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Refactor VM, chunk and parser to pass tests

This commit is contained in:
Jeff 2024-10-05 00:11:03 -04:00
parent 9b1dc6c55c
commit 9d0aa13e8a
5 changed files with 90 additions and 65 deletions

View File

@ -308,7 +308,7 @@ impl PartialEq for Chunk {
#[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)] #[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
pub struct Local { pub struct Local {
pub identifier: Identifier, pub identifier: Identifier,
pub mutable: bool, pub is_mutable: bool,
pub depth: usize, pub depth: usize,
pub register_index: Option<u8>, pub register_index: Option<u8>,
} }
@ -322,7 +322,7 @@ impl Local {
) -> Self { ) -> Self {
Self { Self {
identifier, identifier,
mutable, is_mutable: mutable,
depth, depth,
register_index, register_index,
} }
@ -481,7 +481,7 @@ impl<'a> ChunkDisassembler<'a> {
identifier, identifier,
depth, depth,
register_index, register_index,
mutable, is_mutable: mutable,
}, },
) in self.chunk.locals.iter().enumerate() ) in self.chunk.locals.iter().enumerate()
{ {

View File

@ -206,13 +206,8 @@ impl Instruction {
instruction instruction
} }
pub fn r#return(from_register: u8, to_register: u8) -> Instruction { pub fn r#return() -> Instruction {
let mut instruction = Instruction(Operation::Return as u32); Instruction(Operation::Return as u32)
instruction.set_a(from_register);
instruction.set_b(to_register);
instruction
} }
pub fn operation(&self) -> Operation { pub fn operation(&self) -> Operation {
@ -350,7 +345,14 @@ impl Instruction {
Operation::LoadConstant => { Operation::LoadConstant => {
let register_index = self.a(); let register_index = self.a();
let constant_index = self.b(); let constant_index = self.b();
let jump = if self.c_as_boolean() { "&& JUMP" } else { "" }; let jump = if self.c_as_boolean() {
jump_offset = Some(1);
"&& JUMP"
} else {
""
};
let constant = if let Some(chunk) = chunk { let constant = if let Some(chunk) = chunk {
match chunk.get_constant(constant_index, Span(0, 0)) { match chunk.get_constant(constant_index, Span(0, 0)) {
Ok(constant) => constant.to_string(), Ok(constant) => constant.to_string(),
@ -531,12 +533,7 @@ impl Instruction {
None None
} }
Operation::Return => { Operation::Return => None,
let from_register = self.a();
let to_register = self.b();
Some(format!("R{from_register}..=R{to_register}"))
}
}; };
(info, jump_offset) (info, jump_offset)
@ -745,10 +742,8 @@ mod tests {
#[test] #[test]
fn r#return() { fn r#return() {
let instruction = Instruction::r#return(4, 8); let instruction = Instruction::r#return();
assert_eq!(instruction.operation(), Operation::Return); assert_eq!(instruction.operation(), Operation::Return);
assert_eq!(instruction.a(), 4);
assert_eq!(instruction.b(), 8);
} }
} }

View File

@ -585,7 +585,10 @@ impl<'src> Parser<'src> {
let local_index = self.parse_identifier_from(token, start_position)?; let local_index = self.parse_identifier_from(token, start_position)?;
if allow_assignment && self.allow(TokenKind::Equal)? { if allow_assignment && self.allow(TokenKind::Equal)? {
let is_mutable = self.chunk.get_local(local_index, start_position)?.mutable; let is_mutable = self
.chunk
.get_local(local_index, start_position)?
.is_mutable;
if !is_mutable { if !is_mutable {
return Err(ParseError::CannotMutateImmutableVariable { return Err(ParseError::CannotMutateImmutableVariable {
@ -729,8 +732,10 @@ impl<'src> Parser<'src> {
self.parse_block(allow_assignment, allow_return)?; self.parse_block(allow_assignment, allow_return)?;
} }
if self.chunk.get_last_operation()? == Operation::LoadConstant let last_operation = self.chunk.get_last_operation()?;
&& self.current_token == Token::Else
if let (Operation::LoadConstant | Operation::LoadBoolean, Token::Else) =
(last_operation, self.current_token)
{ {
let (mut load_constant, load_constant_position) = let (mut load_constant, load_constant_position) =
self.chunk.pop_instruction(self.current_position)?; self.chunk.pop_instruction(self.current_position)?;
@ -803,7 +808,6 @@ impl<'src> Parser<'src> {
Instruction::load_boolean(self.current_register, false, false), Instruction::load_boolean(self.current_register, false, false),
comparison_position, comparison_position,
); );
self.increment_register()?;
} }
} }
@ -824,12 +828,7 @@ impl<'src> Parser<'src> {
self.parse_expression()?; self.parse_expression()?;
if !self.allow(TokenKind::Semicolon)? && self.is_eof() { if !self.allow(TokenKind::Semicolon)? && self.is_eof() {
let register = self.current_register.saturating_sub(1); self.emit_instruction(Instruction::r#return(), self.current_position);
self.emit_instruction(
Instruction::r#return(register, register),
self.current_position,
);
} }
} }
}; };

View File

@ -146,14 +146,13 @@ impl Vm {
let register_index = instruction.a(); let register_index = instruction.a();
let local_index = instruction.b(); let local_index = instruction.b();
let local = self.chunk.get_local(local_index, position)?; let local = self.chunk.get_local(local_index, position)?;
let value = if let Some(index) = local.register_index {
self.take(index, position)? if !local.is_mutable {
} else { return Err(VmError::CannotMutateImmutableLocal {
return Err(VmError::UndefinedVariable {
identifier: local.identifier.clone(), identifier: local.identifier.clone(),
position, position,
}); });
}; }
let new_value = if instruction.b_is_constant() { let new_value = if instruction.b_is_constant() {
self.chunk.take_constant(register_index, position)? self.chunk.take_constant(register_index, position)?
@ -161,10 +160,9 @@ impl Vm {
self.take(register_index, position)? self.take(register_index, position)?
}; };
value self.insert(new_value, register_index, position)?;
.mutate(new_value) self.chunk
.map_err(|error| VmError::Value { error, position })?; .define_local(local_index, register_index, position)?;
self.insert(value, register_index, position)?;
} }
Operation::Add => { Operation::Add => {
let (left, right) = get_arguments(self, instruction, position)?; let (left, right) = get_arguments(self, instruction, position)?;
@ -469,7 +467,7 @@ impl Vm {
position, position,
}); });
}; };
let clone_result = if local.mutable { let clone_result = if local.is_mutable {
self._clone_mutable(index, position) self._clone_mutable(index, position)
} else { } else {
self.clone(index, position) self.clone(index, position)
@ -508,6 +506,10 @@ impl Vm {
#[derive(Debug, Clone, PartialEq)] #[derive(Debug, Clone, PartialEq)]
pub enum VmError { pub enum VmError {
CannotMutateImmutableLocal {
identifier: Identifier,
position: Span,
},
EmptyRegister { EmptyRegister {
index: usize, index: usize,
position: Span, position: Span,
@ -555,6 +557,7 @@ impl AnnotatedError for VmError {
fn description(&self) -> &'static str { fn description(&self) -> &'static str {
match self { match self {
Self::CannotMutateImmutableLocal { .. } => "Cannot mutate immutable variable",
Self::EmptyRegister { .. } => "Empty register", Self::EmptyRegister { .. } => "Empty register",
Self::ExpectedBoolean { .. } => "Expected boolean", Self::ExpectedBoolean { .. } => "Expected boolean",
Self::RegisterIndexOutOfBounds { .. } => "Register index out of bounds", Self::RegisterIndexOutOfBounds { .. } => "Register index out of bounds",
@ -581,6 +584,7 @@ impl AnnotatedError for VmError {
fn position(&self) -> Span { fn position(&self) -> Span {
match self { match self {
Self::CannotMutateImmutableLocal { position, .. } => *position,
Self::EmptyRegister { position, .. } => *position, Self::EmptyRegister { position, .. } => *position,
Self::ExpectedBoolean { position, .. } => *position, Self::ExpectedBoolean { position, .. } => *position,
Self::RegisterIndexOutOfBounds { position } => *position, Self::RegisterIndexOutOfBounds { position } => *position,

View File

@ -13,7 +13,7 @@ fn add() {
.set_c_is_constant(), .set_c_is_constant(),
Span(2, 3) Span(2, 3)
), ),
(Instruction::r#return(0, 0), Span(5, 5)) (Instruction::r#return(), Span(5, 5))
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -35,7 +35,7 @@ fn and() {
(Instruction::test(0, false), Span(5, 7)), (Instruction::test(0, false), Span(5, 7)),
(Instruction::jump(1, true), Span(5, 7)), (Instruction::jump(1, true), Span(5, 7)),
(Instruction::load_boolean(1, false, false), Span(8, 13)), (Instruction::load_boolean(1, false, false), Span(8, 13)),
(Instruction::r#return(0, 0), Span(13, 13)), (Instruction::r#return(), Span(13, 13)),
], ],
vec![], vec![],
vec![] vec![]
@ -102,7 +102,7 @@ fn constant() {
Ok(Chunk::with_data( Ok(Chunk::with_data(
vec![ vec![
(Instruction::load_constant(0, 0, false), Span(0, 2)), (Instruction::load_constant(0, 0, false), Span(0, 2)),
(Instruction::r#return(0, 0), Span(2, 2)) (Instruction::r#return(), Span(2, 2))
], ],
vec![Value::integer(42)], vec![Value::integer(42)],
vec![] vec![]
@ -143,7 +143,7 @@ fn divide() {
.set_c_is_constant(), .set_c_is_constant(),
Span(2, 3) Span(2, 3)
), ),
(Instruction::r#return(0, 0), Span(5, 5)) (Instruction::r#return(), Span(5, 5))
], ],
vec![Value::integer(2), Value::integer(2)], vec![Value::integer(2), Value::integer(2)],
vec![] vec![]
@ -177,6 +177,7 @@ fn equal() {
(Instruction::jump(1, true), Span(2, 4)), (Instruction::jump(1, true), Span(2, 4)),
(Instruction::load_boolean(0, true, true), Span(2, 4)), (Instruction::load_boolean(0, true, true), Span(2, 4)),
(Instruction::load_boolean(0, false, false), Span(2, 4)), (Instruction::load_boolean(0, false, false), Span(2, 4)),
(Instruction::r#return(), Span(6, 6)),
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -188,7 +189,7 @@ fn equal() {
#[test] #[test]
fn equality_assignment_long() { fn equality_assignment_long() {
let source = "let a = if 4 == 4 { true } else { false };"; let source = "let a = if 4 == 4 { true } else { false }; a";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -200,10 +201,12 @@ fn equality_assignment_long() {
.set_c_is_constant(), .set_c_is_constant(),
Span(13, 15) Span(13, 15)
), ),
(Instruction::jump(1, true), Span(27, 31)), (Instruction::jump(1, true), Span(13, 15)),
(Instruction::load_boolean(0, true, false), Span(20, 24)), (Instruction::load_boolean(0, true, true), Span(20, 24)),
(Instruction::load_boolean(0, false, false), Span(34, 39)), (Instruction::load_boolean(0, false, false), Span(34, 39)),
(Instruction::define_local(0, 0, false), Span(4, 5)), (Instruction::define_local(0, 0, false), Span(4, 5)),
(Instruction::get_local(1, 0), Span(43, 44)),
(Instruction::r#return(), Span(44, 44)),
], ],
vec![Value::integer(4), Value::integer(4)], vec![Value::integer(4), Value::integer(4)],
vec![Local::new(Identifier::new("a"), false, 0, Some(0))] vec![Local::new(Identifier::new("a"), false, 0, Some(0))]
@ -215,7 +218,7 @@ fn equality_assignment_long() {
#[test] #[test]
fn equality_assignment_short() { fn equality_assignment_short() {
let source = "let a = 4 == 4;"; let source = "let a = 4 == 4; a";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -231,18 +234,20 @@ fn equality_assignment_short() {
(Instruction::load_boolean(0, true, true), Span(10, 12)), (Instruction::load_boolean(0, true, true), Span(10, 12)),
(Instruction::load_boolean(0, false, false), Span(10, 12)), (Instruction::load_boolean(0, false, false), Span(10, 12)),
(Instruction::define_local(0, 0, false), Span(4, 5)), (Instruction::define_local(0, 0, false), Span(4, 5)),
(Instruction::get_local(1, 0), Span(16, 17)),
(Instruction::r#return(), Span(17, 17)),
], ],
vec![Value::integer(4), Value::integer(4)], vec![Value::integer(4), Value::integer(4)],
vec![Local::new(Identifier::new("a"), false, 0, Some(0))] vec![Local::new(Identifier::new("a"), false, 0, Some(0))]
)), )),
); );
assert_eq!(run(source), Ok(None)); assert_eq!(run(source), Ok(Some(Value::boolean(true))));
} }
#[test] #[test]
fn greater() { fn greater() {
let source = "1 > 2;"; let source = "1 > 2";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -257,6 +262,7 @@ fn greater() {
(Instruction::jump(1, true), Span(2, 3)), (Instruction::jump(1, true), Span(2, 3)),
(Instruction::load_boolean(0, true, true), Span(2, 3)), (Instruction::load_boolean(0, true, true), Span(2, 3)),
(Instruction::load_boolean(0, false, false), Span(2, 3)), (Instruction::load_boolean(0, false, false), Span(2, 3)),
(Instruction::r#return(), Span(5, 5)),
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -268,7 +274,7 @@ fn greater() {
#[test] #[test]
fn greater_than_or_equal() { fn greater_than_or_equal() {
let source = "1 >= 2;"; let source = "1 >= 2";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -283,6 +289,7 @@ fn greater_than_or_equal() {
(Instruction::jump(1, true), Span(2, 4)), (Instruction::jump(1, true), Span(2, 4)),
(Instruction::load_boolean(0, true, true), Span(2, 4)), (Instruction::load_boolean(0, true, true), Span(2, 4)),
(Instruction::load_boolean(0, false, false), Span(2, 4)), (Instruction::load_boolean(0, false, false), Span(2, 4)),
(Instruction::r#return(), Span(6, 6)),
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -306,9 +313,10 @@ fn if_else_expression() {
.set_c_is_constant(), .set_c_is_constant(),
Span(5, 7) Span(5, 7)
), ),
(Instruction::jump(1, true), Span(16, 20)), (Instruction::jump(1, true), Span(5, 7)),
(Instruction::load_constant(0, 2, true), Span(12, 13)), (Instruction::load_constant(0, 2, true), Span(12, 13)),
(Instruction::load_constant(0, 3, false), Span(23, 24)), (Instruction::load_constant(0, 3, false), Span(23, 24)),
(Instruction::r#return(), Span(26, 26)),
], ],
vec![ vec![
Value::integer(1), Value::integer(1),
@ -337,8 +345,9 @@ fn if_expression() {
.set_c_is_constant(), .set_c_is_constant(),
Span(5, 7) Span(5, 7)
), ),
(Instruction::jump(1, true), Span(15, 15)), (Instruction::jump(1, true), Span(5, 7)),
(Instruction::load_constant(0, 2, false), Span(12, 13)), (Instruction::load_constant(0, 2, false), Span(12, 13)),
(Instruction::r#return(), Span(15, 15)),
], ],
vec![Value::integer(1), Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -350,7 +359,7 @@ fn if_expression() {
#[test] #[test]
fn less_than() { fn less_than() {
let source = "1 < 2;"; let source = "1 < 2";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -365,6 +374,7 @@ fn less_than() {
(Instruction::jump(1, true), Span(2, 3)), (Instruction::jump(1, true), Span(2, 3)),
(Instruction::load_boolean(0, true, true), Span(2, 3)), (Instruction::load_boolean(0, true, true), Span(2, 3)),
(Instruction::load_boolean(0, false, false), Span(2, 3)), (Instruction::load_boolean(0, false, false), Span(2, 3)),
(Instruction::r#return(), Span(5, 5)),
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -376,7 +386,7 @@ fn less_than() {
#[test] #[test]
fn less_than_or_equal() { fn less_than_or_equal() {
let source = "1 <= 2;"; let source = "1 <= 2";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -391,6 +401,7 @@ fn less_than_or_equal() {
(Instruction::jump(1, true), Span(2, 4)), (Instruction::jump(1, true), Span(2, 4)),
(Instruction::load_boolean(0, true, true), Span(2, 4)), (Instruction::load_boolean(0, true, true), Span(2, 4)),
(Instruction::load_boolean(0, false, false), Span(2, 4)), (Instruction::load_boolean(0, false, false), Span(2, 4)),
(Instruction::r#return(), Span(6, 6)),
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -412,6 +423,7 @@ fn list() {
(Instruction::load_constant(1, 1, false), Span(4, 5)), (Instruction::load_constant(1, 1, false), Span(4, 5)),
(Instruction::load_constant(2, 2, false), Span(7, 8)), (Instruction::load_constant(2, 2, false), Span(7, 8)),
(Instruction::load_list(3, 0, 2), Span(0, 9)), (Instruction::load_list(3, 0, 2), Span(0, 9)),
(Instruction::r#return(), Span(9, 9)),
], ],
vec![Value::integer(1), Value::integer(2), Value::integer(3),], vec![Value::integer(1), Value::integer(2), Value::integer(3),],
vec![] vec![]
@ -452,6 +464,7 @@ fn list_with_complex_expression() {
(Instruction::subtract(3, 1, 2), Span(10, 11)), (Instruction::subtract(3, 1, 2), Span(10, 11)),
(Instruction::close(1, 3), Span(17, 18)), (Instruction::close(1, 3), Span(17, 18)),
(Instruction::load_list(4, 0, 3), Span(0, 18)), (Instruction::load_list(4, 0, 3), Span(0, 18)),
(Instruction::r#return(), Span(18, 18)),
], ],
vec![ vec![
Value::integer(1), Value::integer(1),
@ -468,7 +481,7 @@ fn list_with_complex_expression() {
run(source), run(source),
Ok(Some(Value::list(vec![ Ok(Some(Value::list(vec![
Value::integer(1), Value::integer(1),
Value::integer(1) Value::integer(-15)
]))) ])))
); );
} }
@ -490,6 +503,7 @@ fn list_with_simple_expression() {
), ),
(Instruction::load_constant(2, 3, false), Span(11, 12)), (Instruction::load_constant(2, 3, false), Span(11, 12)),
(Instruction::load_list(3, 0, 2), Span(0, 13)), (Instruction::load_list(3, 0, 2), Span(0, 13)),
(Instruction::r#return(), Span(13, 13)),
], ],
vec![ vec![
Value::integer(1), Value::integer(1),
@ -535,6 +549,7 @@ fn math_operator_precedence() {
Span(14, 15) Span(14, 15)
), ),
(Instruction::subtract(3, 0, 2), Span(6, 7)), (Instruction::subtract(3, 0, 2), Span(6, 7)),
(Instruction::r#return(), Span(17, 17)),
], ],
vec![ vec![
Value::integer(1), Value::integer(1),
@ -556,12 +571,15 @@ fn multiply() {
assert_eq!( assert_eq!(
parse(source), parse(source),
Ok(Chunk::with_data( Ok(Chunk::with_data(
vec![( vec![
*Instruction::multiply(0, 0, 1) (
.set_b_is_constant() *Instruction::multiply(0, 0, 1)
.set_c_is_constant(), .set_b_is_constant()
Span(2, 3) .set_c_is_constant(),
),], Span(2, 3)
),
(Instruction::r#return(), Span(5, 5)),
],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
)) ))
@ -577,7 +595,10 @@ fn negate() {
assert_eq!( assert_eq!(
parse(source), parse(source),
Ok(Chunk::with_data( Ok(Chunk::with_data(
vec![(*Instruction::negate(0, 0).set_b_is_constant(), Span(0, 1)),], vec![
(*Instruction::negate(0, 0).set_b_is_constant(), Span(0, 1)),
(Instruction::r#return(), Span(5, 5)),
],
vec![Value::integer(42)], vec![Value::integer(42)],
vec![] vec![]
)), )),
@ -596,6 +617,7 @@ fn not() {
vec![ vec![
(Instruction::load_boolean(0, true, false), Span(1, 5)), (Instruction::load_boolean(0, true, false), Span(1, 5)),
(Instruction::not(1, 0), Span(0, 1)), (Instruction::not(1, 0), Span(0, 1)),
(Instruction::r#return(), Span(5, 5)),
], ],
vec![], vec![],
vec![] vec![]
@ -607,7 +629,7 @@ fn not() {
#[test] #[test]
fn not_equal() { fn not_equal() {
let source = "1 != 2;"; let source = "1 != 2";
assert_eq!( assert_eq!(
parse(source), parse(source),
@ -622,6 +644,7 @@ fn not_equal() {
(Instruction::jump(1, true), Span(2, 4)), (Instruction::jump(1, true), Span(2, 4)),
(Instruction::load_boolean(0, true, true), Span(2, 4)), (Instruction::load_boolean(0, true, true), Span(2, 4)),
(Instruction::load_boolean(0, false, false), Span(2, 4)), (Instruction::load_boolean(0, false, false), Span(2, 4)),
(Instruction::r#return(), Span(6, 6)),
], ],
vec![Value::integer(1), Value::integer(2)], vec![Value::integer(1), Value::integer(2)],
vec![] vec![]
@ -642,6 +665,7 @@ fn or() {
(Instruction::test(0, true), Span(5, 7)), (Instruction::test(0, true), Span(5, 7)),
(Instruction::jump(1, true), Span(5, 7)), (Instruction::jump(1, true), Span(5, 7)),
(Instruction::load_boolean(1, false, false), Span(8, 13)), (Instruction::load_boolean(1, false, false), Span(8, 13)),
(Instruction::r#return(), Span(13, 13)),
], ],
vec![], vec![],
vec![] vec![]
@ -668,6 +692,7 @@ fn parentheses_precedence() {
*Instruction::multiply(1, 0, 2).set_c_is_constant(), *Instruction::multiply(1, 0, 2).set_c_is_constant(),
Span(8, 9) Span(8, 9)
), ),
(Instruction::r#return(), Span(11, 11)),
], ],
vec![Value::integer(1), Value::integer(2), Value::integer(3)], vec![Value::integer(1), Value::integer(2), Value::integer(3)],
vec![] vec![]
@ -679,7 +704,7 @@ fn parentheses_precedence() {
#[test] #[test]
fn set_local() { fn set_local() {
let source = "let mut x = 41; x = 42;"; let source = "let mut x = 41; x = 42; x";
assert_eq!( assert_eq!(
parse(source), parse(source),
Ok(Chunk::with_data( Ok(Chunk::with_data(
@ -688,6 +713,8 @@ fn set_local() {
(Instruction::define_local(0, 0, true), Span(8, 9)), (Instruction::define_local(0, 0, true), Span(8, 9)),
(Instruction::load_constant(1, 1, false), Span(20, 22)), (Instruction::load_constant(1, 1, false), Span(20, 22)),
(Instruction::set_local(1, 0), Span(16, 17)), (Instruction::set_local(1, 0), Span(16, 17)),
(Instruction::get_local(1, 0), Span(24, 25)),
(Instruction::r#return(), Span(25, 25)),
], ],
vec![Value::integer(41), Value::integer(42)], vec![Value::integer(41), Value::integer(42)],
vec![Local::new(Identifier::new("x"), true, 0, Some(0)),] vec![Local::new(Identifier::new("x"), true, 0, Some(0)),]