Fix a lot of the handling of default methods and type parameters. Closes

 #4099, #4102.

src/librustc/middle/trans/base.rs

@@ -506,9 +506,11 @@ pub fn get_res_dtor(ccx: @CrateContext,
             did
         };
         assert_eq!(did.crate, ast::local_crate);
+        let tsubsts = ty::substs { self_r: None, self_ty: None,
+                                  tps: /*bad*/ substs.to_owned() };
         let (val, _) = monomorphize::monomorphic_fn(ccx,
                                                     did,
-                                                    substs,
+                                                    &tsubsts,
                                                     None,
                                                     None,
                                                     None);

src/librustc/middle/trans/callee.rs

@@ -41,6 +41,7 @@ use middle::trans::meth;
 use middle::trans::monomorphize;
 use middle::trans::type_of;
 use middle::ty;
+use middle::subst::Subst;
 use middle::typeck;
 use util::ppaux::Repr;
 
@@ -230,11 +231,75 @@ pub fn trans_fn_ref_with_vtables(
     // Polytype of the function item (may have type params)
     let fn_tpt = ty::lookup_item_type(tcx, def_id);
 
-    // Modify the def_id if this is a default method; we want to be
-    // monomorphizing the trait's code.
-    let (def_id, opt_impl_did) = match tcx.provided_method_sources.find(&def_id) {
-        None => (def_id, None),
-        Some(source) => (source.method_id, Some(source.impl_id))
+    let substs = ty::substs { self_r: None, self_ty: None,
+                              tps: /*bad*/ type_params.to_owned() };
+
+
+    // We need to do a bunch of special handling for default methods.
+    // We need to modify the def_id and our substs in order to monomorphize
+    // the function.
+    let (def_id, opt_impl_did, substs) = match tcx.provided_method_sources.find(&def_id) {
+        None => (def_id, None, substs),
+        Some(source) => {
+            // There are two relevant substitutions when compiling
+            // default methods. First, there is the substitution for
+            // the type parameters of the impl we are using and the
+            // method we are calling. This substitution is the substs
+            // argument we already have.
+            // In order to compile a default method, though, we need
+            // to consider another substitution: the substitution for
+            // the type parameters on trait; the impl we are using
+            // implements the trait at some particular type
+            // parameters, and we need to substitute for those first.
+            // So, what we need to do is find this substitution and
+            // compose it with the one we already have.
+
+            // In order to find the substitution for the trait params,
+            // we look up the impl in the ast map, find its trait_ref
+            // id, then look up its trait ref. I feel like there
+            // should be a better way.
+            let map_node = session::expect(
+                ccx.sess,
+                ccx.tcx.items.find_copy(&source.impl_id.node),
+                || fmt!("couldn't find node while monomorphizing \
+                         default method: %?", source.impl_id.node));
+            let item = match map_node {
+                ast_map::node_item(item, _) => item,
+                _ => ccx.tcx.sess.bug("Not an item")
+            };
+            let ast_trait_ref = match copy item.node {
+                ast::item_impl(_, Some(tr), _, _) => tr,
+                _ => ccx.tcx.sess.bug("Not an impl with trait_ref")
+            };
+            let trait_ref = ccx.tcx.trait_refs.get(&ast_trait_ref.ref_id);
+
+            // The substs from the trait_ref only substitues for the
+            // trait parameters. Our substitution also needs to be
+            // able to substitute for the actual method type
+            // params. To do this, we figure out how many method
+            // parameters there are and pad out the substitution with
+            // substitution for the variables.
+            let item_ty = ty::lookup_item_type(tcx, source.method_id);
+            let num_params = item_ty.generics.type_param_defs.len() -
+                trait_ref.substs.tps.len();
+            let id_subst = do vec::from_fn(num_params) |i| {
+                ty::mk_param(tcx, i, ast::def_id {crate: 0, node: 0})
+            };
+            // Merge the two substitions together now.
+            let first_subst = ty::substs {tps: trait_ref.substs.tps + id_subst,
+                                          .. trait_ref.substs};
+
+            // And compose them.
+            let new_substs = first_subst.subst(tcx, &substs);
+            debug!("trans_fn_with_vtables - default method: \
+                    substs = %s, id_subst = %s, trait_subst = %s, \
+                    first_subst = %s, new_subst = %s",
+                   substs.repr(tcx),
+                   id_subst.repr(tcx), trait_ref.substs.repr(tcx),
+                   first_subst.repr(tcx), new_substs.repr(tcx));
+
+            (source.method_id, Some(source.impl_id), new_substs)
+        }
     };
 
     // Check whether this fn has an inlined copy and, if so, redirect
@@ -279,7 +344,7 @@ pub fn trans_fn_ref_with_vtables(
         assert_eq!(def_id.crate, ast::local_crate);
 
         let mut (val, must_cast) =
-            monomorphize::monomorphic_fn(ccx, def_id, type_params,
+            monomorphize::monomorphic_fn(ccx, def_id, &substs,
                                          vtables, opt_impl_did, Some(ref_id));
         if must_cast && ref_id != 0 {
             // Monotype of the REFERENCE to the function (type params

src/librustc/middle/trans/monomorphize.rs

@@ -43,7 +43,7 @@ use syntax::abi::AbiSet;
 
 pub fn monomorphic_fn(ccx: @CrateContext,
                       fn_id: ast::def_id,
-                      real_substs: &[ty::t],
+                      real_substs: &ty::substs,
                       vtables: Option<typeck::vtable_res>,
                       impl_did_opt: Option<ast::def_id>,
                       ref_id: Option<ast::node_id>)
@@ -61,17 +61,17 @@ pub fn monomorphic_fn(ccx: @CrateContext,
            impl_did_opt.repr(ccx.tcx),
            ref_id);
 
-    assert!(real_substs.all(|t| !ty::type_needs_infer(*t)));
+    assert!(real_substs.tps.all(|t| !ty::type_needs_infer(*t)));
     let _icx = ccx.insn_ctxt("monomorphic_fn");
     let mut must_cast = false;
-    let substs = vec::map(real_substs, |t| {
+    let substs = vec::map(real_substs.tps, |t| {
         match normalize_for_monomorphization(ccx.tcx, *t) {
           Some(t) => { must_cast = true; t }
           None => *t
         }
     });
 
-    for real_substs.each() |s| { assert!(!ty::type_has_params(*s)); }
+    for real_substs.tps.each() |s| { assert!(!ty::type_has_params(*s)); }
     for substs.each() |s| { assert!(!ty::type_has_params(*s)); }
     let param_uses = type_use::type_uses_for(ccx, fn_id, substs.len());
     let hash_id = make_mono_id(ccx, fn_id, substs, vtables, impl_did_opt,
@@ -145,17 +145,8 @@ pub fn monomorphic_fn(ccx: @CrateContext,
       ast_map::node_struct_ctor(_, i, pt) => (pt, i.ident, i.span)
     };
 
-    // Look up the impl type if we're translating a default method.
-    // XXX: Generics.
-    let impl_ty_opt;
-    match impl_did_opt {
-        None => impl_ty_opt = None,
-        Some(impl_did) => {
-            impl_ty_opt = Some(ty::lookup_item_type(ccx.tcx, impl_did).ty);
-        }
-    }
-
-    let mono_ty = ty::subst_tps(ccx.tcx, substs, impl_ty_opt, llitem_ty);
+    let mono_ty = ty::subst_tps(ccx.tcx, substs,
+                                real_substs.self_ty, llitem_ty);
     let llfty = type_of_fn_from_ty(ccx, mono_ty);
 
     ccx.stats.n_monos += 1;
@@ -186,7 +177,7 @@ pub fn monomorphic_fn(ccx: @CrateContext,
         tys: substs,
         vtables: vtables,
         type_param_defs: tpt.generics.type_param_defs,
-        self_ty: impl_ty_opt
+        self_ty: real_substs.self_ty
     });
 
     let lldecl = match map_node {

src/test/run-pass/trait-default-method-bound-subst.rs

@@ -8,10 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// xfail-test
+#[allow(default_methods)];
 
 trait A<T> {
-    fn g<U>(x: T, y: U) -> (T, U) { (x, y) }
+    fn g<U>(&self, x: T, y: U) -> (T, U) { (x, y) }
 }
 
 impl A<int> for int { }

src/test/run-pass/trait-default-method-bound-subst2.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// xfail-test
+#[allow(default_methods)];
 
 trait A<T> {
     fn g(&self, x: T) -> T { x }