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, currently --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).

Trac metadata

Trac field	Value
Version	7.11
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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