import syntax::visit; import syntax::ast::*; type ctx = {tcx: ty::ctxt, mutable allow_block: bool}; fn check_crate(tcx: ty::ctxt, crate: @crate) { let cx = {tcx: tcx, mutable allow_block: false}; let v = visit::mk_vt(@{visit_expr: visit_expr with *visit::default_visitor()}); visit::visit_crate(*crate, cx, v); } fn visit_expr(ex: @expr, cx: ctx, v: visit::vt) { if !cx.allow_block { alt ty::struct(cx.tcx, ty::expr_ty(cx.tcx, ex)) { ty::ty_fn({proto: proto_block., _}) { cx.tcx.sess.span_err(ex.span, "expressions with block type \ can only appear in callee or (by-ref) argument position"); } _ {} } } let outer = cx.allow_block; alt ex.node { expr_call(f, args, _) { cx.allow_block = true; v.visit_expr(f, cx, v); let i = 0u; for arg_t in ty::ty_fn_args(cx.tcx, ty::expr_ty(cx.tcx, f)) { cx.allow_block = arg_t.mode == by_ref; v.visit_expr(args[i], cx, v); i += 1u; } } _ { cx.allow_block = false; visit::visit_expr(ex, cx, v); } } cx.allow_block = outer; }