vim-patch:9.2.1288: E110 "missing ')'" error does not say where the problem is (#42698)

Problem:  An invalid nested expression such as "echo (0!)" gives
          "E110: Missing ')'" although the ")" is there, and does not say
          where the expression is not valid.
Solution: When text follows the expression, add it to the E110 message, as
          E697 does for a List (zuloloxi).

Without parentheses "echo 0!" already gives E15 with the text "!".  When
nothing follows the expression the ")" is really missing and the message
is as before.

related: vim/vim#17602
closes:  vim/vim#21607

https://github.com/vim/vim/commit/d06691450ab0dc2ea72a997f8426002f66da2ac2

Co-authored-by: zuloloxi <10588750+zuloloxi@users.noreply.github.com>

runtime/doc/vimeval.txt

@@ -1566,9 +1566,17 @@ When using the '=' register you get the expression itself, not what it
 evaluates to.  Use |eval()| to evaluate it.
 
 
+------------------------------------------------------------------------------
 nesting							*expr-nesting* *E110*
+
 (expr1)			nested expression
 
+If text follows the expression, E110 includes it, to show where the expression
+should end: >
+	echo (0!)
+<	E110: Missing ')': !) ~
+Vim expects the ")" where the "!" is.
+
 
 ------------------------------------------------------------------------------
 environment variable					*expr-env*

scripts/linterrcodes.lua

@@ -10,7 +10,7 @@
 local dup_allowed = {
   E109 = 2,
   E1098 = 2,
-  E110 = 2,
+  E110 = 3,
   E112 = 2,
   E114 = 2,
   E115 = 2,

src/nvim/errors.h

@@ -130,6 +130,8 @@ EXTERN const char e_write[] INIT(= N_("E80: Error while writing"));
 EXTERN const char e_zerocount[] INIT(= N_("E939: Positive count required"));
 EXTERN const char e_usingsid[] INIT(= N_("E81: Using <SID> not in a script context"));
 EXTERN const char e_missingparen[] INIT(= N_("E107: Missing parentheses: %s"));
+EXTERN const char e_missing_closing_paren[] INIT(= N_("E110: Missing ')'"));
+EXTERN const char e_missing_closing_paren_str[] INIT(= N_("E110: Missing ')': %s"));
 EXTERN const char e_empty_buffer[] INIT(= N_("E749: Empty buffer"));
 EXTERN const char e_nobufnr[] INIT(= N_("E86: Buffer %" PRId64 " does not exist"));
 

src/nvim/eval.c

@@ -2755,7 +2755,12 @@ static int eval7(char **arg, typval_T *rettv, evalarg_T *const evalarg, bool wan
     if (**arg == ')') {
       (*arg)++;
     } else if (ret == OK) {
-      emsg(_("E110: Missing ')'"));
+      // Show where the expression stopped, unless at the end.
+      if (**arg == NUL) {
+        emsg(_(e_missing_closing_paren));
+      } else {
+        semsg(_(e_missing_closing_paren_str), *arg);
+      }
       tv_clear(rettv);
       ret = FAIL;
     }

test/old/testdir/test_expr.vim

@@ -209,6 +209,23 @@ func Test_special_char()
   call CheckLegacyAndVim9Failure(['echo "\<C-">'], ['E15:', 'E1004:', 'E1004:'])
 endfunc
 
+" When something else than ")" follows a nested expression, E110 shows where
+" the expression ended; when nothing follows, the ")" is really missing.
+func Test_missing_closing_paren()
+  call CheckLegacyAndVim9Failure(['echo (0!)'], "E110: Missing ')': !)")
+  call CheckLegacyAndVim9Failure(['echo (1 2)'], "E110: Missing ')': 2)")
+  call CheckLegacyAndVim9Failure(['echo (1 + 2 ]'], "E110: Missing ')': ]")
+  call CheckLegacyAndVim9Failure(['echo ("a" "b")'], "E110: Missing ')': \"b\")")
+  " in a :def function the expression may continue on the next line
+  call CheckLegacyAndVim9Failure(['VAR x = ((1)'], ["E110: Missing ')'", 'E1097:', "E110: Missing ')'"])
+  try
+    echo ((1)
+    call assert_report('should not get here')
+  catch
+    call assert_equal("Vim(echo):E110: Missing ')'", v:exception)
+  endtry
+endfunc
+
 func Test_method_with_prefix()
   let lines =<< trim END
       call assert_equal(TRUE, !range(5)->empty())