Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 495 insertions, 0 deletions

diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
new file mode 100644
index 000000000..246f5aad8
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -0,0 +1,495 @@
+use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
+use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::{get_item_name, get_parent_as_impl, is_lint_allowed};
+use if_chain::if_chain;
+use rustc_ast::ast::LitKind;
+use rustc_errors::Applicability;
+use rustc_hir::def_id::DefIdSet;
+use rustc_hir::{
+    def_id::DefId, AssocItemKind, BinOpKind, Expr, ExprKind, FnRetTy, ImplItem, ImplItemKind, ImplicitSelfKind, Item,
+    ItemKind, Mutability, Node, TraitItemRef, TyKind,
+};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::{self, AssocKind, FnSig, Ty};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::{
+    source_map::{Span, Spanned, Symbol},
+    symbol::sym,
+};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for getting the length of something via `.len()`
+    /// just to compare to zero, and suggests using `.is_empty()` where applicable.
+    ///
+    /// ### Why is this bad?
+    /// Some structures can answer `.is_empty()` much faster
+    /// than calculating their length. So it is good to get into the habit of using
+    /// `.is_empty()`, and having it is cheap.
+    /// Besides, it makes the intent clearer than a manual comparison in some contexts.
+    ///
+    /// ### Example
+    /// ```ignore
+    /// if x.len() == 0 {
+    ///     ..
+    /// }
+    /// if y.len() != 0 {
+    ///     ..
+    /// }
+    /// ```
+    /// instead use
+    /// ```ignore
+    /// if x.is_empty() {
+    ///     ..
+    /// }
+    /// if !y.is_empty() {
+    ///     ..
+    /// }
+    /// ```
+    #[clippy::version = "pre 1.29.0"]
+    pub LEN_ZERO,
+    style,
+    "checking `.len() == 0` or `.len() > 0` (or similar) when `.is_empty()` could be used instead"
+}
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for items that implement `.len()` but not
+    /// `.is_empty()`.
+    ///
+    /// ### Why is this bad?
+    /// It is good custom to have both methods, because for
+    /// some data structures, asking about the length will be a costly operation,
+    /// whereas `.is_empty()` can usually answer in constant time. Also it used to
+    /// lead to false positives on the [`len_zero`](#len_zero) lint – currently that
+    /// lint will ignore such entities.
+    ///
+    /// ### Example
+    /// ```ignore
+    /// impl X {
+    ///     pub fn len(&self) -> usize {
+    ///         ..
+    ///     }
+    /// }
+    /// ```
+    #[clippy::version = "pre 1.29.0"]
+    pub LEN_WITHOUT_IS_EMPTY,
+    style,
+    "traits or impls with a public `len` method but no corresponding `is_empty` method"
+}
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for comparing to an empty slice such as `""` or `[]`,
+    /// and suggests using `.is_empty()` where applicable.
+    ///
+    /// ### Why is this bad?
+    /// Some structures can answer `.is_empty()` much faster
+    /// than checking for equality. So it is good to get into the habit of using
+    /// `.is_empty()`, and having it is cheap.
+    /// Besides, it makes the intent clearer than a manual comparison in some contexts.
+    ///
+    /// ### Example
+    ///
+    /// ```ignore
+    /// if s == "" {
+    ///     ..
+    /// }
+    ///
+    /// if arr == [] {
+    ///     ..
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```ignore
+    /// if s.is_empty() {
+    ///     ..
+    /// }
+    ///
+    /// if arr.is_empty() {
+    ///     ..
+    /// }
+    /// ```
+    #[clippy::version = "1.49.0"]
+    pub COMPARISON_TO_EMPTY,
+    style,
+    "checking `x == \"\"` or `x == []` (or similar) when `.is_empty()` could be used instead"
+}
+
+declare_lint_pass!(LenZero => [LEN_ZERO, LEN_WITHOUT_IS_EMPTY, COMPARISON_TO_EMPTY]);
+
+impl<'tcx> LateLintPass<'tcx> for LenZero {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
+        if item.span.from_expansion() {
+            return;
+        }
+
+        if let ItemKind::Trait(_, _, _, _, trait_items) = item.kind {
+            check_trait_items(cx, item, trait_items);
+        }
+    }
+
+    fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
+        if_chain! {
+            if item.ident.name == sym::len;
+            if let ImplItemKind::Fn(sig, _) = &item.kind;
+            if sig.decl.implicit_self.has_implicit_self();
+            if cx.access_levels.is_exported(item.def_id);
+            if matches!(sig.decl.output, FnRetTy::Return(_));
+            if let Some(imp) = get_parent_as_impl(cx.tcx, item.hir_id());
+            if imp.of_trait.is_none();
+            if let TyKind::Path(ty_path) = &imp.self_ty.kind;
+            if let Some(ty_id) = cx.qpath_res(ty_path, imp.self_ty.hir_id).opt_def_id();
+            if let Some(local_id) = ty_id.as_local();
+            let ty_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_id);
+            if !is_lint_allowed(cx, LEN_WITHOUT_IS_EMPTY, ty_hir_id);
+            if let Some(output) = parse_len_output(cx, cx.tcx.fn_sig(item.def_id).skip_binder());
+            then {
+                let (name, kind) = match cx.tcx.hir().find(ty_hir_id) {
+                    Some(Node::ForeignItem(x)) => (x.ident.name, "extern type"),
+                    Some(Node::Item(x)) => match x.kind {
+                        ItemKind::Struct(..) => (x.ident.name, "struct"),
+                        ItemKind::Enum(..) => (x.ident.name, "enum"),
+                        ItemKind::Union(..) => (x.ident.name, "union"),
+                        _ => (x.ident.name, "type"),
+                    }
+                    _ => return,
+                };
+                check_for_is_empty(cx, sig.span, sig.decl.implicit_self, output, ty_id, name, kind)
+            }
+        }
+    }
+
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        if expr.span.from_expansion() {
+            return;
+        }
+
+        if let ExprKind::Binary(Spanned { node: cmp, .. }, left, right) = expr.kind {
+            match cmp {
+                BinOpKind::Eq => {
+                    check_cmp(cx, expr.span, left, right, "", 0); // len == 0
+                    check_cmp(cx, expr.span, right, left, "", 0); // 0 == len
+                },
+                BinOpKind::Ne => {
+                    check_cmp(cx, expr.span, left, right, "!", 0); // len != 0
+                    check_cmp(cx, expr.span, right, left, "!", 0); // 0 != len
+                },
+                BinOpKind::Gt => {
+                    check_cmp(cx, expr.span, left, right, "!", 0); // len > 0
+                    check_cmp(cx, expr.span, right, left, "", 1); // 1 > len
+                },
+                BinOpKind::Lt => {
+                    check_cmp(cx, expr.span, left, right, "", 1); // len < 1
+                    check_cmp(cx, expr.span, right, left, "!", 0); // 0 < len
+                },
+                BinOpKind::Ge => check_cmp(cx, expr.span, left, right, "!", 1), // len >= 1
+                BinOpKind::Le => check_cmp(cx, expr.span, right, left, "!", 1), // 1 <= len
+                _ => (),
+            }
+        }
+    }
+}
+
+fn check_trait_items(cx: &LateContext<'_>, visited_trait: &Item<'_>, trait_items: &[TraitItemRef]) {
+    fn is_named_self(cx: &LateContext<'_>, item: &TraitItemRef, name: Symbol) -> bool {
+        item.ident.name == name
+            && if let AssocItemKind::Fn { has_self } = item.kind {
+                has_self && { cx.tcx.fn_sig(item.id.def_id).inputs().skip_binder().len() == 1 }
+            } else {
+                false
+            }
+    }
+
+    // fill the set with current and super traits
+    fn fill_trait_set(traitt: DefId, set: &mut DefIdSet, cx: &LateContext<'_>) {
+        if set.insert(traitt) {
+            for supertrait in rustc_trait_selection::traits::supertrait_def_ids(cx.tcx, traitt) {
+                fill_trait_set(supertrait, set, cx);
+            }
+        }
+    }
+
+    if cx.access_levels.is_exported(visited_trait.def_id) && trait_items.iter().any(|i| is_named_self(cx, i, sym::len))
+    {
+        let mut current_and_super_traits = DefIdSet::default();
+        fill_trait_set(visited_trait.def_id.to_def_id(), &mut current_and_super_traits, cx);
+        let is_empty = sym!(is_empty);
+
+        let is_empty_method_found = current_and_super_traits
+            .iter()
+            .flat_map(|&i| cx.tcx.associated_items(i).filter_by_name_unhygienic(is_empty))
+            .any(|i| {
+                i.kind == ty::AssocKind::Fn
+                    && i.fn_has_self_parameter
+                    && cx.tcx.fn_sig(i.def_id).inputs().skip_binder().len() == 1
+            });
+
+        if !is_empty_method_found {
+            span_lint(
+                cx,
+                LEN_WITHOUT_IS_EMPTY,
+                visited_trait.span,
+                &format!(
+                    "trait `{}` has a `len` method but no (possibly inherited) `is_empty` method",
+                    visited_trait.ident.name
+                ),
+            );
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy)]
+enum LenOutput<'tcx> {
+    Integral,
+    Option(DefId),
+    Result(DefId, Ty<'tcx>),
+}
+fn parse_len_output<'tcx>(cx: &LateContext<'_>, sig: FnSig<'tcx>) -> Option<LenOutput<'tcx>> {
+    match *sig.output().kind() {
+        ty::Int(_) | ty::Uint(_) => Some(LenOutput::Integral),
+        ty::Adt(adt, subs) if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) => {
+            subs.type_at(0).is_integral().then(|| LenOutput::Option(adt.did()))
+        },
+        ty::Adt(adt, subs) if cx.tcx.is_diagnostic_item(sym::Result, adt.did()) => subs
+            .type_at(0)
+            .is_integral()
+            .then(|| LenOutput::Result(adt.did(), subs.type_at(1))),
+        _ => None,
+    }
+}
+
+impl<'tcx> LenOutput<'tcx> {
+    fn matches_is_empty_output(self, ty: Ty<'tcx>) -> bool {
+        match (self, ty.kind()) {
+            (_, &ty::Bool) => true,
+            (Self::Option(id), &ty::Adt(adt, subs)) if id == adt.did() => subs.type_at(0).is_bool(),
+            (Self::Result(id, err_ty), &ty::Adt(adt, subs)) if id == adt.did() => {
+                subs.type_at(0).is_bool() && subs.type_at(1) == err_ty
+            },
+            _ => false,
+        }
+    }
+
+    fn expected_sig(self, self_kind: ImplicitSelfKind) -> String {
+        let self_ref = match self_kind {
+            ImplicitSelfKind::ImmRef => "&",
+            ImplicitSelfKind::MutRef => "&mut ",
+            _ => "",
+        };
+        match self {
+            Self::Integral => format!("expected signature: `({}self) -> bool`", self_ref),
+            Self::Option(_) => format!(
+                "expected signature: `({}self) -> bool` or `({}self) -> Option<bool>",
+                self_ref, self_ref
+            ),
+            Self::Result(..) => format!(
+                "expected signature: `({}self) -> bool` or `({}self) -> Result<bool>",
+                self_ref, self_ref
+            ),
+        }
+    }
+}
+
+/// Checks if the given signature matches the expectations for `is_empty`
+fn check_is_empty_sig<'tcx>(sig: FnSig<'tcx>, self_kind: ImplicitSelfKind, len_output: LenOutput<'tcx>) -> bool {
+    match &**sig.inputs_and_output {
+        [arg, res] if len_output.matches_is_empty_output(*res) => {
+            matches!(
+                (arg.kind(), self_kind),
+                (ty::Ref(_, _, Mutability::Not), ImplicitSelfKind::ImmRef)
+                    | (ty::Ref(_, _, Mutability::Mut), ImplicitSelfKind::MutRef)
+            ) || (!arg.is_ref() && matches!(self_kind, ImplicitSelfKind::Imm | ImplicitSelfKind::Mut))
+        },
+        _ => false,
+    }
+}
+
+/// Checks if the given type has an `is_empty` method with the appropriate signature.
+fn check_for_is_empty<'tcx>(
+    cx: &LateContext<'tcx>,
+    span: Span,
+    self_kind: ImplicitSelfKind,
+    output: LenOutput<'tcx>,
+    impl_ty: DefId,
+    item_name: Symbol,
+    item_kind: &str,
+) {
+    let is_empty = Symbol::intern("is_empty");
+    let is_empty = cx
+        .tcx
+        .inherent_impls(impl_ty)
+        .iter()
+        .flat_map(|&id| cx.tcx.associated_items(id).filter_by_name_unhygienic(is_empty))
+        .find(|item| item.kind == AssocKind::Fn);
+
+    let (msg, is_empty_span, self_kind) = match is_empty {
+        None => (
+            format!(
+                "{} `{}` has a public `len` method, but no `is_empty` method",
+                item_kind,
+                item_name.as_str(),
+            ),
+            None,
+            None,
+        ),
+        Some(is_empty) if !cx.access_levels.is_exported(is_empty.def_id.expect_local()) => (
+            format!(
+                "{} `{}` has a public `len` method, but a private `is_empty` method",
+                item_kind,
+                item_name.as_str(),
+            ),
+            Some(cx.tcx.def_span(is_empty.def_id)),
+            None,
+        ),
+        Some(is_empty)
+            if !(is_empty.fn_has_self_parameter
+                && check_is_empty_sig(cx.tcx.fn_sig(is_empty.def_id).skip_binder(), self_kind, output)) =>
+        {
+            (
+                format!(
+                    "{} `{}` has a public `len` method, but the `is_empty` method has an unexpected signature",
+                    item_kind,
+                    item_name.as_str(),
+                ),
+                Some(cx.tcx.def_span(is_empty.def_id)),
+                Some(self_kind),
+            )
+        },
+        Some(_) => return,
+    };
+
+    span_lint_and_then(cx, LEN_WITHOUT_IS_EMPTY, span, &msg, |db| {
+        if let Some(span) = is_empty_span {
+            db.span_note(span, "`is_empty` defined here");
+        }
+        if let Some(self_kind) = self_kind {
+            db.note(&output.expected_sig(self_kind));
+        }
+    });
+}
+
+fn check_cmp(cx: &LateContext<'_>, span: Span, method: &Expr<'_>, lit: &Expr<'_>, op: &str, compare_to: u32) {
+    if let (&ExprKind::MethodCall(method_path, args, _), &ExprKind::Lit(ref lit)) = (&method.kind, &lit.kind) {
+        // check if we are in an is_empty() method
+        if let Some(name) = get_item_name(cx, method) {
+            if name.as_str() == "is_empty" {
+                return;
+            }
+        }
+
+        check_len(cx, span, method_path.ident.name, args, &lit.node, op, compare_to);
+    } else {
+        check_empty_expr(cx, span, method, lit, op);
+    }
+}
+
+fn check_len(
+    cx: &LateContext<'_>,
+    span: Span,
+    method_name: Symbol,
+    args: &[Expr<'_>],
+    lit: &LitKind,
+    op: &str,
+    compare_to: u32,
+) {
+    if let LitKind::Int(lit, _) = *lit {
+        // check if length is compared to the specified number
+        if lit != u128::from(compare_to) {
+            return;
+        }
+
+        if method_name == sym::len && args.len() == 1 && has_is_empty(cx, &args[0]) {
+            let mut applicability = Applicability::MachineApplicable;
+            span_lint_and_sugg(
+                cx,
+                LEN_ZERO,
+                span,
+                &format!("length comparison to {}", if compare_to == 0 { "zero" } else { "one" }),
+                &format!("using `{}is_empty` is clearer and more explicit", op),
+                format!(
+                    "{}{}.is_empty()",
+                    op,
+                    snippet_with_applicability(cx, args[0].span, "_", &mut applicability)
+                ),
+                applicability,
+            );
+        }
+    }
+}
+
+fn check_empty_expr(cx: &LateContext<'_>, span: Span, lit1: &Expr<'_>, lit2: &Expr<'_>, op: &str) {
+    if (is_empty_array(lit2) || is_empty_string(lit2)) && has_is_empty(cx, lit1) {
+        let mut applicability = Applicability::MachineApplicable;
+        span_lint_and_sugg(
+            cx,
+            COMPARISON_TO_EMPTY,
+            span,
+            "comparison to empty slice",
+            &format!("using `{}is_empty` is clearer and more explicit", op),
+            format!(
+                "{}{}.is_empty()",
+                op,
+                snippet_with_applicability(cx, lit1.span, "_", &mut applicability)
+            ),
+            applicability,
+        );
+    }
+}
+
+fn is_empty_string(expr: &Expr<'_>) -> bool {
+    if let ExprKind::Lit(ref lit) = expr.kind {
+        if let LitKind::Str(lit, _) = lit.node {
+            let lit = lit.as_str();
+            return lit.is_empty();
+        }
+    }
+    false
+}
+
+fn is_empty_array(expr: &Expr<'_>) -> bool {
+    if let ExprKind::Array(arr) = expr.kind {
+        return arr.is_empty();
+    }
+    false
+}
+
+/// Checks if this type has an `is_empty` method.
+fn has_is_empty(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
+    /// Gets an `AssocItem` and return true if it matches `is_empty(self)`.
+    fn is_is_empty(cx: &LateContext<'_>, item: &ty::AssocItem) -> bool {
+        if item.kind == ty::AssocKind::Fn {
+            let sig = cx.tcx.fn_sig(item.def_id);
+            let ty = sig.skip_binder();
+            ty.inputs().len() == 1
+        } else {
+            false
+        }
+    }
+
+    /// Checks the inherent impl's items for an `is_empty(self)` method.
+    fn has_is_empty_impl(cx: &LateContext<'_>, id: DefId) -> bool {
+        let is_empty = sym!(is_empty);
+        cx.tcx.inherent_impls(id).iter().any(|imp| {
+            cx.tcx
+                .associated_items(*imp)
+                .filter_by_name_unhygienic(is_empty)
+                .any(|item| is_is_empty(cx, item))
+        })
+    }
+
+    let ty = &cx.typeck_results().expr_ty(expr).peel_refs();
+    match ty.kind() {
+        ty::Dynamic(tt, ..) => tt.principal().map_or(false, |principal| {
+            let is_empty = sym!(is_empty);
+            cx.tcx
+                .associated_items(principal.def_id())
+                .filter_by_name_unhygienic(is_empty)
+                .any(|item| is_is_empty(cx, item))
+        }),
+        ty::Projection(ref proj) => has_is_empty_impl(cx, proj.item_def_id),
+        ty::Adt(id, _) => has_is_empty_impl(cx, id.did()),
+        ty::Array(..) | ty::Slice(..) | ty::Str => true,
+        _ => false,
+    }
+}