Commit 5a08f7d4 authored by Committed by Marge Bot
Make warnings for TH splices opt-in
In #17270 we have the pattern-match checker emit incorrect warnings. The reason for that behavior is ultimately an inconsistency in whether we treat TH splices as written by the user (`FromSource :: Origin`) or as generated code (`Generated`). This was first reported in #14838. The current solution is to TH splices as `Generated` by default and only treat them as `FromSource` when the user requests so (-fenable-th-splice-warnings). There are multiple reasons for opt-in rather than opt-out: * It's not clear that the user that compiles a splice is the author of the code that produces the warning. Think of the situation where she just splices in code from a third-party library that produces incomplete pattern matches. In this scenario, the user isn't even able to fix that warning. * Gathering information for producing the warnings (pattern-match check warnings in particular) is costly. There's no point in doing so if the user is not interested in those warnings. Fixes #17270, but not #14838, because the proper solution needs a GHC proposal extending the TH AST syntax.