#11102: `ghc --supported-extension` shall not list `TemplateHaskell` when unsupported -------------------------------------+------------------------------------- Reporter: hvr | Owner: bgamari Type: bug | Status: new Priority: normal | Milestone: 8.0.1 Component: Compiler | Version: 7.10.2 Keywords: | Operating System: Unknown/Multiple Architecture: | Type of failure: None/Unknown Unknown/Multiple | Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): phab:D1484 | Wiki Page: -------------------------------------+------------------------------------- Currently GHC advertises `TemplateHaskell` even though it's statically known to fail: {{{ $ ghc --supported-extensions | grep Template TemplateHaskell NoTemplateHaskell # `NoTemplateHaskell` works: $ ghc -XNoTemplateHaskell -c hello.hs # `TemplateHaskell` however fails even though advertised: $ ghc -XTemplateHaskell -c hello.hs ghc: on the commandline: Template Haskell requires GHC with interpreter support Perhaps you are using a stage-1 compiler? Usage: For basic information, try the `--help' option. }}} Having properly advertised extensions is particularly useful in combination with [[https://github.com/haskell/cabal/issues/2644|Cabal#2644]] allowing the solver to toggle flags depending on the availability of `-XTemplateHaskell`. For instance, cross-compilers and/or unregisterised GHC builds often don't have TemplateHaskell support. Having support for toggling flags based on availability of `-XTemplateHaskell` allows `cabal` to support such environments with less manual intervention. (See also https://github.com/haskell/cabal/pull/2930 for pre-GHC8 emulation of this feature) -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11102 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler