#13837: Calling qReifyInstances on out-of-scope Name leads to GHC internal error -------------------------------------+------------------------------------- Reporter: RyanGlScott | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Template | Version: 8.0.1 Haskell | Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: Compile-time Unknown/Multiple | crash or panic Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | Wiki Page: -------------------------------------+------------------------------------- {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Bug where import Language.Haskell.TH.Lib import Language.Haskell.TH.Syntax test_local_tyfam_expansion :: String test_local_tyfam_expansion = $(do fam_name <- newName "Fam" stringE . show =<< qReifyInstances fam_name []) }}} {{{ $ /opt/ghc/8.2.1/bin/ghci Bug2.hs GHCi, version 8.2.0.20170523: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug2.hs, interpreted ) Bug2.hs:9:5: error: • The exact Name ‘Fam_a4pX’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the argument of reifyInstances: Fam_0 In the untyped splice: $(do fam_name <- newName "Fam" stringE . show =<< qReifyInstances fam_name []) | 9 | $(do fam_name <- newName "Fam" | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^... Bug2.hs:9:5: error: • GHC internal error: ‘Fam_a4pX’ is not in scope during type checking, but it passed the renamer tcl_env of environment: [] • In the type ‘Fam_a4pX’ In the argument of reifyInstances: Fam_0 In the untyped splice: $(do fam_name <- newName "Fam" stringE . show =<< qReifyInstances fam_name []) | 9 | $(do fam_name <- newName "Fam" | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^... }}} This appears to have started happening in GHC 7.10, since with 7.8, you only get this: {{{ GHCi, version 7.8.4: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Bug ( Bug2.hs, interpreted ) Loading package array-0.5.0.0 ... linking ... done. Loading package deepseq-1.3.0.2 ... linking ... done. Loading package containers-0.5.5.1 ... linking ... done. Loading package pretty-1.1.1.1 ... linking ... done. Loading package template-haskell ... linking ... done. Bug2.hs:9:5: The exact Name ‘Fam_a2gK’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful In the argument of reifyInstances: Fam_0 In the splice: $(do { fam_name <- newName "Fam"; stringE . show =<< qReifyInstances fam_name [] }) }}} This problem appears to be somewhat specific to `qReifyInstances`, since switching it out with `qReify` does not trigger the internal error: {{{#!hs {-# LANGUAGE TemplateHaskell #-} module Bug where import Language.Haskell.TH.Lib import Language.Haskell.TH.Syntax test_local_tyfam_expansion :: String test_local_tyfam_expansion = $(do fam_name <- newName "Fam" stringE . show =<< qReify fam_name) }}} {{{ GHCi, version 8.2.0.20170523: http://www.haskell.org/ghc/ :? for help Loaded GHCi configuration from /home/rgscott/.ghci [1 of 1] Compiling Bug ( Bug2.hs, interpreted ) Bug2.hs:9:5: error: • The exact Name ‘Fam_a4od’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the untyped splice: $(do fam_name <- newName "Fam" stringE . show =<< qReify fam_name) | 9 | $(do fam_name <- newName "Fam" | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^... Bug2.hs:9:5: error: • The exact Name ‘Fam_a4od’ is not in scope Probable cause: you used a unique Template Haskell name (NameU), perhaps via newName, but did not bind it If that's it, then -ddump-splices might be useful • In the untyped splice: $(do fam_name <- newName "Fam" stringE . show =<< qReify fam_name) | 9 | $(do fam_name <- newName "Fam" | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^... Bug2.hs:9:5: error: • ‘Fam_a4od’ is not in the type environment at a reify • In the untyped splice: $(do fam_name <- newName "Fam" stringE . show =<< qReify fam_name) | 9 | $(do fam_name <- newName "Fam" | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^... }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13837 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler