Fix bug in type parameter handling for impl methods

The parameters of the impl weren't being combined in the right way
with the parameters of the methods. The test worked only by accident.

Issue #1227

Author: marijnh

src/comp/middle/resolve.rs

@@ -370,7 +370,17 @@ fn resolve_names(e: @env, c: @ast::crate) {
 
 // Visit helper functions
 fn visit_item_with_scope(i: @ast::item, sc: scopes, v: vt<scopes>) {
-    visit::visit_item(i, cons(scope_item(i), @sc), v);
+    let sc = cons(scope_item(i), @sc);
+    alt i.node {
+      ast::item_impl(tps, sty, methods) {
+        visit::visit_ty(sty, sc, v);
+        for m in methods {
+            v.visit_fn(m.node.meth, tps + m.node.tps, m.span,
+                       some(m.node.ident), m.node.id, sc, v);
+        }
+      }
+      _ { visit::visit_item(i, sc, v); }
+    }
 }
 
 fn visit_native_item_with_scope(ni: @ast::native_item, sc: scopes,

src/comp/middle/typeck.rs

@@ -692,7 +692,8 @@ mod collect {
                 let ty = ty::method_ty_to_fn_ty(
                     cx.tcx, ty_of_method(cx.tcx, m_collect, m));
                 cx.tcx.tcache.insert(local_def(m.node.id),
-                                     {kinds: [], ty: ty});
+                                     {kinds: ty_param_kinds(m.node.tps),
+                                      ty: ty});
                 write::ty_only(cx.tcx, m.node.id, ty);
             }
             write::ty_only(cx.tcx, it.id, ast_ty_to_ty(cx.tcx, m_collect,
@@ -2174,12 +2175,19 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
                       }
                     }
                 } else { csearch::get_type(tcx, method.did).ty };
-                let ids = ids;
-                if method.n_tps > 0u {
+                let tvars = vec::map(ids, {|id| ty::mk_var(tcx, id)});
+                let n_tps = vec::len(ids);
+                if method.n_tps + n_tps  > 0u {
                     let b = bind_params_in_type(expr.span, tcx,
-                                                bind next_ty_var_id(fcx),
-                                                fty, method.n_tps);
-                    ids += b.ids;
+                                                bind next_ty_var_id(fcx), fty,
+                                                n_tps + method.n_tps);
+                    let _tvars = vec::map(b.ids, {|id| ty::mk_var(tcx, id)});
+                    let i = 0;
+                    for v in tvars {
+                        demand::simple(fcx, expr.span, v, _tvars[i]);
+                        i += 1;
+                    }
+                    tvars = _tvars;
                     fty = b.ty;
                     if n_tys > 0u {
                         if n_tys != method.n_tps {
@@ -2190,7 +2198,7 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
                         }
                         let i = 0u;
                         for ty in tys {
-                            let tvar = ty::mk_var(fcx.ccx.tcx, b.ids[i]);
+                            let tvar = tvars[i + n_tps];
                             let t_subst = ast_ty_to_ty_crate(fcx.ccx, ty);
                             demand::simple(fcx, expr.span, tvar, t_subst);
                             i += 1u;
@@ -2201,8 +2209,7 @@ fn check_expr_with_unifier(fcx: @fn_ctxt, expr: @ast::expr, unify: unifier,
                                         "this method does not take type \
                                          parameters");
                 }
-                let substs = vec::map(ids, {|id| ty::mk_var(tcx, id)});
-                write::ty_fixup(fcx, id, {substs: some(substs), ty: fty});
+                write::ty_fixup(fcx, id, {substs: some(tvars), ty: fty});
                 fcx.ccx.method_map.insert(id, method.did);
               }
               none. {