improve error messages

src/rustc/middle/infer.rs

@@ -493,7 +493,7 @@ impl unify_methods for infer_ctxt {
                     if b == r {
                         self.uok()
                     } else {
-                        err(ty::terr_regions_differ(false, b, a))
+                        err(ty::terr_regions_differ(b, a))
                     }
                 }
               }
@@ -521,21 +521,23 @@ impl unify_methods for infer_ctxt {
         }
     }
 
-    /* mk_subty passes the "smaller" type as the first argument
-     and the "bigger" type as the second -- so the first arg
-    is the actual type, and the second is the expected type */
-    fn flds(a: ty::field, e: ty::field) -> ures {
-        if e.ident != a.ident {
-            ret self.uerr(ty::terr_record_fields(e.ident, a.ident));
+    fn flds(a: ty::field, b: ty::field) -> ures {
+        if b.ident != a.ident {
+            // Note: the error object expects the "expected" field to
+            // come first, which is generally the supertype (b).
+            ret self.uerr(ty::terr_record_fields(b.ident, a.ident));
+        }
+
+        self.mts(a.mt, b.mt).chain_err {|err|
+            self.uerr(ty::terr_in_field(@err, a.ident))
         }
-        self.mts(a.mt, e.mt)
     }
 
     fn tps(as: [ty::t], bs: [ty::t]) -> ures {
         if check vec::same_length(as, bs) {
             iter2(as, bs) {|a, b| self.tys(a, b) }
         } else {
-            self.uerr(ty::terr_ty_param_size(as.len(), bs.len()))
+            self.uerr(ty::terr_ty_param_size(bs.len(), as.len()))
         }
     }
 
@@ -544,7 +546,7 @@ impl unify_methods for infer_ctxt {
           (_, ast::proto_any) { self.uok() }
           (ast::proto_bare, _) { self.uok() }
           (_, _) if a == b { self.uok() }
-          _ { self.uerr(ty::terr_proto_mismatch(a, b)) }
+          _ { self.uerr(ty::terr_proto_mismatch(b, a)) }
         }
     }
 
@@ -558,7 +560,7 @@ impl unify_methods for infer_ctxt {
                this check is necessary to ensure that the
                annotation in an object method matches the
                declared object type */
-            self.uerr(ty::terr_ret_style_mismatch(a_ret_style, b_ret_style))
+            self.uerr(ty::terr_ret_style_mismatch(b_ret_style, a_ret_style))
         } else {
             self.uok()
         }
@@ -672,7 +674,7 @@ impl unify_methods for infer_ctxt {
                 self.constrs(a, b)
             }
         } else {
-            self.uerr(ty::terr_constr_len(as.len(), bs.len()))
+            self.uerr(ty::terr_constr_len(bs.len(), as.len()))
         }
     }
 
@@ -713,7 +715,7 @@ impl unify_methods for infer_ctxt {
             if ty::mach_sty(cfg, a) == ty::mach_sty(cfg, b) {
                 self.uok()
             } else {
-                self.uerr(ty::terr_mismatch)
+                self.uerr(ty::terr_sorts(b, a))
             }
           }
 
@@ -757,8 +759,8 @@ impl unify_methods for infer_ctxt {
                     self.flds(a, b)
                 }
             } else {
-                ret self.uerr(ty::terr_record_size(a_fields.len(),
-                                             b_fields.len()));
+                ret self.uerr(ty::terr_record_size(b_fields.len(),
+                                                   a_fields.len()));
             }
           }
 
@@ -766,7 +768,7 @@ impl unify_methods for infer_ctxt {
             if check vec::same_length(a_tys, b_tys) {
                 iter2(a_tys, b_tys) {|a,b| self.tys(a,b) }
             } else {
-                self.uerr(ty::terr_tuple_size(a_tys.len(), b_tys.len()))
+                self.uerr(ty::terr_tuple_size(b_tys.len(), a_tys.len()))
             }
           }
 
@@ -780,7 +782,7 @@ impl unify_methods for infer_ctxt {
             }
           }
 
-          _ { self.uerr(ty::terr_mismatch) }
+          _ { self.uerr(ty::terr_sorts(b, a)) }
         }
     }
 }
@@ -1066,7 +1068,7 @@ fn c_tuptys<C:combine>(self: C, as: [ty::t], bs: [ty::t])
     if check vec::same_length(as, bs) {
         map2(as, bs) {|a, b| self.c_tys(a, b) }
     } else {
-        err(ty::terr_tuple_size(as.len(), bs.len()))
+        err(ty::terr_tuple_size(bs.len(), as.len()))
     }
 }
 
@@ -1077,7 +1079,7 @@ fn c_tps<C:combine>(self: C, _did: ast::def_id, as: [ty::t], bs: [ty::t])
     if check vec::same_length(as, bs) {
         map2(as, bs) {|a,b| self.c_tys(a, b) }
     } else {
-        err(ty::terr_ty_param_size(as.len(), bs.len()))
+        err(ty::terr_ty_param_size(bs.len(), as.len()))
     }
 }
 
@@ -1087,17 +1089,17 @@ fn c_fieldvecs<C:combine>(self: C, as: [ty::field], bs: [ty::field])
     if check vec::same_length(as, bs) {
         map2(as, bs) {|a,b| c_flds(self, a, b) }
     } else {
-        err(ty::terr_record_size(as.len(), bs.len()))
+        err(ty::terr_record_size(bs.len(), as.len()))
     }
 }
 
-fn c_flds<C:combine>(self: C, e: ty::field, a: ty::field) -> cres<ty::field> {
-    if e.ident == a.ident {
-        self.c_mts(e.mt, a.mt).chain {|mt|
-            ok({ident: e.ident, mt: mt})
+fn c_flds<C:combine>(self: C, a: ty::field, b: ty::field) -> cres<ty::field> {
+    if a.ident == b.ident {
+        self.c_mts(a.mt, b.mt).chain {|mt|
+            ok({ident: a.ident, mt: mt})
         }
     } else {
-        err(ty::terr_record_fields(e.ident, a.ident))
+        err(ty::terr_record_fields(b.ident, a.ident))
     }
 }
 
@@ -1196,7 +1198,7 @@ fn c_tys<C:combine>(
         if ty::mach_sty(cfg, a) == ty::mach_sty(cfg, b) {
             ok(a)
         } else {
-            err(ty::terr_mismatch)
+            err(ty::terr_sorts(b, a))
         }
       }
 
@@ -1293,7 +1295,7 @@ fn c_tys<C:combine>(
         }
       }
 
-      _ { err(ty::terr_mismatch) }
+      _ { err(ty::terr_sorts(b, a)) }
     }
     }
 }
@@ -1350,14 +1352,14 @@ fn c_regions<C:combine>(
             #debug["... no, %s != %s.",
                    a.to_str(self.infcx()),
                    b.to_str(self.infcx())];
-            err(ty::terr_regions_differ(false, b, a))
+            err(ty::terr_regions_differ(b, a))
         }
       }
 
       (ty::re_default, _) |
       (_, ty::re_default) {
         // actually a compiler bug, I think.
-        err(ty::terr_regions_differ(false, b, a))
+        err(ty::terr_regions_differ(b, a))
       }
     }
     }
@@ -1480,7 +1482,7 @@ impl of combine for lub {
         let rm = self.infcx().tcx.region_map;
         alt region::nearest_common_ancestor(rm, a_id, b_id) {
           some(r_id) { ok(ty::re_scope(r_id)) }
-          _ { err(ty::terr_regions_differ(false, b, a)) }
+          _ { err(ty::terr_regions_differ(b, a)) }
         }
     }
 }
@@ -1623,7 +1625,7 @@ impl of combine for glb {
         alt region::nearest_common_ancestor(rm, a_id, b_id) {
           some(r_id) if a_id == r_id { ok(b) }
           some(r_id) if b_id == r_id { ok(a) }
-          _ { err(ty::terr_regions_differ(false, b, a)) }
+          _ { err(ty::terr_regions_differ(b, a)) }
         }
     }
 }

src/rustc/middle/ty.rs

@@ -341,7 +341,9 @@ enum type_err {
     terr_mode_mismatch(mode, mode),
     terr_constr_len(uint, uint),
     terr_constr_mismatch(@type_constr, @type_constr),
-    terr_regions_differ(bool /* variance */, region, region),
+    terr_regions_differ(region, region),
+    terr_in_field(@type_err, str),
+    terr_sorts(t, t)
 }
 
 enum param_bound {
@@ -1837,6 +1839,33 @@ fn set_default_mode(cx: ctxt, m: ast::mode, m_def: ast::rmode) {
     }
 }
 
+fn ty_sort_str(cx: ctxt, t: t) -> str {
+    alt get(t).struct {
+      ty_nil | ty_bot | ty_bool | ty_int(_) |
+      ty_uint(_) | ty_float(_) | ty_str | ty_type | ty_opaque_box |
+      ty_opaque_closure_ptr(_) {
+        ty_to_str(cx, t)
+      }
+
+      ty_enum(_, _) { "enum" }
+      ty_box(_) { "@-ptr" }
+      ty_uniq(_) { "~-ptr" }
+      ty_vec(_) { "vector" }
+      ty_ptr(_) { "*-ptr" }
+      ty_rptr(_, _) { "&-ptr" }
+      ty_rec(_) { "record" }
+      ty_fn(_) { "fn" }
+      ty_iface(_, _) { "iface" }
+      ty_class(_, _) { "class" }
+      ty_res(_, _, _) { "resource" }
+      ty_tup(_) { "tuple" }
+      ty_var(_) { "variable" }
+      ty_param(_, _) { "type parameter" }
+      ty_self(_) { "self" }
+      ty_constr(t, _) { ty_sort_str(cx, t) }
+    }
+}
+
 fn type_err_to_str(cx: ctxt, err: type_err) -> str {
     alt err {
       terr_mismatch { ret "types differ"; }
@@ -1876,8 +1905,8 @@ fn type_err_to_str(cx: ctxt, err: type_err) -> str {
       }
       terr_record_mutability { ret "record elements differ in mutability"; }
       terr_record_fields(e_fld, a_fld) {
-        ret "expected a record with field '" + e_fld +
-                "' but found one with field '" + a_fld + "'";
+        ret "expected a record with field `" + e_fld +
+                "` but found one with field `" + a_fld + "`";
       }
       terr_arg_count { ret "incorrect number of function parameters"; }
       terr_mode_mismatch(e_mode, a_mode) {
@@ -1894,16 +1923,18 @@ fn type_err_to_str(cx: ctxt, err: type_err) -> str {
                 " but found one with constraint " +
                 ty_constr_to_str(a_constr);
       }
-      terr_regions_differ(true, region_a, region_b) {
-        ret #fmt("reference lifetime %s does not match reference lifetime %s",
-                 region_to_str(cx, region_a), region_to_str(cx, region_b));
-      }
-      terr_regions_differ(false, subregion, superregion) {
+      terr_regions_differ(subregion, superregion) {
         ret #fmt("references with lifetime %s do not outlive references with \
                   lifetime %s",
                  region_to_str(cx, subregion),
                  region_to_str(cx, superregion));
       }
+      terr_in_field(err, fname) {
+        ret #fmt("in field `%s`, %s", fname, type_err_to_str(cx, *err));
+      }
+      terr_sorts(exp, act) {
+        ret #fmt("%s vs %s", ty_sort_str(cx, exp), ty_sort_str(cx, act));
+      }
     }
 }
 

src/test/compile-fail/bad-bang-ann-3.rs

@@ -3,7 +3,7 @@
 
 fn bad_bang(i: uint) -> ! {
     ret 7u;
-    //!^ ERROR expected `_|_` but found `uint` (types differ)
+    //!^ ERROR expected `_|_` but found `uint`
 }
 
 fn main() { bad_bang(5u); }

src/test/compile-fail/bad-bang-ann.rs

@@ -3,7 +3,7 @@
 
 fn bad_bang(i: uint) -> ! {
     if i < 0u { } else { fail; }
-    //!^ ERROR expected `_|_` but found `()` (types differ)
+    //!^ ERROR expected `_|_` but found `()`
 }
 
 fn main() { bad_bang(5u); }

src/test/compile-fail/bang-tailexpr.rs

@@ -1,4 +1,4 @@
 fn f() -> ! {
-    3 //! ERROR expected `_|_` but found `int` (types differ)
+    3 //! ERROR expected `_|_` but found `int`
 }
 fn main() { }

src/test/compile-fail/issue-897-2.rs

@@ -1,6 +1,6 @@
 fn g() -> ! { fail; }
 fn f() -> ! {
-    ret 42; //! ERROR expected `_|_` but found `int` (types differ)
+    ret 42; //! ERROR expected `_|_` but found `int`
     g(); //! WARNING unreachable statement
 }
 fn main() { }

src/test/compile-fail/issue-897.rs

@@ -1,5 +1,5 @@
 fn f() -> ! {
-    ret 42; //! ERROR expected `_|_` but found `int` (types differ)
+    ret 42; //! ERROR expected `_|_` but found `int`
     fail; //! WARNING unreachable statement
 }
 fn main() { }

src/test/compile-fail/loop-does-not-diverge.rs

@@ -4,7 +4,7 @@ fn forever() -> ! {
   loop {
     break;
   }
-  ret 42; //! ERROR expected `_|_` but found `int` (types differ)
+  ret 42; //! ERROR expected `_|_` but found `int`
 }
 
 fn main() {

src/test/compile-fail/rec-expected.rs

@@ -0,0 +1,9 @@
+type foo = {a: int};
+type bar = {b: int};
+
+fn want_foo(f: foo) {}
+fn have_bar(b: bar) {
+    want_foo(b); //! ERROR expected a record with field `a`
+}
+
+fn main() {}

src/test/compile-fail/terr-in-field.rs

@@ -0,0 +1,9 @@
+type foo = {a: int, b: int};
+type bar = {a: int, b: uint};
+
+fn want_foo(f: foo) {}
+fn have_bar(b: bar) {
+    want_foo(b); //! ERROR (in field `b`, int vs uint)
+}
+
+fn main() {}

src/test/compile-fail/terr-sorts.rs

@@ -0,0 +1,9 @@
+type foo = {a: int, b: int};
+type bar = @foo;
+
+fn want_foo(f: foo) {}
+fn have_bar(b: bar) {
+    want_foo(b); //! ERROR (record vs @-ptr)
+}
+
+fn main() {}