Rollup merge of rust-lang#81176 - camsteffen:qpath-res, r=oli-obk

Improve safety of `LateContext::qpath_res`

This is my first rustc code change, inspired by hacking on clippy!

The first change is to clear cached `TypeckResults` from `LateContext` when visiting a nested item. I took a hint from [here](https://github.com/rust-lang/rust/blob/5e91c4ecc09312d8b63d250a432b0f3ef83f1df7/compiler/rustc_privacy/src/lib.rs#L1300).

Clippy has a `qpath_res` util function to avoid a possible ICE in `LateContext::qpath_res`. But the docs of `LateContext::qpath_res` promise no ICE. So this updates the `LateContext` method to keep its promises, and removes the util function.

Related: rust-lang/rust-clippy#4545

CC ````````````@eddyb```````````` since you've done related work
CC ````````````@flip1995```````````` FYI

Author: JohnTitor

compiler/rustc_lint/src/context.rs

@@ -746,6 +746,14 @@ impl<'tcx> LateContext<'tcx> {
             hir::QPath::Resolved(_, ref path) => path.res,
             hir::QPath::TypeRelative(..) | hir::QPath::LangItem(..) => self
                 .maybe_typeck_results()
+                .filter(|typeck_results| typeck_results.hir_owner == id.owner)
+                .or_else(|| {
+                    if self.tcx.has_typeck_results(id.owner.to_def_id()) {
+                        Some(self.tcx.typeck(id.owner))
+                    } else {
+                        None
+                    }
+                })
                 .and_then(|typeck_results| typeck_results.type_dependent_def(id))
                 .map_or(Res::Err, |(kind, def_id)| Res::Def(kind, def_id)),
         }

compiler/rustc_lint/src/late.rs

@@ -140,13 +140,17 @@ impl<'tcx, T: LateLintPass<'tcx>> hir_visit::Visitor<'tcx> for LateContextAndPas
     fn visit_item(&mut self, it: &'tcx hir::Item<'tcx>) {
         let generics = self.context.generics.take();
         self.context.generics = it.kind.generics();
+        let old_cached_typeck_results = self.context.cached_typeck_results.take();
+        let old_enclosing_body = self.context.enclosing_body.take();
         self.with_lint_attrs(it.hir_id, &it.attrs, |cx| {
             cx.with_param_env(it.hir_id, |cx| {
                 lint_callback!(cx, check_item, it);
                 hir_visit::walk_item(cx, it);
                 lint_callback!(cx, check_item_post, it);
             });
         });
+        self.context.enclosing_body = old_enclosing_body;
+        self.context.cached_typeck_results.set(old_cached_typeck_results);
         self.context.generics = generics;
     }
 

src/tools/clippy/clippy_lints/src/default.rs

@@ -1,5 +1,5 @@
 use crate::utils::{
-    any_parent_is_automatically_derived, contains_name, match_def_path, paths, qpath_res, snippet_with_macro_callsite,
+    any_parent_is_automatically_derived, contains_name, match_def_path, paths, snippet_with_macro_callsite,
 };
 use crate::utils::{span_lint_and_note, span_lint_and_sugg};
 use if_chain::if_chain;
@@ -231,7 +231,7 @@ fn is_expr_default<'tcx>(expr: &'tcx Expr<'tcx>, cx: &LateContext<'tcx>) -> bool
     if_chain! {
         if let ExprKind::Call(ref fn_expr, _) = &expr.kind;
         if let ExprKind::Path(qpath) = &fn_expr.kind;
-        if let Res::Def(_, def_id) = qpath_res(cx, qpath, fn_expr.hir_id);
+        if let Res::Def(_, def_id) = cx.qpath_res(qpath, fn_expr.hir_id);
         then {
             // right hand side of assignment is `Default::default`
             match_def_path(cx, def_id, &paths::DEFAULT_TRAIT_METHOD)

src/tools/clippy/clippy_lints/src/drop_forget_ref.rs

@@ -1,4 +1,4 @@
-use crate::utils::{is_copy, match_def_path, paths, qpath_res, span_lint_and_note};
+use crate::utils::{is_copy, match_def_path, paths, span_lint_and_note};
 use if_chain::if_chain;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
@@ -114,7 +114,7 @@ impl<'tcx> LateLintPass<'tcx> for DropForgetRef {
             if let ExprKind::Call(ref path, ref args) = expr.kind;
             if let ExprKind::Path(ref qpath) = path.kind;
             if args.len() == 1;
-            if let Some(def_id) = qpath_res(cx, qpath, path.hir_id).opt_def_id();
+            if let Some(def_id) = cx.qpath_res(qpath, path.hir_id).opt_def_id();
             then {
                 let lint;
                 let msg;

src/tools/clippy/clippy_lints/src/exit.rs

@@ -1,4 +1,4 @@
-use crate::utils::{is_entrypoint_fn, match_def_path, paths, qpath_res, span_lint};
+use crate::utils::{is_entrypoint_fn, match_def_path, paths, span_lint};
 use if_chain::if_chain;
 use rustc_hir::{Expr, ExprKind, Item, ItemKind, Node};
 use rustc_lint::{LateContext, LateLintPass};
@@ -29,7 +29,7 @@ impl<'tcx> LateLintPass<'tcx> for Exit {
         if_chain! {
             if let ExprKind::Call(ref path_expr, ref _args) = e.kind;
             if let ExprKind::Path(ref path) = path_expr.kind;
-            if let Some(def_id) = qpath_res(cx, path, path_expr.hir_id).opt_def_id();
+            if let Some(def_id) = cx.qpath_res(path, path_expr.hir_id).opt_def_id();
             if match_def_path(cx, def_id, &paths::EXIT);
             then {
                 let parent = cx.tcx.hir().get_parent_item(e.hir_id);

src/tools/clippy/clippy_lints/src/functions.rs

@@ -1,7 +1,7 @@
 use crate::utils::{
     attr_by_name, attrs::is_proc_macro, is_must_use_ty, is_trait_impl_item, is_type_diagnostic_item, iter_input_pats,
-    last_path_segment, match_def_path, must_use_attr, qpath_res, return_ty, snippet, snippet_opt, span_lint,
-    span_lint_and_help, span_lint_and_then, trait_ref_of_method, type_is_unsafe_function,
+    last_path_segment, match_def_path, must_use_attr, return_ty, snippet, snippet_opt, span_lint, span_lint_and_help,
+    span_lint_and_then, trait_ref_of_method, type_is_unsafe_function,
 };
 use if_chain::if_chain;
 use rustc_ast::ast::Attribute;
@@ -659,7 +659,7 @@ impl<'a, 'tcx> intravisit::Visitor<'tcx> for DerefVisitor<'a, 'tcx> {
 impl<'a, 'tcx> DerefVisitor<'a, 'tcx> {
     fn check_arg(&self, ptr: &hir::Expr<'_>) {
         if let hir::ExprKind::Path(ref qpath) = ptr.kind {
-            if let Res::Local(id) = qpath_res(self.cx, qpath, ptr.hir_id) {
+            if let Res::Local(id) = self.cx.qpath_res(qpath, ptr.hir_id) {
                 if self.ptrs.contains(&id) {
                     span_lint(
                         self.cx,
@@ -722,7 +722,7 @@ fn is_mutated_static(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> bool {
     use hir::ExprKind::{Field, Index, Path};
 
     match e.kind {
-        Path(ref qpath) => !matches!(qpath_res(cx, qpath, e.hir_id), Res::Local(_)),
+        Path(ref qpath) => !matches!(cx.qpath_res(qpath, e.hir_id), Res::Local(_)),
         Field(ref inner, _) | Index(ref inner, _) => is_mutated_static(cx, inner),
         _ => false,
     }

src/tools/clippy/clippy_lints/src/let_if_seq.rs

@@ -1,4 +1,4 @@
-use crate::utils::{qpath_res, snippet, span_lint_and_then, visitors::LocalUsedVisitor};
+use crate::utils::{snippet, span_lint_and_then, visitors::LocalUsedVisitor};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
@@ -145,7 +145,7 @@ fn check_assign<'tcx>(
         if let hir::StmtKind::Semi(ref expr) = expr.kind;
         if let hir::ExprKind::Assign(ref var, ref value, _) = expr.kind;
         if let hir::ExprKind::Path(ref qpath) = var.kind;
-        if let Res::Local(local_id) = qpath_res(cx, qpath, var.hir_id);
+        if let Res::Local(local_id) = cx.qpath_res(qpath, var.hir_id);
         if decl == local_id;
         then {
             let mut v = LocalUsedVisitor::new(decl);

src/tools/clippy/clippy_lints/src/loops.rs

@@ -6,9 +6,9 @@ use crate::utils::visitors::LocalUsedVisitor;
 use crate::utils::{
     contains_name, get_enclosing_block, get_parent_expr, get_trait_def_id, has_iter_method, higher, implements_trait,
     indent_of, is_in_panic_handler, is_integer_const, is_no_std_crate, is_refutable, is_type_diagnostic_item,
-    last_path_segment, match_trait_method, match_type, match_var, multispan_sugg, qpath_res, single_segment_path,
-    snippet, snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_help,
-    span_lint_and_sugg, span_lint_and_then, sugg, SpanlessEq,
+    last_path_segment, match_trait_method, match_type, match_var, multispan_sugg, single_segment_path, snippet,
+    snippet_with_applicability, snippet_with_macro_callsite, span_lint, span_lint_and_help, span_lint_and_sugg,
+    span_lint_and_then, sugg, SpanlessEq,
 };
 use if_chain::if_chain;
 use rustc_ast::ast;
@@ -848,7 +848,7 @@ fn same_var<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, var: HirId) -> bool {
         if let ExprKind::Path(qpath) = &expr.kind;
         if let QPath::Resolved(None, path) = qpath;
         if path.segments.len() == 1;
-        if let Res::Local(local_id) = qpath_res(cx, qpath, expr.hir_id);
+        if let Res::Local(local_id) = cx.qpath_res(qpath, expr.hir_id);
         then {
             // our variable!
             local_id == var
@@ -1420,7 +1420,7 @@ fn detect_same_item_push<'tcx>(
                 // Make sure that the push does not involve possibly mutating values
                 match pushed_item.kind {
                     ExprKind::Path(ref qpath) => {
-                        match qpath_res(cx, qpath, pushed_item.hir_id) {
+                        match cx.qpath_res(qpath, pushed_item.hir_id) {
                             // immutable bindings that are initialized with literal or constant
                             Res::Local(hir_id) => {
                                 if_chain! {
@@ -1437,7 +1437,7 @@ fn detect_same_item_push<'tcx>(
                                             ExprKind::Lit(..) => emit_lint(cx, vec, pushed_item),
                                             // immutable bindings that are initialized with constant
                                             ExprKind::Path(ref path) => {
-                                                if let Res::Def(DefKind::Const, ..) = qpath_res(cx, path, init.hir_id) {
+                                                if let Res::Def(DefKind::Const, ..) = cx.qpath_res(path, init.hir_id) {
                                                     emit_lint(cx, vec, pushed_item);
                                                 }
                                             }
@@ -2028,7 +2028,7 @@ fn check_for_mutability(cx: &LateContext<'_>, bound: &Expr<'_>) -> Option<HirId>
         if let ExprKind::Path(ref qpath) = bound.kind;
         if let QPath::Resolved(None, _) = *qpath;
         then {
-            let res = qpath_res(cx, qpath, bound.hir_id);
+            let res = cx.qpath_res(qpath, bound.hir_id);
             if let Res::Local(hir_id) = res {
                 let node_str = cx.tcx.hir().get(hir_id);
                 if_chain! {
@@ -2120,7 +2120,7 @@ impl<'a, 'tcx> VarVisitor<'a, 'tcx> {
                     if self.prefer_mutable {
                         self.indexed_mut.insert(seqvar.segments[0].ident.name);
                     }
-                    let res = qpath_res(self.cx, seqpath, seqexpr.hir_id);
+                    let res = self.cx.qpath_res(seqpath, seqexpr.hir_id);
                     match res {
                         Res::Local(hir_id) => {
                             let parent_id = self.cx.tcx.hir().get_parent_item(expr.hir_id);
@@ -2184,7 +2184,7 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
             if let QPath::Resolved(None, ref path) = *qpath;
             if path.segments.len() == 1;
             then {
-                if let Res::Local(local_id) = qpath_res(self.cx, qpath, expr.hir_id) {
+                if let Res::Local(local_id) = self.cx.qpath_res(qpath, expr.hir_id) {
                     if local_id == self.var {
                         self.nonindex = true;
                     } else {
@@ -2589,7 +2589,7 @@ impl<'a, 'tcx> Visitor<'tcx> for InitializeVisitor<'a, 'tcx> {
 
 fn var_def_id(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<HirId> {
     if let ExprKind::Path(ref qpath) = expr.kind {
-        let path_res = qpath_res(cx, qpath, expr.hir_id);
+        let path_res = cx.qpath_res(qpath, expr.hir_id);
         if let Res::Local(hir_id) = path_res {
             return Some(hir_id);
         }
@@ -2819,7 +2819,7 @@ impl<'a, 'tcx> VarCollectorVisitor<'a, 'tcx> {
         if_chain! {
             if let ExprKind::Path(ref qpath) = ex.kind;
             if let QPath::Resolved(None, _) = *qpath;
-            let res = qpath_res(self.cx, qpath, ex.hir_id);
+            let res = self.cx.qpath_res(qpath, ex.hir_id);
             then {
                 match res {
                     Res::Local(hir_id) => {

src/tools/clippy/clippy_lints/src/manual_strip.rs

@@ -1,7 +1,7 @@
 use crate::consts::{constant, Constant};
 use crate::utils::usage::mutated_variables;
 use crate::utils::{
-    eq_expr_value, higher, match_def_path, meets_msrv, multispan_sugg, paths, qpath_res, snippet, span_lint_and_then,
+    eq_expr_value, higher, match_def_path, meets_msrv, multispan_sugg, paths, snippet, span_lint_and_then,
 };
 
 use if_chain::if_chain;
@@ -92,7 +92,7 @@ impl<'tcx> LateLintPass<'tcx> for ManualStrip {
                 } else {
                     return;
                 };
-                let target_res = qpath_res(cx, &target_path, target_arg.hir_id);
+                let target_res = cx.qpath_res(&target_path, target_arg.hir_id);
                 if target_res == Res::Err {
                     return;
                 };
@@ -221,7 +221,7 @@ fn find_stripping<'tcx>(
                 if let ExprKind::Index(indexed, index) = &unref.kind;
                 if let Some(higher::Range { start, end, .. }) = higher::range(index);
                 if let ExprKind::Path(path) = &indexed.kind;
-                if qpath_res(self.cx, path, ex.hir_id) == self.target;
+                if self.cx.qpath_res(path, ex.hir_id) == self.target;
                 then {
                     match (self.strip_kind, start, end) {
                         (StripKind::Prefix, Some(start), None) => {
@@ -235,7 +235,7 @@ fn find_stripping<'tcx>(
                                 if let ExprKind::Binary(Spanned { node: BinOpKind::Sub, .. }, left, right) = end.kind;
                                 if let Some(left_arg) = len_arg(self.cx, left);
                                 if let ExprKind::Path(left_path) = &left_arg.kind;
-                                if qpath_res(self.cx, left_path, left_arg.hir_id) == self.target;
+                                if self.cx.qpath_res(left_path, left_arg.hir_id) == self.target;
                                 if eq_pattern_length(self.cx, self.pattern, right);
                                 then {
                                     self.results.push(ex.span);

src/tools/clippy/clippy_lints/src/mem_forget.rs

@@ -1,4 +1,4 @@
-use crate::utils::{match_def_path, paths, qpath_res, span_lint};
+use crate::utils::{match_def_path, paths, span_lint};
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -29,7 +29,7 @@ impl<'tcx> LateLintPass<'tcx> for MemForget {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
         if let ExprKind::Call(ref path_expr, ref args) = e.kind {
             if let ExprKind::Path(ref qpath) = path_expr.kind {
-                if let Some(def_id) = qpath_res(cx, qpath, path_expr.hir_id).opt_def_id() {
+                if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id() {
                     if match_def_path(cx, def_id, &paths::MEM_FORGET) {
                         let forgot_ty = cx.typeck_results().expr_ty(&args[0]);