expr_use_ctxt changes:

* Delay the parsing of the use node
* Mark when the `SyntaxContext` changes rather than return `None`
* Return a default value if the HIR tree is broken rather than `None`

clippy_lints/src/casts/ref_as_ptr.rs

@@ -22,9 +22,9 @@ pub(super) fn check<'tcx>(
 
     if matches!(cast_from.kind(), ty::Ref(..))
         && let ty::RawPtr(_, to_mutbl) = cast_to.kind()
-        && let Some(use_cx) = expr_use_ctxt(cx, expr)
+        && let use_cx = expr_use_ctxt(cx, expr)
         // TODO: only block the lint if `cast_expr` is a temporary
-        && !matches!(use_cx.node, ExprUseNode::LetStmt(_) | ExprUseNode::ConstStatic(_))
+        && !matches!(use_cx.use_node(cx), ExprUseNode::LetStmt(_) | ExprUseNode::ConstStatic(_))
     {
         let core_or_std = if is_no_std_crate(cx) { "core" } else { "std" };
         let fn_name = match to_mutbl {

clippy_lints/src/dereference.rs

@@ -260,18 +260,13 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
             (None, kind) => {
                 let expr_ty = typeck.expr_ty(expr);
                 let use_cx = expr_use_ctxt(cx, expr);
-                let adjusted_ty = match &use_cx {
+                let adjusted_ty = use_cx.adjustments.last().map_or(expr_ty, |a| a.target);
-                    Some(use_cx) => match use_cx.adjustments {
-                        [.., a] => a.target,
-                        _ => expr_ty,
-                    },
-                    _ => typeck.expr_ty_adjusted(expr),
-                };
 
-                match (use_cx, kind) {
+                match kind {
-                    (Some(use_cx), RefOp::Deref) => {
+                    RefOp::Deref if use_cx.same_ctxt => {
+                        let use_node = use_cx.use_node(cx);
                         let sub_ty = typeck.expr_ty(sub_expr);
-                        if let ExprUseNode::FieldAccess(name) = use_cx.node
+                        if let ExprUseNode::FieldAccess(name) = use_node
                             && !use_cx.moved_before_use
                             && !ty_contains_field(sub_ty, name.name)
                         {
@@ -288,9 +283,9 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                         } else if sub_ty.is_ref()
                             // Linting method receivers would require verifying that name lookup
                             // would resolve the same way. This is complicated by trait methods.
-                            && !use_cx.node.is_recv()
+                            && !use_node.is_recv()
-                            && let Some(ty) = use_cx.node.defined_ty(cx)
+                            && let Some(ty) = use_node.defined_ty(cx)
-                            && TyCoercionStability::for_defined_ty(cx, ty, use_cx.node.is_return()).is_deref_stable()
+                            && TyCoercionStability::for_defined_ty(cx, ty, use_node.is_return()).is_deref_stable()
                         {
                             self.state = Some((
                                 State::ExplicitDeref { mutability: None },
@@ -301,7 +296,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                             ));
                         }
                     },
-                    (_, RefOp::Method { mutbl, is_ufcs })
+                    RefOp::Method { mutbl, is_ufcs }
                         if !is_lint_allowed(cx, EXPLICIT_DEREF_METHODS, expr.hir_id)
                             // Allow explicit deref in method chains. e.g. `foo.deref().bar()`
                             && (is_ufcs || !in_postfix_position(cx, expr)) =>
@@ -319,7 +314,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                             },
                         ));
                     },
-                    (Some(use_cx), RefOp::AddrOf(mutability)) => {
+                    RefOp::AddrOf(mutability) if use_cx.same_ctxt => {
                         // Find the number of times the borrow is auto-derefed.
                         let mut iter = use_cx.adjustments.iter();
                         let mut deref_count = 0usize;
@@ -338,10 +333,11 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                             };
                         };
 
-                        let stability = use_cx.node.defined_ty(cx).map_or(TyCoercionStability::None, |ty| {
+                        let use_node = use_cx.use_node(cx);
-                            TyCoercionStability::for_defined_ty(cx, ty, use_cx.node.is_return())
+                        let stability = use_node.defined_ty(cx).map_or(TyCoercionStability::None, |ty| {
+                            TyCoercionStability::for_defined_ty(cx, ty, use_node.is_return())
                         });
-                        let can_auto_borrow = match use_cx.node {
+                        let can_auto_borrow = match use_node {
                             ExprUseNode::FieldAccess(_)
                                 if !use_cx.moved_before_use && matches!(sub_expr.kind, ExprKind::Field(..)) =>
                             {
@@ -353,7 +349,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                                 // deref through `ManuallyDrop<_>` will not compile.
                                 !adjust_derefs_manually_drop(use_cx.adjustments, expr_ty)
                             },
-                            ExprUseNode::Callee | ExprUseNode::FieldAccess(_) => true,
+                            ExprUseNode::Callee | ExprUseNode::FieldAccess(_) if !use_cx.moved_before_use => true,
                             ExprUseNode::MethodArg(hir_id, _, 0) if !use_cx.moved_before_use => {
                                 // Check for calls to trait methods where the trait is implemented
                                 // on a reference.
@@ -363,9 +359,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                                 //   priority.
                                 if let Some(fn_id) = typeck.type_dependent_def_id(hir_id)
                                     && let Some(trait_id) = cx.tcx.trait_of_item(fn_id)
-                                    && let arg_ty = cx
+                                    && let arg_ty = cx.tcx.erase_regions(adjusted_ty)
-                                        .tcx
-                                        .erase_regions(use_cx.adjustments.last().map_or(expr_ty, |a| a.target))
                                     && let ty::Ref(_, sub_ty, _) = *arg_ty.kind()
                                     && let args =
                                         typeck.node_args_opt(hir_id).map(|args| &args[1..]).unwrap_or_default()
@@ -443,7 +437,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                                     count: deref_count - required_refs,
                                     msg,
                                     stability,
-                                    for_field_access: if let ExprUseNode::FieldAccess(name) = use_cx.node
+                                    for_field_access: if let ExprUseNode::FieldAccess(name) = use_node
                                         && !use_cx.moved_before_use
                                     {
                                         Some(name.name)
@@ -453,7 +447,7 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                                 }),
                                 StateData {
                                     first_expr: expr,
-                                    adjusted_ty: use_cx.adjustments.last().map_or(expr_ty, |a| a.target),
+                                    adjusted_ty,
                                 },
                             ));
                         } else if stability.is_deref_stable()
@@ -465,12 +459,12 @@ impl<'tcx> LateLintPass<'tcx> for Dereferencing<'tcx> {
                                 State::Borrow { mutability },
                                 StateData {
                                     first_expr: expr,
-                                    adjusted_ty: use_cx.adjustments.last().map_or(expr_ty, |a| a.target),
+                                    adjusted_ty,
                                 },
                             ));
                         }
                     },
-                    (None, _) | (_, RefOp::Method { .. }) => (),
+                    _ => {},
                 }
             },
             (

clippy_lints/src/needless_borrows_for_generic_args.rs

@@ -80,11 +80,13 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessBorrowsForGenericArgs<'tcx> {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         if matches!(expr.kind, ExprKind::AddrOf(..))
             && !expr.span.from_expansion()
-            && let Some(use_cx) = expr_use_ctxt(cx, expr)
+            && let use_cx = expr_use_ctxt(cx, expr)
+            && use_cx.same_ctxt
             && !use_cx.is_ty_unified
-            && let Some(DefinedTy::Mir(ty)) = use_cx.node.defined_ty(cx)
+            && let use_node = use_cx.use_node(cx)
+            && let Some(DefinedTy::Mir(ty)) = use_node.defined_ty(cx)
             && let ty::Param(ty) = *ty.value.skip_binder().kind()
-            && let Some((hir_id, fn_id, i)) = match use_cx.node {
+            && let Some((hir_id, fn_id, i)) = match use_node {
                 ExprUseNode::MethodArg(_, _, 0) => None,
                 ExprUseNode::MethodArg(hir_id, None, i) => cx
                     .typeck_results()

clippy_utils/src/lib.rs

@@ -1,6 +1,7 @@
 #![feature(array_chunks)]
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
+#![feature(exhaustive_patterns)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
 #![feature(lint_reasons)]
@@ -2664,13 +2665,80 @@ pub enum DefinedTy<'tcx> {
 /// The context an expressions value is used in.
 pub struct ExprUseCtxt<'tcx> {
     /// The parent node which consumes the value.
-    pub node: ExprUseNode<'tcx>,
+    pub node: Node<'tcx>,
+    /// The child id of the node the value came from.
+    pub child_id: HirId,
     /// Any adjustments applied to the type.
     pub adjustments: &'tcx [Adjustment<'tcx>],
-    /// Whether or not the type must unify with another code path.
+    /// Whether the type must unify with another code path.
     pub is_ty_unified: bool,
-    /// Whether or not the value will be moved before it's used.
+    /// Whether the value will be moved before it's used.
     pub moved_before_use: bool,
+    /// Whether the use site has the same `SyntaxContext` as the value.
+    pub same_ctxt: bool,
+}
+impl<'tcx> ExprUseCtxt<'tcx> {
+    pub fn use_node(&self, cx: &LateContext<'tcx>) -> ExprUseNode<'tcx> {
+        match self.node {
+            Node::LetStmt(l) => ExprUseNode::LetStmt(l),
+            Node::ExprField(field) => ExprUseNode::Field(field),
+
+            Node::Item(&Item {
+                kind: ItemKind::Static(..) | ItemKind::Const(..),
+                owner_id,
+                ..
+            })
+            | Node::TraitItem(&TraitItem {
+                kind: TraitItemKind::Const(..),
+                owner_id,
+                ..
+            })
+            | Node::ImplItem(&ImplItem {
+                kind: ImplItemKind::Const(..),
+                owner_id,
+                ..
+            }) => ExprUseNode::ConstStatic(owner_id),
+
+            Node::Item(&Item {
+                kind: ItemKind::Fn(..),
+                owner_id,
+                ..
+            })
+            | Node::TraitItem(&TraitItem {
+                kind: TraitItemKind::Fn(..),
+                owner_id,
+                ..
+            })
+            | Node::ImplItem(&ImplItem {
+                kind: ImplItemKind::Fn(..),
+                owner_id,
+                ..
+            }) => ExprUseNode::Return(owner_id),
+
+            Node::Expr(use_expr) => match use_expr.kind {
+                ExprKind::Ret(_) => ExprUseNode::Return(OwnerId {
+                    def_id: cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()),
+                }),
+
+                ExprKind::Closure(closure) => ExprUseNode::Return(OwnerId { def_id: closure.def_id }),
+                ExprKind::Call(func, args) => match args.iter().position(|arg| arg.hir_id == self.child_id) {
+                    Some(i) => ExprUseNode::FnArg(func, i),
+                    None => ExprUseNode::Callee,
+                },
+                ExprKind::MethodCall(name, _, args, _) => ExprUseNode::MethodArg(
+                    use_expr.hir_id,
+                    name.args,
+                    args.iter()
+                        .position(|arg| arg.hir_id == self.child_id)
+                        .map_or(0, |i| i + 1),
+                ),
+                ExprKind::Field(_, name) => ExprUseNode::FieldAccess(name),
+                ExprKind::AddrOf(kind, mutbl, _) => ExprUseNode::AddrOf(kind, mutbl),
+                _ => ExprUseNode::Other,
+            },
+            _ => ExprUseNode::Other,
+        }
+    }
 }
 
 /// The node which consumes a value.
@@ -2691,7 +2759,8 @@ pub enum ExprUseNode<'tcx> {
     Callee,
     /// Access of a field.
     FieldAccess(Ident),
-    Expr,
+    /// Borrow expression.
+    AddrOf(ast::BorrowKind, Mutability),
     Other,
 }
 impl<'tcx> ExprUseNode<'tcx> {
@@ -2768,26 +2837,25 @@ impl<'tcx> ExprUseNode<'tcx> {
                 let sig = cx.tcx.fn_sig(id).skip_binder();
                 Some(DefinedTy::Mir(cx.tcx.param_env(id).and(sig.input(i))))
             },
-            Self::LetStmt(_) | Self::FieldAccess(..) | Self::Callee | Self::Expr | Self::Other => None,
+            Self::LetStmt(_) | Self::FieldAccess(..) | Self::Callee | Self::Other | Self::AddrOf(..) => None,
         }
     }
 }
 
 /// Gets the context an expression's value is used in.
-pub fn expr_use_ctxt<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> Option<ExprUseCtxt<'tcx>> {
+pub fn expr_use_ctxt<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> ExprUseCtxt<'tcx> {
     let mut adjustments = [].as_slice();
     let mut is_ty_unified = false;
     let mut moved_before_use = false;
+    let mut same_ctxt = true;
     let ctxt = e.span.ctxt();
-    walk_to_expr_usage(cx, e, &mut |parent_id, parent, child_id| {
+    let node = walk_to_expr_usage(cx, e, &mut |parent_id, parent, child_id| -> ControlFlow<!> {
         if adjustments.is_empty()
             && let Node::Expr(e) = cx.tcx.hir_node(child_id)
         {
             adjustments = cx.typeck_results().expr_adjustments(e);
         }
-        if cx.tcx.hir().span(parent_id).ctxt() != ctxt {
+        same_ctxt &= cx.tcx.hir().span(parent_id).ctxt() == ctxt;
-            return ControlFlow::Break(());
-        }
         if let Node::Expr(e) = parent {
             match e.kind {
                 ExprKind::If(e, _, _) | ExprKind::Match(e, _, _) if e.hir_id != child_id => {
@@ -2803,71 +2871,25 @@ pub fn expr_use_ctxt<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> Optio
             }
         }
         ControlFlow::Continue(())
-    })?
+    });
-    .continue_value()
+    match node {
-    .map(|(use_node, child_id)| {
+        Some(ControlFlow::Continue((node, child_id))) => ExprUseCtxt {
-        let node = match use_node {
-            Node::LetStmt(l) => ExprUseNode::LetStmt(l),
-            Node::ExprField(field) => ExprUseNode::Field(field),
-
-            Node::Item(&Item {
-                kind: ItemKind::Static(..) | ItemKind::Const(..),
-                owner_id,
-                ..
-            })
-            | Node::TraitItem(&TraitItem {
-                kind: TraitItemKind::Const(..),
-                owner_id,
-                ..
-            })
-            | Node::ImplItem(&ImplItem {
-                kind: ImplItemKind::Const(..),
-                owner_id,
-                ..
-            }) => ExprUseNode::ConstStatic(owner_id),
-
-            Node::Item(&Item {
-                kind: ItemKind::Fn(..),
-                owner_id,
-                ..
-            })
-            | Node::TraitItem(&TraitItem {
-                kind: TraitItemKind::Fn(..),
-                owner_id,
-                ..
-            })
-            | Node::ImplItem(&ImplItem {
-                kind: ImplItemKind::Fn(..),
-                owner_id,
-                ..
-            }) => ExprUseNode::Return(owner_id),
-
-            Node::Expr(use_expr) => match use_expr.kind {
-                ExprKind::Ret(_) => ExprUseNode::Return(OwnerId {
-                    def_id: cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()),
-                }),
-                ExprKind::Closure(closure) => ExprUseNode::Return(OwnerId { def_id: closure.def_id }),
-                ExprKind::Call(func, args) => match args.iter().position(|arg| arg.hir_id == child_id) {
-                    Some(i) => ExprUseNode::FnArg(func, i),
-                    None => ExprUseNode::Callee,
-                },
-                ExprKind::MethodCall(name, _, args, _) => ExprUseNode::MethodArg(
-                    use_expr.hir_id,
-                    name.args,
-                    args.iter().position(|arg| arg.hir_id == child_id).map_or(0, |i| i + 1),
-                ),
-                ExprKind::Field(child, name) if child.hir_id == e.hir_id => ExprUseNode::FieldAccess(name),
-                _ => ExprUseNode::Expr,
-            },
-            _ => ExprUseNode::Other,
-        };
-        ExprUseCtxt {
             node,
+            child_id,
             adjustments,
             is_ty_unified,
             moved_before_use,
-        }
+            same_ctxt,
-    })
+        },
+        None => ExprUseCtxt {
+            node: Node::Crate(cx.tcx.hir().root_module()),
+            child_id: HirId::INVALID,
+            adjustments: &[],
+            is_ty_unified: true,
+            moved_before_use: true,
+            same_ctxt: false,
+        },
+    }
 }
 
 /// Tokenizes the input while keeping the text associated with each token.