gdb/dwarf: Use the function scope for DW_TAG_imported_declaration

All Fortran imported variable aliases (`use module, alias => var`)
were being added to "global scope", regardless of whether they appeared
in:
- Program/module scope (should be global)
- Function scope (should be local)

This caused conflicts when different functions had the same alias name
pointing to different variables.

DW_TAG_imported_declaration and DW_TAG_namespace cases are now handled
separately.  This patch modifies the case for DW_TAG_imported_
declaration in the function new_symbol () to use cu->list_in_scope
instead of global symbols for all languages.  This ensures that
function-scoped aliases use the current scope rather than being forced
into the global scope.

Bug Scenario:

  subroutine sub1
    use mod1, var_i_alias=>var_i  ! alias points to mod1::var_i
    var_i_alias = 3
    var_i = 4
  end subroutine

  subroutine sub2
    use mod2, var_i_alias=>var_i  ! alias points to mod2::var_i
    var_i_alias = 23
    var_i = 25
  end subroutine

Before: var_i_alias in sub2 incorrectly resolved to mod1::var_i
(value 25)
After: Each function's alias correctly resolves to its own imported
variable (value 23)

New test files verify the fix and include regression tests for global
program-scope imports:
  - gdb/testsuite/gdb.fortran/module_declarations.exp
  - gdb/testsuite/gdb.fortran/module_declarations.f90

Before the change:
(gdb) print var_i_alias
$4 = 25
FAIL: gdb.fortran/module_declarations.exp: sub2_test: print var_i_alias

After the change:
(gdb) print var_i_alias
$4 = 23
PASS: gdb.fortran/module_declarations.exp: sub2_test: print var_i_alias

Approved-By: Tom Tromey <tom@tromey.com>

gdb/dwarf2/read.c

@@ -15846,6 +15846,16 @@ new_symbol (struct die_info *die, struct dwarf2_cu *cu, struct symbol *sym,
 	   : cu->list_in_scope);
       break;
     case DW_TAG_imported_declaration:
+      sym->set_domain (TYPE_DOMAIN);
+      sym->set_loc_class_index (LOC_TYPEDEF);
+      /* Use current scope context rather than forcing global scope.  This
+	 ensures variable aliases are scoped correctly (function-level,
+	 module-level, or program-level).  */
+      list_to_add
+	= ((cu->list_in_scope == &cu->get_builder ()->get_file_symbols ())
+	   ? &cu->get_builder ()->get_global_symbols ()
+	   : cu->list_in_scope);
+      break;
     case DW_TAG_namespace:
       sym->set_domain (TYPE_DOMAIN);
       sym->set_loc_class_index (LOC_TYPEDEF);

gdb/testsuite/gdb.fortran/module_declarations.exp

@@ -0,0 +1,62 @@
+# Copyright 2026 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+load_lib "fortran.exp"
+
+require allow_fortran_tests
+
+standard_testfile .f90
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile {debug f90}] } {
+    return
+}
+
+if {![fortran_runto_main]} {
+    return
+}
+
+# Test global alias at program scope
+gdb_breakpoint [gdb_get_line_number "bp-main"]
+gdb_continue_to_breakpoint "bp-main" ".*bp-main.*"
+
+with_test_prefix "global_test" {
+    gdb_test "print global_alias" " = 200"
+    gdb_test "print global_var_i_from_mod1" " = 300"
+}
+
+gdb_breakpoint [gdb_get_line_number "bp-sub1"]
+gdb_continue_to_breakpoint "bp-sub1" ".*bp-sub1.*"
+
+with_test_prefix "sub1_test" {
+    gdb_test "print var_i_alias" " = 3"
+    gdb_test "print var_i" " = 4"
+}
+
+gdb_breakpoint [gdb_get_line_number "bp-sub2"]
+gdb_continue_to_breakpoint "bp-sub2" ".*bp-sub2.*"
+
+with_test_prefix "sub2_test" {
+    gdb_test "print var_i_alias" " = 23"
+    gdb_test "print var_i" " = 25"
+}
+
+# Test same-name variables shadowed within same function
+gdb_breakpoint [gdb_get_line_number "bp-sub3"]
+gdb_continue_to_breakpoint "bp-sub3" ".*bp-sub3.*"
+
+with_test_prefix "sub3_shadow_test" {
+    gdb_test "print var_i_from_mod1" " = 31"
+    gdb_test "print var_i_from_mod2" " = 32"
+}

gdb/testsuite/gdb.fortran/module_declarations.f90

@@ -0,0 +1,59 @@
+! Copyright 2026 Free Software Foundation, Inc.
+!
+! This program is free software; you can redistribute it and/or modify
+! it under the terms of the GNU General Public License as published by
+! the Free Software Foundation; either version 3 of the License, or
+! (at your option) any later version.
+!
+! This program is distributed in the hope that it will be useful,
+! but WITHOUT ANY WARRANTY; without even the implied warranty of
+! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+! GNU General Public License for more details.
+!
+! You should have received a copy of the GNU General Public License
+! along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+module mod1
+  implicit none
+  integer :: var_i = 1
+  integer :: global_var = 100
+end module mod1
+
+module mod2
+  implicit none
+  integer :: var_i = 2
+end module mod2
+
+subroutine sub1
+  use mod1, var_i_alias=>var_i
+  use mod2
+  implicit none
+  var_i_alias = 3
+  var_i = 4
+end subroutine  ! bp-sub1
+
+subroutine sub2
+  use mod1
+  use mod2, var_i_alias=>var_i
+  implicit none
+  var_i_alias = 23
+  var_i = 25
+end subroutine ! bp-sub2
+
+subroutine sub3
+  use mod1, var_i_from_mod1=>var_i
+  use mod2, var_i_from_mod2=>var_i
+  implicit none
+  var_i_from_mod1 = 31
+  var_i_from_mod2 = 32
+end subroutine ! bp-sub3
+
+program main
+  use mod1, global_alias=>global_var, global_var_i_from_mod1=>var_i
+  implicit none
+  global_alias = 200
+  global_var_i_from_mod1 = 300
+  call sub1  ! bp-main
+  call sub2
+  call sub3
+end