Re: [PATCH] c++: -Wconversion vs value-dependent expressions [PR99331]

[Jason Merrill via Gcc-patches]

On 3/4/21 9:37 PM, Marek Polacek wrote:
This PR complains that we issue a -Wconversion warning in
   template <int N> struct X {};
   template <class T> X<sizeof(T)> foo();

saying "conversion from 'long unsigned int' to 'int' may change value".
While it's not technically wrong, I suspect -Wconversion warnings aren't
all that useful for value-dependent expressions.  So this patch disables
them, though I'm open to other ideas.

How about suppressing -Wconversion in 
build_converted_constant_expr_internal?  If the size_t value ended up 
being too large for the int parameter, we would give an error about 
overflow in a constant expression, not just a warning.

Jason