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th-desugar does not currently support or-patterns (introduced in GHC 9.12), and attempting to desugar an or-pattern will result in an error. In order to support or-patterns, we will need to answer the following questions:
Should we add a DOrP constructor to DPat, or should we attempt to desugar or-patterns into simpler patterns (à la match flattening)? See this issue.
Relatedly, GHC flattens matches on or-patterns by desugaring them into view patterns (see this Note), but th-desugardoesn't support view patterns. How should match flattening be handled on the th-desugar side?
How should we handle an as-pattern such as p@(A ; B ; C)? Note that or-patterns are not invertible, which means that they are susceptible to this issue.
The text was updated successfully, but these errors were encountered:
Handling or-patterns in full generality is tricky (see #232), so for now, we
simply error if we attempt to desugar an or-pattern.
Checks off one box in #231.
Handling or-patterns in full generality is tricky (see #232), so for now, we
simply error if we attempt to desugar an or-pattern.
Checks off one box in #231.
th-desugardoes not currently support or-patterns (introduced in GHC 9.12), and attempting to desugar an or-pattern will result in an error. In order to support or-patterns, we will need to answer the following questions:DOrPconstructor toDPat, or should we attempt to desugar or-patterns into simpler patterns (à la match flattening)? See this issue.th-desugardoesn't support view patterns. How should match flattening be handled on theth-desugarside?p@(A ; B ; C)? Note that or-patterns are not invertible, which means that they are susceptible to this issue.The text was updated successfully, but these errors were encountered: