Auto merge of #10416 - Jarcho:explicit_iter_loop_ext, r=Manishearth

Extend `explicit_iter_loop` and `explicit_into_iter_loop`

fixes #1518

Some included cleanups
* Split `for_loop` test into different files for each lint (partially).
* Move handling of some `into_iter` cases from `explicit_into_iter`.

---

changelog: Enhancement: [`explicit_iter_loop`]: Now also handles types that implement `IntoIterator`.
[#10416](#10416)

changelog: Sugg: [`explicit_into_iter_loop`]: The suggestion now works on mutable references.
[#10416](#10416)
<!-- changelog_checked -->

clippy_lints/src/attrs.rs

@@ -808,7 +808,7 @@ fn check_deprecated_cfg_attr(cx: &EarlyContext<'_>, attr: &Attribute, msrv: &Msr
 }
 
 fn check_nested_cfg(cx: &EarlyContext<'_>, items: &[NestedMetaItem]) {
-    for item in items.iter() {
+    for item in items {
         if let NestedMetaItem::MetaItem(meta) = item {
             if !meta.has_name(sym::any) && !meta.has_name(sym::all) {
                 continue;
@@ -842,7 +842,7 @@ fn check_nested_cfg(cx: &EarlyContext<'_>, items: &[NestedMetaItem]) {
 }
 
 fn check_nested_misused_cfg(cx: &EarlyContext<'_>, items: &[NestedMetaItem]) {
-    for item in items.iter() {
+    for item in items {
         if let NestedMetaItem::MetaItem(meta) = item {
             if meta.has_name(sym!(features)) && let Some(val) = meta.value_str() {
                 span_lint_and_sugg(

clippy_lints/src/default_numeric_fallback.rs

@@ -161,7 +161,7 @@ impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
                         let fields_def = &variant.fields;
 
                         // Push field type then visit each field expr.
-                        for field in fields.iter() {
+                        for field in *fields {
                             let bound =
                                 fields_def
                                     .iter()

clippy_lints/src/lib.rs

@@ -680,7 +680,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     });
     store.register_late_pass(|_| Box::<shadow::Shadow>::default());
     store.register_late_pass(|_| Box::new(unit_types::UnitTypes));
-    store.register_late_pass(|_| Box::new(loops::Loops));
+    store.register_late_pass(move |_| Box::new(loops::Loops::new(msrv())));
     store.register_late_pass(|_| Box::<main_recursion::MainRecursion>::default());
     store.register_late_pass(|_| Box::new(lifetimes::Lifetimes));
     store.register_late_pass(|_| Box::new(entry::HashMapPass));

clippy_lints/src/lifetimes.rs

@@ -562,7 +562,7 @@ fn has_where_lifetimes<'tcx>(cx: &LateContext<'tcx>, generics: &'tcx Generics<'_
                 // if the bounds define new lifetimes, they are fine to occur
                 let allowed_lts = allowed_lts_from(pred.bound_generic_params);
                 // now walk the bounds
-                for bound in pred.bounds.iter() {
+                for bound in pred.bounds {
                     walk_param_bound(&mut visitor, bound);
                 }
                 // and check that all lifetimes are allowed

clippy_lints/src/loops/explicit_into_iter_loop.rs

@@ -5,15 +5,76 @@ use clippy_utils::source::snippet_with_applicability;
 use rustc_errors::Applicability;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
+use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow, AutoBorrowMutability};
 use rustc_span::symbol::sym;
 
+#[derive(Clone, Copy)]
+enum AdjustKind {
+    None,
+    Borrow,
+    BorrowMut,
+    Reborrow,
+    ReborrowMut,
+}
+impl AdjustKind {
+    fn borrow(mutbl: AutoBorrowMutability) -> Self {
+        match mutbl {
+            AutoBorrowMutability::Not => Self::Borrow,
+            AutoBorrowMutability::Mut { .. } => Self::BorrowMut,
+        }
+    }
+
+    fn reborrow(mutbl: AutoBorrowMutability) -> Self {
+        match mutbl {
+            AutoBorrowMutability::Not => Self::Reborrow,
+            AutoBorrowMutability::Mut { .. } => Self::ReborrowMut,
+        }
+    }
+
+    fn display(self) -> &'static str {
+        match self {
+            Self::None => "",
+            Self::Borrow => "&",
+            Self::BorrowMut => "&mut ",
+            Self::Reborrow => "&*",
+            Self::ReborrowMut => "&mut *",
+        }
+    }
+}
+
 pub(super) fn check(cx: &LateContext<'_>, self_arg: &Expr<'_>, call_expr: &Expr<'_>) {
-    let self_ty = cx.typeck_results().expr_ty(self_arg);
-    let self_ty_adjusted = cx.typeck_results().expr_ty_adjusted(self_arg);
-    if !(self_ty == self_ty_adjusted && is_trait_method(cx, call_expr, sym::IntoIterator)) {
+    if !is_trait_method(cx, call_expr, sym::IntoIterator) {
         return;
     }
 
+    let typeck = cx.typeck_results();
+    let self_ty = typeck.expr_ty(self_arg);
+    let adjust = match typeck.expr_adjustments(self_arg) {
+        [] => AdjustKind::None,
+        &[
+            Adjustment {
+                kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl)),
+                ..
+            },
+        ] => AdjustKind::borrow(mutbl),
+        &[
+            Adjustment {
+                kind: Adjust::Deref(_), ..
+            },
+            Adjustment {
+                kind: Adjust::Borrow(AutoBorrow::Ref(_, mutbl)),
+                target,
+            },
+        ] => {
+            if self_ty == target && matches!(mutbl, AutoBorrowMutability::Not) {
+                AdjustKind::None
+            } else {
+                AdjustKind::reborrow(mutbl)
+            }
+        },
+        _ => return,
+    };
+
     let mut applicability = Applicability::MachineApplicable;
     let object = snippet_with_applicability(cx, self_arg.span, "_", &mut applicability);
     span_lint_and_sugg(
@@ -23,7 +84,7 @@ pub(super) fn check(cx: &LateContext<'_>, self_arg: &Expr<'_>, call_expr: &Expr<
         "it is more concise to loop over containers instead of using explicit \
             iteration methods",
         "to write this more concisely, try",
-        object.to_string(),
+        format!("{}{object}", adjust.display()),
         applicability,
     );
 }