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//! Pattern matching evaluation.
use std::cell::RefCell;
use std::collections::HashSet;
use std::rc::Rc;
use crate::ast::expr::MatchPattern;
use crate::interpreter::value::{HashKey, Value};
use indexmap::IndexMap;
use super::{Interpreter, RuntimeResult};
impl Interpreter {
/// Match a value against a pattern.
/// Returns Some(bindings) if the pattern matches, None otherwise.
/// Bindings are (name, value) pairs for variable patterns.
pub(crate) fn match_pattern(
&mut self,
value: &Value,
pattern: &MatchPattern,
) -> RuntimeResult<Option<Vec<(String, Value)>>> {
match pattern {
MatchPattern::Wildcard => Ok(Some(Vec::new())),
MatchPattern::Variable(name) => Ok(Some(vec![(name.clone(), value.clone())])),
MatchPattern::Typed { name, type_name } => {
let matches = match type_name.as_str() {
"Int" => matches!(value, Value::Int(_)),
"Float" => matches!(value, Value::Float(_)),
"Bool" => matches!(value, Value::Bool(_)),
"String" => matches!(value, Value::String(_)),
"Void" => matches!(value, Value::Null),
_ => {
if let Value::Instance(inst) = value {
inst.borrow().class.name == *type_name
} else {
false
}
}
};
if matches {
Ok(Some(vec![(name.clone(), value.clone())]))
} else {
Ok(None)
}
}
MatchPattern::Literal(literal) => {
let literal_value = self.evaluate_literal(literal)?;
if self.values_equal(&literal_value, value) {
Ok(Some(Vec::new()))
} else {
Ok(None)
}
}
MatchPattern::Array { elements, rest } => {
let arr = match value {
Value::Array(arr) => arr.borrow().clone(),
_ => return Ok(None),
};
if rest.is_none() {
if elements.len() != arr.len() {
return Ok(None);
}
} else if elements.len() > arr.len() {
return Ok(None);
}
let mut bindings = Vec::new();
for (i, elem_pattern) in elements.iter().enumerate() {
if i >= arr.len() {
return Ok(None);
}
match self.match_pattern(&arr[i], elem_pattern)? {
Some(elem_bindings) => {
bindings.extend(elem_bindings);
}
_ => {
return Ok(None);
}
}
}
if let Some(rest_name) = rest {
let rest_values =
Value::Array(Rc::new(RefCell::new(arr[elements.len()..].to_vec())));
bindings.push((rest_name.clone(), rest_values));
}
Ok(Some(bindings))
}
MatchPattern::Hash { fields, rest } => {
let hash = match value {
Value::Hash(hash) => hash.borrow().clone(),
_ => return Ok(None),
};
let mut bindings = Vec::new();
for (field_name, field_pattern) in fields {
let hash_key = HashKey::String(field_name.clone());
if let Some(val) = hash.get(&hash_key) {
match self.match_pattern(val, field_pattern)? {
Some(field_bindings) => {
bindings.extend(field_bindings);
}
_ => {
return Ok(None);
}
}
} else {
return Ok(None);
}
}
if let Some(rest_name) = rest {
let matched_keys: HashSet<HashKey> = fields
.iter()
.map(|(f, _)| HashKey::String(f.clone()))
.collect();
let rest_map: IndexMap<HashKey, Value> = hash
.into_iter()
.filter(|(k, _)| !matched_keys.contains(k))
.collect();
let rest_values = Value::Hash(Rc::new(RefCell::new(rest_map)));
bindings.push((rest_name.clone(), rest_values));
}
Ok(Some(bindings))
}
MatchPattern::Destructuring { type_name, fields } => {
let instance = match value {
Value::Instance(inst) => inst.clone(),
_ => return Ok(None),
};
if instance.borrow().class.name != *type_name {
return Ok(None);
}
let mut bindings = Vec::new();
for (field_name, field_pattern) in fields {
match instance.borrow().fields.get(field_name) {
Some(field_value) => {
match self.match_pattern(field_value, field_pattern)? {
Some(field_bindings) => {
bindings.extend(field_bindings);
}
_ => {
return Ok(None);
}
}
}
_ => {
return Ok(None);
}
}
}
Ok(Some(bindings))
}
MatchPattern::And(patterns) => {
let mut all_bindings = Vec::new();
for p in patterns {
match self.match_pattern(value, p)? {
Some(bindings) => all_bindings.extend(bindings),
None => return Ok(None),
}
}
Ok(Some(all_bindings))
}
MatchPattern::Or(patterns) => {
for p in patterns {
if let Some(bindings) = self.match_pattern(value, p)? {
return Ok(Some(bindings));
}
}
Ok(None)
}
}
}
}