Certain do blocks cause TH to barf when ApplicativeDo is enabled

The following program fails with an error:

{-# LANGUAGE ApplicativeDo #-}
{-# LANGUAGE TemplateHaskell #-}

main = $([|do
  return ()
  return ()
  return ()|])

Exotic.hs:4:12: error:
    Exotic statement not (yet) handled by Template Haskell
      [return ();
       return (),
       return ()]

It only happens when ApplicativeDo is enabled.

Furthermore, while this example is extremely minimal, this issue isn’t restricted to ApplicativeDo’s special handling of return. The following example produces the same error:

{-# LANGUAGE ApplicativeDo #-}
{-# LANGUAGE TemplateHaskell #-}

main = $([|do
  getLine
  getLine
  getLine|])

Exotic.hs:4:12: error:
    Exotic statement not (yet) handled by Template Haskell
      [getLine;
       getLine,
       getLine]

This doesn’t happen with fewer than three statements in the do block, but it does happen with more.

Trac metadata

Trac field	Value
Version	8.2.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Template Haskell
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