diff --git a/src/librustc/infer/type_variable.rs b/src/librustc/infer/type_variable.rs
index 91df6cabf3a8b..5e96f4eb576f5 100644
--- a/src/librustc/infer/type_variable.rs
+++ b/src/librustc/infer/type_variable.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use syntax::ast;
+use syntax::symbol::InternedString;
 use syntax_pos::Span;
 use ty::{self, Ty};
 
@@ -53,7 +53,7 @@ pub enum TypeVariableOrigin {
     MiscVariable(Span),
     NormalizeProjectionType(Span),
     TypeInference(Span),
-    TypeParameterDefinition(Span, ast::Name),
+    TypeParameterDefinition(Span, InternedString),
 
     /// one of the upvars or closure kind parameters in a `ClosureSubsts`
     /// (before it has been determined)
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index d2bde14732bbc..2af4c3f9fd463 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -378,7 +378,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
         }
 
         for param in generics.types.iter() {
-            let name = param.name.as_str().to_string();
+            let name = param.name.to_string();
             let ty = trait_ref.substs.type_for_def(param);
             let ty_str = ty.to_string();
             flags.push((name.clone(),
diff --git a/src/librustc/traits/on_unimplemented.rs b/src/librustc/traits/on_unimplemented.rs
index 8c2c1cfa45472..f7ce55c2e1df2 100644
--- a/src/librustc/traits/on_unimplemented.rs
+++ b/src/librustc/traits/on_unimplemented.rs
@@ -289,7 +289,7 @@ impl<'a, 'gcx, 'tcx> OnUnimplementedFormatString {
         let trait_str = tcx.item_path_str(trait_ref.def_id);
         let generics = tcx.generics_of(trait_ref.def_id);
         let generic_map = generics.types.iter().map(|param| {
-            (param.name.as_str().to_string(),
+            (param.name.to_string(),
              trait_ref.substs.type_for_def(param).to_string())
         }).collect::<FxHashMap<String, String>>();
 
diff --git a/src/librustc/ty/context.rs b/src/librustc/ty/context.rs
index 3326af21bd604..88668578efb05 100644
--- a/src/librustc/ty/context.rs
+++ b/src/librustc/ty/context.rs
@@ -70,11 +70,11 @@ use std::iter;
 use std::sync::mpsc;
 use std::sync::Arc;
 use syntax::abi;
-use syntax::ast::{self, Name, NodeId};
+use syntax::ast::{self, NodeId};
 use syntax::attr;
 use syntax::codemap::MultiSpan;
 use syntax::feature_gate;
-use syntax::symbol::{Symbol, keywords};
+use syntax::symbol::{Symbol, keywords, InternedString};
 use syntax_pos::Span;
 
 use hir;
@@ -2395,12 +2395,12 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
     pub fn mk_param(self,
                     index: u32,
-                    name: Name) -> Ty<'tcx> {
+                    name: InternedString) -> Ty<'tcx> {
         self.mk_ty(TyParam(ParamTy { idx: index, name: name }))
     }
 
     pub fn mk_self_type(self) -> Ty<'tcx> {
-        self.mk_param(0, keywords::SelfType.name())
+        self.mk_param(0, keywords::SelfType.name().as_str())
     }
 
     pub fn mk_param_from_def(self, def: &ty::TypeParameterDef) -> Ty<'tcx> {
diff --git a/src/librustc/ty/maps/plumbing.rs b/src/librustc/ty/maps/plumbing.rs
index bc5a14c96f004..21ffb47029cb7 100644
--- a/src/librustc/ty/maps/plumbing.rs
+++ b/src/librustc/ty/maps/plumbing.rs
@@ -636,7 +636,16 @@ macro_rules! define_maps {
                                map: LockGuard<'_, QueryMap<$tcx, Self>>,
                                dep_node: DepNode)
                                -> Result<($V, DepNodeIndex), CycleError<$tcx>> {
-                debug_assert!(!tcx.dep_graph.dep_node_exists(&dep_node));
+                // If the following assertion triggers, it can have two reasons:
+                // 1. Something is wrong with DepNode creation, either here or
+                //    in DepGraph::try_mark_green()
+                // 2. Two distinct query keys get mapped to the same DepNode
+                //    (see for example #48923)
+                assert!(!tcx.dep_graph.dep_node_exists(&dep_node),
+                        "Forcing query with already existing DepNode.\n\
+                          - query-key: {:?}\n\
+                          - dep-node: {:?}",
+                        key, dep_node);
 
                 profq_msg!(tcx, ProfileQueriesMsg::ProviderBegin);
                 let res = Self::start_job(tcx,
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 72ba199eb2412..43c5ba46b44c9 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -712,7 +712,7 @@ pub struct FloatVarValue(pub ast::FloatTy);
 
 #[derive(Copy, Clone, RustcEncodable, RustcDecodable)]
 pub struct TypeParameterDef {
-    pub name: Name,
+    pub name: InternedString,
     pub def_id: DefId,
     pub index: u32,
     pub has_default: bool,
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index ed04d41ba1457..7a9174cbfaf73 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -24,7 +24,7 @@ use std::iter;
 use std::cmp::Ordering;
 use syntax::abi;
 use syntax::ast::{self, Name};
-use syntax::symbol::keywords;
+use syntax::symbol::{keywords, InternedString};
 
 use serialize;
 
@@ -864,16 +864,16 @@ impl<'tcx> PolyFnSig<'tcx> {
 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub struct ParamTy {
     pub idx: u32,
-    pub name: Name,
+    pub name: InternedString,
 }
 
 impl<'a, 'gcx, 'tcx> ParamTy {
-    pub fn new(index: u32, name: Name) -> ParamTy {
+    pub fn new(index: u32, name: InternedString) -> ParamTy {
         ParamTy { idx: index, name: name }
     }
 
     pub fn for_self() -> ParamTy {
-        ParamTy::new(0, keywords::SelfType.name())
+        ParamTy::new(0, keywords::SelfType.name().as_str())
     }
 
     pub fn for_def(def: &ty::TypeParameterDef) -> ParamTy {
@@ -885,7 +885,7 @@ impl<'a, 'gcx, 'tcx> ParamTy {
     }
 
     pub fn is_self(&self) -> bool {
-        if self.name == keywords::SelfType.name() {
+        if self.name == keywords::SelfType.name().as_str() {
             assert_eq!(self.idx, 0);
             true
         } else {
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index 22f851a908b25..c170c2a63e829 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -729,7 +729,7 @@ impl<'a, 'gcx, 'tcx, W> TypeVisitor<'tcx> for TypeIdHasher<'a, 'gcx, 'tcx, W>
             }
             TyParam(p) => {
                 self.hash(p.idx);
-                self.hash(p.name.as_str());
+                self.hash(p.name);
             }
             TyProjection(ref data) => {
                 self.def_id(data.item_def_id);
diff --git a/src/librustc_driver/test.rs b/src/librustc_driver/test.rs
index 9efd8844977f9..971855ee2d007 100644
--- a/src/librustc_driver/test.rs
+++ b/src/librustc_driver/test.rs
@@ -303,7 +303,7 @@ impl<'a, 'gcx, 'tcx> Env<'a, 'gcx, 'tcx> {
 
     pub fn t_param(&self, index: u32) -> Ty<'tcx> {
         let name = format!("T{}", index);
-        self.infcx.tcx.mk_param(index, Symbol::intern(&name))
+        self.infcx.tcx.mk_param(index, Symbol::intern(&name).as_str())
     }
 
     pub fn re_early_bound(&self, index: u32, name: &'static str) -> ty::Region<'tcx> {
diff --git a/src/librustc_trans/debuginfo/mod.rs b/src/librustc_trans/debuginfo/mod.rs
index 7664c88679e0e..87d9623e40038 100644
--- a/src/librustc_trans/debuginfo/mod.rs
+++ b/src/librustc_trans/debuginfo/mod.rs
@@ -42,7 +42,7 @@ use std::ptr;
 
 use syntax_pos::{self, Span, Pos};
 use syntax::ast;
-use syntax::symbol::Symbol;
+use syntax::symbol::{Symbol, InternedString};
 use rustc::ty::layout::{self, LayoutOf};
 
 pub mod gdb;
@@ -393,7 +393,7 @@ pub fn create_function_debug_context<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
             substs.types().zip(names).map(|(ty, name)| {
                 let actual_type = cx.tcx.normalize_erasing_regions(ParamEnv::reveal_all(), ty);
                 let actual_type_metadata = type_metadata(cx, actual_type, syntax_pos::DUMMY_SP);
-                let name = CString::new(name.as_str().as_bytes()).unwrap();
+                let name = CString::new(name.as_bytes()).unwrap();
                 unsafe {
                     llvm::LLVMRustDIBuilderCreateTemplateTypeParameter(
                         DIB(cx),
@@ -412,7 +412,7 @@ pub fn create_function_debug_context<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
         return create_DIArray(DIB(cx), &template_params[..]);
     }
 
-    fn get_type_parameter_names(cx: &CodegenCx, generics: &ty::Generics) -> Vec<ast::Name> {
+    fn get_type_parameter_names(cx: &CodegenCx, generics: &ty::Generics) -> Vec<InternedString> {
         let mut names = generics.parent.map_or(vec![], |def_id| {
             get_type_parameter_names(cx, cx.tcx.generics_of(def_id))
         });
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 0e93277983f8d..c4ea543ab36b6 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -979,7 +979,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> AstConv<'gcx, 'tcx>+'o {
                 let item_def_id = tcx.hir.local_def_id(item_id);
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.type_param_to_index[&tcx.hir.local_def_id(node_id)];
-                tcx.mk_param(index, tcx.hir.name(node_id))
+                tcx.mk_param(index, tcx.hir.name(node_id).as_str())
             }
             Def::SelfTy(_, Some(def_id)) => {
                 // Self in impl (we know the concrete type).
diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs
index 377e3a891840f..da0d4509353b5 100644
--- a/src/librustc_typeck/check/intrinsic.rs
+++ b/src/librustc_typeck/check/intrinsic.rs
@@ -76,7 +76,7 @@ fn equate_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 /// and in libcore/intrinsics.rs
 pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                       it: &hir::ForeignItem) {
-    let param = |n| tcx.mk_param(n, Symbol::intern(&format!("P{}", n)));
+    let param = |n| tcx.mk_param(n, Symbol::intern(&format!("P{}", n)).as_str());
     let name = it.name.as_str();
     let (n_tps, inputs, output) = if name.starts_with("atomic_") {
         let split : Vec<&str> = name.split('_').collect();
@@ -341,7 +341,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 pub fn check_platform_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                                                it: &hir::ForeignItem) {
     let param = |n| {
-        let name = Symbol::intern(&format!("P{}", n));
+        let name = Symbol::intern(&format!("P{}", n)).as_str();
         tcx.mk_param(n, name)
     };
 
diff --git a/src/librustc_typeck/check/wfcheck.rs b/src/librustc_typeck/check/wfcheck.rs
index 406ff9463a03c..c67327232ea3f 100644
--- a/src/librustc_typeck/check/wfcheck.rs
+++ b/src/librustc_typeck/check/wfcheck.rs
@@ -649,7 +649,7 @@ fn reject_shadowing_type_parameters(tcx: TyCtxt, def_id: DefId) {
             // local so it should be okay to just unwrap everything.
             let trait_def_id = impl_params[&method_param.name];
             let trait_decl_span = tcx.def_span(trait_def_id);
-            error_194(tcx, type_span, trait_decl_span, method_param.name);
+            error_194(tcx, type_span, trait_decl_span, &method_param.name[..]);
         }
     }
 }
@@ -753,7 +753,7 @@ fn error_392<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, span: Span, param_name: ast:
     err
 }
 
-fn error_194(tcx: TyCtxt, span: Span, trait_decl_span: Span, name: ast::Name) {
+fn error_194(tcx: TyCtxt, span: Span, trait_decl_span: Span, name: &str) {
     struct_span_err!(tcx.sess, span, E0194,
               "type parameter `{}` shadows another type parameter of the same name",
               name)
diff --git a/src/librustc_typeck/collect.rs b/src/librustc_typeck/collect.rs
index 59156bf0dfeaa..a4f820d1fdcf9 100644
--- a/src/librustc_typeck/collect.rs
+++ b/src/librustc_typeck/collect.rs
@@ -241,7 +241,7 @@ fn type_param_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     let param_owner_def_id = tcx.hir.local_def_id(param_owner);
     let generics = tcx.generics_of(param_owner_def_id);
     let index = generics.type_param_to_index[&def_id];
-    let ty = tcx.mk_param(index, tcx.hir.ty_param_name(param_id));
+    let ty = tcx.mk_param(index, tcx.hir.ty_param_name(param_id).as_str());
 
     // Don't look for bounds where the type parameter isn't in scope.
     let parent = if item_def_id == param_owner_def_id {
@@ -839,7 +839,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
                     opt_self = Some(ty::TypeParameterDef {
                         index: 0,
-                        name: keywords::SelfType.name(),
+                        name: keywords::SelfType.name().as_str(),
                         def_id: tcx.hir.local_def_id(param_id),
                         has_default: false,
                         object_lifetime_default: rl::Set1::Empty,
@@ -915,7 +915,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 
         ty::TypeParameterDef {
             index: type_start + i as u32,
-            name: p.name,
+            name: p.name.as_str(),
             def_id: tcx.hir.local_def_id(p.id),
             has_default: p.default.is_some(),
             object_lifetime_default:
@@ -934,7 +934,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // add a dummy parameter for the closure kind
         types.push(ty::TypeParameterDef {
             index: type_start,
-            name: Symbol::intern("<closure_kind>"),
+            name: Symbol::intern("<closure_kind>").as_str(),
             def_id,
             has_default: false,
             object_lifetime_default: rl::Set1::Empty,
@@ -945,7 +945,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         // add a dummy parameter for the closure signature
         types.push(ty::TypeParameterDef {
             index: type_start + 1,
-            name: Symbol::intern("<closure_signature>"),
+            name: Symbol::intern("<closure_signature>").as_str(),
             def_id,
             has_default: false,
             object_lifetime_default: rl::Set1::Empty,
@@ -956,7 +956,7 @@ fn generics_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         tcx.with_freevars(node_id, |fv| {
             types.extend(fv.iter().zip(2..).map(|(_, i)| ty::TypeParameterDef {
                 index: type_start + i,
-                name: Symbol::intern("<upvar>"),
+                name: Symbol::intern("<upvar>").as_str(),
                 def_id,
                 has_default: false,
                 object_lifetime_default: rl::Set1::Empty,
@@ -1436,7 +1436,7 @@ fn explicit_predicates_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     // Collect the predicates that were written inline by the user on each
     // type parameter (e.g., `<T:Foo>`).
     for param in ast_generics.ty_params() {
-        let param_ty = ty::ParamTy::new(index, param.name).to_ty(tcx);
+        let param_ty = ty::ParamTy::new(index, param.name.as_str()).to_ty(tcx);
         index += 1;
 
         let bounds = compute_bounds(&icx,
diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index fe4f785aa915e..89fbe1b72ea11 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -260,7 +260,9 @@ impl<'a, 'tcx, 'rcx> AutoTraitFinder<'a, 'tcx, 'rcx> {
                 P(hir::Path {
                     span: DUMMY_SP,
                     def: Def::TyParam(param.def_id),
-                    segments: HirVec::from_vec(vec![hir::PathSegment::from_name(param.name)]),
+                    segments: HirVec::from_vec(vec![
+                        hir::PathSegment::from_name(Symbol::intern(&param.name))
+                    ]),
                 }),
             )),
             span: DUMMY_SP,
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 6ada4ccfbddc2..213e6262caa5c 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -27,7 +27,7 @@ use syntax::codemap::Spanned;
 use syntax::feature_gate::UnstableFeatures;
 use syntax::ptr::P;
 use syntax::symbol::keywords;
-use syntax::symbol::Symbol;
+use syntax::symbol::{Symbol, InternedString};
 use syntax_pos::{self, DUMMY_SP, Pos, FileName};
 
 use rustc::middle::const_val::ConstVal;
@@ -1794,7 +1794,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics,
         // predicates field (see rustc_typeck::collect::ty_generics), so remove
         // them.
         let stripped_typarams = gens.types.iter().filter_map(|tp| {
-            if tp.name == keywords::SelfType.name() {
+            if tp.name == keywords::SelfType.name().as_str() {
                 assert_eq!(tp.index, 0);
                 None
             } else {
@@ -3374,6 +3374,12 @@ impl Clean<String> for ast::Name {
     }
 }
 
+impl Clean<String> for InternedString {
+    fn clean(&self, _: &DocContext) -> String {
+        self.to_string()
+    }
+}
+
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Typedef {
     pub type_: Type,