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use std::fmt::{self, Debug, Formatter};
use std::ops::Deref;
use std::rc::Rc;
use super::{Cast, EvalContext, Value};
use crate::eco::EcoString;
use crate::syntax::{Span, Spanned};
/// An evaluatable function.
#[derive(Clone)]
pub struct Function {
/// The name of the function.
///
/// The string is boxed to make the whole struct fit into 24 bytes, so that
/// a value fits into 32 bytes.
name: Option<Box<EcoString>>,
/// The closure that defines the function.
f: Rc<dyn Fn(&mut EvalContext, &mut FuncArgs) -> Value>,
}
impl Function {
/// Create a new function from a rust closure.
pub fn new<F>(name: Option<EcoString>, f: F) -> Self
where
F: Fn(&mut EvalContext, &mut FuncArgs) -> Value + 'static,
{
Self { name: name.map(Box::new), f: Rc::new(f) }
}
/// The name of the function.
pub fn name(&self) -> Option<&EcoString> {
self.name.as_ref().map(|s| &**s)
}
}
impl Deref for Function {
type Target = dyn Fn(&mut EvalContext, &mut FuncArgs) -> Value;
fn deref(&self) -> &Self::Target {
self.f.as_ref()
}
}
impl Debug for Function {
fn fmt(&self, f: &mut Formatter) -> fmt::Result {
f.debug_struct("ValueFunc").field("name", &self.name).finish()
}
}
impl PartialEq for Function {
fn eq(&self, other: &Self) -> bool {
// We cast to thin pointers because we don't want to compare vtables.
Rc::as_ptr(&self.f) as *const () == Rc::as_ptr(&other.f) as *const ()
}
}
/// Evaluated arguments to a function.
#[derive(Debug, Clone, PartialEq)]
pub struct FuncArgs {
/// The span of the whole argument list.
pub span: Span,
/// The positional arguments.
pub items: Vec<FuncArg>,
}
/// An argument to a function call: `12` or `draw: false`.
#[derive(Debug, Clone, PartialEq)]
pub struct FuncArg {
/// The span of the whole argument.
pub span: Span,
/// The name of the argument (`None` for positional arguments).
pub name: Option<EcoString>,
/// The value of the argument.
pub value: Spanned<Value>,
}
impl FuncArgs {
/// Find and consume the first castable positional argument.
pub fn eat<T>(&mut self) -> Option<T>
where
T: Cast<Spanned<Value>>,
{
(0 .. self.items.len()).find_map(|index| {
let slot = &mut self.items[index];
if slot.name.is_some() {
return None;
}
let value = std::mem::replace(&mut slot.value, Spanned::zero(Value::None));
match T::cast(value) {
Ok(t) => {
self.items.remove(index);
Some(t)
}
Err(value) => {
slot.value = value;
None
}
}
})
}
/// Find and consume the first castable positional argument, producing a
/// `missing argument: {what}` error if no match was found.
pub fn expect<T>(&mut self, ctx: &mut EvalContext, what: &str) -> Option<T>
where
T: Cast<Spanned<Value>>,
{
let found = self.eat();
if found.is_none() {
ctx.diag(error!(self.span, "missing argument: {}", what));
}
found
}
/// Find, consume and collect all castable positional arguments.
pub fn all<T>(&mut self) -> impl Iterator<Item = T> + '_
where
T: Cast<Spanned<Value>>,
{
std::iter::from_fn(move || self.eat())
}
/// Cast and remove the value for the given named argument, producing an
/// error if the conversion fails.
pub fn named<T>(&mut self, ctx: &mut EvalContext, name: &str) -> Option<T>
where
T: Cast<Spanned<Value>>,
{
let index = self
.items
.iter()
.position(|arg| arg.name.as_ref().map_or(false, |other| other == name))?;
let value = self.items.remove(index).value;
let span = value.span;
match T::cast(value) {
Ok(t) => Some(t),
Err(value) => {
ctx.diag(error!(
span,
"expected {}, found {}",
T::TYPE_NAME,
value.v.type_name(),
));
None
}
}
}
/// Produce "unexpected argument" errors for all remaining arguments.
pub fn finish(self, ctx: &mut EvalContext) {
for arg in &self.items {
if arg.value.v != Value::Error {
ctx.diag(error!(arg.span, "unexpected argument"));
}
}
}
}
|
