[Bug c++/68842] Better error output when template needed before dependent name

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68842

Andrew Pinski  changed:

   What|Removed |Added

 CC||soko.slav at yandex dot ru

--- Comment #4 from Andrew Pinski  ---
*** Bug 90495 has been marked as a duplicate of this bug. ***

[Bug c++/68842] Better error output when template needed before dependent name

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68842

Jonathan Wakely  changed:

   What|Removed |Added

   Keywords||diagnostic
 Status|UNCONFIRMED |NEW
   Last reconfirmed||2015-12-11
 Ever confirmed|0   |1

--- Comment #1 from Jonathan Wakely  ---
N.B. GCC 4.8 is no longer supported and the branch is closed, but the
diagnostic is the same in current releases, and I agree a "fix-it" hint would
be better than the current error.

Clang gives a different error, which IMHO is even less helpful despite trying
to give a fix-it hint:

tt.cc:15:5: error: reference to non-static member function must be called
  t.do_nothing(0);
  ~~^~
tt.cc:20:3: note: in instantiation of function template specialization
'do_test<2>' requested here
  do_test<2>();
  ^
tt.cc:5:8: note: possible target for call
  void do_nothing(int value)
   ^
1 error generated.

[Bug c++/68842] Better error output when template needed before dependent name

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68842

--- Comment #2 from Jonathan Wakely  ---
And interestingly EDG compiles it without error!

[Bug c++/68842] Better error output when template needed before dependent name

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68842

--- Comment #3 from Jonathan Wakely  ---
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -4907,8 +4907,13 @@ cp_build_binary_op (location_t location,
   if (!result_type)
 {
   if (complain & tf_error)
-   error ("invalid operands of types %qT and %qT to binary %qO",
-  TREE_TYPE (orig_op0), TREE_TYPE (orig_op1), code);
+{
+  error ("invalid operands of types %qT and %qT to binary %qO",
+ TREE_TYPE (orig_op0), TREE_TYPE (orig_op1), code);
+  if (code == LT_EXPR)
+inform (input_location, "use the keyword % before the "
+"name of a member template belonging to a dependent
type");
+}
   return error_mark_node;
 }

This patch adds the following line after the error:

tt.cc:15:15: note: use the keyword ‘template’ before the name of a member
template belonging to a dependent type

I don't know how to make it only issue that note when the LHS is one of
foo.bar, foo->bar, or foo::bar.