Rollup merge of rust-lang#121563 - Jarcho:use_cf, r=petrochenkov

Use `ControlFlow` in visitors.

Follow up to rust-lang#121256

This does have a few small behaviour changes in some diagnostic output where the visitor will now find the first match rather than the last match. The change in `find_anon_types.rs` has the only affected test. I don't see this being an issue as the last occurrence isn't any better of a choice than the first.

compiler/rustc_ast_lowering/src/format.rs

@@ -1,4 +1,5 @@
 use super::LoweringContext;
+use core::ops::ControlFlow;
 use rustc_ast as ast;
 use rustc_ast::visit::Visitor;
 use rustc_ast::*;
@@ -594,30 +595,32 @@ fn expand_format_args<'hir>(
 }
 
 fn may_contain_yield_point(e: &ast::Expr) -> bool {
-    struct MayContainYieldPoint(bool);
+    struct MayContainYieldPoint;
 
     impl Visitor<'_> for MayContainYieldPoint {
-        fn visit_expr(&mut self, e: &ast::Expr) {
+        type Result = ControlFlow<()>;
+
+        fn visit_expr(&mut self, e: &ast::Expr) -> ControlFlow<()> {
             if let ast::ExprKind::Await(_, _) | ast::ExprKind::Yield(_) = e.kind {
-                self.0 = true;
+                ControlFlow::Break(())
             } else {
                 visit::walk_expr(self, e);
+                ControlFlow::Continue(())
             }
         }
 
-        fn visit_mac_call(&mut self, _: &ast::MacCall) {
+        fn visit_mac_call(&mut self, _: &ast::MacCall) -> ControlFlow<()> {
             // Macros should be expanded at this point.
             unreachable!("unexpanded macro in ast lowering");
         }
 
-        fn visit_item(&mut self, _: &ast::Item) {
+        fn visit_item(&mut self, _: &ast::Item) -> ControlFlow<()> {
             // Do not recurse into nested items.
+            ControlFlow::Continue(())
         }
     }
 
-    let mut visitor = MayContainYieldPoint(false);
-    visitor.visit_expr(e);
-    visitor.0
+    MayContainYieldPoint.visit_expr(e).is_break()
 }
 
 fn for_all_argument_indexes(template: &mut [FormatArgsPiece], mut f: impl FnMut(&mut usize)) {

compiler/rustc_borrowck/src/diagnostics/mutability_errors.rs

@@ -1,6 +1,7 @@
 #![allow(rustc::diagnostic_outside_of_impl)]
 #![allow(rustc::untranslatable_diagnostic)]
 
+use core::ops::ControlFlow;
 use hir::ExprKind;
 use rustc_errors::{Applicability, Diag};
 use rustc_hir as hir;
@@ -727,30 +728,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             _ => local_decl.source_info.span,
         };
 
-        struct BindingFinder {
-            span: Span,
-            hir_id: Option<hir::HirId>,
-        }
-
-        impl<'tcx> Visitor<'tcx> for BindingFinder {
-            fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
-                if let hir::StmtKind::Local(local) = s.kind {
-                    if local.pat.span == self.span {
-                        self.hir_id = Some(local.hir_id);
-                    }
-                }
-                hir::intravisit::walk_stmt(self, s);
-            }
-        }
-
         let def_id = self.body.source.def_id();
         let hir_id = if let Some(local_def_id) = def_id.as_local()
             && let Some(body_id) = self.infcx.tcx.hir().maybe_body_owned_by(local_def_id)
         {
             let body = self.infcx.tcx.hir().body(body_id);
-            let mut v = BindingFinder { span: pat_span, hir_id: None };
-            v.visit_body(body);
-            v.hir_id
+            BindingFinder { span: pat_span }.visit_body(body).break_value()
         } else {
             None
         };
@@ -859,17 +842,18 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         };
 
         let hir_map = self.infcx.tcx.hir();
-        struct Finder<'tcx> {
+        struct Finder {
             span: Span,
-            expr: Option<&'tcx Expr<'tcx>>,
         }
 
-        impl<'tcx> Visitor<'tcx> for Finder<'tcx> {
-            fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
-                if e.span == self.span && self.expr.is_none() {
-                    self.expr = Some(e);
+        impl<'tcx> Visitor<'tcx> for Finder {
+            type Result = ControlFlow<&'tcx Expr<'tcx>>;
+            fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) -> Self::Result {
+                if e.span == self.span {
+                    ControlFlow::Break(e)
+                } else {
+                    hir::intravisit::walk_expr(self, e)
                 }
-                hir::intravisit::walk_expr(self, e);
             }
         }
         if let Some(body_id) = hir_map.maybe_body_owned_by(self.mir_def_id())
@@ -878,9 +862,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             // `span` corresponds to the expression being iterated, find the `for`-loop desugared
             // expression with that span in order to identify potential fixes when encountering a
             // read-only iterator that should be mutable.
-            let mut v = Finder { span, expr: None };
-            v.visit_block(block);
-            if let Some(expr) = v.expr
+            if let ControlFlow::Break(expr) = (Finder { span }).visit_block(block)
                 && let Call(_, [expr]) = expr.kind
             {
                 match expr.kind {
@@ -1179,29 +1161,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 );
             }
             Some((false, err_label_span, message)) => {
-                struct BindingFinder {
-                    span: Span,
-                    hir_id: Option<hir::HirId>,
-                }
-
-                impl<'tcx> Visitor<'tcx> for BindingFinder {
-                    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) {
-                        if let hir::StmtKind::Local(local) = s.kind {
-                            if local.pat.span == self.span {
-                                self.hir_id = Some(local.hir_id);
-                            }
-                        }
-                        hir::intravisit::walk_stmt(self, s);
-                    }
-                }
                 let def_id = self.body.source.def_id();
                 let hir_id = if let Some(local_def_id) = def_id.as_local()
                     && let Some(body_id) = self.infcx.tcx.hir().maybe_body_owned_by(local_def_id)
                 {
                     let body = self.infcx.tcx.hir().body(body_id);
-                    let mut v = BindingFinder { span: err_label_span, hir_id: None };
-                    v.visit_body(body);
-                    v.hir_id
+                    BindingFinder { span: err_label_span }.visit_body(body).break_value()
                 } else {
                     None
                 };
@@ -1333,6 +1298,23 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     }
 }
 
+struct BindingFinder {
+    span: Span,
+}
+
+impl<'tcx> Visitor<'tcx> for BindingFinder {
+    type Result = ControlFlow<hir::HirId>;
+    fn visit_stmt(&mut self, s: &'tcx hir::Stmt<'tcx>) -> Self::Result {
+        if let hir::StmtKind::Local(local) = s.kind
+            && local.pat.span == self.span
+        {
+            ControlFlow::Break(local.hir_id)
+        } else {
+            hir::intravisit::walk_stmt(self, s)
+        }
+    }
+}
+
 pub fn mut_borrow_of_mutable_ref(local_decl: &LocalDecl<'_>, local_name: Option<Symbol>) -> bool {
     debug!("local_info: {:?}, ty.kind(): {:?}", local_decl.local_info, local_decl.ty.kind());
 

compiler/rustc_borrowck/src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(assert_matches)]
 #![feature(associated_type_bounds)]
 #![feature(box_patterns)]
+#![feature(control_flow_enum)]
 #![feature(let_chains)]
 #![feature(min_specialization)]
 #![feature(never_type)]

compiler/rustc_builtin_macros/src/cfg_eval.rs

@@ -1,5 +1,6 @@
 use crate::util::{check_builtin_macro_attribute, warn_on_duplicate_attribute};
 
+use core::ops::ControlFlow;
 use rustc_ast as ast;
 use rustc_ast::mut_visit::MutVisitor;
 use rustc_ast::ptr::P;
@@ -87,41 +88,40 @@ fn flat_map_annotatable(
     }
 }
 
-struct CfgFinder {
-    has_cfg_or_cfg_attr: bool,
-}
-
-impl CfgFinder {
-    fn has_cfg_or_cfg_attr(annotatable: &Annotatable) -> bool {
-        let mut finder = CfgFinder { has_cfg_or_cfg_attr: false };
-        match annotatable {
-            Annotatable::Item(item) => finder.visit_item(item),
-            Annotatable::TraitItem(item) => finder.visit_assoc_item(item, visit::AssocCtxt::Trait),
-            Annotatable::ImplItem(item) => finder.visit_assoc_item(item, visit::AssocCtxt::Impl),
-            Annotatable::ForeignItem(item) => finder.visit_foreign_item(item),
-            Annotatable::Stmt(stmt) => finder.visit_stmt(stmt),
-            Annotatable::Expr(expr) => finder.visit_expr(expr),
-            Annotatable::Arm(arm) => finder.visit_arm(arm),
-            Annotatable::ExprField(field) => finder.visit_expr_field(field),
-            Annotatable::PatField(field) => finder.visit_pat_field(field),
-            Annotatable::GenericParam(param) => finder.visit_generic_param(param),
-            Annotatable::Param(param) => finder.visit_param(param),
-            Annotatable::FieldDef(field) => finder.visit_field_def(field),
-            Annotatable::Variant(variant) => finder.visit_variant(variant),
-            Annotatable::Crate(krate) => finder.visit_crate(krate),
-        };
-        finder.has_cfg_or_cfg_attr
-    }
-}
+fn has_cfg_or_cfg_attr(annotatable: &Annotatable) -> bool {
+    struct CfgFinder;
 
-impl<'ast> visit::Visitor<'ast> for CfgFinder {
-    fn visit_attribute(&mut self, attr: &'ast Attribute) {
-        // We want short-circuiting behavior, so don't use the '|=' operator.
-        self.has_cfg_or_cfg_attr = self.has_cfg_or_cfg_attr
-            || attr
+    impl<'ast> visit::Visitor<'ast> for CfgFinder {
+        type Result = ControlFlow<()>;
+        fn visit_attribute(&mut self, attr: &'ast Attribute) -> ControlFlow<()> {
+            if attr
                 .ident()
-                .is_some_and(|ident| ident.name == sym::cfg || ident.name == sym::cfg_attr);
+                .is_some_and(|ident| ident.name == sym::cfg || ident.name == sym::cfg_attr)
+            {
+                ControlFlow::Break(())
+            } else {
+                ControlFlow::Continue(())
+            }
+        }
     }
+
+    let res = match annotatable {
+        Annotatable::Item(item) => CfgFinder.visit_item(item),
+        Annotatable::TraitItem(item) => CfgFinder.visit_assoc_item(item, visit::AssocCtxt::Trait),
+        Annotatable::ImplItem(item) => CfgFinder.visit_assoc_item(item, visit::AssocCtxt::Impl),
+        Annotatable::ForeignItem(item) => CfgFinder.visit_foreign_item(item),
+        Annotatable::Stmt(stmt) => CfgFinder.visit_stmt(stmt),
+        Annotatable::Expr(expr) => CfgFinder.visit_expr(expr),
+        Annotatable::Arm(arm) => CfgFinder.visit_arm(arm),
+        Annotatable::ExprField(field) => CfgFinder.visit_expr_field(field),
+        Annotatable::PatField(field) => CfgFinder.visit_pat_field(field),
+        Annotatable::GenericParam(param) => CfgFinder.visit_generic_param(param),
+        Annotatable::Param(param) => CfgFinder.visit_param(param),
+        Annotatable::FieldDef(field) => CfgFinder.visit_field_def(field),
+        Annotatable::Variant(variant) => CfgFinder.visit_variant(variant),
+        Annotatable::Crate(krate) => CfgFinder.visit_crate(krate),
+    };
+    res.is_break()
 }
 
 impl CfgEval<'_, '_> {
@@ -132,7 +132,7 @@ impl CfgEval<'_, '_> {
     fn configure_annotatable(&mut self, mut annotatable: Annotatable) -> Option<Annotatable> {
         // Tokenizing and re-parsing the `Annotatable` can have a significant
         // performance impact, so try to avoid it if possible
-        if !CfgFinder::has_cfg_or_cfg_attr(&annotatable) {
+        if !has_cfg_or_cfg_attr(&annotatable) {
             return Some(annotatable);
         }
 

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -1,6 +1,7 @@
 use crate::deriving::generic::ty::*;
 use crate::deriving::generic::*;
 use crate::errors;
+use core::ops::ControlFlow;
 use rustc_ast as ast;
 use rustc_ast::visit::walk_list;
 use rustc_ast::{attr, EnumDef, VariantData};
@@ -231,20 +232,19 @@ impl<'a, 'b> rustc_ast::visit::Visitor<'a> for DetectNonVariantDefaultAttr<'a, '
 }
 
 fn has_a_default_variant(item: &Annotatable) -> bool {
-    struct HasDefaultAttrOnVariant {
-        found: bool,
-    }
+    struct HasDefaultAttrOnVariant;
 
     impl<'ast> rustc_ast::visit::Visitor<'ast> for HasDefaultAttrOnVariant {
-        fn visit_variant(&mut self, v: &'ast rustc_ast::Variant) {
+        type Result = ControlFlow<()>;
+        fn visit_variant(&mut self, v: &'ast rustc_ast::Variant) -> ControlFlow<()> {
             if v.attrs.iter().any(|attr| attr.has_name(kw::Default)) {
-                self.found = true;
+                ControlFlow::Break(())
+            } else {
+                // no need to subrecurse.
+                ControlFlow::Continue(())
             }
-            // no need to subrecurse.
         }
     }
 
-    let mut visitor = HasDefaultAttrOnVariant { found: false };
-    item.visit_with(&mut visitor);
-    visitor.found
+    item.visit_with(&mut HasDefaultAttrOnVariant).is_break()
 }

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -1,5 +1,6 @@
 use super::potentially_plural_count;
 use crate::errors::{LifetimesOrBoundsMismatchOnTrait, MethodShouldReturnFuture};
+use core::ops::ControlFlow;
 use hir::def_id::{DefId, DefIdMap, LocalDefId};
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::{codes::*, pluralize, struct_span_code_err, Applicability, ErrorGuaranteed};
@@ -1565,24 +1566,24 @@ fn compare_synthetic_generics<'tcx>(
                     let (sig, _) = impl_m.expect_fn();
                     let input_tys = sig.decl.inputs;
 
-                    struct Visitor(Option<Span>, hir::def_id::LocalDefId);
+                    struct Visitor(hir::def_id::LocalDefId);
                     impl<'v> intravisit::Visitor<'v> for Visitor {
-                        fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
-                            intravisit::walk_ty(self, ty);
+                        type Result = ControlFlow<Span>;
+                        fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) -> Self::Result {
                             if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = ty.kind
                                 && let Res::Def(DefKind::TyParam, def_id) = path.res
-                                && def_id == self.1.to_def_id()
+                                && def_id == self.0.to_def_id()
                             {
-                                self.0 = Some(ty.span);
+                                ControlFlow::Break(ty.span)
+                            } else {
+                                intravisit::walk_ty(self, ty)
                             }
                         }
                     }
 
-                    let mut visitor = Visitor(None, impl_def_id);
-                    for ty in input_tys {
-                        intravisit::Visitor::visit_ty(&mut visitor, ty);
-                    }
-                    let span = visitor.0?;
+                    let span = input_tys.iter().find_map(|ty| {
+                        intravisit::Visitor::visit_ty(&mut Visitor(impl_def_id), ty).break_value()
+                    })?;
 
                     let bounds = impl_m.generics.bounds_for_param(impl_def_id).next()?.bounds;
                     let bounds = bounds.first()?.span().to(bounds.last()?.span());

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -6,6 +6,7 @@
 //! the types in HIR to identify late-bound lifetimes and assign their Debruijn indices. This file
 //! is also responsible for assigning their semantics to implicit lifetimes in trait objects.
 
+use core::ops::ControlFlow;
 use rustc_ast::visit::walk_list;
 use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_errors::{codes::*, struct_span_code_err};
@@ -417,23 +418,18 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
         {
             if let &hir::ClosureBinder::For { span: for_sp, .. } = binder {
                 fn span_of_infer(ty: &hir::Ty<'_>) -> Option<Span> {
-                    struct V(Option<Span>);
-
+                    struct V;
                     impl<'v> Visitor<'v> for V {
-                        fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
-                            match t.kind {
-                                _ if self.0.is_some() => (),
-                                hir::TyKind::Infer => {
-                                    self.0 = Some(t.span);
-                                }
-                                _ => intravisit::walk_ty(self, t),
+                        type Result = ControlFlow<Span>;
+                        fn visit_ty(&mut self, t: &'v hir::Ty<'v>) -> Self::Result {
+                            if matches!(t.kind, hir::TyKind::Infer) {
+                                ControlFlow::Break(t.span)
+                            } else {
+                                intravisit::walk_ty(self, t)
                             }
                         }
                     }
-
-                    let mut v = V(None);
-                    v.visit_ty(ty);
-                    v.0
+                    V.visit_ty(ty).break_value()
                 }
 
                 let infer_in_rt_sp = match fn_decl.output {