Emit an error if time is used past the first command in a pipeline

Fixes #8841

CHANGELOG.rst

@@ -36,6 +36,7 @@ Interactive improvements
 - Case-changing autosuggestions generated mid-token now correctly append only the suffix, instead of duplicating the token (:issue:`8820`).
 - ``ulimit`` learned a number of new options for the resource limits available on Linux, FreeBSD and NetBSD, and returns a specific warning if the limit specified is not available on the active operating system (:issue:`8823`).
 - The ``vared`` command can now successfully edit variables named "tmp" or "prompt" (:issue:`8836`).
+- ``time`` now emits an error if used after the first command in a pipeline (:issue:`8841`).
 
 New or improved bindings
 ^^^^^^^^^^^^^^^^^^^^^^^^

src/parse_util.cpp

@@ -39,6 +39,9 @@
 /// Error message for arguments to 'end'
 #define END_ARG_ERR_MSG _(L"'end' does not take arguments. Did you forget a ';'?")
 
+/// Error message when 'time' is in a pipeline.
+#define TIME_IN_PIPELINE_ERR_MSG _(L"The 'time' command may only be at the beginning of a pipeline")
+
 /// Maximum length of a variable name to show in error reports before truncation
 static constexpr int var_err_len = 16;
 
@@ -1123,6 +1126,11 @@ static bool detect_errors_in_decorated_statement(const wcstring &buff_src,
             errored = append_syntax_error(parse_errors, source_start, INVALID_PIPELINE_CMD_ERR_MSG,
                                           command.c_str());
         }
+
+        // Similarly for time (#8841).
+        if (command == L"time") {
+            errored = append_syntax_error(parse_errors, source_start, TIME_IN_PIPELINE_ERR_MSG);
+        }
     }
 
     // $status specifically is invalid as a command,

tests/checks/syntax-error-location.fish

@@ -11,6 +11,12 @@ $status
 # CHECK: <echo foo | exec grep # this exec is not allowed!>
 # CHECK: <           ^>
 
+echo 'true | time false' | $fish 2>| string replace -r '(.*)' '<$1>'
+# CHECK: <fish: The 'time' command may only be at the beginning of a pipeline>
+# CHECK: <true | time false>
+# CHECK: <       ^>
+
+
 echo '
 
 (true one)