From 59957746e91c1322a8ca6d228bcaa0f31941ee1b Mon Sep 17 00:00:00 2001
From: Marmare314 <49279081+Marmare314@users.noreply.github.com>
Date: Wed, 26 Apr 2023 11:32:11 +0200
Subject: Pattern as parameter (#854)

---
 src/eval/func.rs | 29 ++++++++++++++++++-----------
 src/eval/mod.rs  |  5 +----
 2 files changed, 19 insertions(+), 15 deletions(-)

(limited to 'src/eval')

diff --git a/src/eval/func.rs b/src/eval/func.rs
index e3b6a99c..a6e0de84 100644
--- a/src/eval/func.rs
+++ b/src/eval/func.rs
@@ -276,13 +276,11 @@ pub(super) struct Closure {
 #[derive(Hash)]
 pub enum Param {
     /// A positional parameter: `x`.
-    Pos(Ident),
+    Pos(ast::Pattern),
     /// A named parameter with a default value: `draw: false`.
     Named(Ident, Value),
     /// An argument sink: `..args`.
     Sink(Option<Ident>),
-    /// A placeholder: `_`.
-    Placeholder,
 }
 
 impl Closure {
@@ -330,9 +328,18 @@ impl Closure {
         let mut sink_pos_values = None;
         for p in &closure.params {
             match p {
-                Param::Pos(ident) => {
-                    vm.define(ident.clone(), args.expect::<Value>(ident)?);
-                }
+                Param::Pos(pattern) => match pattern {
+                    ast::Pattern::Normal(ast::Expr::Ident(ident)) => {
+                        vm.define(ident.clone(), args.expect::<Value>(ident)?)
+                    }
+                    ast::Pattern::Normal(_) => unreachable!(),
+                    _ => {
+                        pattern.define(
+                            &mut vm,
+                            args.expect::<Value>("pattern parameter")?,
+                        )?;
+                    }
+                },
                 Param::Sink(ident) => {
                     sink = ident.clone();
                     if let Some(sink_size) = sink_size {
@@ -344,9 +351,6 @@ impl Closure {
                         args.named::<Value>(ident)?.unwrap_or_else(|| default.clone());
                     vm.define(ident.clone(), value);
                 }
-                Param::Placeholder => {
-                    args.eat::<Value>()?;
-                }
             }
         }
 
@@ -443,12 +447,15 @@ impl<'a> CapturesVisitor<'a> {
 
                 for param in expr.params().children() {
                     match param {
-                        ast::Param::Pos(ident) => self.bind(ident),
+                        ast::Param::Pos(pattern) => {
+                            for ident in pattern.idents() {
+                                self.bind(ident);
+                            }
+                        }
                         ast::Param::Named(named) => self.bind(named.name()),
                         ast::Param::Sink(spread) => {
                             self.bind(spread.name().unwrap_or_default())
                         }
-                        _ => {}
                     }
                 }
 
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index d2ca0e74..e8e1af51 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -1207,14 +1207,11 @@ impl Eval for ast::Closure {
         let mut params = Vec::new();
         for param in self.params().children() {
             match param {
-                ast::Param::Pos(name) => {
-                    params.push(Param::Pos(name));
-                }
+                ast::Param::Pos(pattern) => params.push(Param::Pos(pattern)),
                 ast::Param::Named(named) => {
                     params.push(Param::Named(named.name(), named.expr().eval(vm)?));
                 }
                 ast::Param::Sink(spread) => params.push(Param::Sink(spread.name())),
-                ast::Param::Placeholder(_) => params.push(Param::Placeholder),
             }
         }
 
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