103 lines
2.9 KiB
Rust
103 lines
2.9 KiB
Rust
import syntax::ast::*;
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import syntax::visit;
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fn check_crate(&ty::ctxt tcx, &@crate crate) {
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auto v = @rec(visit_expr=bind check_expr(tcx, _, _, _)
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with *visit::default_visitor[()]());
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visit::visit_crate(*crate, (), visit::mk_vt(v));
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tcx.sess.abort_if_errors();
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}
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fn check_expr(&ty::ctxt tcx, &@expr ex, &() s, &visit::vt[()] v) {
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visit::visit_expr(ex, s, v);
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alt ex.node {
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expr_alt(_, ?arms) { check_arms(tcx, arms); }
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_ {}
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}
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}
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fn check_arms(&ty::ctxt tcx, &arm[] arms) {
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auto i = 0;
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for (arm arm in arms) {
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for (@pat arm_pat in arm.pats) {
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auto reachable = true;
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auto j = 0;
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while j < i {
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for (@pat prev_pat in arms.(j).pats) {
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if pattern_supersedes(tcx, prev_pat, arm_pat) {
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reachable = false;
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}
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}
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j += 1;
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}
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if !reachable {
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tcx.sess.span_err(arm_pat.span, "unreachable pattern");
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}
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}
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i += 1;
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}
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}
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fn pattern_supersedes(&ty::ctxt tcx, &@pat a, &@pat b) -> bool {
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fn patterns_supersede(&ty::ctxt tcx, &(@pat)[] as, &(@pat)[] bs) -> bool {
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auto i = 0;
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for (@pat a in as) {
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if !pattern_supersedes(tcx, a, bs.(i)) { ret false; }
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i += 1;
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}
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ret true;
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}
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fn field_patterns_supersede(&ty::ctxt tcx, &field_pat[] fas,
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&field_pat[] fbs) -> bool {
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auto wild = @rec(id=0, node=pat_wild, span=rec(lo=0u, hi=0u));
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for (field_pat fa in fas) {
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auto pb = wild;
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for (field_pat fb in fbs) {
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if fa.ident == fb.ident { pb = fb.pat; }
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}
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if !pattern_supersedes(tcx, fa.pat, pb) { ret false; }
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}
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ret true;
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}
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alt a.node {
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pat_wild | pat_bind(_) { ret true; }
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pat_lit(?la) {
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alt b.node {
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pat_lit(?lb) { ret util::common::lit_eq(la, lb); }
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_ { ret false; }
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}
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}
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pat_tag(?va, ?suba) {
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alt b.node {
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pat_tag(?vb, ?subb) {
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ret tcx.def_map.get(a.id) == tcx.def_map.get(b.id) &&
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patterns_supersede(tcx, suba, subb);
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}
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_ { ret false; }
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}
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}
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pat_rec(?suba, _) {
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alt b.node {
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pat_rec(?subb, _) { ret field_patterns_supersede(tcx, suba, subb); }
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_ { ret false; }
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}
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}
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pat_box(?suba) {
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alt b.node {
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pat_box(?subb) { ret pattern_supersedes(tcx, suba, subb); }
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_ { ret pattern_supersedes(tcx, suba, b); }
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}
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}
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}
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}
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// Local Variables:
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// mode: rust
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// fill-column: 78;
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// indent-tabs-mode: nil
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// c-basic-offset: 4
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// buffer-file-coding-system: utf-8-unix
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// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
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// End:
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