patch 8.1.0747: map() with a bad expression doesn't give an error

Problem:    map() with a bad expression doesn't give an error. (Ingo Karkat)
Solution:   Check for giving an error message. (closes #3800)

src/eval.c

@@ -696,6 +696,30 @@ eval_to_bool(
     return (int)retval;
 }
 
+/*
+ * Call eval1() and give an error message if not done at a lower level.
+ */
+    static int
+eval1_emsg(char_u **arg, typval_T *rettv, int evaluate)
+{
+    int		ret;
+    int		did_emsg_before = did_emsg;
+    int		called_emsg_before = called_emsg;
+
+    ret = eval1(arg, rettv, evaluate);
+    if (ret == FAIL)
+    {
+	// Report the invalid expression unless the expression evaluation has
+	// been cancelled due to an aborting error, an interrupt, or an
+	// exception, or we already gave a more specific error.
+	// Also check called_emsg for when using assert_fails().
+	if (!aborting() && did_emsg == did_emsg_before
+					  && called_emsg == called_emsg_before)
+	    semsg(_(e_invexpr2), arg);
+    }
+    return ret;
+}
+
     static int
 eval_expr_typval(typval_T *expr, typval_T *argv, int argc, typval_T *rettv)
 {
@@ -729,7 +753,7 @@ eval_expr_typval(typval_T *expr, typval_T *argv, int argc, typval_T *rettv)
 	if (s == NULL)
 	    return FAIL;
 	s = skipwhite(s);
-	if (eval1(&s, rettv, TRUE) == FAIL)
+	if (eval1_emsg(&s, rettv, TRUE) == FAIL)
 	    return FAIL;
 	if (*s != NUL)  /* check for trailing chars after expr */
 	{
@@ -8464,18 +8488,9 @@ ex_execute(exarg_T *eap)
     while (*arg != NUL && *arg != '|' && *arg != '\n')
     {
 	p = arg;
-	if (eval1(&arg, &rettv, !eap->skip) == FAIL)
+	ret = eval1_emsg(&arg, &rettv, !eap->skip);
-	{
+	if (ret == FAIL)
-	    /*
-	     * Report the invalid expression unless the expression evaluation
-	     * has been cancelled due to an aborting error, an interrupt, or an
-	     * exception.
-	     */
-	    if (!aborting() && did_emsg == save_did_emsg)
-		semsg(_(e_invexpr2), p);
-	    ret = FAIL;
 	    break;
-	}
 
 	if (!eap->skip)
 	{
@@ -10758,6 +10773,7 @@ filter_map(typval_T *argvars, typval_T *rettv, int map)
 	}
 	else
 	{
+	    // argvars[0].v_type == VAR_LIST
 	    vimvars[VV_KEY].vv_type = VAR_NUMBER;
 
 	    for (li = l->lv_first; li != NULL; li = nli)

src/testdir/test_filter_map.vim

@@ -79,3 +79,8 @@ func Test_filter_map_dict_expr_funcref()
   endfunc
   call assert_equal({"foo": "f", "bar": "b", "baz": "b"}, map(copy(dict), function('s:filter4')))
 endfunc
+
+func Test_map_fails()
+  call assert_fails('call map([1], "42 +")', 'E15:')
+  call assert_fails('call filter([1], "42 +")', 'E15:')
+endfunc

src/version.c

@@ -795,6 +795,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    747,
 /**/
     746,
 /**/