[Patch, Fortran] PR 31600 - Better diagnosis when redeclaring used-assoc symbol

[Tobias Burnus <burnus at net-b dot de>]

Before, one got the following error for the attached test case:
------------------------------------
integer :: bar
              1
Error: Symbol 'bar' at (1) already has basic type of INTEGER
------------------------------------

Which can be a bit puzzling in larger programs. With the patch, one gets:
------------------------------------
use_16.f90:15.14:
integer :: bar
              1
use_16.f90:13.83:
use a
     2
Error: Symbol 'bar' at (1) conflicts with symbol from module 'a', 
use-associated at (2)
------------------------------------


The module change is a bit unrelated but makes the error a bit more 
readable. Instead of having:

 dg-error "Symbol 'bar' at \\(1\\) conflicts with symbol from module 'a'" }
                                                                           2

One now has:

use a ! { dg-error "Symbol 'bar' at \\(1\\) conflicts with symbol from 
module '
    2


Build and regtested on x86-64-linux.
OK for the trunk?

Tobias
2011-08-23  Tobias Burnus  <burnus@net-b.de>

	PR fortran/31600
	* symbol.c (gfc_add_type): Better diagnostic if redefining
	use-associated symbol.
	* module.c (gfc_use_module): Use module name as locus.

2011-08-23  Tobias Burnus  <burnus@net-b.de>

	PR fortran/31600
	* gfortran.dg/use_16.f90: New.

diff --git a/gcc/fortran/module.c b/gcc/fortran/module.c
index aef3404..4250a17 100644
--- a/gcc/fortran/module.c
+++ b/gcc/fortran/module.c
@@ -5727,6 +5727,9 @@ gfc_use_module (void)
   int c, line, start;
   gfc_symtree *mod_symtree;
   gfc_use_list *use_stmt;
+  locus old_locus = gfc_current_locus;
+
+  gfc_current_locus = use_locus;
 
   filename = (char *) alloca (strlen (module_name) + strlen (MODULE_EXTENSION)
 			      + 1);
@@ -5748,6 +5751,7 @@ gfc_use_module (void)
 			     "intrinsic module at %C") != FAILURE)
        {
 	 use_iso_fortran_env_module ();
+	 gfc_current_locus = old_locus;
 	 return;
        }
 
@@ -5756,6 +5760,7 @@ gfc_use_module (void)
 			     "ISO_C_BINDING module at %C") != FAILURE)
 	{
 	  import_iso_c_binding_module();
+	  gfc_current_locus = old_locus;
 	  return;
 	}
 
@@ -5845,6 +5850,8 @@ gfc_use_module (void)
   gfc_rename_list = NULL;
   use_stmt->next = gfc_current_ns->use_stmts;
   gfc_current_ns->use_stmts = use_stmt;
+
+  gfc_current_locus = old_locus;
 }
 
 
diff --git a/gcc/fortran/symbol.c b/gcc/fortran/symbol.c
index 4463460..126a52b 100644
--- a/gcc/fortran/symbol.c
+++ b/gcc/fortran/symbol.c
@@ -1672,7 +1672,12 @@ gfc_add_type (gfc_symbol *sym, gfc_typespec *ts, locus *where)
 
   if (type != BT_UNKNOWN && !(sym->attr.function && sym->attr.implicit_type))
     {
-      gfc_error ("Symbol '%s' at %L already has basic type of %s", sym->name,
+      if (sym->attr.use_assoc)
+	gfc_error ("Symbol '%s' at %L conflicts with symbol from module '%s', "
+		   "use-associated at %L", sym->name, where, sym->module,
+		   &sym->declared_at);
+      else
+	gfc_error ("Symbol '%s' at %L already has basic type of %s", sym->name,
 		 where, gfc_basic_typename (type));
       return FAILURE;
     }
--- /dev/null	2011-08-23 07:28:57.751883742 +0200
+++ gcc/gcc/testsuite/gfortran.dg/use_16.f90	2011-08-23 09:59:19.000000000 +0200
@@ -0,0 +1,18 @@
+! { dg-do compile }
+!
+! PR fortran/31600
+!
+module a
+implicit none
+contains
+  integer function bar()
+    bar = 42
+  end function
+end module a
+
+use a ! { dg-error "Symbol 'bar' at \\(1\\) conflicts with symbol from module 'a'" }
+implicit none
+integer :: bar ! { dg-error "Symbol 'bar' at \\(1\\) conflicts with symbol from module 'a'" }
+end
+
+! { dg-final { cleanup-modules "a" } }