#15599: typeclass inference depends on whether a module is exposed. -------------------------------------+------------------------------------- Reporter: gleachkr | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: 8.2.3 Component: Compiler | Version: 8.2.2 Resolution: | Keywords: Operating System: Linux | Architecture: Type of failure: Incorrect result | Unknown/Multiple at runtime | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by gleachkr): Sorry, my mistake. it looks like the `-package-db` flag won't suffice to make this more portable and to disentangle it from stack. The included pkgdb directories refer back to the `.stack-work` directory, which isn't around unless you build the package with stack. Here's what I get when I run the two included scripts, though: {{{ GHC-Repro master ❯ ./test.sh Building project... These two results should be the same, since the only difference between the files is that one is an exported module λ ❯ Flag {checkFlag = True} λ ❯ Flag {checkFlag = False} Here it is again with 8.4.3: Building project... λ ❯ Flag {checkFlag = True} λ ❯ Flag {checkFlag = True} GHC-Repro master ❯ ./test-ghci.sh Behavior in 8.2.2 with pkgdb λ ❯ Flag {checkFlag = False} Behavior in 8.2.2 without pkgdb λ ❯ Flag {checkFlag = True} Behavior in 8.4.3 with pkgdb λ ❯ Flag {checkFlag = True} Behavior in 8.4.3 without pkgdb λ ❯ Flag {checkFlag = True} }}} When I run ghci as you did, with everything in the same directory (or with `-isrc`), I get the same results as you, `True` throughout. The difference that made me try the package-db route was that it seems (from a fair amount of experimentation) that you get `checkFlag=False` when the modules from GHC-Repro are not compiled by ghci, but just included, so when you get this loading message: {{{ [1 of 1] Compiling Tests.Good ( src/Tests/Good.hs, interpreted ) [Tests.Link changed] Ok, one module loaded. }}} rather than {{{ [1 of 2] Compiling Tests.Link ( src/Tests/Link.hs, interpreted ) [2 of 2] Compiling Tests.Good ( src/Tests/Good.hs, interpreted ) Ok, two modules loaded. }}} This suggested to me that `Tests.Link` needed to be available as part of a package rather than being loaded into ghci, which I think the second script confirms. In case it might be helpful, I've added the `.stack-work` directory to the github repo, and changed the paths on the `test-ghci.sh` script to point to the pkgdbs inside of that directory. I don't know how portable this is, though, (I hope it would run on other x86 linux machines, but I'm not sure) and it is pretty far from a clean reproduction. Do you know of a better approach? -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15599#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler