Missing syntax error for package qualified import with version number

Consider the following test file:

{-# LANGUAGE PackageImports #-}
module Foo where
import "containers-0.5.0.0" Data.Map

where we have

ezyang@sabre:~$ ghc-pkg list | grep containers
    containers-0.5.0.0
    unordered-containers-0.2.3.0

GHC will fail to compile this, but in an unusual way:

ezyang@sabre:~$ ghc test.hs
[1 of 1] Compiling Foo              ( test.hs, test.o )

test.hs:3:1:
    Failed to load interface for `Data.Map'
    It is not a module in the current program, or in any known package.

That's misleading: the real reason the import failed is because this is a package qualified import (not package ID qualified imports). For my purposes, it would be useful to also support package ID imports, but in the meantime, it would be a good idea to run Cabal's syntax check on the package name, which requires every hyphenated component to contain an alphabetic character.

Trac metadata

Trac field	Value
Version	7.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler (Parser)
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