<no location info> for shadowing warnings in TH-generated code

See attached test case, which causes this warning to be printed when THShadowSplice.hs is compiled with -Wall:

<no location info>:
    Warning: This binding for `x' shadows the existing binding
               bound at THShadowSplice.hs:7:3

There ought to be some location info. I have also seen warnings of the form

<no location info>:
    Warning: This binding for `x' shadows the existing binding
               bound at <no location info>

although I have not yet been able to construct a small test case which exhibits this behavior.