1 files changed, 100 insertions, 146 deletions

diff --git a/src/eval/args.rs b/src/eval/args.rs
index 43c30daf..ea248ec4 100644
--- a/src/eval/args.rs
+++ b/src/eval/args.rs
@@ -1,184 +1,138 @@
-//! Simplifies argument parsing.
+use super::*;
+
+/// Evaluated arguments to a function.
+#[derive(Debug)]
+pub struct Args {
+    span: Span,
+    pos: SpanVec<Value>,
+    named: Vec<(Spanned<String>, Spanned<Value>)>,
+}
 
-use std::mem;
+impl Eval for Spanned<&Arguments> {
+    type Output = Args;
 
-use super::{Conv, EvalContext, RefKey, TryFromValue, Value, ValueDict};
-use crate::diag::Diag;
-use crate::syntax::{Span, SpanVec, Spanned, WithSpan};
+    fn eval(self, ctx: &mut EvalContext) -> Self::Output {
+        let mut pos = vec![];
+        let mut named = vec![];
 
-/// A wrapper around a dictionary value that simplifies argument parsing in
-/// functions.
-pub struct Args(pub Spanned<ValueDict>);
+        for arg in self.v {
+            match arg {
+                Argument::Pos(expr) => {
+                    pos.push(expr.as_ref().eval(ctx).with_span(expr.span));
+                }
+                Argument::Named(Named { name, expr }) => {
+                    named.push((
+                        name.as_ref().map(|id| id.0.clone()),
+                        expr.as_ref().eval(ctx).with_span(expr.span),
+                    ));
+                }
+            }
+        }
 
-impl Args {
-    /// Retrieve and remove the argument associated with the given key if there
-    /// is any.
-    ///
-    /// Generates an error if the key exists, but the value can't be converted
-    /// into the type `T`.
-    pub fn get<'a, K, T>(&mut self, ctx: &mut EvalContext, key: K) -> Option<T>
-    where
-        K: Into<RefKey<'a>>,
-        T: TryFromValue,
-    {
-        self.0.v.remove(key).and_then(|entry| {
-            let span = entry.value.span;
-            conv_diag(
-                T::try_from_value(entry.value),
-                &mut ctx.feedback.diags,
-                span,
-            )
-        })
+        Args { span: self.span, pos, named }
     }
+}
 
-    /// This is the same as [`get`](Self::get), except that it generates an error about a
-    /// missing argument with the given `name` if the key does not exist.
-    pub fn need<'a, K, T>(
-        &mut self,
-        ctx: &mut EvalContext,
-        key: K,
-        name: &str,
-    ) -> Option<T>
+impl Args {
+    /// Find the first convertible positional argument.
+    pub fn find<T>(&mut self, ctx: &mut EvalContext) -> Option<T>
     where
-        K: Into<RefKey<'a>>,
-        T: TryFromValue,
+        T: Cast<Spanned<Value>>,
     {
-        if let Some(entry) = self.0.v.remove(key) {
-            let span = entry.value.span;
-            conv_diag(
-                T::try_from_value(entry.value),
-                &mut ctx.feedback.diags,
-                span,
-            )
-        } else {
-            ctx.diag(error!(self.0.span, "missing argument: {}", name));
-            None
-        }
+        self.pos.iter_mut().find_map(move |slot| try_cast(ctx, slot))
     }
 
-    /// Retrieve and remove the first matching positional argument.
-    pub fn find<T>(&mut self) -> Option<T>
+    /// Find the first convertible positional argument, producing an error if
+    /// no match was found.
+    pub fn require<T>(&mut self, ctx: &mut EvalContext, what: &str) -> Option<T>
     where
-        T: TryFromValue,
+        T: Cast<Spanned<Value>>,
     {
-        for (&key, entry) in self.0.v.nums_mut() {
-            let span = entry.value.span;
-            let slot = &mut entry.value;
-            let conv = conv_put_back(T::try_from_value(mem::take(slot)), slot, span);
-            if let Some(t) = conv {
-                self.0.v.remove(key);
-                return Some(t);
-            }
+        let found = self.find(ctx);
+        if found.is_none() {
+            ctx.diag(error!(self.span, "missing argument: {}", what));
         }
-        None
+        found
     }
 
-    /// Retrieve and remove all matching positional arguments.
-    pub fn find_all<T>(&mut self) -> impl Iterator<Item = T> + '_
+    /// Filter out all convertible positional arguments.
+    pub fn filter<'a, T>(
+        &'a mut self,
+        ctx: &'a mut EvalContext,
+    ) -> impl Iterator<Item = T> + 'a
     where
-        T: TryFromValue,
+        T: Cast<Spanned<Value>>,
     {
-        let mut skip = 0;
-        std::iter::from_fn(move || {
-            for (&key, entry) in self.0.v.nums_mut().skip(skip) {
-                let span = entry.value.span;
-                let slot = &mut entry.value;
-                let conv = conv_put_back(T::try_from_value(mem::take(slot)), slot, span);
-                if let Some(t) = conv {
-                    self.0.v.remove(key);
-                    return Some(t);
-                }
-                skip += 1;
-            }
-            None
-        })
+        self.pos.iter_mut().filter_map(move |slot| try_cast(ctx, slot))
     }
 
-    /// Retrieve and remove all matching named arguments.
-    pub fn find_all_str<T>(&mut self) -> impl Iterator<Item = (String, T)> + '_
+    /// Convert the value for the given named argument.
+    ///
+    /// Generates an error if the conversion fails.
+    pub fn get<'a, T>(&mut self, ctx: &mut EvalContext, name: &str) -> Option<T>
     where
-        T: TryFromValue,
+        T: Cast<Spanned<Value>>,
     {
-        let mut skip = 0;
-        std::iter::from_fn(move || {
-            for (key, entry) in self.0.v.strs_mut().skip(skip) {
-                let span = entry.value.span;
-                let slot = &mut entry.value;
-                let conv = conv_put_back(T::try_from_value(mem::take(slot)), slot, span);
-                if let Some(t) = conv {
-                    let key = key.clone();
-                    self.0.v.remove(&key);
-                    return Some((key, t));
-                }
-                skip += 1;
-            }
-
-            None
-        })
+        let index = self.named.iter().position(|(k, _)| k.v.as_str() == name)?;
+        let value = self.named.remove(index).1;
+        cast(ctx, value)
     }
 
-    /// Generated _unexpected argument_ errors for all remaining entries.
-    pub fn done(&self, ctx: &mut EvalContext) {
-        for entry in self.0.v.values() {
-            let span = entry.key_span.join(entry.value.span);
-            ctx.diag(error!(span, "unexpected argument"));
+    /// Generate "unexpected argument" errors for all remaining arguments.
+    pub fn finish(self, ctx: &mut EvalContext) {
+        let a = self.pos.iter().map(|v| v.as_ref());
+        let b = self.named.iter().map(|(k, v)| (&v.v).with_span(k.span.join(v.span)));
+        for value in a.chain(b) {
+            if value.v != &Value::Error {
+                ctx.diag(error!(value.span, "unexpected argument"));
+            }
         }
     }
 }
 
-fn conv_diag<T>(conv: Conv<T>, diags: &mut SpanVec<Diag>, span: Span) -> Option<T> {
-    match conv {
-        Conv::Ok(t) => Some(t),
-        Conv::Warn(t, warn) => {
-            diags.push(warn.with_span(span));
+/// Cast the value into `T`, generating an error if the conversion fails.
+fn cast<T>(ctx: &mut EvalContext, value: Spanned<Value>) -> Option<T>
+where
+    T: Cast<Spanned<Value>>,
+{
+    let span = value.span;
+    match T::cast(value) {
+        CastResult::Ok(t) => Some(t),
+        CastResult::Warn(t, m) => {
+            ctx.diag(warning!(span, "{}", m));
             Some(t)
         }
-        Conv::Err(_, err) => {
-            diags.push(err.with_span(span));
+        CastResult::Err(value) => {
+            ctx.diag(error!(
+                span,
+                "expected {}, found {}",
+                T::TYPE_NAME,
+                value.v.type_name()
+            ));
             None
         }
     }
 }
 
-fn conv_put_back<T>(conv: Conv<T>, slot: &mut Spanned<Value>, span: Span) -> Option<T> {
-    match conv {
-        Conv::Ok(t) => Some(t),
-        Conv::Warn(t, _) => Some(t),
-        Conv::Err(v, _) => {
-            *slot = v.with_span(span);
+/// Try to cast the value in the slot into `T`, putting it back if the
+/// conversion fails.
+fn try_cast<T>(ctx: &mut EvalContext, slot: &mut Spanned<Value>) -> Option<T>
+where
+    T: Cast<Spanned<Value>>,
+{
+    // Replace with error placeholder when conversion works since error values
+    // are ignored when generating "unexpected argument" errors.
+    let value = std::mem::replace(slot, Spanned::zero(Value::Error));
+    let span = value.span;
+    match T::cast(value) {
+        CastResult::Ok(t) => Some(t),
+        CastResult::Warn(t, m) => {
+            ctx.diag(warning!(span, "{}", m));
+            Some(t)
+        }
+        CastResult::Err(value) => {
+            *slot = value;
             None
         }
     }
 }
-
-#[cfg(test)]
-mod tests {
-    use super::super::{Dict, SpannedEntry, Value};
-    use super::*;
-
-    fn entry(value: Value) -> SpannedEntry<Value> {
-        SpannedEntry::value(Spanned::zero(value))
-    }
-
-    #[test]
-    fn test_args_find() {
-        let mut args = Args(Spanned::zero(Dict::new()));
-        args.0.v.insert(1, entry(Value::Bool(false)));
-        args.0.v.insert(2, entry(Value::Str("hi".to_string())));
-        assert_eq!(args.find::<String>(), Some("hi".to_string()));
-        assert_eq!(args.0.v.len(), 1);
-        assert_eq!(args.find::<bool>(), Some(false));
-        assert!(args.0.v.is_empty());
-    }
-
-    #[test]
-    fn test_args_find_all() {
-        let mut args = Args(Spanned::zero(Dict::new()));
-        args.0.v.insert(1, entry(Value::Bool(false)));
-        args.0.v.insert(3, entry(Value::Float(0.0)));
-        args.0.v.insert(7, entry(Value::Bool(true)));
-        assert_eq!(args.find_all::<bool>().collect::<Vec<_>>(), [false, true]);
-        assert_eq!(args.0.v.len(), 1);
-        assert_eq!(args.0.v[3].value.v, Value::Float(0.0));
-    }
-}