Provide Alternate Number Formats plugin for Haskell Language Server.

Please see the README on GitHub at https://github.com/haskell/haskell-language-server#readme

Alternate Number Format Plugin

The alternate number format plugin provides alternative formatting for Numeric Literals in source code. These can be any numeric literal such as 123, 0x45 or any of the other numeric formats. The Code Action will provide all possible formatting suggestions (and when required insert the associated Language Extension)

Setup

The plugin requires no extra setup to work. Simply place your cursor on top of a literal and invoke the codeAction command for your editor.

Demo

Currently Supported GHC Extensions:

• BinaryLiterals
• HexFloatLiterals
• NumDecimalLiterals

Design

The plugin is relatively simple, it traverses a files source contents using the GHC API. As it encounters Literals (of the type HsExpr with the constructor of either HsLit or HsOverLit), it will construct an internal Literal datatype that has additional information for use to generate suggestions. Currently, the traversal is done in the file, Literal.hs, using the package SYB for most of the heavy lifting.

To generate suggestions, the plugin leverages the Numeric package which provides a multitude of conversion functions to and from strings/numerics.

Known Quirks

• Anything that produces a bad Source Span (i.e. can't be easily replaced by an edit) is ignored as well.

Changelog

1.0.0.0

• First Release

1.0.1.0

• Dependency upgrades

1.0.1.1

• Buildable with GHC 9.2

1.0.2.0

• Test Suite upgraded for 9.2 semantics (GHC2021)
• Fix SYB parsing with GHC 9.2

1.1.0.0

• Provide ALL possible formats as suggestions
• Insert Language Extensions when needed.