Rework precise capturing syntax

compiler/rustc_ast/src/ast.rs

@@ -307,6 +307,8 @@ impl TraitBoundModifiers {
 pub enum GenericBound {
     Trait(PolyTraitRef, TraitBoundModifiers),
     Outlives(Lifetime),
+    /// Precise capturing syntax: `impl Sized + use<'a>`
+    Use(ThinVec<PreciseCapturingArg>, Span),
 }
 
 impl GenericBound {
@@ -314,6 +316,7 @@ impl GenericBound {
         match self {
             GenericBound::Trait(t, ..) => t.span,
             GenericBound::Outlives(l) => l.ident.span,
+            GenericBound::Use(_, span) => *span,
         }
     }
 }
@@ -2162,7 +2165,7 @@ pub enum TyKind {
     /// The `NodeId` exists to prevent lowering from having to
     /// generate `NodeId`s on the fly, which would complicate
     /// the generation of opaque `type Foo = impl Trait` items significantly.
-    ImplTrait(NodeId, GenericBounds, Option<P<(ThinVec<PreciseCapturingArg>, Span)>>),
+    ImplTrait(NodeId, GenericBounds),
     /// No-op; kept solely so that we can pretty-print faithfully.
     Paren(P<Ty>),
     /// Unused for now.

compiler/rustc_ast/src/mut_visit.rs

@@ -523,14 +523,9 @@ pub fn noop_visit_ty<T: MutVisitor>(ty: &mut P<Ty>, vis: &mut T) {
         TyKind::TraitObject(bounds, _syntax) => {
             visit_vec(bounds, |bound| vis.visit_param_bound(bound))
         }
-        TyKind::ImplTrait(id, bounds, precise_capturing) => {
+        TyKind::ImplTrait(id, bounds) => {
             vis.visit_id(id);
             visit_vec(bounds, |bound| vis.visit_param_bound(bound));
-            if let Some((precise_capturing, _span)) = precise_capturing.as_deref_mut() {
-                for arg in precise_capturing {
-                    vis.visit_precise_capturing_arg(arg);
-                }
-            }
         }
         TyKind::MacCall(mac) => vis.visit_mac_call(mac),
         TyKind::AnonStruct(id, fields) | TyKind::AnonUnion(id, fields) => {
@@ -923,6 +918,11 @@ fn noop_visit_param_bound<T: MutVisitor>(pb: &mut GenericBound, vis: &mut T) {
     match pb {
         GenericBound::Trait(ty, _modifier) => vis.visit_poly_trait_ref(ty),
         GenericBound::Outlives(lifetime) => noop_visit_lifetime(lifetime, vis),
+        GenericBound::Use(args, _) => {
+            for arg in args {
+                vis.visit_precise_capturing_arg(arg);
+            }
+        }
     }
 }
 

compiler/rustc_ast/src/util/classify.rs

@@ -184,7 +184,7 @@ fn type_trailing_braced_mac_call(mut ty: &ast::Ty) -> Option<&ast::MacCall> {
                 None => break None,
             },
 
-            ast::TyKind::TraitObject(bounds, _) | ast::TyKind::ImplTrait(_, bounds, _) => {
+            ast::TyKind::TraitObject(bounds, _) | ast::TyKind::ImplTrait(_, bounds) => {
                 match bounds.last() {
                     Some(ast::GenericBound::Trait(bound, _)) => {
                         match path_return_type(&bound.trait_ref.path) {
@@ -192,7 +192,9 @@ fn type_trailing_braced_mac_call(mut ty: &ast::Ty) -> Option<&ast::MacCall> {
                             None => break None,
                         }
                     }
-                    Some(ast::GenericBound::Outlives(_)) | None => break None,
+                    Some(ast::GenericBound::Outlives(_) | ast::GenericBound::Use(..)) | None => {
+                        break None;
+                    }
                 }
             }
 

compiler/rustc_ast/src/visit.rs

@@ -52,6 +52,16 @@ pub enum BoundKind {
     /// E.g., `trait A: B`
     SuperTraits,
 }
+impl BoundKind {
+    pub fn descr(self) -> &'static str {
+        match self {
+            BoundKind::Bound => "bounds",
+            BoundKind::Impl => "`impl Trait`",
+            BoundKind::TraitObject => "`dyn` trait object bounds",
+            BoundKind::SuperTraits => "supertrait bounds",
+        }
+    }
+}
 
 #[derive(Copy, Clone, Debug)]
 pub enum FnKind<'a> {
@@ -497,13 +507,8 @@ pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
         TyKind::TraitObject(bounds, ..) => {
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::TraitObject);
         }
-        TyKind::ImplTrait(_, bounds, precise_capturing) => {
+        TyKind::ImplTrait(_, bounds) => {
             walk_list!(visitor, visit_param_bound, bounds, BoundKind::Impl);
-            if let Some((precise_capturing, _span)) = precise_capturing.as_deref() {
-                for arg in precise_capturing {
-                    try_visit!(visitor.visit_precise_capturing_arg(arg));
-                }
-            }
         }
         TyKind::Typeof(expression) => try_visit!(visitor.visit_anon_const(expression)),
         TyKind::Infer | TyKind::ImplicitSelf | TyKind::Dummy | TyKind::Err(_) => {}
@@ -688,6 +693,10 @@ pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericB
     match bound {
         GenericBound::Trait(typ, _modifier) => visitor.visit_poly_trait_ref(typ),
         GenericBound::Outlives(lifetime) => visitor.visit_lifetime(lifetime, LifetimeCtxt::Bound),
+        GenericBound::Use(args, _) => {
+            walk_list!(visitor, visit_precise_capturing_arg, args);
+            V::Result::output()
+        }
     }
 }