Let "return" exit a script (#8148)

Currently, if a "return" is given outside of a function, we'd just
throw an error.

That always struck me as a bit weird, given that scripts can also
return a value.

So simply let "return" outside also exit the script, kinda like "exit"
does.

However, unlike "exit" it doesn't quit an interactive shell - it seems
weird to have "return" do that as well. It sets $status, so it can be
used to quickly set that, in case you want to test something.

doc_src/cmds/return.rst

@@ -17,6 +17,7 @@ Description
 
 It is usually added inside of a conditional block such as an :ref:`if <cmd-if>` statement or a :ref:`switch <cmd-switch>` statement to conditionally stop the executing function and return to the caller, but it can also be used to specify the exit status of a function.
 
+If run at the top level of a script, it exits that script and returns the given status, like :ref:`exit <cmd-exit>`. If run at the top level in an interactive session, it will set ``$status``, but not exit the shell.
 
 Example
 -------

src/builtin_return.cpp

@@ -97,10 +97,13 @@ maybe_t<int> builtin_return(parser_t &parser, io_streams_t &streams, const wchar
         }
     }
 
+    // If we're not in a function, exit the current script,
+    // but not an interactive shell.
     if (!has_function_block) {
-        streams.err.append_format(_(L"%ls: Not inside of function\n"), cmd);
-        builtin_print_error_trailer(parser, streams.err, cmd);
-        return STATUS_CMD_ERROR;
+        if (!parser.libdata().is_interactive) {
+            parser.libdata().exit_current_script = true;
+        }
+        return retval;
     }
 
     // Mark a return in the libdata.

src/parse_constants.h

@@ -235,9 +235,6 @@ enum class pipeline_position_t {
 /// Error when using continue outside of loop.
 #define INVALID_CONTINUE_ERR_MSG _(L"'continue' while not inside of loop")
 
-/// Error when using return builtin outside of function definition.
-#define INVALID_RETURN_ERR_MSG _(L"'return' outside of function definition")
-
 // Error messages. The number is a reminder of how many format specifiers are contained.
 
 /// Error for $^.

src/parse_util.cpp

@@ -1141,25 +1141,6 @@ static bool detect_errors_in_decorated_statement(const wcstring &buff_src,
                 append_syntax_error(parse_errors, source_start, EXEC_ERR_MSG, command.c_str());
         }
 
-        // Check that we don't return from outside a function. But we allow it if it's
-        // 'return --help'.
-        if (!errored && command == L"return" && !first_arg_is_help) {
-            // See if we are in a function.
-            bool found_function = false;
-            for (const node_t *cursor = &dst; cursor != nullptr; cursor = cursor->parent) {
-                if (const auto *bs = cursor->try_as<block_statement_t>()) {
-                    if (bs->header->type == type_t::function_header) {
-                        found_function = true;
-                        break;
-                    }
-                }
-            }
-
-            if (!found_function) {
-                errored = append_syntax_error(parse_errors, source_start, INVALID_RETURN_ERR_MSG);
-            }
-        }
-
         // Check that we don't break or continue from outside a loop.
         if (!errored && (command == L"break" || command == L"continue") && !first_arg_is_help) {
             // Walk up until we hit a 'for' or 'while' loop. If we hit a function first,

tests/checks/return.fish

@@ -0,0 +1,22 @@
+#RUN: %fish -C 'set -l fish %fish' %s
+# Some tests of the "return" builtin.
+
+$fish -c 'return 5'
+echo $status
+# CHECK: 5
+
+$fish -c 'exit 5'
+echo $status
+# CHECK: 5
+
+$fish -c 'echo foo; return 2; echo bar'
+# CHECK: foo
+# but not bar
+echo $status
+# CHECK: 2
+
+$fish -ic 'echo interactive-foo; return 69; echo interactive-bar'
+# CHECK: interactive-foo
+# but not bar
+echo $status
+# CHECK: 69