Auto merge of #58503 - varkor:const-generics-hir, r=petrochenkov

Add const generics to the HIR

Split out from #53645.

cc @yodaldevoid

r? @eddyb

Author: bors

src/librustc/hir/def.rs

@@ -52,13 +52,13 @@ pub enum Def {
     AssociatedExistential(DefId),
     PrimTy(hir::PrimTy),
     TyParam(DefId),
-    ConstParam(DefId),
     SelfTy(Option<DefId> /* trait */, Option<DefId> /* impl */),
     ToolMod, // e.g., `rustfmt` in `#[rustfmt::skip]`
 
     // Value namespace
     Fn(DefId),
     Const(DefId),
+    ConstParam(DefId),
     Static(DefId, bool /* is_mutbl */),
     StructCtor(DefId, CtorKind), // `DefId` refers to `NodeId` of the struct's constructor
     VariantCtor(DefId, CtorKind), // `DefId` refers to the enum variant

src/librustc/hir/intravisit.rs

@@ -334,6 +334,7 @@ pub trait Visitor<'v> : Sized {
         match generic_arg {
             GenericArg::Lifetime(lt) => self.visit_lifetime(lt),
             GenericArg::Type(ty) => self.visit_ty(ty),
+            GenericArg::Const(ct) => self.visit_anon_const(&ct.value),
         }
     }
     fn visit_lifetime(&mut self, lifetime: &'v Lifetime) {
@@ -752,6 +753,7 @@ pub fn walk_generic_param<'v, V: Visitor<'v>>(visitor: &mut V, param: &'v Generi
     match param.kind {
         GenericParamKind::Lifetime { .. } => {}
         GenericParamKind::Type { ref default, .. } => walk_list!(visitor, visit_ty, default),
+        GenericParamKind::Const { ref ty } => visitor.visit_ty(ty),
     }
     walk_list!(visitor, visit_param_bound, &param.bounds);
 }

src/librustc/hir/lowering.rs

@@ -36,7 +36,7 @@ use crate::hir::HirVec;
 use crate::hir::map::{DefKey, DefPathData, Definitions};
 use crate::hir::def_id::{DefId, DefIndex, DefIndexAddressSpace, CRATE_DEF_INDEX};
 use crate::hir::def::{Def, PathResolution, PerNS};
-use crate::hir::GenericArg;
+use crate::hir::{GenericArg, ConstArg};
 use crate::lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
                     ELIDED_LIFETIMES_IN_PATHS};
 use crate::middle::cstore::CrateStore;
@@ -1172,13 +1172,10 @@ impl<'a> LoweringContext<'a> {
             ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(&lt)),
             ast::GenericArg::Type(ty) => GenericArg::Type(self.lower_ty_direct(&ty, itctx)),
             ast::GenericArg::Const(ct) => {
-                // FIXME(const_generics): const generics are not yet defined in the HIR.
-                self.sess.struct_span_err(
-                    ct.value.span,
-                    "const generics in any position are currently unsupported",
-                ).emit();
-                self.sess.abort_if_errors();
-                bug!();
+                GenericArg::Const(ConstArg {
+                    value: self.lower_anon_const(&ct),
+                    span: ct.value.span,
+                })
             }
         }
     }
@@ -2520,14 +2517,10 @@ impl<'a> LoweringContext<'a> {
 
                 (hir::ParamName::Plain(ident), kind)
             }
-            GenericParamKind::Const { .. } => {
-                // FIXME(const_generics): const generics are not yet defined in the HIR.
-                self.sess.struct_span_err(
-                    param.ident.span,
-                    "const generics in any position are currently unsupported",
-                ).emit();
-                self.sess.abort_if_errors();
-                bug!();
+            GenericParamKind::Const { ref ty } => {
+                (hir::ParamName::Plain(param.ident), hir::GenericParamKind::Const {
+                    ty: self.lower_ty(&ty, ImplTraitContext::disallowed()),
+                })
             }
         };
 

src/librustc/hir/map/mod.rs

@@ -398,6 +398,7 @@ impl<'hir> Map<'hir> {
                 Some(match param.kind {
                     GenericParamKind::Lifetime { .. } => Def::Local(param.id),
                     GenericParamKind::Type { .. } => Def::TyParam(self.local_def_id(param.id)),
+                    GenericParamKind::Const { .. } => Def::ConstParam(self.local_def_id(param.id)),
                 })
             }
         }

src/librustc/hir/mod.rs

@@ -389,24 +389,33 @@ impl PathSegment {
     }
 }
 
+#[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
+pub struct ConstArg {
+    pub value: AnonConst,
+    pub span: Span,
+}
+
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub enum GenericArg {
     Lifetime(Lifetime),
     Type(Ty),
+    Const(ConstArg),
 }
 
 impl GenericArg {
     pub fn span(&self) -> Span {
         match self {
             GenericArg::Lifetime(l) => l.span,
             GenericArg::Type(t) => t.span,
+            GenericArg::Const(c) => c.span,
         }
     }
 
     pub fn id(&self) -> NodeId {
         match self {
             GenericArg::Lifetime(l) => l.id,
             GenericArg::Type(t) => t.id,
+            GenericArg::Const(c) => c.value.id,
         }
     }
 }
@@ -448,6 +457,7 @@ impl GenericArgs {
                         }
                         break;
                     }
+                    GenericArg::Const(_) => {}
                 }
             }
         }
@@ -464,6 +474,7 @@ impl GenericArgs {
             match arg {
                 GenericArg::Lifetime(_) => own_counts.lifetimes += 1,
                 GenericArg::Type(_) => own_counts.types += 1,
+                GenericArg::Const(_) => own_counts.consts += 1,
             };
         }
 
@@ -528,6 +539,9 @@ pub enum GenericParamKind {
     Type {
         default: Option<P<Ty>>,
         synthetic: Option<SyntheticTyParamKind>,
+    },
+    Const {
+        ty: P<Ty>,
     }
 }
 
@@ -548,6 +562,7 @@ pub struct GenericParam {
 pub struct GenericParamCount {
     pub lifetimes: usize,
     pub types: usize,
+    pub consts: usize,
 }
 
 /// Represents lifetimes and type parameters attached to a declaration
@@ -582,6 +597,7 @@ impl Generics {
             match param.kind {
                 GenericParamKind::Lifetime { .. } => own_counts.lifetimes += 1,
                 GenericParamKind::Type { .. } => own_counts.types += 1,
+                GenericParamKind::Const { .. } => own_counts.consts += 1,
             };
         }
 
@@ -1302,7 +1318,7 @@ impl BodyOwnerKind {
 /// These are usually found nested inside types (e.g., array lengths)
 /// or expressions (e.g., repeat counts), and also used to define
 /// explicit discriminant values for enum variants.
-#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
 pub struct AnonConst {
     pub id: NodeId,
     pub hir_id: HirId,

src/librustc/hir/pat_util.rs

@@ -64,19 +64,6 @@ impl hir::Pat {
         }
     }
 
-    pub fn is_const(&self) -> bool {
-        match self.node {
-            PatKind::Path(hir::QPath::TypeRelative(..)) => true,
-            PatKind::Path(hir::QPath::Resolved(_, ref path)) => {
-                match path.def {
-                    Def::Const(..) | Def::AssociatedConst(..) => true,
-                    _ => false
-                }
-            }
-            _ => false
-        }
-    }
-
     /// Call `f` on every "binding" in a pattern, e.g., on `a` in
     /// `match foo() { Some(a) => (), None => () }`
     pub fn each_binding<F>(&self, mut f: F)

src/librustc/hir/print.rs

@@ -1711,31 +1711,25 @@ impl<'a> State<'a> {
                 }
             };
 
-            let mut types = vec![];
-            let mut elide_lifetimes = true;
-            for arg in &generic_args.args {
-                match arg {
-                    GenericArg::Lifetime(lt) => {
-                        if !lt.is_elided() {
-                            elide_lifetimes = false;
-                        }
-                    }
-                    GenericArg::Type(ty) => {
-                        types.push(ty);
-                    }
+            let mut nonelided_generic_args: bool = false;
+            let elide_lifetimes = generic_args.args.iter().all(|arg| match arg {
+                GenericArg::Lifetime(lt) => lt.is_elided(),
+                _ => {
+                    nonelided_generic_args = true;
+                    true
                 }
-            }
-            if !elide_lifetimes {
+            });
+
+            if nonelided_generic_args {
                 start_or_comma(self)?;
                 self.commasep(Inconsistent, &generic_args.args, |s, generic_arg| {
                     match generic_arg {
-                        GenericArg::Lifetime(lt) => s.print_lifetime(lt),
+                        GenericArg::Lifetime(lt) if !elide_lifetimes => s.print_lifetime(lt),
+                        GenericArg::Lifetime(_) => Ok(()),
                         GenericArg::Type(ty) => s.print_type(ty),
+                        GenericArg::Const(ct) => s.print_anon_const(&ct.value),
                     }
                 })?;
-            } else if !types.is_empty() {
-                start_or_comma(self)?;
-                self.commasep(Inconsistent, &types, |s, ty| s.print_type(&ty))?;
             }
 
             // FIXME(eddyb) This would leak into error messages, e.g.:
@@ -2106,7 +2100,12 @@ impl<'a> State<'a> {
     }
 
     pub fn print_generic_param(&mut self, param: &GenericParam) -> io::Result<()> {
+        if let GenericParamKind::Const { .. } = param.kind {
+            self.word_space("const")?;
+        }
+
         self.print_ident(param.name.ident())?;
+
         match param.kind {
             GenericParamKind::Lifetime { .. } => {
                 let mut sep = ":";
@@ -2133,6 +2132,10 @@ impl<'a> State<'a> {
                     _ => Ok(()),
                 }
             }
+            GenericParamKind::Const { ref ty } => {
+                self.word_space(":")?;
+                self.print_type(ty)
+            }
         }
     }
 

src/librustc/ich/impls_hir.rs

@@ -179,9 +179,15 @@ impl_stable_hash_for!(struct hir::PathSegment {
     args
 });
 
+impl_stable_hash_for!(struct hir::ConstArg {
+    value,
+    span,
+});
+
 impl_stable_hash_for!(enum hir::GenericArg {
     Lifetime(lt),
-    Type(ty)
+    Type(ty),
+    Const(ct),
 });
 
 impl_stable_hash_for!(struct hir::GenericArgs {
@@ -231,6 +237,9 @@ impl<'a> HashStable<StableHashingContext<'a>> for hir::GenericParamKind {
                 default.hash_stable(hcx, hasher);
                 synthetic.hash_stable(hcx, hasher);
             }
+            hir::GenericParamKind::Const { ref ty } => {
+                ty.hash_stable(hcx, hasher);
+            }
         }
     }
 }

src/librustc/middle/mem_categorization.rs

@@ -704,7 +704,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
                hir_id, expr_ty, def);
 
         match def {
-            Def::StructCtor(..) | Def::VariantCtor(..) | Def::Const(..) |
+            Def::StructCtor(..) | Def::VariantCtor(..) | Def::Const(..) | Def::ConstParam(..) |
             Def::AssociatedConst(..) | Def::Fn(..) | Def::Method(..) | Def::SelfCtor(..) => {
                 Ok(self.cat_rvalue_node(hir_id, span, expr_ty))
             }

src/librustc/middle/reachable.rs

@@ -315,8 +315,11 @@ impl<'a, 'tcx> ReachableContext<'a, 'tcx> {
             Node::Ty(_) |
             Node::MacroDef(_) => {}
             _ => {
-                bug!("found unexpected thingy in worklist: {}",
-                     self.tcx.hir().node_to_string(search_item))
+                bug!(
+                    "found unexpected node kind in worklist: {} ({:?})",
+                    self.tcx.hir().node_to_string(search_item),
+                    node,
+                );
             }
         }
     }