From 4524539c2bc5f3a9f53bc57a1902264fc894969b Mon Sep 17 00:00:00 2001
From: Marmare314 <49279081+Marmare314@users.noreply.github.com>
Date: Thu, 20 Apr 2023 11:05:11 +0200
Subject: forbid underscore as identifier closes #513 (#837)

---
 src/eval/func.rs | 5 +++++
 src/eval/mod.rs  | 4 ++++
 2 files changed, 9 insertions(+)

(limited to 'src/eval')

diff --git a/src/eval/func.rs b/src/eval/func.rs
index faf2d696..29b85f7a 100644
--- a/src/eval/func.rs
+++ b/src/eval/func.rs
@@ -274,6 +274,8 @@ pub enum Param {
     Named(Ident, Value),
     /// An argument sink: `..args`.
     Sink(Option<Ident>),
+    /// A placeholder: `_`.
+    Placeholder,
 }
 
 impl Closure {
@@ -334,6 +336,9 @@ impl Closure {
                         args.named::<Value>(ident)?.unwrap_or_else(|| default.clone());
                     vm.define(ident.clone(), value);
                 }
+                Param::Placeholder => {
+                    args.eat::<Value>()?;
+                }
             }
         }
 
diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 797e1fef..0a963faf 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -1160,6 +1160,7 @@ impl Eval for ast::Closure {
                     params.push(Param::Named(named.name(), named.expr().eval(vm)?));
                 }
                 ast::Param::Sink(name) => params.push(Param::Sink(name)),
+                ast::Param::Placeholder => params.push(Param::Placeholder),
             }
         }
 
@@ -1184,6 +1185,7 @@ impl ast::Pattern {
                 vm.define(ident.clone(), value);
                 Ok(Value::None)
             }
+            ast::Pattern::Placeholder => Ok(Value::None),
             ast::Pattern::Destructuring(destruct) => {
                 match value {
                     Value::Array(value) => {
@@ -1215,6 +1217,7 @@ impl ast::Pattern {
                                         "cannot destructure named elements from an array"
                                     )
                                 }
+                                ast::DestructuringKind::Placeholder => i += 1,
                             }
                         }
                         if i < value.len() {
@@ -1243,6 +1246,7 @@ impl ast::Pattern {
                                     vm.define(ident.clone(), v.clone());
                                     used.insert(key.clone().take());
                                 }
+                                ast::DestructuringKind::Placeholder => {}
                             }
                         }
 
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