Add term

Instead of having a separate enum variant for types and consts have one but have either a const
or type.

compiler/rustc_ast/src/ast.rs

@@ -1851,13 +1851,30 @@ pub struct AssocConstraint {
     pub span: Span,
 }
 
+/// The kinds of an `AssocConstraint`.
+#[derive(Clone, Encodable, Decodable, Debug)]
+pub enum Term {
+    Ty(P<Ty>),
+    Const(AnonConst),
+}
+
+impl From<P<Ty>> for Term {
+    fn from(v: P<Ty>) -> Self {
+        Term::Ty(v)
+    }
+}
+
+impl From<AnonConst> for Term {
+    fn from(v: AnonConst) -> Self {
+        Term::Const(v)
+    }
+}
+
 /// The kinds of an `AssocConstraint`.
 #[derive(Clone, Encodable, Decodable, Debug)]
 pub enum AssocConstraintKind {
-    /// E.g., `A = Bar` in `Foo<A = Bar>` where A is an associated type.
-    Equality { ty: P<Ty> },
-    /// E.g., `A = 3` in `Foo<N = 3>` where N is an associated const.
-    ConstEquality { c: AnonConst },
+    /// E.g., `A = Bar`, `A = 3` in `Foo<A = Bar>` where A is an associated type.
+    Equality { term: Term },
     /// E.g. `A: TraitA + TraitB` in `Foo<A: TraitA + TraitB>`.
     Bound { bounds: GenericBounds },
 }

compiler/rustc_ast/src/mut_visit.rs

@@ -440,8 +440,10 @@ pub fn noop_visit_constraint<T: MutVisitor>(
         vis.visit_generic_args(gen_args);
     }
     match kind {
-        AssocConstraintKind::Equality { ref mut ty } => vis.visit_ty(ty),
-        AssocConstraintKind::ConstEquality { ref mut c } => vis.visit_anon_const(c),
+        AssocConstraintKind::Equality { ref mut term } => match term {
+            Term::Ty(ty) => vis.visit_ty(ty),
+            Term::Const(c) => vis.visit_anon_const(c),
+        },
         AssocConstraintKind::Bound { ref mut bounds } => visit_bounds(bounds, vis),
     }
     vis.visit_span(span);

compiler/rustc_ast/src/visit.rs

@@ -492,8 +492,10 @@ pub fn walk_assoc_constraint<'a, V: Visitor<'a>>(visitor: &mut V, constraint: &'
         visitor.visit_generic_args(gen_args.span(), gen_args);
     }
     match constraint.kind {
-        AssocConstraintKind::Equality { ref ty } => visitor.visit_ty(ty),
-        AssocConstraintKind::ConstEquality { ref c } => visitor.visit_anon_const(c),
+        AssocConstraintKind::Equality { ref term } => match term {
+            Term::Ty(ty) => visitor.visit_ty(ty),
+            Term::Const(c) => visitor.visit_anon_const(c),
+        },
         AssocConstraintKind::Bound { ref bounds } => {
             walk_list!(visitor, visit_param_bound, bounds);
         }

compiler/rustc_ast_lowering/src/lib.rs

@@ -997,12 +997,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         };
 
         let kind = match constraint.kind {
-            AssocConstraintKind::Equality { ref ty } => {
-                hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) }
-            }
-            AssocConstraintKind::ConstEquality { ref c } => {
-                hir::TypeBindingKind::Const { c: self.lower_anon_const(c) }
-            }
+            AssocConstraintKind::Equality { ref term } => match term {
+                Term::Ty(ref ty) => hir::TypeBindingKind::Equality { ty: self.lower_ty(ty, itctx) },
+                Term::Const(ref c) => hir::TypeBindingKind::Const { c: self.lower_anon_const(c) },
+            },
             AssocConstraintKind::Bound { ref bounds } => {
                 let mut capturable_lifetimes;
                 let mut parent_def_id = self.current_hir_id_owner;

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -141,7 +141,6 @@ impl<'a> AstValidator<'a> {
     fn visit_assoc_constraint_from_generic_args(&mut self, constraint: &'a AssocConstraint) {
         match constraint.kind {
             AssocConstraintKind::Equality { .. } => {}
-            AssocConstraintKind::ConstEquality { .. } => {}
             AssocConstraintKind::Bound { .. } => {
                 if self.is_assoc_ty_bound_banned {
                     self.err_handler().span_err(
@@ -1592,7 +1591,7 @@ fn deny_equality_constraints(
                                         ident: *ident,
                                         gen_args,
                                         kind: AssocConstraintKind::Equality {
-                                            ty: predicate.rhs_ty.clone(),
+                                            term: predicate.rhs_ty.clone().into(),
                                         },
                                         span: ident.span,
                                     });

compiler/rustc_ast_pretty/src/pprust/state.rs

@@ -1,7 +1,6 @@
 use crate::pp::Breaks::{Consistent, Inconsistent};
 use crate::pp::{self, Breaks};
 
-use rustc_ast::attr;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, BinOpToken, CommentKind, DelimToken, Nonterminal, Token, TokenKind};
 use rustc_ast::tokenstream::{TokenStream, TokenTree};
@@ -9,6 +8,7 @@ use rustc_ast::util::classify;
 use rustc_ast::util::comments::{gather_comments, Comment, CommentStyle};
 use rustc_ast::util::parser::{self, AssocOp, Fixity};
 use rustc_ast::{self as ast, BlockCheckMode, PatKind, RangeEnd, RangeSyntax};
+use rustc_ast::{attr, Term};
 use rustc_ast::{GenericArg, MacArgs, ModKind};
 use rustc_ast::{GenericBound, SelfKind, TraitBoundModifier};
 use rustc_ast::{InlineAsmOperand, InlineAsmRegOrRegClass};
@@ -957,13 +957,12 @@ impl<'a> State<'a> {
         constraint.gen_args.as_ref().map(|args| self.print_generic_args(args, false));
         self.space();
         match &constraint.kind {
-            ast::AssocConstraintKind::Equality { ty } => {
+            ast::AssocConstraintKind::Equality { term } => {
                 self.word_space("=");
-                self.print_type(ty);
-            }
-            ast::AssocConstraintKind::ConstEquality { c } => {
-                self.word_space("=");
-                self.print_expr_anon_const(c);
+                match term {
+                    Term::Ty(ty) => self.print_type(ty),
+                    Term::Const(c) => self.print_expr_anon_const(c),
+                }
             }
             ast::AssocConstraintKind::Bound { bounds } => {
                 self.print_type_bounds(":", &*bounds);

compiler/rustc_interface/src/util.rs

@@ -1,7 +1,7 @@
 use libloading::Library;
 use rustc_ast::mut_visit::{visit_clobber, MutVisitor, *};
 use rustc_ast::ptr::P;
-use rustc_ast::{self as ast, AttrVec, BlockCheckMode};
+use rustc_ast::{self as ast, AttrVec, BlockCheckMode, Term};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 #[cfg(parallel_compiler)]
@@ -739,9 +739,11 @@ impl<'a, 'b> ReplaceBodyWithLoop<'a, 'b> {
                                     },
                                     ast::AngleBracketedArg::Constraint(c) => match c.kind {
                                         ast::AssocConstraintKind::Bound { .. } => true,
-                                        ast::AssocConstraintKind::ConstEquality { .. } => false,
-                                        ast::AssocConstraintKind::Equality { ref ty } => {
-                                            involves_impl_trait(ty)
+                                        ast::AssocConstraintKind::Equality { ref term } => {
+                                            match term {
+                                                Term::Ty(ty) => involves_impl_trait(ty),
+                                                Term::Const(_) => false,
+                                            }
                                         }
                                     },
                                 })

compiler/rustc_middle/src/ty/mod.rs

@@ -799,6 +799,7 @@ pub type PolyCoercePredicate<'tcx> = ty::Binder<'tcx, CoercePredicate<'tcx>>;
 /// syntax, but it roughly corresponds to the syntactic forms:
 ///
 /// 1. `T: TraitRef<..., Item = Type>`
+/// - Or `T: TraitRef<..., Item = Const>`
 /// 2. `<T as TraitRef<...>>::Item == Type` (NYI)
 ///
 /// In particular, form #1 is "desugared" to the combination of a

compiler/rustc_parse/src/parser/path.rs

@@ -505,7 +505,9 @@ impl<'a> Parser<'a> {
         let span = ident.span.to(self.prev_token.span);
         let ty = match arg {
             Some(GenericArg::Type(ty)) => ty,
-            Some(GenericArg::Const(c)) => return Ok(AssocConstraintKind::ConstEquality { c }),
+            Some(GenericArg::Const(c)) => {
+                return Ok(AssocConstraintKind::Equality { term: c.into() });
+            }
             Some(GenericArg::Lifetime(lt)) => {
                 self.struct_span_err(span, "associated lifetimes are not supported")
                     .span_label(lt.ident.span, "the lifetime is given here")
@@ -540,7 +542,7 @@ impl<'a> Parser<'a> {
                 return Err(err);
             }
         };
-        Ok(AssocConstraintKind::Equality { ty })
+        Ok(AssocConstraintKind::Equality { term: ty.into() })
     }
 
     /// We do not permit arbitrary expressions as const arguments. They must be one of:

src/tools/clippy/clippy_utils/src/ast_utils.rs

@@ -645,13 +645,20 @@ pub fn eq_generic_bound(l: &GenericBound, r: &GenericBound) -> bool {
     }
 }
 
+fn eq_term(l: &Term, r: &Term) -> bool {
+  match (l, r) {
+    (Term::Ty(l), Term::Ty(r)) => eq_ty(l,r),
+    (Term::Const(l), Term::Const(r)) => eq_anon_const(l,r),
+    _ => false,
+  }
+}
+
 pub fn eq_assoc_constraint(l: &AssocConstraint, r: &AssocConstraint) -> bool {
     use AssocConstraintKind::*;
     eq_id(l.ident, r.ident)
         && match (&l.kind, &r.kind) {
-            (Equality { ty: l }, Equality { ty: r }) => eq_ty(l, r),
+            (Equality { term: l }, Equality { term: r }) => eq_term(l, r),
             (Bound { bounds: l }, Bound { bounds: r }) => over(l, r, eq_generic_bound),
-            (ConstEquality { c: l }, ConstEquality { c: r }) => eq_anon_const(l, r),
             _ => false,
         }
 }

src/tools/rustfmt/src/types.rs

@@ -1,7 +1,7 @@
 use std::iter::ExactSizeIterator;
 use std::ops::Deref;
 
-use rustc_ast::ast::{self, FnRetTy, Mutability};
+use rustc_ast::ast::{self, FnRetTy, Mutability, Term};
 use rustc_ast::ptr;
 use rustc_span::{symbol::kw, BytePos, Pos, Span};
 
@@ -178,7 +178,7 @@ impl<'a> Rewrite for SegmentParam<'a> {
 
 impl Rewrite for ast::AssocConstraint {
     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
-        use ast::AssocConstraintKind::{Bound, Equality, ConstEquality};
+        use ast::AssocConstraintKind::{Bound, Equality};
 
         let mut result = String::with_capacity(128);
         result.push_str(rewrite_ident(context, self.ident));
@@ -192,8 +192,8 @@ impl Rewrite for ast::AssocConstraint {
 
         let infix = match (&self.kind, context.config.type_punctuation_density()) {
             (Bound { .. }, _) => ": ",
-            (ConstEquality { .. } | Equality { .. }, TypeDensity::Wide) => " = ",
-            (ConstEquality { .. } | Equality { .. }, TypeDensity::Compressed) => "=",
+            (Equality { .. }, TypeDensity::Wide) => " = ",
+            (Equality { .. }, TypeDensity::Compressed) => "=",
         };
         result.push_str(infix);
 
@@ -209,8 +209,10 @@ impl Rewrite for ast::AssocConstraint {
 impl Rewrite for ast::AssocConstraintKind {
     fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
         match self {
-            ast::AssocConstraintKind::Equality { ty } => ty.rewrite(context, shape),
-            ast::AssocConstraintKind::ConstEquality { c } => c.rewrite(context, shape),
+            ast::AssocConstraintKind::Equality { term } => match term {
+                Term::Ty(ty) => ty.rewrite(context, shape),
+                Term::Const(c) => c.rewrite(context,shape),
+            },
             ast::AssocConstraintKind::Bound { bounds } => bounds.rewrite(context, shape),
         }
     }