Restrict acceptable characters for placeholders

Co-authored-by: Josh Holmer <jholmer.in@gmail.com>

Author: lu-zero

src/tokenizer.rs

@@ -384,18 +384,22 @@ fn get_ident_named_placeholder_token<'i>(input: &mut &'i str) -> Result<Token<'i
 }
 
 fn get_braced_named_placeholder_token<'i>(input: &mut &'i str) -> Result<Token<'i>> {
-    delimited('{', take_until(1.., '}'), '}')
-        .with_taken()
-        .parse_next(input)
-        .map(|(index, token)| {
-            let index = Cow::Borrowed(index);
-            Token {
-                kind: TokenKind::Placeholder,
-                value: token,
-                key: Some(PlaceholderKind::Named(index)),
-                alias: token,
-            }
-        })
+    delimited(
+        '{',
+        take_while(1.., |c: char| c.is_alphanumeric() || c == '_'),
+        '}',
+    )
+    .with_taken()
+    .parse_next(input)
+    .map(|(index, token)| {
+        let index = Cow::Borrowed(index);
+        Token {
+            kind: TokenKind::Placeholder,
+            value: token,
+            key: Some(PlaceholderKind::Named(index)),
+            alias: token,
+        }
+    })
 }
 
 fn get_string_named_placeholder_token<'i>(