Fix wrong parsing of signatures in predecl scan (#10637)

crates/nu-parser/src/parse_keywords.rs

@@ -31,7 +31,7 @@ use crate::{
     lite_parser::{lite_parse, LiteCommand, LiteElement},
     parser::{
         check_call, check_name, garbage, garbage_pipeline, parse, parse_call, parse_expression,
-        parse_import_pattern, parse_internal_call, parse_multispan_value, parse_signature,
+        parse_full_signature, parse_import_pattern, parse_internal_call, parse_multispan_value,
         parse_string, parse_value, parse_var_with_opt_type, trim_quotes, ParsedInternalCall,
     },
     unescape_unquote_string, Token, TokenContents,
@@ -228,7 +228,7 @@ pub fn parse_def_predecl(working_set: &mut StateWorkingSet, spans: &[Span]) {
     // The second time is when we actually parse the body itworking_set.
     // We can't reuse the first time because the variables that are created during parse_signature
     // are lost when we exit the scope below.
-    let sig = parse_signature(working_set, spans[signature_pos]);
+    let sig = parse_full_signature(working_set, &spans[signature_pos..]);
     working_set.parse_errors.truncate(starting_error_count);
     working_set.exit_scope();
 

tests/parsing/mod.rs

@@ -102,6 +102,23 @@ fn parse_file_relative_to_parsed_file_simple() {
     })
 }
 
+#[test]
+fn predecl_signature_parse() {
+    Playground::setup("predecl_signature_parse", |dirs, sandbox| {
+        sandbox.with_files(vec![FileWithContentToBeTrimmed(
+            "spam.nu",
+            "
+                def main [] { foo }
+
+                def foo []: nothing -> nothing { print 'foo' }
+            ",
+        )]);
+
+        let actual = nu!(cwd: dirs.test(), pipeline("nu spam.nu"));
+
+        assert_eq!(actual.out, "foo");
+    })
+}
 #[ignore]
 #[test]
 fn parse_file_relative_to_parsed_file() {