Clean up generic param handling

src/librustc/traits/error_reporting.rs

@@ -382,13 +382,12 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         for param in generics.params.iter() {
             let value = match param.kind {
                 GenericParamDefKind::Type(_) => {
-                    let ty = trait_ref.substs.type_for_def(&param);
-                    ty.to_string()
+                    trait_ref.substs[param.index as usize].to_string()
                 },
                 GenericParamDefKind::Lifetime => continue,
             };
             let name = param.name.to_string();
-            flags.push((name.clone(), Some(value.clone())));
+            flags.push((name, Some(value)));
         }
 
         if let Some(true) = self_ty.ty_to_def_id().map(|def_id| def_id.is_local()) {

src/librustc/traits/on_unimplemented.rs

@@ -290,7 +290,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
         let generic_map = generics.params.iter().filter_map(|param| {
             let value = match param.kind {
                 GenericParamDefKind::Type(_) => {
-                    trait_ref.substs.type_for_def(&param).to_string()
+                    trait_ref.substs[param.index as usize].to_string()
                 },
                 GenericParamDefKind::Lifetime => return None
             };

src/librustc/ty/mod.rs

@@ -837,7 +837,7 @@ impl<'a, 'gcx, 'tcx> Generics {
             let param = &self.params[index as usize];
             match param.kind {
                 ty::GenericParamDefKind::Lifetime => param,
-                _ => bug!("expected region parameter, but found another generic parameter")
+                _ => bug!("expected lifetime parameter, but found another generic parameter")
             }
         } else {
             tcx.generics_of(self.parent.expect("parent_count>0 but no parent?"))
@@ -851,7 +851,11 @@ impl<'a, 'gcx, 'tcx> Generics {
                       tcx: TyCtxt<'a, 'gcx, 'tcx>)
                       -> &'tcx GenericParamDef {
         if let Some(index) = param.idx.checked_sub(self.parent_count as u32) {
-            &self.params[index as usize]
+            let param = &self.params[index as usize];
+            match param.kind {
+                ty::GenericParamDefKind::Type(_) => param,
+                _ => bug!("expected type parameter, but found another generic parameter")
+            }
         } else {
             tcx.generics_of(self.parent.expect("parent_count>0 but no parent?"))
                 .type_param(param, tcx)

src/librustc_typeck/astconv.rs

@@ -87,6 +87,11 @@ struct ConvertedBinding<'tcx> {
     span: Span,
 }
 
+struct ParamRange {
+    required: usize,
+    accepted: usize
+}
+
 /// Dummy type used for the `Self` of a `TraitRef` created for converting
 /// a trait object, and which gets removed in `ExistentialTraitRef`.
 /// This type must not appear anywhere in other converted types.
@@ -212,23 +217,23 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         let lt_provided = parameters.lifetimes.len();
 
         let mut lt_accepted = 0;
-        let mut ty_range = (0, 0);
+        let mut ty_params = ParamRange { required: 0, accepted: 0 };
         for param in &decl_generics.params {
             match param.kind {
                 GenericParamDefKind::Lifetime => {
                     lt_accepted += 1;
                 }
                 GenericParamDefKind::Type(ty) => {
-                    ty_range.1 += 1;
+                    ty_params.accepted += 1;
                     if !ty.has_default {
-                        ty_range.0 += 1;
+                        ty_params.required += 1;
                     }
                 }
             };
         }
         if self_ty.is_some() {
-            ty_range.0 -= 1;
-            ty_range.1 -= 1;
+            ty_params.required -= 1;
+            ty_params.accepted -= 1;
         }
 
         if lt_accepted != lt_provided {
@@ -239,8 +244,8 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
         assert_eq!(decl_generics.has_self, self_ty.is_some());
 
         // Check the number of type parameters supplied by the user.
-        if !infer_types || ty_provided > ty_range.0 {
-            check_type_argument_count(tcx, span, ty_provided, ty_range);
+        if !infer_types || ty_provided > ty_params.required {
+            check_type_argument_count(tcx, span, ty_provided, ty_params);
         }
 
         let is_object = self_ty.map_or(false, |ty| ty.sty == TRAIT_OBJECT_DUMMY_SELF);
@@ -1327,9 +1332,9 @@ fn split_auto_traits<'a, 'b, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
 fn check_type_argument_count(tcx: TyCtxt,
                              span: Span,
                              supplied: usize,
-                             ty_range: (usize, usize))
+                             ty_params: ParamRange)
 {
-    let (required, accepted) = ty_range;
+    let (required, accepted) = (ty_params.required, ty_params.accepted);
     if supplied < required {
         let expected = if required < accepted {
             "expected at least"

src/librustc_typeck/check/mod.rs

@@ -4925,27 +4925,32 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
         // Check provided parameters.
         let ((ty_required, ty_accepted), lt_accepted) =
             segment.map_or(((0, 0), 0), |(_, generics)| {
+                struct ParamRange {
+                    required: usize,
+                    accepted: usize
+                };
+
                 let mut lt_accepted = 0;
-                let mut ty_range = (0, 0);
+                let mut ty_params = ParamRange { required: 0, accepted: 0 };
                 for param in &generics.params {
                     match param.kind {
                         GenericParamDefKind::Lifetime => {
                             lt_accepted += 1;
                         }
                         GenericParamDefKind::Type(ty) => {
-                            ty_range.1 += 1;
+                            ty_params.accepted += 1;
                             if !ty.has_default {
-                                ty_range.0 += 1;
+                                ty_params.required += 1;
                             }
                         }
                     };
                 }
                 if generics.parent.is_none() && generics.has_self {
-                    ty_range.0 -= 1;
-                    ty_range.1 -= 1;
+                    ty_params.required -= 1;
+                    ty_params.accepted -= 1;
                 }
 
-                ((ty_range.0, ty_range.1), lt_accepted)
+                ((ty_params.required, ty_params.accepted), lt_accepted)
             });
 
         if types.len() > ty_accepted {

src/librustc_typeck/impl_wf_check.rs

@@ -72,7 +72,7 @@ struct ImplWfCheck<'a, 'tcx: 'a> {
 impl<'a, 'tcx> ItemLikeVisitor<'tcx> for ImplWfCheck<'a, 'tcx> {
     fn visit_item(&mut self, item: &'tcx hir::Item) {
         match item.node {
-            hir::ItemImpl(.., _, _, _, ref impl_item_refs) => {
+            hir::ItemImpl(.., ref impl_item_refs) => {
                 let impl_def_id = self.tcx.hir.local_def_id(item.id);
                 enforce_impl_params_are_constrained(self.tcx,
                                                     impl_def_id,