Hello world,

the attached patch improves the rather hard to read error
messages for argument mismatches.  With this patch, this reads

argument_checking_21.f90:7:11:

     6 |   call foo(1.0) ! { dg-warning "Rank mismatch" }
       |           2
     7 |   call foo(b)   ! { dg-warning "Rank mismatch" }
       |           1
Fehler: Rank mismatch between actual argument at (1) and actual argument 
at (2) (scalar and rank-2)

which I think is fairly clear.  It also makes sure that warnings are
always emitted by -fallow-argument-mismatch by removing
-Wargument-mismatch.  Finally, for people who do not want to have too
many warnings cluttering up their logs, a type mismatch is only
shown once if it is a warning.

While I was going on about fixing warnings, I also fixed PR 91557 with
the bit in trans-expr.c.  This part is trivial, I will backport it
to the other affected branches.

After this, I think we can close PR 91556. Regression-tested. OK for
trunk?

2019-09-13  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/91557
	PR fortran/91556
	* frontend-passes.c (check_externals_procedure): Reformat argument
	list. Use gfc_compare_actual_formal instead of gfc_procedure_use.
	* gfortran.h (gfc_symbol): Add flag error.
	* interface.c (gfc_compare_interfaces): Reformat.
	(argument_rank_mismatch): Add where_formal argument. If it is
	present, note that the error is between different calls.
	(compare_parameter): Change warnings that previously dependended
	on -Wargument-mismatch to unconditional.  Issue an error / warning
	on type mismatch only once.  Pass where_formal to
	argument_rank_mismatch for artificial variables.
	(compare_actual_formal): Change warnings that previously
	dependeded on -Wargument-mismatch to unconditional.
	(gfc_check_typebound_override): Likewise.
	(gfc_get_formal_from_actual_arglist): Set declared_at for
	artificial symbol.
	* invoke.texi: Extend description of -fallow-argument-mismatch.
	Delete -Wargument-mismatch.
	* lang.opt: Change -Wargument-mismatch to do-nothing option.
	* resolve.c (resolve_structure_cons): Change warnings that
	previously depended on -Wargument-mismatch to unconditional.
	* trans-decl.c (generate_local_decl): Do not warn if the symbol is
	artificial.

2019-09-13  Thomas Koenig  <tkoenig@gcc.gnu.org>

	PR fortran/91557
	PR fortran/91556
	* gfortran.dg/argument_checking_20.f90: New test.
	* gfortran.dg/argument_checking_21.f90: New test.
	* gfortran.dg/argument_checking_22.f90: New test.
	* gfortran.dg/argument_checking_23.f90: New test.
	* gfortran.dg/warn_unused_dummy_argument_5.f90: New test.
	* gfortran.dg/bessel_3.f90: Add pattern for type mismatch.
	* gfortran.dg/g77/20010519-1.f: Adjust dg-warning messages to new
	handling.
	* gfortran.dg/pr24823.f: Likewise.
	* gfortran.dg/pr39937.f: Likewise.