Incorrect parsing of unbalanced braces based on issue 6914 (#7621)

crates/nu-parser/src/errors.rs

@@ -34,6 +34,10 @@ pub enum ParseError {
     #[diagnostic(code(nu::parser::unclosed_delimiter), url(docsrs))]
     Unclosed(String, #[label("unclosed {0}")] Span),
 
+    #[error("Unbalanced delimiter.")]
+    #[diagnostic(code(nu::parser::unbalanced_delimiter), url(docsrs))]
+    Unbalanced(String, String, #[label("unbalanced {0} and {1}")] Span),
+
     #[error("Parse mismatch during operation.")]
     #[diagnostic(code(nu::parser::parse_mismatch), url(docsrs))]
     Expected(String, #[label("expected {0}")] Span),
@@ -450,6 +454,7 @@ impl ParseError {
             ParseError::ExtraPositional(_, s) => *s,
             ParseError::UnexpectedEof(_, s) => *s,
             ParseError::Unclosed(_, s) => *s,
+            ParseError::Unbalanced(_, _, s) => *s,
             ParseError::Expected(_, s) => *s,
             ParseError::Mismatch(_, _, s) => *s,
             ParseError::UnsupportedOperation(_, _, _, s, _) => *s,

crates/nu-parser/src/lex.rs

@@ -170,6 +170,23 @@ pub fn lex_item(
             // We encountered a closing `}` delimiter. Pop off the opening `{`.
             if let Some(BlockKind::CurlyBracket) = block_level.last() {
                 let _ = block_level.pop();
+            } else {
+                // We encountered a closing `}` delimiter, but the last opening
+                // delimiter was not a `{`. This is an error.
+                let span = Span::new(span_offset + token_start, span_offset + *curr_offset);
+
+                *curr_offset += 1;
+                return (
+                    Token {
+                        contents: TokenContents::Item,
+                        span,
+                    },
+                    Some(ParseError::Unbalanced(
+                        "{".to_string(),
+                        "}".to_string(),
+                        Span::new(span.end, span.end),
+                    )),
+                );
             }
         } else if c == b'(' {
             // We encountered an opening `(` delimiter.

crates/nu-parser/src/parser.rs

@@ -4392,10 +4392,15 @@ pub fn parse_value(
         }
         b'{' => {
             if !matches!(shape, SyntaxShape::Closure(..)) && !matches!(shape, SyntaxShape::Block) {
-                if let (expr, None) =
-                    parse_full_cell_path(working_set, None, span, expand_aliases_denylist)
-                {
-                    return (expr, None);
+                let (expr, err) =
+                    parse_full_cell_path(working_set, None, span, expand_aliases_denylist);
+                match err {
+                    Some(err) => {
+                        if let ParseError::Unbalanced(_, _, _) = err {
+                            return (expr, Some(err));
+                        }
+                    }
+                    None => return (expr, None),
                 }
             }
             if matches!(shape, SyntaxShape::Closure(_)) || matches!(shape, SyntaxShape::Any) {