Merge commit '7c21f91b15b7604f818565646b686d90f99d1baf' into clippyup

12 files changed, 241 insertions, 35 deletions

diff --git a/src/tools/clippy/clippy_utils/src/consts.rs b/src/tools/clippy/clippy_utils/src/consts.rs
index be46b791aa4..fdb822c3e5b 100644
--- a/src/tools/clippy/clippy_utils/src/consts.rs
+++ b/src/tools/clippy/clippy_utils/src/consts.rs
@@ -5,7 +5,7 @@ use if_chain::if_chain;
 use rustc_ast::ast::{self, LitFloatType, LitKind};
 use rustc_data_structures::sync::Lrc;
 use rustc_hir::def::{DefKind, Res};
-use rustc_hir::{BinOp, BinOpKind, Block, Expr, ExprKind, HirId, QPath, UnOp};
+use rustc_hir::{BinOp, BinOpKind, Block, Expr, ExprKind, HirId, Item, ItemKind, Node, QPath, UnOp};
 use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::ty::subst::{Subst, SubstsRef};
@@ -400,6 +400,22 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
         let res = self.typeck_results.qpath_res(qpath, id);
         match res {
             Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
+                // Check if this constant is based on `cfg!(..)`,
+                // which is NOT constant for our purposes.
+                if let Some(node) = self.lcx.tcx.hir().get_if_local(def_id) &&
+                let Node::Item(&Item {
+                    kind: ItemKind::Const(_, body_id),
+                    ..
+                }) = node &&
+                let Node::Expr(&Expr {
+                    kind: ExprKind::Lit(_),
+                    span,
+                    ..
+                }) = self.lcx.tcx.hir().get(body_id.hir_id) &&
+                is_direct_expn_of(span, "cfg").is_some() {
+                    return None;
+                }
+
                 let substs = self.typeck_results.node_substs(id);
                 let substs = if self.substs.is_empty() {
                     substs
diff --git a/src/tools/clippy/clippy_utils/src/hir_utils.rs b/src/tools/clippy/clippy_utils/src/hir_utils.rs
index c05317f59b7..f4da625f1e3 100644
--- a/src/tools/clippy/clippy_utils/src/hir_utils.rs
+++ b/src/tools/clippy/clippy_utils/src/hir_utils.rs
@@ -1,4 +1,4 @@
-use crate::consts::{constant_context, constant_simple};
+use crate::consts::constant_simple;
 use crate::source::snippet_opt;
 use rustc_ast::ast::InlineAsmTemplatePiece;
 use rustc_data_structures::fx::FxHasher;
@@ -16,15 +16,14 @@ use rustc_span::Symbol;
 use std::hash::{Hash, Hasher};
 
 /// Type used to check whether two ast are the same. This is different from the
-/// operator
-/// `==` on ast types as this operator would compare true equality with ID and
-/// span.
+/// operator `==` on ast types as this operator would compare true equality with
+/// ID and span.
 ///
 /// Note that some expressions kinds are not considered but could be added.
 pub struct SpanlessEq<'a, 'tcx> {
     /// Context used to evaluate constant expressions.
     cx: &'a LateContext<'tcx>,
-    maybe_typeck_results: Option<&'tcx TypeckResults<'tcx>>,
+    maybe_typeck_results: Option<(&'tcx TypeckResults<'tcx>, &'tcx TypeckResults<'tcx>)>,
     allow_side_effects: bool,
     expr_fallback: Option<Box<dyn FnMut(&Expr<'_>, &Expr<'_>) -> bool + 'a>>,
 }
@@ -33,7 +32,7 @@ impl<'a, 'tcx> SpanlessEq<'a, 'tcx> {
     pub fn new(cx: &'a LateContext<'tcx>) -> Self {
         Self {
             cx,
-            maybe_typeck_results: cx.maybe_typeck_results(),
+            maybe_typeck_results: cx.maybe_typeck_results().map(|x| (x, x)),
             allow_side_effects: true,
             expr_fallback: None,
         }
@@ -102,9 +101,9 @@ impl HirEqInterExpr<'_, '_, '_> {
             (&StmtKind::Local(l), &StmtKind::Local(r)) => {
                 // This additional check ensures that the type of the locals are equivalent even if the init
                 // expression or type have some inferred parts.
-                if let Some(typeck) = self.inner.maybe_typeck_results {
-                    let l_ty = typeck.pat_ty(l.pat);
-                    let r_ty = typeck.pat_ty(r.pat);
+                if let Some((typeck_lhs, typeck_rhs)) = self.inner.maybe_typeck_results {
+                    let l_ty = typeck_lhs.pat_ty(l.pat);
+                    let r_ty = typeck_rhs.pat_ty(r.pat);
                     if l_ty != r_ty {
                         return false;
                     }
@@ -182,9 +181,17 @@ impl HirEqInterExpr<'_, '_, '_> {
     }
 
     pub fn eq_body(&mut self, left: BodyId, right: BodyId) -> bool {
-        let cx = self.inner.cx;
-        let eval_const = |body| constant_context(cx, cx.tcx.typeck_body(body)).expr(&cx.tcx.hir().body(body).value);
-        eval_const(left) == eval_const(right)
+        // swap out TypeckResults when hashing a body
+        let old_maybe_typeck_results = self.inner.maybe_typeck_results.replace((
+            self.inner.cx.tcx.typeck_body(left),
+            self.inner.cx.tcx.typeck_body(right),
+        ));
+        let res = self.eq_expr(
+            &self.inner.cx.tcx.hir().body(left).value,
+            &self.inner.cx.tcx.hir().body(right).value,
+        );
+        self.inner.maybe_typeck_results = old_maybe_typeck_results;
+        res
     }
 
     #[allow(clippy::similar_names)]
@@ -193,10 +200,10 @@ impl HirEqInterExpr<'_, '_, '_> {
             return false;
         }
 
-        if let Some(typeck_results) = self.inner.maybe_typeck_results {
+        if let Some((typeck_lhs, typeck_rhs)) = self.inner.maybe_typeck_results {
             if let (Some(l), Some(r)) = (
-                constant_simple(self.inner.cx, typeck_results, left),
-                constant_simple(self.inner.cx, typeck_results, right),
+                constant_simple(self.inner.cx, typeck_lhs, left),
+                constant_simple(self.inner.cx, typeck_rhs, right),
             ) {
                 if l == r {
                     return true;
@@ -674,8 +681,9 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
                                 self.hash_expr(out_expr);
                             }
                         },
-                        InlineAsmOperand::Const { anon_const } => self.hash_body(anon_const.body),
-                        InlineAsmOperand::SymFn { anon_const } => self.hash_body(anon_const.body),
+                        InlineAsmOperand::Const { anon_const } | InlineAsmOperand::SymFn { anon_const } => {
+                            self.hash_body(anon_const.body);
+                        },
                         InlineAsmOperand::SymStatic { path, def_id: _ } => self.hash_qpath(path),
                     }
                 }
diff --git a/src/tools/clippy/clippy_utils/src/macros.rs b/src/tools/clippy/clippy_utils/src/macros.rs
index e7d4c5a4952..a268e339bb1 100644
--- a/src/tools/clippy/clippy_utils/src/macros.rs
+++ b/src/tools/clippy/clippy_utils/src/macros.rs
@@ -367,7 +367,7 @@ impl<'tcx> FormatArgsExpn<'tcx> {
         expr_visitor_no_bodies(|e| {
             // if we're still inside of the macro definition...
             if e.span.ctxt() == expr.span.ctxt() {
-                // ArgumnetV1::new_<format_trait>(<value>)
+                // ArgumentV1::new_<format_trait>(<value>)
                 if_chain! {
                     if let ExprKind::Call(callee, [val]) = e.kind;
                     if let ExprKind::Path(QPath::TypeRelative(ty, seg)) = callee.kind;
diff --git a/src/tools/clippy/clippy_utils/src/msrvs.rs b/src/tools/clippy/clippy_utils/src/msrvs.rs
index 0424e067202..134fd1ce505 100644
--- a/src/tools/clippy/clippy_utils/src/msrvs.rs
+++ b/src/tools/clippy/clippy_utils/src/msrvs.rs
@@ -32,4 +32,5 @@ msrv_aliases! {
     1,28,0 { FROM_BOOL }
     1,17,0 { FIELD_INIT_SHORTHAND, STATIC_IN_CONST, EXPECT_ERR }
     1,16,0 { STR_REPEAT }
+    1,24,0 { IS_ASCII_DIGIT }
 }
diff --git a/src/tools/clippy/clippy_utils/src/numeric_literal.rs b/src/tools/clippy/clippy_utils/src/numeric_literal.rs
index 908ff822712..b92d42e8323 100644
--- a/src/tools/clippy/clippy_utils/src/numeric_literal.rs
+++ b/src/tools/clippy/clippy_utils/src/numeric_literal.rs
@@ -57,7 +57,7 @@ impl<'a> NumericLiteral<'a> {
                 .trim_start()
                 .chars()
                 .next()
-                .map_or(false, |c| c.is_digit(10))
+                .map_or(false, |c| c.is_ascii_digit())
         {
             let (unsuffixed, suffix) = split_suffix(src, lit_kind);
             let float = matches!(lit_kind, LitKind::Float(..));
diff --git a/src/tools/clippy/clippy_utils/src/paths.rs b/src/tools/clippy/clippy_utils/src/paths.rs
index e5fa6deefc5..60971fb716d 100644
--- a/src/tools/clippy/clippy_utils/src/paths.rs
+++ b/src/tools/clippy/clippy_utils/src/paths.rs
@@ -61,6 +61,7 @@ pub const IO_READ: [&str; 3] = ["std", "io", "Read"];
 pub const IO_WRITE: [&str; 3] = ["std", "io", "Write"];
 pub const IPADDR_V4: [&str; 5] = ["std", "net", "ip", "IpAddr", "V4"];
 pub const IPADDR_V6: [&str; 5] = ["std", "net", "ip", "IpAddr", "V6"];
+pub const ITER_COUNT: [&str; 6] = ["core", "iter", "traits", "iterator", "Iterator", "count"];
 pub const ITER_REPEAT: [&str; 5] = ["core", "iter", "sources", "repeat", "repeat"];
 #[allow(clippy::invalid_paths)] // internal lints do not know about all external crates
 pub const ITERTOOLS_NEXT_TUPLE: [&str; 3] = ["itertools", "Itertools", "next_tuple"];
@@ -148,6 +149,8 @@ pub const CONVERT_IDENTITY: [&str; 3] = ["core", "convert", "identity"];
 pub const STD_FS_CREATE_DIR: [&str; 3] = ["std", "fs", "create_dir"];
 pub const STRING_AS_MUT_STR: [&str; 4] = ["alloc", "string", "String", "as_mut_str"];
 pub const STRING_AS_STR: [&str; 4] = ["alloc", "string", "String", "as_str"];
+pub const STRING_NEW: [&str; 4] = ["alloc", "string", "String", "new"];
+pub const STR_BYTES: [&str; 4] = ["core", "str", "<impl str>", "bytes"];
 pub const STR_ENDS_WITH: [&str; 4] = ["core", "str", "<impl str>", "ends_with"];
 pub const STR_FROM_UTF8: [&str; 4] = ["core", "str", "converts", "from_utf8"];
 pub const STR_LEN: [&str; 4] = ["core", "str", "<impl str>", "len"];
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index fe411220484..75808b1b174 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -211,8 +211,9 @@ fn check_statement<'tcx>(
 
         StatementKind::FakeRead(box (_, place)) => check_place(tcx, *place, span, body),
         // just an assignment
-        StatementKind::SetDiscriminant { place, .. } | StatementKind::Deinit(place) => 
-            check_place(tcx, **place, span, body),
+        StatementKind::SetDiscriminant { place, .. } | StatementKind::Deinit(place) => {
+            check_place(tcx, **place, span, body)
+        },
 
         StatementKind::CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping { dst, src, count }) => {
             check_operand(tcx, dst, span, body)?;
diff --git a/src/tools/clippy/clippy_utils/src/source.rs b/src/tools/clippy/clippy_utils/src/source.rs
index dbad607c58e..c69a3d8d2a1 100644
--- a/src/tools/clippy/clippy_utils/src/source.rs
+++ b/src/tools/clippy/clippy_utils/src/source.rs
@@ -7,9 +7,28 @@ use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LintContext};
 use rustc_span::hygiene;
+use rustc_span::source_map::SourceMap;
 use rustc_span::{BytePos, Pos, Span, SyntaxContext};
 use std::borrow::Cow;
 
+/// Checks if the span starts with the given text. This will return false if the span crosses
+/// multiple files or if source is not available.
+///
+/// This is used to check for proc macros giving unhelpful spans to things.
+pub fn span_starts_with<T: LintContext>(cx: &T, span: Span, text: &str) -> bool {
+    fn helper(sm: &SourceMap, span: Span, text: &str) -> bool {
+        let pos = sm.lookup_byte_offset(span.lo());
+        let Some(ref src) = pos.sf.src else {
+            return false;
+        };
+        let end = span.hi() - pos.sf.start_pos;
+        src.get(pos.pos.0 as usize..end.0 as usize)
+            // Expression spans can include wrapping parenthesis. Remove them first.
+            .map_or(false, |s| s.trim_start_matches('(').starts_with(text))
+    }
+    helper(cx.sess().source_map(), span, text)
+}
+
 /// Like `snippet_block`, but add braces if the expr is not an `ExprKind::Block`.
 /// Also takes an `Option<String>` which can be put inside the braces.
 pub fn expr_block<'a, T: LintContext>(
@@ -89,7 +108,7 @@ pub fn is_present_in_source<T: LintContext>(cx: &T, span: Span) -> bool {
     true
 }
 
-/// Returns the positon just before rarrow
+/// Returns the position just before rarrow
 ///
 /// ```rust,ignore
 /// fn into(self) -> () {}
diff --git a/src/tools/clippy/clippy_utils/src/sugg.rs b/src/tools/clippy/clippy_utils/src/sugg.rs
index 794d2e1026f..18915553e61 100644
--- a/src/tools/clippy/clippy_utils/src/sugg.rs
+++ b/src/tools/clippy/clippy_utils/src/sugg.rs
@@ -18,7 +18,7 @@ use rustc_span::source_map::{BytePos, CharPos, Pos, Span, SyntaxContext};
 use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
 use std::borrow::Cow;
 use std::convert::TryInto;
-use std::fmt::Display;
+use std::fmt::{Display, Write as _};
 use std::iter;
 use std::ops::{Add, Neg, Not, Sub};
 
@@ -902,7 +902,7 @@ impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
             if cmt.place.projections.is_empty() {
                 // handle item without any projection, that needs an explicit borrowing
                 // i.e.: suggest `&x` instead of `x`
-                self.suggestion_start.push_str(&format!("{}&{}", start_snip, ident_str));
+                let _ = write!(self.suggestion_start, "{}&{}", start_snip, ident_str);
             } else {
                 // cases where a parent `Call` or `MethodCall` is using the item
                 // i.e.: suggest `.contains(&x)` for `.find(|x| [1, 2, 3].contains(x)).is_none()`
@@ -917,8 +917,7 @@ impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
                         // given expression is the self argument and will be handled completely by the compiler
                         // i.e.: `|x| x.is_something()`
                         ExprKind::MethodCall(_, [self_expr, ..], _) if self_expr.hir_id == cmt.hir_id => {
-                            self.suggestion_start
-                                .push_str(&format!("{}{}", start_snip, ident_str_with_proj));
+                            let _ = write!(self.suggestion_start, "{}{}", start_snip, ident_str_with_proj);
                             self.next_pos = span.hi();
                             return;
                         },
@@ -1026,8 +1025,7 @@ impl<'tcx> Delegate<'tcx> for DerefDelegate<'_, 'tcx> {
                     }
                 }
 
-                self.suggestion_start
-                    .push_str(&format!("{}{}", start_snip, replacement_str));
+                let _ = write!(self.suggestion_start, "{}{}", start_snip, replacement_str);
             }
             self.next_pos = span.hi();
         }
diff --git a/src/tools/clippy/clippy_utils/src/ty.rs b/src/tools/clippy/clippy_utils/src/ty.rs
index e3fc76f4e1a..901e3e5390c 100644
--- a/src/tools/clippy/clippy_utils/src/ty.rs
+++ b/src/tools/clippy/clippy_utils/src/ty.rs
@@ -3,11 +3,11 @@
 #![allow(clippy::module_name_repetitions)]
 
 use rustc_ast::ast::Mutability;
-use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir as hir;
 use rustc_hir::def::{CtorKind, DefKind, Res};
 use rustc_hir::def_id::DefId;
-use rustc_hir::{Expr, TyKind, Unsafety};
+use rustc_hir::{Expr, LangItem, TyKind, Unsafety};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::{ConstValue, Scalar};
@@ -22,7 +22,7 @@ use rustc_trait_selection::infer::InferCtxtExt;
 use rustc_trait_selection::traits::query::normalize::AtExt;
 use std::iter;
 
-use crate::{match_def_path, must_use_attr, path_res};
+use crate::{match_def_path, must_use_attr, path_res, paths};
 
 // Checks if the given type implements copy.
 pub fn is_copy<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
@@ -83,6 +83,20 @@ pub fn get_associated_type<'tcx>(
         })
 }
 
+/// Get the diagnostic name of a type, e.g. `sym::HashMap`. To check if a type
+/// implements a trait marked with a diagnostic item use [`implements_trait`].
+///
+/// For a further exploitation what diagnostic items are see [diagnostic items] in
+/// rustc-dev-guide.
+///
+/// [Diagnostic Items]: https://rustc-dev-guide.rust-lang.org/diagnostics/diagnostic-items.html
+pub fn get_type_diagnostic_name(cx: &LateContext<'_>, ty: Ty<'_>) -> Option<Symbol> {
+    match ty.kind() {
+        ty::Adt(adt, _) => cx.tcx.get_diagnostic_name(adt.did()),
+        _ => None,
+    }
+}
+
 /// Returns true if ty has `iter` or `iter_mut` methods
 pub fn has_iter_method(cx: &LateContext<'_>, probably_ref_ty: Ty<'_>) -> Option<Symbol> {
     // FIXME: instead of this hard-coded list, we should check if `<adt>::iter`
@@ -319,6 +333,57 @@ pub fn match_type(cx: &LateContext<'_>, ty: Ty<'_>, path: &[&str]) -> bool {
     }
 }
 
+/// Checks if the drop order for a type matters. Some std types implement drop solely to
+/// deallocate memory. For these types, and composites containing them, changing the drop order
+/// won't result in any observable side effects.
+pub fn needs_ordered_drop<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
+    fn needs_ordered_drop_inner<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, seen: &mut FxHashSet<Ty<'tcx>>) -> bool {
+        if !seen.insert(ty) {
+            return false;
+        }
+        if !ty.has_significant_drop(cx.tcx, cx.param_env) {
+            false
+        }
+        // Check for std types which implement drop, but only for memory allocation.
+        else if is_type_lang_item(cx, ty, LangItem::OwnedBox)
+            || matches!(
+                get_type_diagnostic_name(cx, ty),
+                Some(sym::HashSet | sym::Rc | sym::Arc | sym::cstring_type)
+            )
+            || match_type(cx, ty, &paths::WEAK_RC)
+            || match_type(cx, ty, &paths::WEAK_ARC)
+        {
+            // Check all of the generic arguments.
+            if let ty::Adt(_, subs) = ty.kind() {
+                subs.types().any(|ty| needs_ordered_drop_inner(cx, ty, seen))
+            } else {
+                true
+            }
+        } else if !cx
+            .tcx
+            .lang_items()
+            .drop_trait()
+            .map_or(false, |id| implements_trait(cx, ty, id, &[]))
+        {
+            // This type doesn't implement drop, so no side effects here.
+            // Check if any component type has any.
+            match ty.kind() {
+                ty::Tuple(fields) => fields.iter().any(|ty| needs_ordered_drop_inner(cx, ty, seen)),
+                ty::Array(ty, _) => needs_ordered_drop_inner(cx, *ty, seen),
+                ty::Adt(adt, subs) => adt
+                    .all_fields()
+                    .map(|f| f.ty(cx.tcx, subs))
+                    .any(|ty| needs_ordered_drop_inner(cx, ty, seen)),
+                _ => true,
+            }
+        } else {
+            true
+        }
+    }
+
+    needs_ordered_drop_inner(cx, ty, &mut FxHashSet::default())
+}
+
 /// Peels off all references on the type. Returns the underlying type and the number of references
 /// removed.
 pub fn peel_mid_ty_refs(ty: Ty<'_>) -> (Ty<'_>, usize) {
diff --git a/src/tools/clippy/clippy_utils/src/usage.rs b/src/tools/clippy/clippy_utils/src/usage.rs
index 405e306359b..4236e3aae2f 100644
--- a/src/tools/clippy/clippy_utils/src/usage.rs
+++ b/src/tools/clippy/clippy_utils/src/usage.rs
@@ -3,7 +3,7 @@ use crate::visitors::{expr_visitor, expr_visitor_no_bodies};
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::HirIdSet;
-use rustc_hir::{Expr, ExprKind, HirId};
+use rustc_hir::{Expr, ExprKind, HirId, Node};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::hir::nested_filter;
@@ -169,6 +169,32 @@ pub fn contains_return_break_continue_macro(expression: &Expr<'_>) -> bool {
 
 pub fn local_used_after_expr(cx: &LateContext<'_>, local_id: HirId, after: &Expr<'_>) -> bool {
     let Some(block) = utils::get_enclosing_block(cx, local_id) else { return false };
+
+    // for _ in 1..3 {
+    //    local
+    // }
+    //
+    // let closure = || local;
+    // closure();
+    // closure();
+    let in_loop_or_closure = cx
+        .tcx
+        .hir()
+        .parent_iter(after.hir_id)
+        .take_while(|&(id, _)| id != block.hir_id)
+        .any(|(_, node)| {
+            matches!(
+                node,
+                Node::Expr(Expr {
+                    kind: ExprKind::Loop(..) | ExprKind::Closure(..),
+                    ..
+                })
+            )
+        });
+    if in_loop_or_closure {
+        return true;
+    }
+
     let mut used_after_expr = false;
     let mut past_expr = false;
     expr_visitor(cx, |expr| {
@@ -178,7 +204,10 @@ pub fn local_used_after_expr(cx: &LateContext<'_>, local_id: HirId, after: &Expr
 
         if expr.hir_id == after.hir_id {
             past_expr = true;
-        } else if past_expr && utils::path_to_local_id(expr, local_id) {
+            return false;
+        }
+
+        if past_expr && utils::path_to_local_id(expr, local_id) {
             used_after_expr = true;
         }
         !used_after_expr
diff --git a/src/tools/clippy/clippy_utils/src/visitors.rs b/src/tools/clippy/clippy_utils/src/visitors.rs
index 40451b17a9c..c00bc2bd213 100644
--- a/src/tools/clippy/clippy_utils/src/visitors.rs
+++ b/src/tools/clippy/clippy_utils/src/visitors.rs
@@ -1,9 +1,11 @@
 use crate::path_to_local_id;
+use core::ops::ControlFlow;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::{self, walk_block, walk_expr, Visitor};
 use rustc_hir::{
-    Arm, Block, BlockCheckMode, Body, BodyId, Expr, ExprKind, HirId, ItemId, ItemKind, Stmt, UnOp, Unsafety,
+    Arm, Block, BlockCheckMode, Body, BodyId, Expr, ExprKind, HirId, ItemId, ItemKind, Stmt, UnOp, UnsafeSource,
+    Unsafety,
 };
 use rustc_lint::LateContext;
 use rustc_middle::hir::map::Map;
@@ -370,3 +372,67 @@ pub fn is_expr_unsafe<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
     v.visit_expr(e);
     v.is_unsafe
 }
+
+/// Checks if the given expression contains an unsafe block
+pub fn contains_unsafe_block<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> bool {
+    struct V<'cx, 'tcx> {
+        cx: &'cx LateContext<'tcx>,
+        found_unsafe: bool,
+    }
+    impl<'tcx> Visitor<'tcx> for V<'_, 'tcx> {
+        type NestedFilter = nested_filter::OnlyBodies;
+        fn nested_visit_map(&mut self) -> Self::Map {
+            self.cx.tcx.hir()
+        }
+
+        fn visit_block(&mut self, b: &'tcx Block<'_>) {
+            if self.found_unsafe {
+                return;
+            }
+            if b.rules == BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) {
+                self.found_unsafe = true;
+                return;
+            }
+            walk_block(self, b);
+        }
+    }
+    let mut v = V {
+        cx,
+        found_unsafe: false,
+    };
+    v.visit_expr(e);
+    v.found_unsafe
+}
+
+/// Runs the given function for each sub-expression producing the final value consumed by the parent
+/// of the give expression.
+///
+/// e.g. for the following expression
+/// ```rust,ignore
+/// if foo {
+///     f(0)
+/// } else {
+///     1 + 1
+/// }
+/// ```
+/// this will pass both `f(0)` and `1+1` to the given function.
+pub fn for_each_value_source<'tcx, B>(
+    e: &'tcx Expr<'tcx>,
+    f: &mut impl FnMut(&'tcx Expr<'tcx>) -> ControlFlow<B>,
+) -> ControlFlow<B> {
+    match e.kind {
+        ExprKind::Block(Block { expr: Some(e), .. }, _) => for_each_value_source(e, f),
+        ExprKind::Match(_, arms, _) => {
+            for arm in arms {
+                for_each_value_source(arm.body, f)?;
+            }
+            ControlFlow::Continue(())
+        },
+        ExprKind::If(_, if_expr, Some(else_expr)) => {
+            for_each_value_source(if_expr, f)?;
+            for_each_value_source(else_expr, f)
+        },
+        ExprKind::DropTemps(e) => for_each_value_source(e, f),
+        _ => f(e),
+    }
+}