misc nameres changes for anon consts

compiler/rustc_ast/src/ast.rs

@@ -120,6 +120,12 @@ impl Path {
     pub fn is_global(&self) -> bool {
         !self.segments.is_empty() && self.segments[0].ident.name == kw::PathRoot
     }
+
+    /// If this path is a single identifier with no arguments, does not ensure
+    /// that the path resolves to a const param, the caller should check this.
+    pub fn is_potential_trivial_const_arg(&self) -> bool {
+        self.segments.len() == 1 && self.segments[0].args.is_none()
+    }
 }
 
 /// A segment of a path: an identifier, an optional lifetime, and a set of types.
@@ -1154,7 +1160,9 @@ impl Expr {
     ///
     /// If this is not the case, name resolution does not resolve `N` when using
     /// `min_const_generics` as more complex expressions are not supported.
-    pub fn is_potential_trivial_const_param(&self) -> bool {
+    ///
+    /// Does not ensure that the path resolves to a const param, the caller should check this.
+    pub fn is_potential_trivial_const_arg(&self) -> bool {
         let this = if let ExprKind::Block(block, None) = &self.kind
             && block.stmts.len() == 1
             && let StmtKind::Expr(expr) = &block.stmts[0].kind
@@ -1165,8 +1173,7 @@ impl Expr {
         };
 
         if let ExprKind::Path(None, path) = &this.kind
-            && path.segments.len() == 1
-            && path.segments[0].args.is_none()
+            && path.is_potential_trivial_const_arg()
         {
             true
         } else {

compiler/rustc_ast/src/visit.rs

@@ -188,6 +188,9 @@ pub trait Visitor<'ast>: Sized {
     fn visit_variant(&mut self, v: &'ast Variant) {
         walk_variant(self, v)
     }
+    fn visit_variant_discr(&mut self, discr: &'ast AnonConst) {
+        self.visit_anon_const(discr);
+    }
     fn visit_label(&mut self, label: &'ast Label) {
         walk_label(self, label)
     }
@@ -380,7 +383,7 @@ where
     visitor.visit_ident(variant.ident);
     visitor.visit_vis(&variant.vis);
     visitor.visit_variant_data(&variant.data);
-    walk_list!(visitor, visit_anon_const, &variant.disr_expr);
+    walk_list!(visitor, visit_variant_discr, &variant.disr_expr);
     walk_list!(visitor, visit_attribute, &variant.attrs);
 }
 

compiler/rustc_ast_lowering/src/lib.rs

@@ -1190,13 +1190,15 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     // parsing. We try to resolve that ambiguity by attempting resolution in both the
                     // type and value namespaces. If we resolved the path in the value namespace, we
                     // transform it into a generic const argument.
-                    TyKind::Path(qself, path) => {
+                    TyKind::Path(None, path) => {
                         if let Some(res) = self
                             .resolver
                             .get_partial_res(ty.id)
                             .and_then(|partial_res| partial_res.full_res())
                         {
-                            if !res.matches_ns(Namespace::TypeNS) {
+                            if !res.matches_ns(Namespace::TypeNS)
+                                && path.is_potential_trivial_const_arg()
+                            {
                                 debug!(
                                     "lower_generic_arg: Lowering type argument as const argument: {:?}",
                                     ty,
@@ -1218,7 +1220,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
                                 let path_expr = Expr {
                                     id: ty.id,
-                                    kind: ExprKind::Path(qself.clone(), path.clone()),
+                                    kind: ExprKind::Path(None, path.clone()),
                                     span,
                                     attrs: AttrVec::new(),
                                     tokens: None,

compiler/rustc_error_codes/src/error_codes/E0771.md

@@ -1,9 +1,11 @@
+#### Note: this error code is no longer emitted by the compiler
+
 A non-`'static` lifetime was used in a const generic. This is currently not
 allowed.
 
 Erroneous code example:
 
-```compile_fail,E0771
+```compile_fail,E0770
 #![feature(adt_const_params)]
 
 fn function_with_str<'a, const STRING: &'a str>() {} // error!

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -51,7 +51,15 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                 // of a const parameter type, e.g. `struct Foo<const N: usize, const M: [u8; N]>` is not allowed.
                 None
             } else if tcx.lazy_normalization() {
-                if let Some(param_id) = tcx.hir().opt_const_param_default_param_def_id(hir_id) {
+                let parent_node = tcx.hir().get_parent(hir_id);
+                if let Node::Variant(Variant { disr_expr: Some(constant), .. }) = parent_node
+                    && constant.hir_id == hir_id
+                {
+                    // enum variant discriminants are not allowed to use any kind of generics
+                    None
+                } else if let Some(param_id) =
+                    tcx.hir().opt_const_param_default_param_def_id(hir_id)
+                {
                     // If the def_id we are calling generics_of on is an anon ct default i.e:
                     //
                     // struct Foo<const N: usize = { .. }>;
@@ -94,15 +102,15 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                         has_self: generics.has_self,
                         has_late_bound_regions: generics.has_late_bound_regions,
                     };
+                } else {
+                    // HACK(eddyb) this provides the correct generics when
+                    // `feature(generic_const_expressions)` is enabled, so that const expressions
+                    // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
+                    //
+                    // Note that we do not supply the parent generics when using
+                    // `min_const_generics`.
+                    Some(parent_def_id.to_def_id())
                 }
-
-                // HACK(eddyb) this provides the correct generics when
-                // `feature(generic_const_expressions)` is enabled, so that const expressions
-                // used with const generics, e.g. `Foo<{N+1}>`, can work at all.
-                //
-                // Note that we do not supply the parent generics when using
-                // `min_const_generics`.
-                Some(parent_def_id.to_def_id())
             } else {
                 let parent_node = tcx.hir().get_parent(hir_id);
                 match parent_node {
@@ -115,11 +123,6 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     {
                         Some(parent_def_id.to_def_id())
                     }
-                    Node::Variant(Variant { disr_expr: Some(constant), .. })
-                        if constant.hir_id == hir_id =>
-                    {
-                        Some(parent_def_id.to_def_id())
-                    }
                     Node::Expr(&Expr { kind: ExprKind::ConstBlock(_), .. }) => {
                         Some(tcx.typeck_root_def_id(def_id.to_def_id()))
                     }

compiler/rustc_resolve/src/ident.rs

@@ -1188,11 +1188,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         }
 
                         RibKind::ConstantItem(trivial, _) => {
-                            let features = self.tcx.sess.features_untracked();
-                            // HACK(min_const_generics): We currently only allow `N` or `{ N }`.
-                            if !(trivial == ConstantHasGenerics::Yes
-                                || features.generic_const_exprs)
-                            {
+                            if let ConstantHasGenerics::No(cause) = trivial {
                                 // HACK(min_const_generics): If we encounter `Self` in an anonymous
                                 // constant we can't easily tell if it's generic at this stage, so
                                 // we instead remember this and then enforce the self type to be
@@ -1264,11 +1260,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         | RibKind::ForwardGenericParamBan => continue,
 
                         RibKind::ConstantItem(trivial, _) => {
-                            let features = self.tcx.sess.features_untracked();
-                            // HACK(min_const_generics): We currently only allow `N` or `{ N }`.
-                            if !(trivial == ConstantHasGenerics::Yes
-                                || features.generic_const_exprs)
-                            {
+                            if let ConstantHasGenerics::No(cause) = trivial {
                                 if let Some(span) = finalize {
                                     self.report_error(
                                         span,