ghc --make reports bad import errors too eagerly
Consider this A.hs file, with a valid header (no B.hs file) and a syntax error:
module A where import B = as7df89a235r a23jk @A#$(&#$A
We get different behavior when one-shot compiling and make compiling:
ezyang@sabre:~$ ghc -c A.hs A.hs:4:1: parse error on input `=' ezyang@sabre:~$ ghc --make A.hs A.hs:2:8: Could not find module `B' Use -v to see a list of the files searched for.
I feel like the
--make error is wrong, and we shouldn't actually complain that an import is missing until we build it. But it cuts both ways; if you have a big module graph and you try to
--make will report instantaneously if any import is wrong; if we changed this behavior,
--make would chug along until it actually tried to compile the offending file.
It's easy to fix and I can easily submit a patch for it, if people think we should defer the error. Doing this will also let me remove a grievous hack from my fix to #11244 (closed).