re PR c++/30274 (bool bit-field: wrong increment and decremenet)

re PR c++/30274 (bool bit-field: wrong increment and decremenet)

	PR c++/30274
	* cp-tree.h (unlowered_expr_type): New function.
	* typeck.c (is_bitfield_expr_with_lowered_type): Handle
	COMPOUND_EXPR, MODIFY_EXPR, and SAVE_EXPR.
	(unlowered_expr_type): New function.
	(build_unary_op): Disallow predecrements of bool bitfields.
	* call.c (build_conditional_expr): Use unlowered_expr_type.
	* pt.c (type_unification_real): Likewise.
	PR c++/30274
	* g++.dg/expr/bitfield3.C: New test.
	* g++.dg/expr/bitfield4.C: Likewise.
	* g++.dg/expr/bitfield5.C: Likewise.
	* g++.dg/expr/bitfield6.C: Likewise.

From-SVN: r122813