Fix broken assertion in regionck for code like (a[])()

Author: nikomatsakis

src/rustc/middle/typeck/check/regionck.rs

@@ -183,16 +183,15 @@ fn visit_expr(expr: @ast::expr, &&rcx: @rcx, v: rvt) {
             // `constrain_auto_ref()` on all exprs.  But that causes a
             // lot of spurious errors because of how the region
             // hierarchy is setup.
-            let tcx = rcx.fcx.tcx();
             if rcx.fcx.ccx.method_map.contains_key(callee.id) {
                 match callee.node {
                     ast::expr_field(base, _, _) => {
                         constrain_auto_ref(rcx, base);
                     }
                     _ => {
-                        tcx.sess.span_bug(
-                            callee.span,
-                            ~"call of method that is not a field");
+                        // This can happen if you have code like
+                        // (x[0])() where `x[0]` is overloaded.  Just
+                        // ignore it.
                     }
                 }
             } else {

src/test/run-pass/call-closure-from-overloaded-op.rs

@@ -0,0 +1,9 @@
+use dvec::DVec;
+
+fn foo() -> int { 22 }
+
+fn main() {
+    let x = DVec::<@fn() -> int>();
+    x.push(foo);
+    assert (x[0])() == 22;
+}