#10946: Typed hole inside typed Template Haskell bracket causes panic -------------------------------------+------------------------------------- Reporter: jstolarek | Owner: (none) Type: bug | Status: new Priority: high | Milestone: 8.4.1 Component: Template Haskell | Version: 7.10.1 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Compile-time | Unknown/Multiple crash | Test Case: th/T10946 Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by elliottt): The problem seems to be that the quoted expression {{{[|| _x ||]}}} will introduce a hole constraint of the form {{{ _x :: a }}} when spliced, but that the error will be reported outside of the implication introduced by the signature. When checking the following program: {{{ m :: a m = _x }}} {{{simplifyTop}}} will report that it's found an unsolved wanted constraint of the form {{{ forall (a :: *). () => _x :: a }}}. However, when checking the original program, {{{simplifyTop}}} is called from a different path ({{{tcTopSpliceExpr}}}), and reports the wanted constraint as being of the form {{{ _x :: a }}}. As it lacks the context of the binding for {{{a}}}, it falls through to the base case of {{{getSkolemInfo}}}, which causes the panic. At this point, I'm not sure what the right path forward is. Should {{{tcTopSpliceExpr}}} be using {{{simplifyTop}}}, or is there just some additional context needed to be setup before that call? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10946#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler