patch 8.2.1512: failure after trinary expression fails

Problem:    Failure after trinary expression fails.
Solution:   Restore eval_flags. (Yasuhiro Matsumoto, closes #6776)

src/eval.c

@@ -2167,7 +2167,10 @@ eval1(char_u **arg, typval_T *rettv, evalarg_T *evalarg)
 	evalarg_used->eval_flags = result ? orig_flags
 						 : orig_flags & ~EVAL_EVALUATE;
 	if (eval1(arg, rettv, evalarg_used) == FAIL)
+	{
+	    evalarg_used->eval_flags = orig_flags;
 	    return FAIL;
+	}
 
 	/*
 	 * Check for the ":".
@@ -2178,6 +2181,7 @@ eval1(char_u **arg, typval_T *rettv, evalarg_T *evalarg)
 	    emsg(_(e_missing_colon));
 	    if (evaluate && result)
 		clear_tv(rettv);
+	    evalarg_used->eval_flags = orig_flags;
 	    return FAIL;
 	}
 	if (getnext)
@@ -2188,6 +2192,7 @@ eval1(char_u **arg, typval_T *rettv, evalarg_T *evalarg)
 	    {
 		error_white_both(p, 1);
 		clear_tv(rettv);
+		evalarg_used->eval_flags = orig_flags;
 		return FAIL;
 	    }
 	    *arg = p;
@@ -2200,6 +2205,7 @@ eval1(char_u **arg, typval_T *rettv, evalarg_T *evalarg)
 	{
 	    error_white_both(p, 1);
 	    clear_tv(rettv);
+	    evalarg_used->eval_flags = orig_flags;
 	    return FAIL;
 	}
 	*arg = skipwhite_and_linebreak(*arg + 1, evalarg_used);
@@ -2209,6 +2215,7 @@ eval1(char_u **arg, typval_T *rettv, evalarg_T *evalarg)
 	{
 	    if (evaluate && result)
 		clear_tv(rettv);
+	    evalarg_used->eval_flags = orig_flags;
 	    return FAIL;
 	}
 	if (evaluate && !result)

src/testdir/test_vim9_expr.vim

@@ -114,6 +114,27 @@ def Test_expr1_vimscript()
       let var = v:true ? 1 :2
   END
   CheckScriptFailure(lines, 'E1004:', 2)
+
+  # check after failure eval_flags is reset
+  lines =<< trim END
+      vim9script
+      try
+        call eval('0 ? 1: 2')
+      catch
+      endtry
+      assert_equal(v:true, eval(string(v:true)))
+  END
+  CheckScriptSuccess(lines)
+
+  lines =<< trim END
+      vim9script
+      try
+        call eval('0 ? 1 :2')
+      catch
+      endtry
+      assert_equal(v:true, eval(string(v:true)))
+  END
+  CheckScriptSuccess(lines)
 enddef
 
 func Test_expr1_fails()

src/testdir/test_vimscript.vim

@@ -7445,6 +7445,30 @@ func Test_typed_script_var()
   call StopVimInTerminal(buf)
 endfunc
 
+" Test for issue6776              {{{1
+func Test_trinary_expression()
+  try
+    call eval('0 ? 0')
+  catch
+  endtry
+  " previous failure should not cause next expression to fail
+  call assert_equal(v:false, eval(string(v:false)))
+
+  try
+    call eval('0 ? "burp')
+  catch
+  endtry
+  " previous failure should not cause next expression to fail
+  call assert_equal(v:false, eval(string(v:false)))
+
+  try
+    call eval('1 ? 0 : "burp')
+  catch
+  endtry
+  " previous failure should not cause next expression to fail
+  call assert_equal(v:false, eval(string(v:false)))
+endfunction
+
 "-------------------------------------------------------------------------------
 " Modelines								    {{{1
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1512,
 /**/
     1511,
 /**/