Commit 9ee58f8d authored by Matthías Páll Gissurarson's avatar Matthías Páll Gissurarson Committed by Facundo Domínguez

Implement the proposed -XQualifiedDo extension

Co-authored-by: default avatarFacundo Domínguez <>

QualifiedDo is implemented using the same placeholders for operation names in
the AST that were devised for RebindableSyntax. Whenever the renamer checks
which names to use for do syntax, it first checks if the do block is qualified
(e.g. { stmts }), in which case it searches for qualified names in
the module M.

This allows users to write

    {-# LANGUAGE QualifiedDo #-}
    import qualified SomeModule as M

    f x =           -- desugars to:
      y <- M.return x    -- M.return x M.>>= \y ->
      M.return y         -- M.return y M.>>
      M.return y         -- M.return y

See Note [QualifiedDo] and the users' guide for more details.

Issue #18214


Since we change the constructors `ITdo` and `ITmdo` to carry the new module
name, we need to bump the haddock submodule to account or the new shape of
these constructors.
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