TH can't attach docs to type operators that don't start with `:`

Summary

When compiling the below module, GHC fails with:

Bug.hs:1:1: error: [GHC-24922] ‘>-:’ is not in scope at a reify
  |
1 | {-# LANGUAGE TemplateHaskell #-}
  | ^

Steps to reproduce

{-# LANGUAGE TemplateHaskell #-}
module Bug where

import Language.Haskell.TH

$(sequence [withDecDoc "doc string" $ tySynD (mkName ">-:") [] [t| () |]])

Note that using mkName ":->" instead succeeds.

Expected behavior

I expect this to compile regardless of whether the type operator name begins with :.

Possibly related: #11046 (closed)

I have a notion of fixing this here: https://gitlab.haskell.org/ghc/ghc/-/blob/420000000e2d3d1a07ff3aa2a24cc88bd3d48e75/compiler/GHC/ThToHs.hs#L2180-2181

isLexCon returns true if a symbol is data-constructor-like, but type constructors can also have names that are variable-like symbols. Maybe insert the below as a third branch?

| isLexVarSym (mkFastString occ_str) = [OccName.tcName,  OccName.varName]

Would that be correct?

Environment

• GHC version used: 9.6.2

Optional:

• Operating System: Linux (NixOS)
• System Architecture: x86_64