Adowrath authored Jun 09, 2024 and Marge Bot committed Jul 04, 2024

Progress towards #21592

This splits HsSrcBang up, creating the new HsBang within
`Language.Haskell.Syntax.Basic`. `HsBang` holds the unpackedness
and strictness information, while `HsSrcBang` only adds the SourceText
for usage within the compiler directly.

Inside the AST, to preserve the SourceText, it is hidden behind the
pre-existing extension point `XBindTy`. All other occurrences of
`HsSrcBang` were adapted to deconstruct the inner `HsBang`, and when
interacting with the `BindTy` constructor, the hidden `SourceText` is
extracted/inserted into the `XBindTy` extension point.

`GHC.Core.DataCon` exports both `HsSrcBang` and `HsBang` for
convenience. A constructor function `mkHsSrcBang` that takes all
individual components has been added.

Two exceptions has been made though:
- The `Outputable HsSrcBang` instance is replaced by
  `Outputable HsBang`. While being only GHC-internal, the only place
  it's used is in outputting `HsBangTy` constructors -- which already
  have `HsBang`. It wouldn't make sense to reconstruct a `HsSrcBang` just
  to ignore the `SourceText` anyway.
- The error `TcRnUnexpectedAnnotation` did not use the `SourceText`,
  so it too now only holds a `HsBang`.