GHC --make should also look for .hi, not only for .hs

Currently, ghc --make will only consider .hs source files from the include path.

Example (assuming Library can't be resolved from the package database):

A.hs

module A where

import B
import Library

B.hs

module B where

Compiling these files with ghc --make -Idir A.hs B.hs will succeed only if GHC finds a Library.hs file.

In a thread on glasgow-haskell-users, Simon proposed relaxing this constraint; namely: In --make mode, when encountering an import X, GHC will try the following in order:

1. resolve the import from a package
2. search the include path for X.hs or X.lhs
3. search the include path for X.hi

It already does 1 and 2, and this proposal would add 3.

Trac metadata

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