hie hangs in typechecking module step with ghc version mismatch (project 8.6.4/hie 8.6.5)

[jneira]

• Using vscode: hie starts as usual until it has to typecheck the module
• Relevant log section:

2019-09-13 00:22:36.1391282 [ThreadId 11] - ghcDispatcher:got request 2 with id: Nothing
2019-09-13 00:22:36.1839489 [ThreadId 11] - ghcDispatcher:Processing request as version matches
2019-09-13 00:22:36.2060281 [ThreadId 11] - setTypecheckedModule: file mapping state is: fromList [("D:\\dev\\ws\\haskell\\stack-test\\src\\Main.hs",FileMapping {fmPath = "C:\\TEMP\\ghc-mod4449\\Mai1252.hs", fmTemp = True})]
2019-09-13 00:22:36.2849894 [ThreadId 11] - setTypecheckedModule: before ghc-mod
2019-09-13 00:22:36.6908832 [ThreadId 5] - <--2--{"jsonrpc":"2.0","params":{"uri":"file:///d:/dev/ws/haskell/stack-test/src/Main.hs","diagnostics":[]},"method":"textDocument/publishDiagnostics"}
2019-09-13 00:22:36.6908832 [ThreadId 5] - <--2--{"jsonrpc":"2.0","params":{"id":"0","cancellable":false,"title":"Typechecking Main.hs"},"method":"window/progress/start"}

• We can observe that the message "setTypecheckedModule: after ghc-mod" is never emitted
• The editor shows the message "Typechecking file" indefinitely
• Relevant code fragment in hie-plugin-api:

haskell-ide-engine/hie-plugin-api/Haskell/Ide/Engine/Ghc.hs

Lines 192 to 201 in 098b180

	debugm "setTypecheckedModule: before ghc-mod"
	-- TODO:AZ: loading this one module may/should trigger loads of any
	-- other modules which currently have a VFS entry. Need to make
	-- sure that their diagnostics are reported, and their module
	-- cache entries are updated.
	-- TODO: Are there any hooks we can use to report back on the progress?
	((Diagnostics diags', errs), mtm, mpm) <- withIndefiniteProgress progTitle NotCancellable $ GM.gcatches
	(GM.getModulesGhc' (myWrapper rfm) fp)
	(errorHandlers ghcErrRes (return . ghcErrRes . show))
	debugm "setTypecheckedModule: after ghc-mod"

• Complete log: hie.log

[fendor]

In the logs, a mismatching ghc version is mentioned. Just for completeness, can you check if the same happens for a matching ghc version?

[jneira]

Sure, i ve just tested it with the same result:
hie.log

[jneira]

It worked for me not much time ago so i've installed version e2f8e32 and it works.
hie.log
I'll try to identify the commit that causes the hang...

[jneira]

Ok, @fendor was right and it seems the cause is i am trying to open a stack project with ghc-8.6.4 with hie compiled with ghc-8.6.5, and it already was warning me.
Not sure if it is the expected behaviour cause hie-wrapper falls back to hie-8.6 (that is, ghc-8.6.5 in my case) when it has not the exact version.
Anyway this has a clear workaround and a existing warning so imho has not a high priority.