I realized something. The `ExnStr` + `ThrowsExn` idea is the wrong idea ''for its purpose'', but it might be the right idea for a ''different''
#14998: Sort out the strictness mess for exceptions -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.4.3 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Exceptions, | DemandAnalysis Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: #11555 #13330 | Differential Rev(s): #10712 #11222 #13380 | Wiki Page: | -------------------------------------+------------------------------------- Comment (by sgraf): Replying to [comment:32 dfeuer]: purpose. Its goal (as I understand it) was to let us say that
{{{#!hs m `catch` h }}}
is sort of strict in `m`, and therefore we can evaluate `m` somewhat
eagerly. This didn't work out, because we don't have enough information to do it right. However, what it ''should'' let us do correctly is a certain amount of dead code elimination. In particular, if we see that `m` definitely ''diverges'' (without throwing an exception), then we can simplify `catch m h` to `m`. But I'm betting this benefit isn't worth the complexity. I'm currently messing with Demand Analysis again and ExnStr has become a huge pain. I'll prepare a patch to remove it. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14998#comment:34 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler