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Support capturing Error backtraces and debug.traceback #121

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d04661e
Support capturing Error backtraces and debug.traceback
rib Jul 8, 2025
8f79c21
debug.traceback: consolidate current thread branches
rib Jul 10, 2025
a87682f
cargo fmt
rib Jul 10, 2025
b603a5c
tests/backtrace: unwrap error + backtrace with let else and dedent code
rib Jul 10, 2025
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2 changes: 1 addition & 1 deletion COMPATIBILITY.md
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Original file line number Diff line number Diff line change
Expand Up @@ -227,6 +227,6 @@ implemented nor are there plans to implement due to differences between the impl
| ⚫️ | `setmetatable(value, table)` | Interesting thing to note is that this is _not_ the base library `setmetatable`, as `debug.setmetatable`'s first argument accepts any Lua value, while `setmetatable`'s first argument _must_ be a table. | |
| ⚫️ | `setupvalue(f, up, value)` | | |
| ⚫️ | `setuservalue(udata, value, n)` | | |
| ⚫️ | `traceback([thread,][message, level])` | | |
| 🔵 | `traceback([thread,][message, level])` | | |
| ⚫️ | `upvalueid(f, n)` | | |
| ⚫️ | `upvaluejoin(f1, n1, f2, n2)` | | |
3 changes: 1 addition & 2 deletions README.md
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Expand Up @@ -72,7 +72,7 @@ that are usable from safe Rust. It achieves this by combining two things:
that such pointers are isolated to a single root object, and to guarantee
that, outside an active call to `mutate`, all such pointers are either
reachable from the root object or are safe to collect.

## Stackless VM

The `mutate` based GC API means that long running calls to `mutate` can be
Expand Down Expand Up @@ -235,7 +235,6 @@ very much WIP, so ensuring this is done correctly is an ongoing effort.
generate and the VM sorely needs optimization (very little effort has gone
here so far).
* Error messages that don't make you want to cry
* Stack traces
* Debugger
* Aggressive optimization and *real* effort towards matching or beating (or
even just being within a respectable distance of) PUC-Rio Lua's performance
Expand Down
6 changes: 6 additions & 0 deletions src/closure.rs
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Expand Up @@ -32,6 +32,7 @@ pub enum CompilerError {
pub struct FunctionPrototype<'gc> {
pub chunk_name: String<'gc>,
pub reference: FunctionRef<String<'gc>>,
pub parameters: boxed::Box<[String<'gc>], MetricsAlloc<'gc>>,
pub fixed_params: u8,
pub has_varargs: bool,
pub stack_size: u16,
Expand Down Expand Up @@ -65,6 +66,10 @@ impl<'gc> FunctionPrototype<'gc> {
) -> FunctionPrototype<'gc> {
let alloc = MetricsAlloc::new(mc);

let mut parameters_vec = vec::Vec::new_in(alloc.clone());
parameters_vec.extend(compiled_function.parameters.iter().map(map_string));
let parameters = parameters_vec.into_boxed_slice();

let mut constants = vec::Vec::new_in(alloc.clone());
constants.extend(
compiled_function
Expand Down Expand Up @@ -95,6 +100,7 @@ impl<'gc> FunctionPrototype<'gc> {
.reference
.as_string_ref()
.map_strings(map_string),
parameters,
fixed_params: compiled_function.fixed_params,
has_varargs: compiled_function.has_varargs,
stack_size: compiled_function.stack_size,
Expand Down
26 changes: 15 additions & 11 deletions src/compiler/compiler.rs
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Expand Up @@ -111,6 +111,7 @@ impl<S> FunctionRef<S> {
#[collect(no_drop)]
pub struct CompiledPrototype<S> {
pub reference: FunctionRef<S>,
pub parameters: Vec<S>,
pub fixed_params: u8,
pub has_varargs: bool,
pub stack_size: u16,
Expand All @@ -132,6 +133,7 @@ impl<S> CompiledPrototype<S> {
) -> CompiledPrototype<S2> {
CompiledPrototype {
reference: this.reference.map_strings(f),
parameters: this.parameters.into_iter().map(f).collect(),
fixed_params: this.fixed_params,
has_varargs: this.has_varargs,
stack_size: this.stack_size,
Expand Down Expand Up @@ -183,6 +185,7 @@ struct Compiler<S: StringInterner> {

struct CompilerFunction<S> {
reference: FunctionRef<S>,
parameters: Vec<S>,

constants: Vec<Constant<S>>,
constant_table: HashMap<IdenticalConstant<S>, ConstantIndex16>,
Expand Down Expand Up @@ -804,14 +807,14 @@ impl<S: StringInterner> Compiler<S> {
parameters.extend_from_slice(&function_statement.definition.parameters);

self.new_prototype(
FunctionRef::Named(name.clone(), self.current_function.current_line_number),
FunctionRef::Named(name.clone(), function_statement.definition.line_number),
&parameters,
function_statement.definition.has_varargs,
&function_statement.definition.body,
)?
} else {
self.new_prototype(
FunctionRef::Named(name.clone(), self.current_function.current_line_number),
FunctionRef::Named(name.clone(), function_statement.definition.line_number),
&function_statement.definition.parameters,
function_statement.definition.has_varargs,
&function_statement.definition.body,
Expand Down Expand Up @@ -1091,7 +1094,7 @@ impl<S: StringInterner> Compiler<S> {
let proto = self.new_prototype(
FunctionRef::Named(
local_function.name.clone(),
self.current_function.current_line_number,
local_function.definition.line_number,
),
&local_function.definition.parameters,
local_function.definition.has_varargs,
Expand Down Expand Up @@ -1185,7 +1188,7 @@ impl<S: StringInterner> Compiler<S> {
function: &FunctionDefinition<S::String>,
) -> Result<ExprDescriptor<S::String>, CompileErrorKind> {
let proto = self.new_prototype(
FunctionRef::Expression(self.current_function.current_line_number),
FunctionRef::Expression(function.line_number),
&function.parameters,
function.has_varargs,
&function.body,
Expand Down Expand Up @@ -2477,14 +2480,9 @@ impl<S: Clone> CompilerFunction<S> {
parameters: &[S],
has_varargs: bool,
) -> Result<CompilerFunction<S>, CompileErrorKind> {
let current_line_number = match reference {
FunctionRef::Named(_, ln) => ln,
FunctionRef::Expression(ln) => ln,
FunctionRef::Chunk => LineNumber(0),
};

let mut function = CompilerFunction {
reference,
parameters: parameters.to_vec(),
constants: Vec::new(),
constant_table: HashMap::default(),
upvalues: Vec::new(),
Expand All @@ -2499,8 +2497,13 @@ impl<S: Clone> CompilerFunction<S> {
pending_jumps: Vec::new(),
operations: Vec::new(),
operation_lines: Vec::new(),
current_line_number,
current_line_number: LineNumber(0),
};
function.set_line_number(match &function.reference {
FunctionRef::Named(_, ln) => *ln,
FunctionRef::Expression(ln) => *ln,
FunctionRef::Chunk => LineNumber(0),
});

let fixed_params: u8 = parameters
.len()
Expand Down Expand Up @@ -2556,6 +2559,7 @@ impl<S: Clone> CompilerFunction<S> {

Ok(CompiledPrototype {
reference: self.reference,
parameters: self.parameters,
fixed_params: self.fixed_params,
has_varargs: self.has_varargs,
stack_size: self.register_allocator.stack_size(),
Expand Down
19 changes: 12 additions & 7 deletions src/compiler/parser.rs
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Expand Up @@ -275,6 +275,7 @@ pub struct SuffixedExpression<S> {

#[derive(Debug, Clone)]
pub struct FunctionDefinition<S> {
pub line_number: LineNumber,
pub parameters: Vec<S>,
pub has_varargs: bool,
pub body: Block<S>,
Expand Down Expand Up @@ -584,7 +585,7 @@ impl<S: StringInterner> Parser<'_, S> {
}

fn parse_function_statement(&mut self) -> Result<FunctionStatement<S::String>, ParseError> {
self.expect_next(Token::Function)?;
let line_number = self.expect_next(Token::Function)?;

let name = self.expect_name()?.inner;
let mut fields = Vec::new();
Expand All @@ -604,7 +605,7 @@ impl<S: StringInterner> Parser<'_, S> {
}
}

let definition = self.parse_function_definition()?;
let definition = self.parse_function_definition(line_number)?;

Ok(FunctionStatement {
name,
Expand All @@ -617,10 +618,10 @@ impl<S: StringInterner> Parser<'_, S> {
fn parse_local_function_statement(
&mut self,
) -> Result<LocalFunctionStatement<S::String>, ParseError> {
self.expect_next(Token::Function)?;
let line_number = self.expect_next(Token::Function)?;

let name = self.expect_name()?.inner;
let definition = self.parse_function_definition()?;
let definition = self.parse_function_definition(line_number)?;

Ok(LocalFunctionStatement { name, definition })
}
Expand Down Expand Up @@ -828,8 +829,8 @@ impl<S: StringInterner> Parser<'_, S> {
}
Token::LeftBrace => SimpleExpression::TableConstructor(self.parse_table_constructor()?),
Token::Function => {
self.take_next()?;
SimpleExpression::Function(self.parse_function_definition()?)
let line_number = self.take_next()?.line_number;
SimpleExpression::Function(self.parse_function_definition(line_number)?)
}
_ => SimpleExpression::Suffixed(self.parse_suffixed_expression()?),
})
Expand Down Expand Up @@ -965,7 +966,10 @@ impl<S: StringInterner> Parser<'_, S> {
Ok(SuffixedExpression { primary, suffixes })
}

fn parse_function_definition(&mut self) -> Result<FunctionDefinition<S::String>, ParseError> {
fn parse_function_definition(
&mut self,
line_number: LineNumber,
) -> Result<FunctionDefinition<S::String>, ParseError> {
self.expect_next(Token::LeftParen)?;

let mut parameters = Vec::new();
Expand Down Expand Up @@ -1002,6 +1006,7 @@ impl<S: StringInterner> Parser<'_, S> {
self.expect_next(Token::End)?;

Ok(FunctionDefinition {
line_number,
parameters,
has_varargs,
body,
Expand Down
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