[Patch, fortran] PR66993 - Spurious ambiguous symbol error with submodules

[Paul Richard Thomas <paul dot richard dot thomas at gmail dot com>]

Dear All,

This is a very straight forward patch of a problem picked up by
Mikael. Since module symbols host associated in the submodule
statement are read using the use association mechanism, the can be
wrongly detected as being ambiguous with use associated symbols. The
latter have precedence, since the module is host. The fix attaches the
host associated symbol to a 'unique symtree' and procedes to process
the use associated symbol, using the existing symtree.

Bootstraps and regtests on FC21/x86_64 - OK for trunk?

Paul

2015-08-10  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/66993
    * module.c (read_module): If a symtree exists and the symbol has
    been associated in a submodule from a parent (sub)module, attach
    the symbol to a 'unique symtree' and the new symbol to the
    existing symtree.

2015-08-10  Paul Thomas  <pault@gcc.gnu.org>

    PR fortran/66993
    * gfortran.dg/submodule_11.f08: New test.

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