diff options
Diffstat (limited to 'lib/xixanta')
| -rw-r--r-- | lib/xixanta/src/assembler.rs | 2 | ||||
| -rw-r--r-- | lib/xixanta/src/parser.rs | 487 |
2 files changed, 296 insertions, 193 deletions
diff --git a/lib/xixanta/src/assembler.rs b/lib/xixanta/src/assembler.rs index 5e94070..dfaff19 100644 --- a/lib/xixanta/src/assembler.rs +++ b/lib/xixanta/src/assembler.rs @@ -3943,7 +3943,7 @@ lda #Variable .segment "THREE" .segment "TWO" - nop' + nop "#, 2, false, diff --git a/lib/xixanta/src/parser.rs b/lib/xixanta/src/parser.rs index dbe5fbe..322bd76 100644 --- a/lib/xixanta/src/parser.rs +++ b/lib/xixanta/src/parser.rs @@ -46,6 +46,21 @@ pub struct Parser { /// The index of the source that explicitely belongs to this session (and /// not subsequent calls done afterwards). Initialized on `parse`. current_source: usize, + + /// A stack of "look ahead" levels. That is, a stack of saved + /// `look_ahead_index` values that functions that deal with having to look + /// ahead (e.g. 'parse_literal') have to push/pop so 'parse_expression' can + /// know when to return early. + look_ahead_levels: Vec<usize>, + + /// The current level of "looking ahead". That is, some expressions like + /// '#$1 >> 2' have to evaluate to '(#$1) >> 2' instead of '#$(1 >> 2)'. + /// This can't be known at first glance because literals, for example, don't + /// have a termination character (i.e. the parser cannot determine where any + /// given literal expression ends). Hence, in this case, the parser has to + /// look ahead to know where the literal ends before dealing with further + /// operators. + look_ahead_index: usize, } impl Parser { @@ -241,16 +256,7 @@ impl Parser { while let Some(c) = chars.next() { // Check for the end of the identifier. For this, it's easier to // simply list what is allowed and negate it. - if !(c.is_ascii_alphanumeric() - || c == '.' - || c == '#' - || c == '$' - || c == '%' - || c == '@' - || c == '_' - || c == '\'' - || c == '"') - { + if !(c.is_ascii_alphanumeric() || c == '@' || c == '_' || c == '.') { // This next match looks scarier than what it actually is. To // sum things up, the ':' character is quite troublesome, since // it can mean three things depending on the context. @@ -577,11 +583,22 @@ impl Parser { } // Parse statements which are neither an instruction nor an assignment. This - // includes stuff like control statements. + // includes stuff like control statements or macro calls. fn parse_other(&mut self, line: &str, id: PString) -> Result<(), Vec<Error>> { - // The main job of this function is to parse the expression and - // afterwards deal with corner cases. So, let's first just parse this. - let node = self.parse_expression_with_identifier(id, line, 0)?; + // This is either a control statement (i.e. starts with '.') or a macro call. + let node = if id.value.starts_with('.') { + self.parse_control(id, line, 0)? + } else { + let args = self.parse_arguments(line, 0)?; + PNode { + node_type: NodeType::Call, + value: id, + left: None, + right: None, + args: if args.is_empty() { None } else { Some(args) }, + source: self.current_source, + } + }; // If this was an .include statement we have to handle it now as this is // not a regular statement but more like a preprocessor statement which @@ -833,7 +850,7 @@ impl Parser { // Parse any possible arguments for the given `line`. The offset is supposed // to be at a point where arguments might appear, either between parens or // not. - fn parse_arguments(&mut self, line: &str) -> Result<Vec<PNode>, Error> { + fn parse_arguments(&mut self, line: &str, level: usize) -> Result<Vec<PNode>, Error> { // Skip any possible whitespace before the optional opening paren. self.skip_whitespace(line); @@ -877,7 +894,7 @@ impl Parser { // Parse the argument, which is trimmed down from the line and hence // the offset needs to be reset. self.offset = 0; - args.push(self.parse_expression(arg, 0)?); + args.push(self.parse_expression(arg, level + 1)?); // After the parsing is done for the current argument, move both // `self.offset` and `self.column` right after the end of the @@ -999,22 +1016,38 @@ impl Parser { // Parses the given line by assuming it's an expression under parenthesis. // This function then grabs whatever is inside of these parenthesis and // parses the expression inside of them. - fn extract_parenthesized_expression( - &mut self, - line: &str, - level: usize, - ) -> Result<PNode, Error> { + fn extract_paren_expression(&mut self, line: &str, level: usize) -> Result<PNode, Error> { // Skip '(' character and whitespace characters in between. self.next(); self.skip_whitespace(line); - // Extract what's inside of the enclosing parenthesis. + // Extract the string inside of the enclosing parenthesis. let paren = self.find_matching_paren(line, self.offset)?; let l = line.get(self.offset..paren).unwrap_or_default(); - // And return what you can parse from the inner expression. + // The offset will be reset since we are trimming the string to be + // parsed. That being said, keep the previous value so it can be added + // afterwards. + let prev = self.offset; self.offset = 0; - self.parse_expression(l, level + 1) + + // Parenthesis reset the index of looking ahead, since ambiguities are + // removed by using parenthesis. Hence, store the current index and + // reset it. + let prev_idx = self.look_ahead_index; + self.look_ahead_index = 0; + + // Parse the inner expression and restore the 'look_ahead_index'. As for + // the 'offset', the inner expression has moved it, so add the previous + // value to it so the value matches the line originally given to this + // function. + let node = self.parse_expression(l, level + 1)?; + self.look_ahead_index = prev_idx; + self.offset += prev; + + // Skip ')' character and return the parsed expression. + self.next(); + Ok(node) } // Consumes the given line by assuming is a string in double quotes. @@ -1066,6 +1099,10 @@ impl Parser { line: &str, level: usize, ) -> Result<PNode, Error> { + // Save the symbol before discarding it, since it's going to be used for + // the PString's value. + let symbol = line.chars().nth(0).unwrap(); + // Skip operator and whitespaces. let start = self.column; self.next(); @@ -1079,7 +1116,7 @@ impl Parser { Ok(PNode { node_type, value: PString { - value: String::from(""), + value: String::from(symbol) + &right.value.value, line: self.line, start, end: right.value.end, @@ -1094,20 +1131,105 @@ impl Parser { // Parse the expression under `line`. Indeces such as `self.column` and // `self.offset` are assumed to be correct at this point for the given // `line` (e.g. the line might not be a full line but rather a limited range - // and the offset has been set accordingly). Returns a new node for the - // expression at hand. + // and the offset has been set accordingly). Moreover, this function is + // expected to be called rather often in a recursive manner. In order to + // avoid stack problems, a `level` of recursivity is passed so we can + // prevent too many nested expressions before exhausting the call stack. + // Returns a new node for the expression at hand. fn parse_expression(&mut self, line: &str, level: usize) -> Result<PNode, Error> { // Avoid stack overflows from too many recursive calls for expressions - // that are too nested. This mainly requires fuzzy testing to get to - // this point, but let's be safe about this anyways. + // that are too nested. I have only seen this recursion level on wild + // inputs while fuzzy testing, so no real human code should reach this + // point. Eitherway, let's be safe. if level >= 16 { return Err(self.parser_error("there are too many nested expressions")); } - // Cases where fetching an "identifier" is really not needed. + // Parse the expression that we have here and now. + let expr = self.parse_expression_at_point(line, level)?; + + // Were we looking ahead? If so simply return so the caller can react to + // it. + let starting_level = *self.look_ahead_levels.last().unwrap_or(&0); + if self.look_ahead_index > starting_level { + return Ok(expr); + } + + // We were not looking ahead at this point. Let's grab the rest of the + // string and check if there is a binary operation at hand. + self.skip_whitespace(line); + let l = line.get(self.offset..).unwrap_or_default().trim_end(); + + let (op, op_size) = self.get_operation_from_line(l)?; + if let Some(node_type) = op { + // The left node of the operator is simply the "identifier" that + // came to us. + let left = Some(Box::new(expr)); + + // Fetch a trimmed version of the string that comes after the + // operator. + self.offset += op_size; + self.column += op_size; + self.skip_whitespace(line); + let right_str = line.get(self.offset..).unwrap_or_default().trim_end(); + + // The right node of the operation will be the parsed expression + // of the string we just got right of the operator. + let prev = self.offset; + self.offset = 0; + let right = self.parse_expression(right_str, level + 1)?; + self.offset += prev; + + return Ok(PNode { + node_type, + value: PString { + value: String::from(""), + line: left.as_ref().unwrap().value.line, + start: left.as_ref().unwrap().value.start, + end: right.value.end, + }, + left, + right: Some(Box::new(right)), + args: None, + source: self.current_source, + }); + } + + // There is no binary operation. Hence, just return the expression as + // expected. + Ok(expr) + } + + // Parse the expression from the very start of the given `line` and by + // assuming that there are no further expressions to be parsed after the + // given one (this is the task for the caller). The `level` of recursivity + // is also passed since it might internally call `parse_expression` again. + fn parse_expression_at_point(&mut self, line: &str, level: usize) -> Result<PNode, Error> { let first = line.chars().next().unwrap_or_default(); + if first == '(' { - return self.extract_parenthesized_expression(line, level); + self.extract_paren_expression(line, level) + } else if first == '.' { + let (id, _) = self.parse_identifier(line)?; + self.parse_control(id, line, level) + } else if first == '\'' { + self.parse_char(line) + } else if first == '$' || first == '#' || first == '%' { + // Literal symbols come with a single character, or with two only on + // '#$' or '#%'. Other variations are illegal and should be avoided + // to prevent crashes. + if let Some(next) = line.chars().nth(1) { + if next == '#' || (first != '#' && (next == '$' || next == '%')) { + return Err(Error { + line: self.line, + global: false, + source: self.sources[self.current_source].clone(), + message: "bad literal syntax".to_string(), + }); + } + } + + self.parse_literal(line, first, level) } else if let Some(node_type) = self.get_unary_from_line(line) { // Only treat this as a unary operator if the next character is not // another unary operator (e.g. disambiguate between '<<' and '<'). @@ -1115,19 +1237,33 @@ impl Parser { .get_unary_from_line(line.get(1..).unwrap_or("")) .is_none() { - return self.parse_unary_operation(node_type, line, level); + self.parse_unary_operation(node_type, line, level) + } else { + self.parse_value(line) } + } else { + self.parse_value(line) } + } - // Now that we have changed specific cases where detecting an - // "identifier" is not really relevant, let's fetch the "identifier" and - // parse the expression with that into consideration. + // Like `parse_identifier` but it returns an error if a label was found. + fn parse_value(&mut self, line: &str) -> Result<PNode, Error> { let (id, nt) = self.parse_identifier(line)?; + if id.is_empty() { + return Err(self.parser_error("invalid identifier")); + } if nt == NodeType::Label { Err(self.parser_error("not expecting a label defined here")) } else { - self.parse_expression_with_identifier(id, line, level) + Ok(PNode { + node_type: NodeType::Value, + value: id, + left: None, + right: None, + args: None, + source: self.current_source, + }) } } @@ -1190,124 +1326,6 @@ impl Parser { } } - // Parse the expression under `line` by taking into consideration that a - // part of it has already been parsed and evaluated as the given `id`. - // Indeces such as `self.column` and `self.offset` are assumed to be correct - // at this point. Returns a new node for the expression at hand. - fn parse_expression_with_identifier( - &mut self, - id: PString, - line: &str, - level: usize, - ) -> Result<PNode, Error> { - // Reaching this condition is usually a bad sign, but there is so many - // ways in which it could go wrong, that an `assert!` wouldn't be fair - // either. Hence, just error out. - if id.is_empty() { - return Err(self.parser_error("invalid identifier")); - } - - // Cache the first character on the next part as it's used in lots of - // places. - let start = line.chars().nth(0).unwrap_or(' '); - - if id.value.starts_with(".") { - self.parse_control(id, line) - } else if start == '$' || start == '#' || start == '%' { - // Literal symbols come with a single character, or with two only on - // '#$' or '#%'. Other variations are illegal and should be avoided - // to prevent crashes. - if let Some(next) = line.chars().nth(1) { - if next == '#' || (start != '#' && (next == '$' || next == '%')) { - return Err(Error { - line: id.line, - global: false, - source: self.sources[self.current_source].clone(), - message: "bad literal syntax".to_string(), - }); - } - } - - self.parse_literal(id, line, level) - } else if start == '\'' { - self.parse_char(id) - } else { - // Skip any whitespace after our identifier. - self.skip_whitespace(line); - let l = line.get(self.offset..).unwrap_or_default().trim_end(); - - // The line might start with a binary operator. This would mean that - // the "id" is actually just the left node of a binary operation and - // that we just need to parse the right arm. - let (op, op_size) = self.get_operation_from_line(l)?; - if let Some(node_type) = op { - // The left node of the operator is simply the "identifier" that - // came to us. - let left = Some(Box::new(PNode { - node_type: NodeType::Value, - value: id.clone(), - left: None, - right: None, - args: None, - source: self.current_source, - })); - - // Fetch a trimmed version of the string that comes after the - // operator. - self.offset += op_size; - self.column += op_size; - self.skip_whitespace(line); - let right_str = line.get(self.offset..).unwrap_or_default().trim_end(); - - // The right node of the operation will be the parsed expression - // of the string we just got right of the operator. - self.offset = 0; - let right = self.parse_expression(right_str, level)?; - - return Ok(PNode { - node_type, - value: PString { - value: String::from(""), - line: id.line, - start: id.start, - end: right.value.end, - }, - left, - right: Some(Box::new(right)), - args: None, - source: self.current_source, - }); - } - - // Ok, so the line did not indicate any sort of operation. That - // being said, if the rest of the line still contains stuff, it - // might as well be a macro call. Try to process it as such. - if !l.is_empty() { - let args = self.parse_arguments(line)?; - return Ok(PNode { - node_type: NodeType::Call, - value: id, - left: None, - right: None, - args: if args.is_empty() { None } else { Some(args) }, - source: self.current_source, - }); - } - - // Blindly return the identifier as a PNode. This might be either a - // value as-is, or a macro call which we can't make sense at the - // moment. Eitherway, let the assembler decide. - Ok(PNode { - node_type: NodeType::Value, - value: id, - left: None, - right: None, - args: None, - source: self.current_source, - }) - } - } - // Generate a unique identifier with the given prefix. fn unique_identifier(&self, prefix: String) -> String { prefix + &String::from("-") + &Alphanumeric.sample_string(&mut rand::thread_rng(), 16) @@ -1315,7 +1333,7 @@ impl Parser { // Returns a NodeType::Control node with whatever could be parsed // considering the given `id` and rest of the `line`. - fn parse_control(&mut self, id: PString, line: &str) -> Result<PNode, Error> { + fn parse_control(&mut self, id: PString, line: &str, level: usize) -> Result<PNode, Error> { let mut left = None; // Ensure that this is a function that we know of. In the past this was @@ -1360,7 +1378,7 @@ impl Parser { self.skip_whitespace(line); vec![self.parse_quoted_string(line)?] } else { - self.parse_arguments(line)? + self.parse_arguments(line, level)? }; if let Some(args_required) = control.required_args { if args.len() < args_required.0 || args.len() > args_required.1 { @@ -1381,25 +1399,19 @@ impl Parser { } // Returns a NodeType::Literal node with whatever could be parsed - // considering the given `id` and rest of the `line`. - fn parse_literal(&mut self, id: PString, line: &str, level: usize) -> Result<PNode, Error> { - // Force the column to point to the literal character just in case - // of expressions like '#.hibyte'. Then skip whitespaces for super - // ugly statements such as '# 20'. This is ugly but we should permit - // it. A later linter can yell at a programmer for this. - self.column = id.start; - self.offset = 0; - self.next(); - + // considering the given `line` which starts with the given `symbol`. The + // recursivity `level` is also provided as it will call again + // `parse_expression`. + fn parse_literal(&mut self, line: &str, symbol: char, level: usize) -> Result<PNode, Error> { // Enforce that literal symbols and their values are not separated by // random white space characters. Other assemblers (e.g. ca65) also take // this stance, and through fuzzy testing I realized that not doing this // could result in general bad behavior. - let inner = line.get(self.offset..).unwrap_or(""); + let inner = line.get(1..).unwrap_or(""); if let Some(c) = inner.chars().nth(0) { if c.is_whitespace() { return Err(Error { - line: id.line, + line: self.line, global: false, source: self.sources[self.current_source].clone(), message: "numeric literals cannot have white spaces".to_string(), @@ -1407,13 +1419,33 @@ impl Parser { } } - // Just fetch the inner expression and return the literal node. + // Preserve the initial column value and advance it to skip the 'symbol' + // character. Then we need to reset the offset as usual since the parsed + // expression has been trimmed. + let start = self.column; + self.column += 1; self.offset = 0; + + // Parse the inner expression while also pushing/popping the look ahead + // status. This is needed as there are no closing characters for a given + // literal, so to disambiguate we must look ahead. + self.look_ahead_levels.push(self.look_ahead_index); + self.look_ahead_index += 1; let left = self.parse_expression(inner, level + 1)?; + self.look_ahead_index -= 1; + self.look_ahead_levels.pop(); + + // Add the 'symbol' to the final offset. + self.offset += 1; Ok(PNode { node_type: NodeType::Literal, - value: id, + value: PString { + value: String::from(symbol) + &left.value.value, + line: self.line, + start, + end: left.value.end, + }, left: Some(Box::new(left)), right: None, args: None, @@ -1424,15 +1456,17 @@ impl Parser { // Returns a NodeType::Literal node with the given `id` parsed as a // character literal. This literal will have on the left node a value which // is the character transformed into a decimal value. - fn parse_char(&mut self, id: PString) -> Result<PNode, Error> { - if id.value.len() != 3 { + fn parse_char(&mut self, line: &str) -> Result<PNode, Error> { + if line.len() != 3 { return Err(self.parser_error("bad character literal")); } - let mut chars = id.value.chars(); + // Grab the actual character and the delimiter. + let mut chars = line.chars(); let del = chars.next().unwrap(); let ch = chars.next().unwrap(); + // Sanity checks. if !ch.is_ascii_alphanumeric() { return Err(self.parser_error( "only alphanumeric ASCII characters are allowed on character literals", @@ -1442,16 +1476,25 @@ impl Parser { return Err(self.parser_error("bad character literal")); } + // Advance the column passed ahead of this literal (note the the PNode + // below will have to take this into account with the start/end values). + self.column += 3; + Ok(PNode { node_type: NodeType::Literal, - value: id.clone(), + value: PString { + value: format!("'{}'", ch), + line: self.line, + start: self.column - 3, + end: self.column, + }, left: Some(Box::new(PNode { node_type: NodeType::Value, value: PString { value: (ch as u8).to_string(), - line: id.line, - start: id.start + 1, - end: id.end - 1, + line: self.line, + start: self.column - 2, + end: self.column - 1, }, left: None, right: None, @@ -1622,11 +1665,20 @@ mod tests { #[test] fn parse_pound_literal() { - for line in vec!["#20", " #20 ", " #20 ; Comment", " label: #20"].into_iter() { + for line in vec![ + "lda #20", + " lda #20 ", + " lda #20 ; Comment", + " label: lda #20", + ] + .into_iter() + { let mut parser = Parser::default(); assert!(parser.parse(line.as_bytes(), SourceInfo::default()).is_ok()); - let node = parser.nodes.last().unwrap().last().unwrap(); + let nodes = parser.nodes(); + + let node = nodes.last().unwrap().left.as_ref().unwrap(); assert_eq!(node.node_type, NodeType::Literal); assert!(node.right.is_none()); assert!(node.args.is_none()); @@ -1640,11 +1692,13 @@ mod tests { #[test] fn parse_compound_literal() { - let line = "#$20"; + let line = "lda #$20"; let mut parser = Parser::default(); assert!(parser.parse(line.as_bytes(), SourceInfo::default()).is_ok()); - let node = parser.nodes.last().unwrap().last().unwrap(); + let nodes = parser.nodes(); + + let node = nodes.last().unwrap().left.as_ref().unwrap(); assert_eq!(node.node_type, NodeType::Literal); assert!(node.right.is_none()); assert!(node.args.is_none()); @@ -1666,11 +1720,13 @@ mod tests { #[test] fn parse_variable_in_literal() { - let line = "#Variable"; + let line = "lda #Variable"; let mut parser = Parser::default(); assert!(parser.parse(line.as_bytes(), SourceInfo::default()).is_ok()); - let node = parser.nodes.last().unwrap().last().unwrap(); + let nodes = parser.nodes(); + + let node = nodes.last().unwrap().left.as_ref().unwrap(); assert_eq!(node.node_type, NodeType::Literal); assert!(node.right.is_none()); assert!(node.args.is_none()); @@ -1711,7 +1767,7 @@ mod tests { #[test] fn parse_bad_literals() { - for line in vec!["#", "#%", "$"].into_iter() { + for line in vec!["lda #", "lda #%", "lda $"].into_iter() { let mut parser = Parser::default(); let err = parser .parse(line.as_bytes(), SourceInfo::default()) @@ -1720,7 +1776,7 @@ mod tests { assert_eq!(err.first().unwrap().message, "invalid identifier"); } - for line in vec!["$ 2", "#% 2", "# 2"].into_iter() { + for line in vec!["lda $ 2", "lda #% 2", "lda # 2"].into_iter() { let mut parser = Parser::default(); let err = parser .parse(line.as_bytes(), SourceInfo::default()) @@ -1732,7 +1788,16 @@ mod tests { ); } - for line in vec!["##2", "#$$2", "$$2", "#$#$2", "#$#2", "###"].into_iter() { + for line in vec![ + "lda ##2", + "lda #$$2", + "lda $$2", + "lda #$#$2", + "lda #$#2", + "lda ###", + ] + .into_iter() + { let mut parser = Parser::default(); let err = parser .parse(line.as_bytes(), SourceInfo::default()) @@ -2162,7 +2227,7 @@ mod tests { assert!(node.right.is_none()); let literal = &node.left.clone().unwrap(); - assert_node(literal, NodeType::Literal, line, "#"); + assert_eq!(literal.node_type, NodeType::Literal); let op = &literal.left.clone().unwrap(); assert_eq!(op.node_type, NodeType::Operation(OperationType::Mul)); @@ -2176,6 +2241,44 @@ mod tests { } #[test] + fn nested_expression_test() { + let line = "lda #$80 >> ((BCD_BITS - 1) & 3)"; + let mut parser = Parser::default(); + assert!(parser.parse(line.as_bytes(), SourceInfo::default()).is_ok()); + + let instr = parser.nodes.last().unwrap().last().unwrap(); + assert_node(instr, NodeType::Instruction, line, "lda"); + assert!(instr.args.is_none()); + assert!(instr.right.is_none()); + + // Shift object + let left = instr.left.as_ref().unwrap(); + assert_eq!(left.node_type, NodeType::Operation(OperationType::Rshift)); + + // Left arm of the shift. + assert_node(left.left.as_ref().unwrap(), NodeType::Literal, line, "#$80"); + + // Right arm of the shift: bitwise and. + let right = left.right.as_ref().unwrap(); + assert_eq!(right.node_type, NodeType::Operation(OperationType::And)); + + // Left arm of the bitwise and. + let left_and = right.left.as_ref().unwrap(); + assert_eq!(left_and.node_type, NodeType::Operation(OperationType::Sub)); + assert_node( + left_and.left.as_ref().unwrap(), + NodeType::Value, + line, + "BCD_BITS", + ); + assert_node(left_and.right.as_ref().unwrap(), NodeType::Value, line, "1"); + + // Right arm of the bitwise and. + let right_and = right.right.as_ref().unwrap(); + assert_node(right_and, NodeType::Value, line, "3"); + } + + #[test] fn unary_operator_test() { let line = "ldx #<NUM_SPRITES"; let mut parser = Parser::default(); @@ -2187,7 +2290,7 @@ mod tests { assert!(node.right.is_none()); let literal = &node.left.clone().unwrap(); - assert_node(literal, NodeType::Literal, line, "#"); + assert_node(literal, NodeType::Literal, line, "#<NUM_SPRITES"); let op = &literal.left.clone().unwrap(); assert_eq!(op.node_type, NodeType::Operation(OperationType::LoByte)); @@ -2450,9 +2553,9 @@ mod tests { #[test] fn parse_control_wrong_close() { let code = r#".scope Scope -.macro Macro -.endscope -.endmacro"#; + .macro Macro + .endscope + .endmacro"#; let mut parser = Parser::default(); let err = parser .parse(code.as_bytes(), SourceInfo::default()) @@ -2784,7 +2887,7 @@ inc $20 assert!(parser.parse(line.as_bytes(), SourceInfo::default()).is_ok()); let node = parser.nodes.last().unwrap().last().unwrap(); - assert_node(node, NodeType::Value, line, "MACRO_CALL"); + assert_node(node, NodeType::Call, line, "MACRO_CALL"); assert!(node.left.is_none()); assert!(node.right.is_none()); assert!(node.args.is_none()); |