpressionNode
  Represents the use of the ^ operator for pinning an expression in a pattern matching expression.
• PinnedVariableNode
  Represents the use of the ^ operator for pinning a variable in a pattern matching expression.
• PostExecutionNode
  Represents the use of the END keyword.
• PreExecutionNode
  Represents the use of the BEGIN keyword.
• ProgramNode
  The top level node of any parse tree.
• RangeNode
  Represents the use of the .. or ... operators.
• RationalNode
  Represents a rational number literal.
• RedoNode
  Represents the use of the redo keyword.
• RegularExpressionNode
  Represents a regular expression literal with no interpolation.
• RequiredKeywordParameterNode
  Represents a required keyword parameter to a method, block, or lambda definition.
• RequiredParameterNode
  Represents a required parameter to a method, block, or lambda definition.
• RescueModifierNode
  Represents an expression modified with a rescue.
• RescueNode
  Represents a rescue statement.
• RestParameterNode
  Represents a rest parameter to a method, block, or lambda definition.
• RetryNode
  Represents the use of the retry keyword.
• ReturnNode
  Represents the use of the return keyword.
• SelfNode
  Represents the self keyword.
• ShareableConstantNode
  This node wraps a constant write to indicate that when the value is written, it should have its shareability state modified.
• SingletonClassNode
  Represents a singleton class declaration involving the class keyword.
• SourceEncodingNode
  Represents the use of the __ENCODING__ keyword.
• SourceFileNode
  Represents the use of the __FILE__ keyword.
• SourceLineNode
  Represents the use of the __LINE__ keyword.
• SplatNode
  Represents the use of the splat operator.
• StatementsNode
  Represents a set of statements contained within some scope.
• StringNode
  Represents a string literal, a string contained within a %w list, or plain string content within an interpolated string.
• SuperNode
  Represents the use of the super keyword with parentheses or arguments.
• SymbolNode
  Represents a symbol literal or a symbol contained within a %i list.
• TrueNode
  Represents the use of the literal true keyword.
• UndefNode
  Represents the use of the undef keyword.
• UnlessNode
  Represents the use of the unless keyword, either in the block form or the modifier form.
• UntilNode
  Represents the use of the until keyword, either in the block form or the modifier form.
• WhenNode
  Represents the use of the when keyword within a case statement.
• WhileNode
  Represents the use of the while keyword, either in the block form or the modifier form.
• XStringNode
  Represents an xstring literal with no interpolation.
• YieldNode
  Represents the use of the yield keyword.

Enums

• Node
  An enum representing the different kinds of nodes that can be parsed.

Traits

• Visit
  A trait for visiting the AST.

Functions

• parse
  Parses the given source string and returns a parse result.
• visit_alias_global_variable_node
  The default visitor implementation for a AliasGlobalVariableNode node.
• visit_alias_method_node
  The default visitor implementation for a AliasMethodNode node.
• visit_alternation_pattern_node
  The default visitor implementation for a AlternationPatternNode node.
• visit_and_node
  The default visitor implementation for a AndNode node.
• visit_arguments_node
  The default visitor implementation for a ArgumentsNode node.
• visit_array_node
  The default visitor implementation for a ArrayNode node.
• visit_array_pattern_node
  The default visitor implementation for a ArrayPatternNode node.
• visit_assoc_node
  The default visitor implementation for a AssocNode node.
• visit_assoc_splat_node
  The default visitor implementation for a AssocSplatNode node.
• visit_back_reference_read_node
  The default visitor implementation for a BackReferenceReadNode node.
• visit_begin_node
  The default visitor implementation for a BeginNode node.
• visit_block_argument_node
  The default visitor implementation for a BlockArgumentNode node.
• visit_block_local_variable_node
  The default visitor implementation for a BlockLocalVariableNode node.
• visit_block_node
  The default visitor implementation for a BlockNode node.
• visit_block_parameter_node
  The default visitor implementation for a BlockParameterNode node.
• visit_block_parameters_node
  The default visitor implementation for a BlockParametersNode node.
• visit_break_node
  The default visitor implementation for a BreakNode node.
• visit_call_and_write_node
  The default visitor implementation for a CallAndWriteNode node.
• visit_call_node
  The default visitor implementation for a CallNode node.
• visit_call_operator_write_node
  The default visitor implementation for a CallOperatorWriteNode node.
• visit_call_or_write_node
  The default visitor implementation for a CallOrWriteNode node.
• visit_call_target_node
  The default visitor implementation for a CallTargetNode node.
• visit_capture_pattern_node
  The default visitor implementation for a CapturePatternNode node.
• visit_case_match_node
  The default visitor implementation for a CaseMatchNode node.
• visit_case_node
  The default visitor implementation for a CaseNode node.
• visit_class_node
  The default visitor implementation for a ClassNode node.
• visit_class_variable_and_write_node
  The default visitor implementation for a ClassVariableAndWriteNode node.
• visit_class_variable_operator_write_node
  The default visitor implementation for a ClassVariableOperatorWriteNode node.
• visit_class_variable_or_write_node
  The default visitor implementation for a ClassVariableOrWriteNode node.
• visit_class_variable_read_node
  The default visitor implementation for a ClassVariableReadNode node.
• visit_class_variable_target_node
  The default visitor implementation for a ClassVariableTargetNode node.
• visit_class_variable_write_node
  The default visitor implementation for a ClassVariableWriteNode node.
• visit_constant_and_write_node
  The default visitor implementation for a ConstantAndWriteNode node.
• visit_constant_operator_write_node
  The default visitor implementation for a ConstantOperatorWriteNode node.
• visit_constant_or_write_node
  The default visitor implementation for a ConstantOrWriteNode node.
• visit_constant_path_and_write_node
  The default visitor implementation for a ConstantPathAndWriteNode node.
• visit_constant_path_node
  The default visitor implementation for a ConstantPathNode node.
• visit_constant_path_operator_write_node
  The default visitor implementation for a ConstantPathOperatorWriteNode node.
• visit_constant_path_or_write_node
  The default visitor implementation for a ConstantPathOrWriteNode node.
• visit_constant_path_target_node
  The default visitor implementation for a ConstantPathTargetNode node.
• visit_constant_path_write_node
  The default visitor implementation for a ConstantPathWriteNode node.
• visit_constant_read_node
  The default visitor implementation for a ConstantReadNode node.
• visit_constant_target_node
  The default visitor implementation for a ConstantTargetNode node.
• visit_constant_write_node
  The default visitor implementation for a ConstantWriteNode node.
• visit_def_node
  The default visitor implementation for a DefNode node.
• visit_defined_node
  The default visitor implementation for a DefinedNode node.
• visit_else_node
  The default visitor implementation for a ElseNode node.
• visit_embedded_statements_node
  The default visitor implementation for a EmbeddedStatementsNode node.
• visit_embedded_variable_node
  The default visitor implementation for a EmbeddedVariableNode node.
• visit_ensure_node
  The default visitor implementation for a EnsureNode node.
• visit_false_node
  The default visitor implementation for a FalseNode node.
• visit_find_pattern_node
  The default visitor implementation for a FindPatternNode node.
• visit_flip_flop_node
  The default visitor implementation for a FlipFlopNode node.
• visit_float_node
  The default visitor implementation for a FloatNode node.
• visit_for_node
  The default visitor implementation for a ForNode node.
• visit_forwarding_arguments_node
  The default visitor implementation for a ForwardingArgumentsNode node.
• visit_forwarding_parameter_node
  The default visitor implementation for a ForwardingParameterNode node.
• visit_forwarding_super_node
  The default visitor implementation for a ForwardingSuperNode node.
• visit_global_variable_and_write_node
  The default visitor implementation for a GlobalVariableAndWriteNode node.
• visit_global_variable_operator_write_node
  The default visitor implementation for a GlobalVariableOperatorWriteNode node.
• visit_global_variable_or_write_node
  The default visitor implementation for a GlobalVariableOrWriteNode node.
• visit_global_variable_read_node
  The default visitor implementation for a GlobalVariableReadNode node.
• visit_global_variable_target_node
  The default visitor implementation for a GlobalVariableTargetNode node.
• visit_global_variable_write_node
  The default visitor implementation for a GlobalVariableWriteNode node.
• visit_hash_node
  The default visitor implementation for a HashNode node.
• visit_hash_pattern_node
  The default visitor implementation for a HashPatternNode node.
• visit_if_node
  The default visitor implementation for a IfNode node.
• visit_imaginary_node
  The default visitor implementation for a ImaginaryNode node.
• visit_implicit_node
  The default visitor implementation for a ImplicitNode node.
• visit_implicit_rest_node
  The default visitor implementation for a ImplicitRestNode node.
• visit_in_node
  The default visitor implementation for a InNode node.
• visit_index_and_write_node
  The default visitor implementation for a IndexAndWriteNode node.
• visit_index_operator_write_node
  The default visitor implementation for a IndexOperatorWriteNode node.
• visit_index_or_write_node
  The default visitor implementation for a IndexOrWriteNode node.
• visit_index_target_node
  The default visitor implementation for a IndexTargetNode node.
• visit_instance_variable_and_write_node
  The default visitor implementation for a InstanceVariableAndWriteNode node.
• visit_instance_variable_operator_write_node
  The default visitor implementation for a InstanceVariableOperatorWriteNode node.
• visit_instance_variable_or_write_node
  The default visitor implementation for a InstanceVariableOrWriteNode node.
• visit_instance_variable_read_node
  The default visitor implementation for a InstanceVariableReadNode node.
• visit_instance_variable_target_node
  The default visitor implementation for a InstanceVariableTargetNode node.
• visit_instance_variable_write_node
  The default visitor implementation for a InstanceVariableWriteNode node.
• visit_integer_node
  The default visitor implementation for a IntegerNode node.
• visit_interpolated_match_last_line_node
  The default visitor implementation for a InterpolatedMatchLastLineNode node.
• visit_interpolated_regular_expression_node
  The default visitor implementation for a InterpolatedRegularExpressionNode node.
• visit_interpolated_string_node
  The default visitor implementation for a InterpolatedStringNode node.
• visit_interpolated_symbol_node
  The default visitor implementation for a InterpolatedSymbolNode node.
• visit_interpolated_x_string_node
  The default visitor implementation for a InterpolatedXStringNode node.
• visit_it_local_variable_read_node
  The default visitor implementation for a ItLocalVariableReadNode node.
• visit_it_parameters_node
  The default visitor implementation for a ItParametersNode node.
• visit_keyword_hash_node
  The default visitor implementation for a KeywordHashNode node.
• visit_keyword_rest_parameter_node
  The default visitor implementation for a KeywordRestParameterNode node.
• visit_lambda_node
  The default visitor implementation for a LambdaNode node.
• visit_local_variable_and_write_node
  The default visitor implementation for a LocalVariableAndWriteNode node.
• visit_local_variable_operator_write_node
  The default visitor implementation for a LocalVariableOperatorWriteNode node.
• visit_local_variable_or_write_node
  The default visitor implementation for a LocalVariableOrWriteNode node.
• visit_local_variable_read_node
  The default visitor implementation for a LocalVariableReadNode node.
• visit_local_variable_target_node
  The default visitor implementation for a LocalVariableTargetNode node.
• visit_local_variable_write_node
  The default visitor implementation for a LocalVariableWriteNode node.
• visit_match_last_line_node
  The default visitor implementation for a MatchLastLineNode node.
• visit_match_predicate_node
  The default visitor implementation for a MatchPredicateNode node.
• visit_match_required_node
  The default visitor implementation for a MatchRequiredNode node.
• visit_match_write_node
  The default visitor implementation for a MatchWriteNode node.
• visit_missing_node
  The default visitor implementation for a MissingNode node.
• visit_module_node
  The default visitor implementation for a ModuleNode node.
• visit_multi_target_node
  The default visitor implementation for a MultiTargetNode node.
• visit_multi_write_node
  The default visitor implementation for a MultiWriteNode node.
• visit_next_node
  The default visitor implementation for a NextNode node.
• visit_nil_node
  The default visitor implementation for a NilNode node.
• visit_no_keywords_parameter_node
  The default visitor implementation for a NoKeywordsParameterNode node.
• visit_numbered_parameters_node
  The default visitor implementation for a NumberedParametersNode node.
• visit_numbered_reference_read_node
  The default visitor implementation for a NumberedReferenceReadNode node.
• visit_optional_keyword_parameter_node
  The default visitor implementation for a OptionalKeywordParameterNode node.
• visit_optional_parameter_node
  The default visitor implementation for a OptionalParameterNode node.
• visit_or_node
  The default visitor implementation for a OrNode node.
• visit_parameters_node
  The default visitor implementation for a ParametersNode node.
• visit_parentheses_node
  The default visitor implementation for a ParenthesesNode node.
• visit_pinned_expression_node
  The default visitor implementation for a PinnedExpressionNode node.
• visit_pinned_variable_node
  The default visitor implementation for a PinnedVariableNode node.
• visit_post_execution_node
  The default visitor implementation for a PostExecutionNode node.
• visit_pre_execution_node
  The default visitor implementation for a PreExecutionNode node.
• visit_program_node
  The default visitor implementation for a ProgramNode node.
• visit_range_node
  The default visitor implementation for a RangeNode node.
• visit_rational_node
  The default visitor implementation for a RationalNode node.
• visit_redo_node
  The default visitor implementation for a RedoNode node.
• visit_regular_expression_node
  The default visitor implementation for a RegularExpressionNode node.
• visit_required_keyword_parameter_node
  The default visitor implementation for a RequiredKeywordParameterNode node.
• visit_required_parameter_node
  The default visitor implementation for a RequiredParameterNode node.
• visit_rescue_modifier_node
  The default visitor implementation for a RescueModifierNode node.
• visit_rescue_node
  The default visitor implementation for a RescueNode node.
• visit_rest_parameter_node
  The default visitor implementation for a RestParameterNode node.
• visit_retry_node
  The default visitor implementation for a RetryNode node.
• visit_return_node
  The default visitor implementation for a ReturnNode node.
• visit_self_node
  The default visitor implementation for a SelfNode node.
• visit_shareable_constant_node
  The default visitor implementation for a ShareableConstantNode node.
• visit_singleton_class_node
  The default visitor implementation for a SingletonClassNode node.
• visit_source_encoding_node
  The default visitor implementation for a SourceEncodingNode node.
• visit_source_file_node
  The default visitor implementation for a SourceFileNode node.
• visit_source_line_node
  The default visitor implementation for a SourceLineNode node.
• visit_splat_node
  The default visitor implementation for a SplatNode node.
• visit_statements_node
  The default visitor implementation for a StatementsNode node.
• visit_string_node
  The default visitor implementation for a StringNode node.
• visit_super_node
  The default visitor implementation for a SuperNode node.
• visit_symbol_node
  The default visitor implementation for a SymbolNode node.
• visit_true_node
  The default visitor implementation for a TrueNode node.
• visit_undef_node
  The default visitor implementation for a UndefNode node.
• visit_unless_node
  The default visitor implementation for a UnlessNode node.
• visit_until_node
  The default visitor implementation for a UntilNode node.
• visit_when_node
  The default visitor implementation for a WhenNode node.
• visit_while_node
  The default visitor implementation for a WhileNode node.
• visit_x_string_node
  The default visitor implementation for a XStringNode node.
• visit_yield_node
  The default visitor implementation for a YieldNode node.