Add Const kind to rustdoc

Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>

src/librustdoc/clean/auto_trait.rs

@@ -773,6 +773,7 @@ impl<'a, 'tcx, 'rcx> AutoTraitFinder<'a, 'tcx, 'rcx> {
                     }
                 }
                 GenericParamDefKind::Lifetime => {}
+                GenericParamDefKind::Const { .. } => {}
             }
         }
 

src/librustdoc/clean/mod.rs

@@ -1253,6 +1253,15 @@ impl Clean<Lifetime> for hir::GenericParam {
     }
 }
 
+impl Clean<Constant> for hir::ConstArg {
+    fn clean(&self, cx: &DocContext) -> Constant {
+        Constant {
+            type_: cx.tcx.type_of(cx.tcx.hir().body_owner_def_id(self.value.body)).clean(cx),
+            expr: print_const_expr(cx, self.value.body),
+        }
+    }
+}
+
 impl<'tcx> Clean<Lifetime> for ty::GenericParamDef {
     fn clean(&self, _cx: &DocContext) -> Lifetime {
         Lifetime(self.name.to_string())
@@ -1418,6 +1427,10 @@ pub enum GenericParamDefKind {
         default: Option<Type>,
         synthetic: Option<hir::SyntheticTyParamKind>,
     },
+    Const {
+        did: DefId,
+        ty: Type,
+    },
 }
 
 #[derive(Clone, RustcEncodable, RustcDecodable, PartialEq, Eq, Debug, Hash)]
@@ -1430,7 +1443,10 @@ pub struct GenericParamDef {
 impl GenericParamDef {
     pub fn is_synthetic_type_param(&self) -> bool {
         match self.kind {
-            GenericParamDefKind::Lifetime => false,
+            GenericParamDefKind::Lifetime |
+            GenericParamDefKind::Const { .. } => {
+                false
+            }
             GenericParamDefKind::Type { ref synthetic, .. } => synthetic.is_some(),
         }
     }
@@ -1494,6 +1510,12 @@ impl Clean<GenericParamDef> for hir::GenericParam {
                     synthetic: synthetic,
                 })
             }
+            hir::GenericParamKind::Const { ref ty } => {
+                (self.name.ident().name.clean(cx), GenericParamDefKind::Const {
+                    did: cx.tcx.hir().local_def_id(self.id),
+                    ty: ty.clean(cx),
+                })
+            }
         };
 
         GenericParamDef {
@@ -1533,6 +1555,7 @@ impl Clean<Generics> for hir::Generics {
                     GenericParamDefKind::Type { did, ref bounds, .. } => {
                         cx.impl_trait_bounds.borrow_mut().insert(did, bounds.clone());
                     }
+                    GenericParamDefKind::Const { .. } => unreachable!(),
                 }
                 param
             })
@@ -1566,6 +1589,7 @@ impl Clean<Generics> for hir::Generics {
                                         break
                                     }
                                 }
+                                GenericParamDefKind::Const { .. } => {}
                             }
                         }
                     }
@@ -2544,6 +2568,7 @@ impl Clean<Type> for hir::Ty {
                     let provided_params = &path.segments.last().expect("segments were empty");
                     let mut ty_substs = FxHashMap::default();
                     let mut lt_substs = FxHashMap::default();
+                    let mut const_substs = FxHashMap::default();
                     provided_params.with_generic_args(|generic_args| {
                         let mut indices: GenericParamCount = Default::default();
                         for param in generics.params.iter() {
@@ -2595,10 +2620,32 @@ impl Clean<Type> for hir::Ty {
                                     }
                                     indices.types += 1;
                                 }
+                                hir::GenericParamKind::Const { .. } => {
+                                    let const_param_def =
+                                        Def::ConstParam(cx.tcx.hir().local_def_id(param.id));
+                                    let mut j = 0;
+                                    let const_ = generic_args.args.iter().find_map(|arg| {
+                                        match arg {
+                                            hir::GenericArg::Const(ct) => {
+                                                if indices.consts == j {
+                                                    return Some(ct);
+                                                }
+                                                j += 1;
+                                                None
+                                            }
+                                            _ => None,
+                                        }
+                                    });
+                                    if let Some(ct) = const_.cloned() {
+                                        const_substs.insert(const_param_def, ct.clean(cx));
+                                    }
+                                    // FIXME(const_generics:defaults)
+                                    indices.consts += 1;
+                                }
                             }
                         }
                     });
-                    return cx.enter_alias(ty_substs, lt_substs, || ty.clean(cx));
+                    return cx.enter_alias(ty_substs, lt_substs, const_substs, || ty.clean(cx));
                 }
                 resolve_type(cx, path.clean(cx), self.id)
             }
@@ -3190,6 +3237,9 @@ impl Clean<GenericArgs> for hir::GenericArgs {
                     GenericArg::Type(ty) => {
                         types.push(ty.clean(cx));
                     }
+                    GenericArg::Const(..) => {
+                        unimplemented!() // FIXME(const_generics)
+                    }
                 }
             }
             GenericArgs::AngleBracketed {

src/librustdoc/core.rs

@@ -65,6 +65,8 @@ pub struct DocContext<'a, 'tcx: 'a, 'rcx: 'a> {
     pub ty_substs: RefCell<FxHashMap<Def, clean::Type>>,
     /// Table `NodeId` of lifetime parameter definition -> substituted lifetime
     pub lt_substs: RefCell<FxHashMap<DefId, clean::Lifetime>>,
+    /// Table node id of const parameter definition -> substituted const
+    pub ct_substs: RefCell<FxHashMap<Def, clean::Constant>>,
     /// Table DefId of `impl Trait` in argument position -> bounds
     pub impl_trait_bounds: RefCell<FxHashMap<DefId, Vec<clean::GenericBound>>>,
     pub send_trait: Option<DefId>,
@@ -85,14 +87,18 @@ impl<'a, 'tcx, 'rcx> DocContext<'a, 'tcx, 'rcx> {
     pub fn enter_alias<F, R>(&self,
                              ty_substs: FxHashMap<Def, clean::Type>,
                              lt_substs: FxHashMap<DefId, clean::Lifetime>,
+                             ct_substs: FxHashMap<Def, clean::Constant>,
                              f: F) -> R
     where F: FnOnce() -> R {
-        let (old_tys, old_lts) =
+        let (old_tys, old_lts, old_cts) = (
-            (mem::replace(&mut *self.ty_substs.borrow_mut(), ty_substs),
+            mem::replace(&mut *self.ty_substs.borrow_mut(), ty_substs),
-             mem::replace(&mut *self.lt_substs.borrow_mut(), lt_substs));
+            mem::replace(&mut *self.lt_substs.borrow_mut(), lt_substs),
+            mem::replace(&mut *self.ct_substs.borrow_mut(), ct_substs),
+        );
         let r = f();
         *self.ty_substs.borrow_mut() = old_tys;
         *self.lt_substs.borrow_mut() = old_lts;
+        *self.ct_substs.borrow_mut() = old_cts;
         r
     }
 
@@ -527,6 +533,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
                 renderinfo: RefCell::new(renderinfo),
                 ty_substs: Default::default(),
                 lt_substs: Default::default(),
+                ct_substs: Default::default(),
                 impl_trait_bounds: Default::default(),
                 send_trait: send_trait,
                 fake_def_ids: Default::default(),

src/librustdoc/html/format.rs

@@ -138,6 +138,16 @@ impl fmt::Display for clean::GenericParamDef {
 
                 Ok(())
             }
+            clean::GenericParamDefKind::Const { ref ty, .. } => {
+                f.write_str("const ")?;
+                f.write_str(&self.name)?;
+
+                if f.alternate() {
+                    write!(f, ": {:#}", ty)
+                } else {
+                    write!(f, ": {}", ty)
+                }
+            }
         }
     }
 }

src/librustdoc/html/render.rs

@@ -1746,7 +1746,8 @@ impl<'a> Cache {
         for param in &generics.params {
             match param.kind {
                 clean::GenericParamDefKind::Lifetime => {}
-                clean::GenericParamDefKind::Type { did, .. } => {
+                clean::GenericParamDefKind::Type { did, .. } |
+                clean::GenericParamDefKind::Const { did, .. } => {
                     self.typarams.insert(did, param.name.clone());
                 }
             }