just/src/assignment_resolver.rs

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use crate::common::*;
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use CompilationErrorKind::*;
pub(crate) struct AssignmentResolver<'a: 'b, 'b> {
assignments: &'b Table<'a, Assignment<'a>>,
stack: Vec<&'a str>,
seen: BTreeSet<&'a str>,
evaluated: BTreeSet<&'a str>,
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}
impl<'a: 'b, 'b> AssignmentResolver<'a, 'b> {
pub(crate) fn resolve_assignments(
assignments: &Table<'a, Assignment<'a>>,
) -> CompilationResult<'a, ()> {
let mut resolver = AssignmentResolver {
stack: empty(),
seen: empty(),
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evaluated: empty(),
assignments,
};
for name in assignments.keys() {
resolver.resolve_assignment(name)?;
}
Ok(())
}
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fn resolve_assignment(&mut self, name: &'a str) -> CompilationResult<'a, ()> {
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if self.evaluated.contains(name) {
return Ok(());
}
self.seen.insert(name);
self.stack.push(name);
if let Some(assignment) = self.assignments.get(name) {
self.resolve_expression(&assignment.expression)?;
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self.evaluated.insert(name);
} else {
let message = format!("attempted to resolve unknown assignment `{}`", name);
let token = Token {
src: "",
offset: 0,
line: 0,
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column: 0,
length: 0,
kind: TokenKind::Unspecified,
};
return Err(CompilationError {
kind: Internal { message },
token,
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});
}
Ok(())
}
fn resolve_expression(&mut self, expression: &Expression<'a>) -> CompilationResult<'a, ()> {
match expression {
Expression::Variable { name } => {
let variable = name.lexeme();
if self.evaluated.contains(variable) {
Ok(())
} else if self.seen.contains(variable) {
let token = self.assignments[variable].name.token();
self.stack.push(variable);
Err(token.error(CircularVariableDependency {
variable,
circle: self.stack.clone(),
}))
} else if self.assignments.contains_key(variable) {
self.resolve_assignment(variable)
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} else {
Err(name.token().error(UndefinedVariable { variable }))
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}
}
Expression::Call { thunk } => match thunk {
Thunk::Nullary { .. } => Ok(()),
Thunk::Unary { arg, .. } => self.resolve_expression(arg),
Thunk::Binary { args: [a, b], .. } => {
self.resolve_expression(a)?;
self.resolve_expression(b)
}
},
Expression::Concatination { lhs, rhs } => {
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self.resolve_expression(lhs)?;
self.resolve_expression(rhs)
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}
Expression::StringLiteral { .. } | Expression::Backtick { .. } => Ok(()),
Expression::Group { contents } => self.resolve_expression(contents),
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}
}
}
#[cfg(test)]
mod tests {
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use super::*;
analysis_error! {
name: circular_variable_dependency,
input: "a = b\nb = a",
offset: 0,
line: 0,
column: 0,
width: 1,
kind: CircularVariableDependency{variable: "a", circle: vec!["a", "b", "a"]},
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}
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analysis_error! {
name: self_variable_dependency,
input: "a = a",
offset: 0,
line: 0,
column: 0,
width: 1,
kind: CircularVariableDependency{variable: "a", circle: vec!["a", "a"]},
}
analysis_error! {
name: unknown_expression_variable,
input: "x = yy",
offset: 4,
line: 0,
column: 4,
width: 2,
kind: UndefinedVariable{variable: "yy"},
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}
analysis_error! {
name: unknown_function_parameter,
input: "x := env_var(yy)",
offset: 13,
line: 0,
column: 13,
width: 2,
kind: UndefinedVariable{variable: "yy"},
}
analysis_error! {
name: unknown_function_parameter_binary_first,
input: "x := env_var_or_default(yy, 'foo')",
offset: 24,
line: 0,
column: 24,
width: 2,
kind: UndefinedVariable{variable: "yy"},
}
analysis_error! {
name: unknown_function_parameter_binary_second,
input: "x := env_var_or_default('foo', yy)",
offset: 31,
line: 0,
column: 31,
width: 2,
kind: UndefinedVariable{variable: "yy"},
}
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}