src/tools/clippy/clippy_lints/src/missing_inline.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use rustc_ast::ast;
   3 use rustc_hir as hir;
   4 use rustc_lint::{LateContext, LateLintPass, LintContext};
   5 use rustc_session::declare_lint_pass;
   6 use rustc_span::{sym, Span};
   7
   8 declare_clippy_lint! {
   9     /// ### What it does
  10     /// It lints if an exported function, method, trait method with default impl,
  11     /// or trait method impl is not `#[inline]`.
  12     ///
  13     /// ### Why is this bad?
  14     /// In general, it is not. Functions can be inlined across
  15     /// crates when that's profitable as long as any form of LTO is used. When LTO is disabled,
  16     /// functions that are not `#[inline]` cannot be inlined across crates. Certain types of crates
  17     /// might intend for most of the methods in their public API to be able to be inlined across
  18     /// crates even when LTO is disabled. For these types of crates, enabling this lint might make
  19     /// sense. It allows the crate to require all exported methods to be `#[inline]` by default, and
  20     /// then opt out for specific methods where this might not make sense.
  21     ///
  22     /// ### Example
  23     /// ```no_run
  24     /// pub fn foo() {} // missing #[inline]
  25     /// fn ok() {} // ok
  26     /// #[inline] pub fn bar() {} // ok
  27     /// #[inline(always)] pub fn baz() {} // ok
  28     ///
  29     /// pub trait Bar {
  30     ///   fn bar(); // ok
  31     ///   fn def_bar() {} // missing #[inline]
  32     /// }
  33     ///
  34     /// struct Baz;
  35     /// impl Baz {
  36     ///    fn private() {} // ok
  37     /// }
  38     ///
  39     /// impl Bar for Baz {
  40     ///   fn bar() {} // ok - Baz is not exported
  41     /// }
  42     ///
  43     /// pub struct PubBaz;
  44     /// impl PubBaz {
  45     ///    fn private() {} // ok
  46     ///    pub fn not_private() {} // missing #[inline]
  47     /// }
  48     ///
  49     /// impl Bar for PubBaz {
  50     ///    fn bar() {} // missing #[inline]
  51     ///    fn def_bar() {} // missing #[inline]
  52     /// }
  53     /// ```
  54     #[clippy::version = "pre 1.29.0"]
  55     pub MISSING_INLINE_IN_PUBLIC_ITEMS,
  56     restriction,
  57     "detects missing `#[inline]` attribute for public callables (functions, trait methods, methods...)"
  58 }
  59
  60 fn check_missing_inline_attrs(cx: &LateContext<'_>, attrs: &[ast::Attribute], sp: Span, desc: &'static str) {
  61     let has_inline = attrs.iter().any(|a| a.has_name(sym::inline));
  62     if !has_inline {
  63         span_lint(
  64             cx,
  65             MISSING_INLINE_IN_PUBLIC_ITEMS,
  66             sp,
  67             format!("missing `#[inline]` for {desc}"),
  68         );
  69     }
  70 }
  71
  72 fn is_executable_or_proc_macro(cx: &LateContext<'_>) -> bool {
  73     use rustc_session::config::CrateType;
  74
  75     cx.tcx
  76         .crate_types()
  77         .iter()
  78         .any(|t: &CrateType| matches!(t, CrateType::Executable | CrateType::ProcMacro))
  79 }
  80
  81 declare_lint_pass!(MissingInline => [MISSING_INLINE_IN_PUBLIC_ITEMS]);
  82
  83 impl<'tcx> LateLintPass<'tcx> for MissingInline {
  84     fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx hir::Item<'_>) {
  85         if rustc_middle::lint::in_external_macro(cx.sess(), it.span) || is_executable_or_proc_macro(cx) {
  86             return;
  87         }
  88
  89         if !cx.effective_visibilities.is_exported(it.owner_id.def_id) {
  90             return;
  91         }
  92         match it.kind {
  93             hir::ItemKind::Fn(..) => {
  94                 let desc = "a function";
  95                 let attrs = cx.tcx.hir().attrs(it.hir_id());
  96                 check_missing_inline_attrs(cx, attrs, it.span, desc);
  97             },
  98             hir::ItemKind::Trait(ref _is_auto, ref _unsafe, _generics, _bounds, trait_items) => {
  99                 // note: we need to check if the trait is exported so we can't use
 100                 // `LateLintPass::check_trait_item` here.
 101                 for tit in trait_items {
 102                     let tit_ = cx.tcx.hir().trait_item(tit.id);
 103                     match tit_.kind {
 104                         hir::TraitItemKind::Const(..) | hir::TraitItemKind::Type(..) => {},
 105                         hir::TraitItemKind::Fn(..) => {
 106                             if cx.tcx.defaultness(tit.id.owner_id).has_value() {
 107                                 // trait method with default body needs inline in case
 108                                 // an impl is not provided
 109                                 let desc = "a default trait method";
 110                                 let item = cx.tcx.hir().trait_item(tit.id);
 111                                 let attrs = cx.tcx.hir().attrs(item.hir_id());
 112                                 check_missing_inline_attrs(cx, attrs, item.span, desc);
 113                             }
 114                         },
 115                     }
 116                 }
 117             },
 118             hir::ItemKind::Const(..)
 119             | hir::ItemKind::Enum(..)
 120             | hir::ItemKind::Macro(..)
 121             | hir::ItemKind::Mod(..)
 122             | hir::ItemKind::Static(..)
 123             | hir::ItemKind::Struct(..)
 124             | hir::ItemKind::TraitAlias(..)
 125             | hir::ItemKind::GlobalAsm(..)
 126             | hir::ItemKind::TyAlias(..)
 127             | hir::ItemKind::Union(..)
 128             | hir::ItemKind::OpaqueTy(..)
 129             | hir::ItemKind::ExternCrate(..)
 130             | hir::ItemKind::ForeignMod { .. }
 131             | hir::ItemKind::Impl { .. }
 132             | hir::ItemKind::Use(..) => {},
 133         };
 134     }
 135
 136     fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx hir::ImplItem<'_>) {
 137         use rustc_middle::ty::{ImplContainer, TraitContainer};
 138         if rustc_middle::lint::in_external_macro(cx.sess(), impl_item.span) || is_executable_or_proc_macro(cx) {
 139             return;
 140         }
 141
 142         // If the item being implemented is not exported, then we don't need #[inline]
 143         if !cx.effective_visibilities.is_exported(impl_item.owner_id.def_id) {
 144             return;
 145         }
 146
 147         let desc = match impl_item.kind {
 148             hir::ImplItemKind::Fn(..) => "a method",
 149             hir::ImplItemKind::Const(..) | hir::ImplItemKind::Type(_) => return,
 150         };
 151
 152         let assoc_item = cx.tcx.associated_item(impl_item.owner_id);
 153         let container_id = assoc_item.container_id(cx.tcx);
 154         let trait_def_id = match assoc_item.container {
 155             TraitContainer => Some(container_id),
 156             ImplContainer => cx.tcx.impl_trait_ref(container_id).map(|t| t.skip_binder().def_id),
 157         };
 158
 159         if let Some(trait_def_id) = trait_def_id {
 160             if trait_def_id.is_local() && !cx.effective_visibilities.is_exported(impl_item.owner_id.def_id) {
 161                 // If a trait is being implemented for an item, and the
 162                 // trait is not exported, we don't need #[inline]
 163                 return;
 164             }
 165         }
 166
 167         let attrs = cx.tcx.hir().attrs(impl_item.hir_id());
 168         check_missing_inline_attrs(cx, attrs, impl_item.span, desc);
 169     }
 170 }