module imports form a cycle instead of failing to parse

Some issue of parsing is causing certain module imports not to respect the proper format for a module name:

modid → {conid .} conid (modules)

A module import ending in numbers or a dot may be treated as if the . or .<numbers> weren't there. I would expect these to be parse errors instead of falling back to their 'parent', that's surely vague so here's examples.

Minimally:

echo "module Lib where import Lib. " > test.hs && ghc test.hs

echo "module Lib where import Lib.123 " > test.hs && ghc test.hs

Will both result in:

Module imports form a cycle:
  module ‘Lib’ (test.hs) imports itself

This is an error because it's not importing itself, it's importing Lib. or Lib.123 which are invalid module names.

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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