[Bug c/69972] duplicate integer overflow diagnostic in constant expressions

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69972

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The first warning is shown by default and comes from parser_build_binary_op:
 3612   if (TREE_OVERFLOW_P (result.value)
 3613       && !TREE_OVERFLOW_P (arg1.value)
 3614       && !TREE_OVERFLOW_P (arg2.value))
 3615     overflow_warning (location, result.value);

The second is emitted with -Wpedantic in build_enumerator:
 8199               constant_expression_warning (value);