Signature tooltip in Haddock source shows unrelated type alias

Originally opened at https://github.com/haskell/haddock/issues/1573 by Lysxia:

In the following hyperlinked source, the function showName :: Name -> String is unexpectedly shown to have type Name -> FilePath in the tooltip that appears when you hover over it https://hackage.haskell.org/package/template-haskell-2.19.0.0/docs/src/Language.Haskell.TH.Syntax.html#showName

I haven't tracked down the cause of the issue, but this may end up being something to be fixed on GHC's side rather than haddock.

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