This isn't the clearest warning, but it is not clear what should in it -- the 18 comes from inlining and constant folding a call, so there are multiple places in the code that are relevant. At the very least, though, it should identify the point in the code that has the shift (line 8)

Before #5333, the warning looked like this:

tmp.p4(8): [--Wwarn=overflow] warning: x << 18: shifting value with 16 bits by 18
        a3(x << (9 + y));
           ^^^^^^^^^^^^

Should #5333 actually be propagating the source info of the argument?

That is definitely better, so maybe #5333 should be doing less. The source info on the shift operation itself should not be changing.

Maybe #5333 should only copy the source info if it is not already set to something else?

@asl Please comment