resolve type variables with no constraints to bot

Author: nikomatsakis

src/rustc/middle/infer.rs

@@ -707,7 +707,7 @@ impl resolve_methods for infer_ctxt {
 
     fn resolve_var<T:copy to_str>(
         vb: vals_and_bindings<T>, bot_guard: fn(T)->bool,
-        vid: int) -> fres<T> {
+        vid: int, unbound: fn() -> fres<T>) -> fres<T> {
 
         let {root:_, bounds} = self.get(vb, vid as uint);
 
@@ -724,16 +724,24 @@ impl resolve_methods for infer_ctxt {
           { ub:_, lb:some(t) } if !bot_guard(t) { ok(t) }
           { ub:some(t), lb:_ } { ok(t) }
           { ub:_, lb:some(t) } { ok(t) }
-          { ub:none, lb:none } { self.rerr(vid) }
+          { ub:none, lb:none } { unbound() }
         }
     }
 
     fn resolve_ty_var(vid: int) -> fres<ty::t> {
-        ret self.resolve_var(self.vb, {|t| type_is_bot(t)}, vid);
+        ret self.resolve_var(
+            self.vb,
+            {|t| type_is_bot(t) },
+            vid,
+            {|| ok(ty::mk_bot(self.tcx)) });
     }
 
     fn resolve_region_var(rid: int) -> fres<ty::region> {
-        ret self.resolve_var(self.rb, {|_t| false}, rid);
+        ret self.resolve_var(
+            self.rb,
+            {|_t| false },
+            rid,
+            {|| err(rid) });
     }
 
     fn resolve_ty(typ: ty::t) -> fres<ty::t> {

src/test/compile-fail/vector-no-ann.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // We will infer this to have the type vec[bot]
+    let _foo = [];
+}

src/test/run-pass/vector-no-ann.rs

@@ -1,6 +1,6 @@
 // Just a grab bag of stuff that you wouldn't want to actually write.
 
-fn strange() -> bool { let _x: bool = ret true; }
+fn strange() -> bool { let _x = ret true; }
 
 fn funny() {
     fn f(_x: ()) { }
@@ -19,8 +19,8 @@ fn zombiejesus() {
     do  {
         while (ret) {
             if (ret) {
-                alt check (ret) {
-                    1 {
+                alt (ret) {
+                    _ {
                         if (ret) {
                             ret
                         } else {
@@ -51,7 +51,7 @@ fn canttouchthis() -> uint {
     pure fn p() -> bool { true }
     let _a = (assert (true)) == (check (p()));
     let _c = (check (p())) == ();
-    let _b: bool = (log(debug, 0) == (ret 0u));
+    let _b = (log(debug, 0) == (ret 0u));
 }
 
 fn angrydome() {