expr.c (gfc_copy_expr): Don't copy 'op1' and 'op2' for EXPR_SUBSTRING.

expr.c (gfc_copy_expr): Don't copy 'op1' and 'op2' for EXPR_SUBSTRING.

fortran/
* expr.c (gfc_copy_expr): Don't copy 'op1' and 'op2' for
EXPR_SUBSTRING.
(gfc_is_constant_expr): Check 'ref' to determine if substring
reference is constant.
(gfc_simplify_expr): Simplify 'ref' instead of 'op1' and 'op2'.
(check_init_expr, check_restricted): Check 'ref' instead of 'op1'
and 'op2'.
* module.c (mio_expr): Read / write 'ref' instead of 'op1' and 'op2'.

testsuite/
* gfortran.dg/substr_1.f90: New test.

From-SVN: r94735