---

yaml
---
r: 15829
b: refs/heads/try
c: da98e14
h: refs/heads/master
i:
  15827: 1429139
v: v3

Author: nikomatsakis

[refs]

@@ -2,5 +2,5 @@
 refs/heads/master: 61b1875c16de39c166b0f4d54bba19f9c6777d1a
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 4a81779abd786ff22d71434c6d9a5917ea4cdfff
-refs/heads/try: 8d1c1720e331ea56cfde33ab047216d232236e4b
+refs/heads/try: da98e14c946d8ac124b845d65c1a52065791febe
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105

branches/try/src/rustc/middle/typeck/check.rs

@@ -559,6 +559,15 @@ fn valid_range_bounds(ccx: @crate_ctxt, from: @ast::expr, to: @ast::expr)
     const_eval::compare_lit_exprs(ccx.tcx, from, to) <= 0
 }
 
+type pat_ctxt = {
+    fcx: @fn_ctxt,
+    map: pat_id_map,
+    alt_region: ty::region,
+    block_region: ty::region,
+    /* Equal to either alt_region or block_region. */
+    pat_region: ty::region
+};
+
 // Helper for the other universally_quantify_*() routines.  Extracts the bound
 // regions from bound_tys and then replaces those same regions with fresh
 // variables in `sty`, returning the resulting type.
@@ -664,6 +673,223 @@ fn replace_bound_regions(
     }
 }
 
+fn check_pat_variant(pcx: pat_ctxt, pat: @ast::pat, path: @ast::path,
+                     subpats: option<[@ast::pat]>, expected: ty::t) {
+
+    // Typecheck the path.
+    let fcx = pcx.fcx;
+    let tcx = pcx.fcx.ccx.tcx;
+
+    // Lookup the enum and variant def ids:
+    let v_def = lookup_def(pcx.fcx, path.span, pat.id);
+    let v_def_ids = ast_util::variant_def_ids(v_def);
+
+    // Assign the pattern the type of the *enum*, not the variant.
+    let enum_tpt = ty::lookup_item_type(tcx, v_def_ids.enm);
+    instantiate_path(pcx.fcx, path, enum_tpt, pat.span, pat.id);
+
+    // Take the enum type params out of `expected`.
+    alt structure_of(pcx.fcx, pat.span, expected) {
+      ty::ty_enum(_, expected_substs) {
+        // check that the type of the value being matched is a subtype
+        // of the type of the pattern:
+        let pat_ty = fcx.node_ty(pat.id);
+        demand::suptype(fcx, pat.span, pat_ty, expected);
+
+        // Get the expected types of the arguments.
+        let arg_types = {
+            let vinfo =
+                ty::enum_variant_with_id(
+                    tcx, v_def_ids.enm, v_def_ids.var);
+            vinfo.args.map { |t| ty::subst(tcx, expected_substs, t) }
+        };
+        let arg_len = arg_types.len(), subpats_len = alt subpats {
+            none { arg_len }
+            some(ps) { ps.len() }};
+        if arg_len > 0u {
+            // N-ary variant.
+            if arg_len != subpats_len {
+                let s = #fmt["this pattern has %u field%s, but the \
+                              corresponding variant has %u field%s",
+                             subpats_len,
+                             if subpats_len == 1u { "" } else { "s" },
+                             arg_len,
+                             if arg_len == 1u { "" } else { "s" }];
+                tcx.sess.span_fatal(pat.span, s);
+            }
+
+            option::iter(subpats) {|pats|
+                vec::iter2(pats, arg_types) {|subpat, arg_ty|
+                  check_pat(pcx, subpat, arg_ty);
+                }
+            };
+        } else if subpats_len > 0u {
+            tcx.sess.span_fatal
+                (pat.span, #fmt["this pattern has %u field%s, \
+                                 but the corresponding variant has no fields",
+                                subpats_len,
+                                if subpats_len == 1u { "" }
+                                else { "s" }]);
+        }
+      }
+      _ {
+        tcx.sess.span_fatal
+            (pat.span,
+             #fmt["mismatched types: expected enum but found `%s`",
+                  fcx.ty_to_str(expected)]);
+      }
+    }
+}
+
+// Pattern checking is top-down rather than bottom-up so that bindings get
+// their types immediately.
+fn check_pat(pcx: pat_ctxt, pat: @ast::pat, expected: ty::t) {
+    let fcx = pcx.fcx;
+    let tcx = pcx.fcx.ccx.tcx;
+    alt pat.node {
+      ast::pat_wild {
+        fcx.write_ty(pat.id, expected);
+      }
+      ast::pat_lit(lt) {
+        check_expr_with(pcx.fcx, lt, expected);
+        fcx.write_ty(pat.id, fcx.expr_ty(lt));
+      }
+      ast::pat_range(begin, end) {
+        check_expr_with(pcx.fcx, begin, expected);
+        check_expr_with(pcx.fcx, end, expected);
+        let b_ty = resolve_type_vars_if_possible(pcx.fcx,
+                                                 fcx.expr_ty(begin));
+        if !require_same_types(
+            tcx, pat.span, b_ty,
+            resolve_type_vars_if_possible(
+                pcx.fcx, fcx.expr_ty(end)),
+            {|| "mismatched types in range" }) {
+            // no-op
+        } else if !ty::type_is_numeric(b_ty) {
+            tcx.sess.span_err(pat.span, "non-numeric type used in range");
+        } else if !valid_range_bounds(pcx.fcx.ccx, begin, end) {
+            tcx.sess.span_err(begin.span, "lower range bound must be less \
+                                           than upper");
+        }
+        fcx.write_ty(pat.id, b_ty);
+      }
+      ast::pat_ident(name, sub) if !pat_is_variant(tcx.def_map, pat) {
+        let vid = lookup_local(pcx.fcx, pat.span, pat.id);
+        let mut typ = ty::mk_var(tcx, vid);
+        demand::suptype(pcx.fcx, pat.span, expected, typ);
+        let canon_id = pcx.map.get(pat_util::path_to_ident(name));
+        if canon_id != pat.id {
+            let tv_id = lookup_local(pcx.fcx, pat.span, canon_id);
+            let ct = ty::mk_var(tcx, tv_id);
+            demand::suptype(pcx.fcx, pat.span, ct, typ);
+        }
+        fcx.write_ty(pat.id, typ);
+        alt sub {
+          some(p) { check_pat(pcx, p, expected); }
+          _ {}
+        }
+      }
+      ast::pat_ident(path, c) {
+        check_pat_variant(pcx, pat, path, some([]), expected);
+      }
+      ast::pat_enum(path, subpats) {
+        check_pat_variant(pcx, pat, path, subpats, expected);
+      }
+      ast::pat_rec(fields, etc) {
+        let ex_fields = alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_rec(fields) { fields }
+          _ {
+            tcx.sess.span_fatal
+                (pat.span,
+                #fmt["mismatched types: expected `%s` but found record",
+                     fcx.ty_to_str(expected)]);
+          }
+        };
+        let f_count = vec::len(fields);
+        let ex_f_count = vec::len(ex_fields);
+        if ex_f_count < f_count || !etc && ex_f_count > f_count {
+            tcx.sess.span_fatal
+                (pat.span, #fmt["mismatched types: expected a record \
+                      with %u fields, found one with %u \
+                      fields",
+                                ex_f_count, f_count]);
+        }
+        fn matches(name: str, f: ty::field) -> bool {
+            ret str::eq(name, f.ident);
+        }
+        for fields.each {|f|
+            alt vec::find(ex_fields, bind matches(f.ident, _)) {
+              some(field) {
+                check_pat(pcx, f.pat, field.mt.ty);
+              }
+              none {
+                tcx.sess.span_fatal(pat.span,
+                                    #fmt["mismatched types: did not \
+                                          expect a record with a field `%s`",
+                                         f.ident]);
+              }
+            }
+        }
+        fcx.write_ty(pat.id, expected);
+      }
+      ast::pat_tup(elts) {
+        let ex_elts = alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_tup(elts) { elts }
+          _ {
+            tcx.sess.span_fatal
+                (pat.span,
+                 #fmt["mismatched types: expected `%s`, found tuple",
+                      fcx.ty_to_str(expected)]);
+          }
+        };
+        let e_count = vec::len(elts);
+        if e_count != vec::len(ex_elts) {
+            tcx.sess.span_fatal
+                (pat.span, #fmt["mismatched types: expected a tuple \
+                      with %u fields, found one with %u \
+                      fields", vec::len(ex_elts), e_count]);
+        }
+        let mut i = 0u;
+        for elts.each {|elt|
+            check_pat(pcx, elt, ex_elts[i]);
+            i += 1u;
+        }
+
+        fcx.write_ty(pat.id, expected);
+      }
+      ast::pat_box(inner) {
+        alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_box(e_inner) {
+            check_pat(pcx, inner, e_inner.ty);
+            fcx.write_ty(pat.id, expected);
+          }
+          _ {
+            tcx.sess.span_fatal(
+                pat.span,
+                "mismatched types: expected `" +
+                pcx.fcx.ty_to_str(expected) +
+                "` found box");
+          }
+        }
+      }
+      ast::pat_uniq(inner) {
+        alt structure_of(pcx.fcx, pat.span, expected) {
+          ty::ty_uniq(e_inner) {
+            check_pat(pcx, inner, e_inner.ty);
+            fcx.write_ty(pat.id, expected);
+          }
+          _ {
+            tcx.sess.span_fatal(
+                pat.span,
+                "mismatched types: expected `" +
+                pcx.fcx.ty_to_str(expected) +
+                "` found uniq");
+          }
+        }
+      }
+    }
+}
+
 fn check_expr_with(fcx: @fn_ctxt, expr: @ast::expr, expected: ty::t) -> bool {
     check_expr(fcx, expr, some(expected))
 }
@@ -1644,7 +1870,38 @@ fn check_expr_with_unifier(fcx: @fn_ctxt,
           bot = !may_break(body);
       }
       ast::expr_alt(discrim, arms, _) {
-        alt::check_alt(expr, discrim, arms);
+        let pattern_ty = fcx.next_ty_var();
+        bot = check_expr_with(fcx, discrim, pattern_ty);
+
+        // Typecheck the patterns first, so that we get types for all the
+        // bindings.
+        //let pattern_ty = fcx.expr_ty(discrim);
+        for arms.each {|arm|
+            let pcx = {
+                fcx: fcx,
+                map: pat_id_map(tcx.def_map, arm.pats[0]),
+                alt_region: ty::re_scope(expr.id),
+                block_region: ty::re_scope(arm.body.node.id),
+                pat_region: ty::re_scope(expr.id)
+            };
+
+            for arm.pats.each {|p| check_pat(pcx, p, pattern_ty);}
+        }
+        // Now typecheck the blocks.
+        let mut result_ty = fcx.next_ty_var();
+        let mut arm_non_bot = false;
+        for arms.each {|arm|
+            alt arm.guard {
+              some(e) { check_expr_with(fcx, e, ty::mk_bool(tcx)); }
+              none { }
+            }
+            if !check_block(fcx, arm.body) { arm_non_bot = true; }
+            let bty = fcx.node_ty(arm.body.node.id);
+            demand::suptype(fcx, arm.body.span, result_ty, bty);
+        }
+        bot |= !arm_non_bot;
+        if !arm_non_bot { result_ty = ty::mk_bot(tcx); }
+        fcx.write_ty(id, result_ty);
       }
       ast::expr_fn(proto, decl, body, cap_clause) {
         check_expr_fn(fcx, expr, proto, decl, body, false, expected);