Matthew Pickering pushed to branch wip/improve-implicit-lifting-error at Glasgow Haskell Compiler / GHC Commits: df4a756c by Matthew Pickering at 2025-06-16T09:42:19+01:00 Improve error messages when implicit lifting fails This patch concerns programs which automatically try to fix level errors by inserting `Lift`. For example: ``` foo x = [| x |] ~> foo x = [| $(lift x) |] ``` Before, there were two problems with the message. 1. (#26031), the location of the error was reported as the whole quotation. 2. (#26035), the message just mentions there is no Lift instance, but gives no indicate why the user program needed a Lift instance in the first place. This problem is especially bad when you disable `ImplicitStagePersistence`, so you just end up with a confusing "No instance for" message rather than an error message about levels This patch fixes both these issues. Firstly, `PendingRnSplice` differentiates between a user-written splice and an implicit lift. Then, the Lift instance is precisely requested with a specific origin in the typechecker. If the instance fails to be solved, the message is reported using the `TcRnBadlyLevelled` constructor (like a normal level error). Fixes #26031, #26035 - - - - - 42 changed files: - compiler/GHC/Hs/Expr.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Rename/Splice.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Errors/Ppr.hs - compiler/GHC/Tc/Errors/Types.hs - compiler/GHC/Tc/Gen/Head.hs - compiler/GHC/Tc/Gen/Splice.hs - compiler/GHC/Tc/Solver/Monad.hs - compiler/GHC/Tc/Types/Origin.hs - testsuite/tests/annotations/should_fail/annfail03.stderr - testsuite/tests/annotations/should_fail/annfail09.stderr - testsuite/tests/quasiquotation/qq001/qq001.stderr - testsuite/tests/quasiquotation/qq002/qq002.stderr - testsuite/tests/quasiquotation/qq003/qq003.stderr - testsuite/tests/quasiquotation/qq004/qq004.stderr - + testsuite/tests/quotes/LiftErrMsg.hs - + testsuite/tests/quotes/LiftErrMsg.stderr - + testsuite/tests/quotes/LiftErrMsgDefer.hs - + testsuite/tests/quotes/LiftErrMsgDefer.stderr - + testsuite/tests/quotes/LiftErrMsgTyped.hs - + testsuite/tests/quotes/LiftErrMsgTyped.stderr - testsuite/tests/quotes/T10384.stderr - testsuite/tests/quotes/TH_localname.stderr - testsuite/tests/quotes/all.T - testsuite/tests/splice-imports/SI03.stderr - testsuite/tests/splice-imports/SI05.stderr - testsuite/tests/splice-imports/SI16.stderr - testsuite/tests/splice-imports/SI18.stderr - testsuite/tests/splice-imports/SI20.stderr - testsuite/tests/splice-imports/SI25.stderr - testsuite/tests/splice-imports/SI28.stderr - testsuite/tests/splice-imports/SI31.stderr - testsuite/tests/th/T16976z.stderr - testsuite/tests/th/T17820a.stderr - testsuite/tests/th/T17820b.stderr - testsuite/tests/th/T17820c.stderr - testsuite/tests/th/T17820d.stderr - testsuite/tests/th/T17820e.stderr - testsuite/tests/th/T23829_hasty.stderr - testsuite/tests/th/T23829_hasty_b.stderr - testsuite/tests/th/T5795.stderr The diff was not included because it is too large. View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/df4a756c890c5cc075575f0c50d2d4d7... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/df4a756c890c5cc075575f0c50d2d4d7... You're receiving this email because of your account on gitlab.haskell.org.