clippy: support QPath::LangItem

This commit updates clippy with the introduction of `QPath::LangItem` so
that it still compiles.

Signed-off-by: David Wood <david@davidtw.co>

src/tools/clippy/clippy_lints/src/default_trait_access.rs

@@ -68,7 +68,7 @@ impl<'tcx> LateLintPass<'tcx> for DefaultTraitAccess {
                             );
                          }
                     },
-                    QPath::TypeRelative(..) => {},
+                    QPath::TypeRelative(..) | QPath::LangItem(..) => {},
                 }
             }
         }

src/tools/clippy/clippy_lints/src/types.rs

@@ -475,6 +475,7 @@ impl Types {
                             }
                         }
                     },
+                    QPath::LangItem(..) => {},
                 }
             },
             TyKind::Rptr(ref lt, ref mut_ty) => self.check_ty_rptr(cx, hir_ty, is_local, lt, mut_ty),

src/tools/clippy/clippy_lints/src/utils/author.rs

@@ -760,5 +760,6 @@ fn print_path(path: &QPath<'_>, first: &mut bool) {
             },
             ref other => print!("/* unimplemented: {:?}*/", other),
         },
+        QPath::LangItem(lang_item, ..) => print!("#[lang = \"{}\"]", lang_item.name()),
     }
 }

src/tools/clippy/clippy_lints/src/utils/hir_utils.rs

@@ -601,6 +601,9 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
             QPath::TypeRelative(_, ref path) => {
                 self.hash_name(path.ident.name);
             },
+            QPath::LangItem(lang_item, ..) => {
+                lang_item.hash_stable(&mut self.cx.tcx.get_stable_hashing_context(), &mut self.s);
+            }
         }
         // self.maybe_typeck_results.unwrap().qpath_res(p, id).hash(&mut self.s);
     }
@@ -710,6 +713,9 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                     self.hash_ty(ty);
                     segment.ident.name.hash(&mut self.s);
                 },
+                QPath::LangItem(lang_item, ..) => {
+                    lang_item.hash(&mut self.s);
+                }
             },
             TyKind::OpaqueDef(_, arg_list) => {
                 self.hash_generic_args(arg_list);

src/tools/clippy/clippy_lints/src/utils/inspector.rs

@@ -266,6 +266,9 @@ fn print_expr(cx: &LateContext<'_>, expr: &hir::Expr<'_>, indent: usize) {
             println!("{}Relative Path, {:?}", ind, ty);
             println!("{}seg: {:?}", ind, seg);
         },
+        hir::ExprKind::Path(hir::QPath::LangItem(lang_item, ..)) => {
+            println!("{}Lang Item Path, {:?}", ind, lang_item.name());
+        },
         hir::ExprKind::AddrOf(kind, ref muta, ref e) => {
             println!("{}AddrOf", ind);
             println!("kind: {:?}", kind);
@@ -488,6 +491,9 @@ fn print_pat(cx: &LateContext<'_>, pat: &hir::Pat<'_>, indent: usize) {
             println!("{}Relative Path, {:?}", ind, ty);
             println!("{}seg: {:?}", ind, seg);
         },
+        hir::PatKind::Path(hir::QPath::LangItem(lang_item, ..)) => {
+            println!("{}Lang Item Path, {:?}", ind, lang_item.name());
+        },
         hir::PatKind::Tuple(pats, opt_dots_position) => {
             println!("{}Tuple", ind);
             if let Some(dot_position) = opt_dots_position {

src/tools/clippy/clippy_lints/src/utils/mod.rs

@@ -163,13 +163,15 @@ pub fn last_path_segment<'tcx>(path: &QPath<'tcx>) -> &'tcx PathSegment<'tcx> {
     match *path {
         QPath::Resolved(_, ref path) => path.segments.last().expect("A path must have at least one segment"),
         QPath::TypeRelative(_, ref seg) => seg,
+        QPath::LangItem(..) => panic!("last_path_segment: lang item has no path segments"),
     }
 }
 
 pub fn single_segment_path<'tcx>(path: &QPath<'tcx>) -> Option<&'tcx PathSegment<'tcx>> {
     match *path {
         QPath::Resolved(_, ref path) => path.segments.get(0),
         QPath::TypeRelative(_, ref seg) => Some(seg),
+        QPath::LangItem(..) => panic!("single_segment_path: lang item has no path segments"),
     }
 }
 
@@ -196,6 +198,7 @@ pub fn match_qpath(path: &QPath<'_>, segments: &[&str]) -> bool {
             },
             _ => false,
         },
+        QPath::LangItem(..) => panic!("match_qpath: lang item has no path segments"),
     }
 }
 
@@ -277,7 +280,7 @@ pub fn path_to_res(cx: &LateContext<'_>, path: &[&str]) -> Option<def::Res> {
 pub fn qpath_res(cx: &LateContext<'_>, qpath: &hir::QPath<'_>, id: hir::HirId) -> Res {
     match qpath {
         hir::QPath::Resolved(_, path) => path.res,
-        hir::QPath::TypeRelative(..) => {
+        hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => {
             if cx.tcx.has_typeck_results(id.owner.to_def_id()) {
                 cx.tcx.typeck(id.owner.to_def_id().expect_local()).qpath_res(qpath, id)
             } else {