Add generic arg infer

Author: JulianKnodt

compiler/rustc_ast/src/ast.rs

@@ -336,14 +336,15 @@ pub enum ParamKindOrd {
     // is active. Specifically, if it's only `min_const_generics`, it will still require
     // ordering consts after types.
     Const { unordered: bool },
+    Infer,
 }
 
 impl Ord for ParamKindOrd {
     fn cmp(&self, other: &Self) -> Ordering {
         use ParamKindOrd::*;
         let to_int = |v| match v {
             Lifetime => 0,
-            Type | Const { unordered: true } => 1,
+            Infer | Type | Const { unordered: true } => 1,
             // technically both consts should be ordered equally,
             // but only one is ever encountered at a time, so this is
             // fine.
@@ -371,6 +372,7 @@ impl fmt::Display for ParamKindOrd {
             ParamKindOrd::Lifetime => "lifetime".fmt(f),
             ParamKindOrd::Type => "type".fmt(f),
             ParamKindOrd::Const { .. } => "const".fmt(f),
+            ParamKindOrd::Infer => "infer".fmt(f),
         }
     }
 }

compiler/rustc_ast_lowering/src/lib.rs

@@ -1218,48 +1218,55 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         match arg {
             ast::GenericArg::Lifetime(lt) => GenericArg::Lifetime(self.lower_lifetime(&lt)),
             ast::GenericArg::Type(ty) => {
-                // We parse const arguments as path types as we cannot distinguish them during
-                // 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.
-                if let TyKind::Path(ref qself, ref path) = ty.kind {
-                    if let Some(partial_res) = self.resolver.get_partial_res(ty.id) {
-                        let res = partial_res.base_res();
-                        if !res.matches_ns(Namespace::TypeNS) {
-                            debug!(
-                                "lower_generic_arg: Lowering type argument as const argument: {:?}",
-                                ty,
-                            );
-
-                            // Construct a AnonConst where the expr is the "ty"'s path.
-
-                            let parent_def_id = self.current_hir_id_owner.0;
-                            let node_id = self.resolver.next_node_id();
-
-                            // Add a definition for the in-band const def.
-                            self.resolver.create_def(
-                                parent_def_id,
-                                node_id,
-                                DefPathData::AnonConst,
-                                ExpnId::root(),
-                                ty.span,
-                            );
-
-                            let path_expr = Expr {
-                                id: ty.id,
-                                kind: ExprKind::Path(qself.clone(), path.clone()),
-                                span: ty.span,
-                                attrs: AttrVec::new(),
-                                tokens: None,
-                            };
-
-                            let ct = self.with_new_scopes(|this| hir::AnonConst {
-                                hir_id: this.lower_node_id(node_id),
-                                body: this.lower_const_body(path_expr.span, Some(&path_expr)),
-                            });
-                            return GenericArg::Const(ConstArg { value: ct, span: ty.span });
+                match ty.kind {
+                    TyKind::Infer => {
+                        let hir_id = self.lower_node_id(ty.id);
+                        return GenericArg::Infer(hir::InferArg { hir_id, span: ty.span });
+                    }
+                    // We parse const arguments as path types as we cannot distinguish them during
+                    // 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(ref qself, ref path) => {
+                        if let Some(partial_res) = self.resolver.get_partial_res(ty.id) {
+                            let res = partial_res.base_res();
+                            if !res.matches_ns(Namespace::TypeNS) {
+                                debug!(
+                                    "lower_generic_arg: Lowering type argument as const argument: {:?}",
+                                    ty,
+                                );
+
+                                // Construct a AnonConst where the expr is the "ty"'s path.
+
+                                let parent_def_id = self.current_hir_id_owner.0;
+                                let node_id = self.resolver.next_node_id();
+
+                                // Add a definition for the in-band const def.
+                                self.resolver.create_def(
+                                    parent_def_id,
+                                    node_id,
+                                    DefPathData::AnonConst,
+                                    ExpnId::root(),
+                                    ty.span,
+                                );
+
+                                let path_expr = Expr {
+                                    id: ty.id,
+                                    kind: ExprKind::Path(qself.clone(), path.clone()),
+                                    span: ty.span,
+                                    attrs: AttrVec::new(),
+                                    tokens: None,
+                                };
+
+                                let ct = self.with_new_scopes(|this| hir::AnonConst {
+                                    hir_id: this.lower_node_id(node_id),
+                                    body: this.lower_const_body(path_expr.span, Some(&path_expr)),
+                                });
+                                return GenericArg::Const(ConstArg { value: ct, span: ty.span });
+                            }
                         }
                     }
+                    _ => {}
                 }
                 GenericArg::Type(self.lower_ty_direct(&ty, itctx))
             }

compiler/rustc_hir/src/hir.rs

@@ -253,11 +253,24 @@ pub struct ConstArg {
     pub span: Span,
 }
 
+#[derive(Encodable, Debug, HashStable_Generic)]
+pub struct InferArg {
+    pub hir_id: HirId,
+    pub span: Span,
+}
+
+impl InferArg {
+    pub fn to_ty(&self) -> Ty<'_> {
+        Ty { kind: TyKind::Infer, span: self.span, hir_id: self.hir_id }
+    }
+}
+
 #[derive(Debug, HashStable_Generic)]
 pub enum GenericArg<'hir> {
     Lifetime(Lifetime),
     Type(Ty<'hir>),
     Const(ConstArg),
+    Infer(InferArg),
 }
 
 impl GenericArg<'_> {
@@ -266,6 +279,7 @@ impl GenericArg<'_> {
             GenericArg::Lifetime(l) => l.span,
             GenericArg::Type(t) => t.span,
             GenericArg::Const(c) => c.span,
+            GenericArg::Infer(i) => i.span,
         }
     }
 
@@ -274,6 +288,7 @@ impl GenericArg<'_> {
             GenericArg::Lifetime(l) => l.hir_id,
             GenericArg::Type(t) => t.hir_id,
             GenericArg::Const(c) => c.value.hir_id,
+            GenericArg::Infer(i) => i.hir_id,
         }
     }
 
@@ -290,6 +305,7 @@ impl GenericArg<'_> {
             GenericArg::Lifetime(_) => "lifetime",
             GenericArg::Type(_) => "type",
             GenericArg::Const(_) => "constant",
+            GenericArg::Infer(_) => "inferred",
         }
     }
 
@@ -300,6 +316,7 @@ impl GenericArg<'_> {
             GenericArg::Const(_) => {
                 ast::ParamKindOrd::Const { unordered: feats.unordered_const_ty_params() }
             }
+            GenericArg::Infer(_) => ast::ParamKindOrd::Infer,
         }
     }
 }
@@ -341,6 +358,7 @@ impl GenericArgs<'_> {
                         break;
                     }
                     GenericArg::Const(_) => {}
+                    GenericArg::Infer(_) => {}
                 }
             }
         }
@@ -358,6 +376,7 @@ impl GenericArgs<'_> {
                 GenericArg::Lifetime(_) => own_counts.lifetimes += 1,
                 GenericArg::Type(_) => own_counts.types += 1,
                 GenericArg::Const(_) => own_counts.consts += 1,
+                GenericArg::Infer(_) => own_counts.infer += 1,
             };
         }
 
@@ -484,6 +503,7 @@ pub struct GenericParamCount {
     pub lifetimes: usize,
     pub types: usize,
     pub consts: usize,
+    pub infer: usize,
 }
 
 /// Represents lifetimes and type parameters attached to a declaration
@@ -2987,6 +3007,8 @@ pub enum Node<'hir> {
     Visibility(&'hir Visibility<'hir>),
 
     Crate(&'hir Mod<'hir>),
+
+    Infer(&'hir InferArg),
 }
 
 impl<'hir> Node<'hir> {
@@ -3055,6 +3077,7 @@ impl<'hir> Node<'hir> {
             | Node::Local(Local { hir_id, .. })
             | Node::Lifetime(Lifetime { hir_id, .. })
             | Node::Param(Param { hir_id, .. })
+            | Node::Infer(InferArg { hir_id, .. })
             | Node::GenericParam(GenericParam { hir_id, .. }) => Some(*hir_id),
             Node::TraitRef(TraitRef { hir_ref_id, .. }) => Some(*hir_ref_id),
             Node::PathSegment(PathSegment { hir_id, .. }) => *hir_id,

compiler/rustc_hir/src/intravisit.rs

@@ -436,13 +436,22 @@ pub trait Visitor<'v>: Sized {
     fn visit_label(&mut self, label: &'v Label) {
         walk_label(self, label)
     }
+    fn visit_infer(&mut self, inf: &'v InferArg) {
+        self.visit_id(inf.hir_id);
+    }
     fn visit_generic_arg(&mut self, generic_arg: &'v GenericArg<'v>) {
         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),
+            GenericArg::Infer(inf) => self.visit_infer(inf),
         }
     }
+    /*
+    fn tcx(&self) -> Option<&TyCtxt<'tcx>> {
+        None
+    }
+    */
     fn visit_lifetime(&mut self, lifetime: &'v Lifetime) {
         walk_lifetime(self, lifetime)
     }
@@ -746,6 +755,10 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v>) {
     }
 }
 
+pub fn walk_inf<'v, V: Visitor<'v>>(visitor: &mut V, inf: &'v InferArg) {
+    visitor.visit_id(inf.hir_id);
+}
+
 pub fn walk_qpath<'v, V: Visitor<'v>>(
     visitor: &mut V,
     qpath: &'v QPath<'v>,

compiler/rustc_hir_pretty/src/lib.rs

@@ -103,6 +103,7 @@ impl<'a> State<'a> {
             Node::TraitRef(a) => self.print_trait_ref(&a),
             Node::Binding(a) | Node::Pat(a) => self.print_pat(&a),
             Node::Arm(a) => self.print_arm(&a),
+            Node::Infer(_) => self.print_string("_", ast::StrStyle::Cooked),
             Node::Block(a) => {
                 // Containing cbox, will be closed by print-block at `}`.
                 self.cbox(INDENT_UNIT);
@@ -437,14 +438,14 @@ impl<'a> State<'a> {
                 self.print_anon_const(e);
                 self.s.word(")");
             }
-            hir::TyKind::Infer => {
-                self.s.word("_");
-            }
             hir::TyKind::Err => {
                 self.popen();
                 self.s.word("/*ERROR*/");
                 self.pclose();
             }
+            hir::TyKind::Infer => {
+                self.s.word("_");
+            }
         }
         self.end()
     }
@@ -1851,6 +1852,7 @@ impl<'a> State<'a> {
                         GenericArg::Lifetime(_) => {}
                         GenericArg::Type(ty) => s.print_type(ty),
                         GenericArg::Const(ct) => s.print_anon_const(&ct.value),
+                        GenericArg::Infer(_inf) => s.word("_"),
                     },
                 );
             }

compiler/rustc_middle/src/hir/map/collector.rs

@@ -404,6 +404,14 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
         });
     }
 
+    fn visit_infer(&mut self, inf: &'hir InferArg) {
+        self.insert(inf.span, inf.hir_id, Node::Infer(inf));
+
+        self.with_parent(inf.hir_id, |this| {
+            intravisit::walk_inf(this, inf);
+        });
+    }
+
     fn visit_trait_ref(&mut self, tr: &'hir TraitRef<'hir>) {
         self.insert(tr.path.span, tr.hir_ref_id, Node::TraitRef(tr));
 

compiler/rustc_middle/src/hir/map/mod.rs

@@ -272,6 +272,7 @@ impl<'hir> Map<'hir> {
                 GenericParamKind::Type { .. } => DefKind::TyParam,
                 GenericParamKind::Const { .. } => DefKind::ConstParam,
             },
+            Node::Infer(_) => todo!(),
             Node::Crate(_) => DefKind::Mod,
             Node::Stmt(_)
             | Node::PathSegment(_)
@@ -882,6 +883,7 @@ impl<'hir> Map<'hir> {
                 node: VisibilityKind::Restricted { ref path, .. },
                 ..
             }) => path.span,
+            Node::Infer(i) => i.span,
             Node::Visibility(v) => bug!("unexpected Visibility {:?}", v),
             Node::Local(local) => local.span,
             Node::MacroDef(macro_def) => macro_def.span,
@@ -1129,6 +1131,7 @@ fn hir_id_to_string(map: &Map<'_>, id: HirId) -> String {
         Some(Node::Param(_)) => node_str("param"),
         Some(Node::Arm(_)) => node_str("arm"),
         Some(Node::Block(_)) => node_str("block"),
+        Some(Node::Infer(_)) => node_str("infer"),
         Some(Node::Local(_)) => node_str("local"),
         Some(Node::Ctor(..)) => format!("ctor {}{}", path_str(), id_str),
         Some(Node::Lifetime(_)) => node_str("lifetime"),

compiler/rustc_middle/src/query/mod.rs

@@ -133,6 +133,11 @@ rustc_queries! {
         cache_on_disk_if { key.is_local() }
     }
 
+    query generic_arg_for_infer_arg(key: DefId) -> hir::GenericArg<'tcx> {
+        desc { |tcx| "computes concrete type for inference, `{}`", tcx.def_path_str(key) }
+        storage(ArenaCacheSelector<'tcx>)
+    }
+
     /// Maps from the `DefId` of an item (trait/struct/enum/fn) to the
     /// predicates (where-clauses) that must be proven true in order
     /// to reference it. This is almost always the "predicates query"

compiler/rustc_privacy/src/lib.rs

@@ -1188,6 +1188,23 @@ impl<'tcx> Visitor<'tcx> for TypePrivacyVisitor<'tcx> {
         self.maybe_typeck_results = old_maybe_typeck_results;
     }
 
+    fn visit_generic_arg(&mut self, generic_arg: &'tcx hir::GenericArg<'tcx>) {
+        match generic_arg {
+            hir::GenericArg::Type(t) => self.visit_ty(t),
+            hir::GenericArg::Infer(inf) => {
+                self.span = inf.span;
+                let parent_hir_id = self.tcx.hir().get_parent_node(inf.hir_id);
+                if let Some(typeck_results) = self.maybe_typeck_results {
+                    let node_substs = typeck_results.node_substs(parent_hir_id);
+                    for ty in node_substs.types() {
+                        self.visit(ty);
+                    }
+                }
+            }
+            hir::GenericArg::Lifetime(_) | hir::GenericArg::Const(_) => {}
+        }
+    }
+
     fn visit_ty(&mut self, hir_ty: &'tcx hir::Ty<'tcx>) {
         self.span = hir_ty.span;
         if let Some(typeck_results) = self.maybe_typeck_results {
@@ -1443,6 +1460,14 @@ impl<'a, 'b, 'tcx, 'v> Visitor<'v> for ObsoleteCheckTypeForPrivatenessVisitor<'a
         NestedVisitorMap::None
     }
 
+    fn visit_generic_arg(&mut self, generic_arg: &'v hir::GenericArg<'v>) {
+        match generic_arg {
+            hir::GenericArg::Type(t) => self.visit_ty(t),
+            hir::GenericArg::Infer(inf) => self.visit_ty(&inf.to_ty()),
+            hir::GenericArg::Lifetime(_) | hir::GenericArg::Const(_) => {}
+        }
+    }
+
     fn visit_ty(&mut self, ty: &hir::Ty<'_>) {
         if let hir::TyKind::Path(hir::QPath::Resolved(_, ref path)) = ty.kind {
             if self.inner.path_is_private_type(path) {

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -2557,6 +2557,10 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                 GenericArg::Const(ct) => {
                     self.visit_anon_const(&ct.value);
                 }
+                GenericArg::Infer(inf) => {
+                    self.visit_id(inf.hir_id);
+                    i += 1;
+                }
             }
         }