Replace elided_named_lifetimes with mismatched_lifetime_syntaxes

Author: shepmaster

compiler/rustc_hir/src/def.rs

@@ -850,12 +850,7 @@ pub enum LifetimeRes {
     /// late resolution. Those lifetimes will be inferred by typechecking.
     Infer,
     /// `'static` lifetime.
-    Static {
-        /// We do not want to emit `elided_named_lifetimes`
-        /// when we are inside of a const item or a static,
-        /// because it would get too annoying.
-        suppress_elision_warning: bool,
-    },
+    Static,
     /// Resolution failure.
     Error,
     /// HACK: This is used to recover the NodeId of an elided lifetime.

compiler/rustc_lint/messages.ftl

@@ -251,11 +251,6 @@ lint_duplicate_macro_attribute =
 
 lint_duplicate_matcher_binding = duplicate matcher binding
 
-lint_elided_named_lifetime = elided lifetime has a name
-    .label_elided = this elided lifetime gets resolved as `{$name}`
-    .label_named = lifetime `{$name}` declared here
-    .suggestion = consider specifying it explicitly
-
 lint_enum_intrinsics_mem_discriminant =
     the return value of `mem::discriminant` is unspecified when called with a non-enum type
     .note = the argument to `discriminant` should be a reference to an enum, but it was passed a reference to a `{$ty_param}`, which is not an enum

compiler/rustc_lint/src/early/diagnostics.rs

@@ -10,11 +10,11 @@ use rustc_errors::{
 use rustc_middle::middle::stability;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::Session;
-use rustc_session::lint::{BuiltinLintDiag, ElidedLifetimeResolution};
-use rustc_span::{BytePos, kw};
+use rustc_session::lint::BuiltinLintDiag;
+use rustc_span::BytePos;
 use tracing::debug;
 
-use crate::lints::{self, ElidedNamedLifetime};
+use crate::lints;
 
 mod check_cfg;
 
@@ -450,16 +450,5 @@ pub(super) fn decorate_lint(
         BuiltinLintDiag::UnexpectedBuiltinCfg { cfg, cfg_name, controlled_by } => {
             lints::UnexpectedBuiltinCfg { cfg, cfg_name, controlled_by }.decorate_lint(diag)
         }
-        BuiltinLintDiag::ElidedNamedLifetimes { elided: (span, kind), resolution } => {
-            match resolution {
-                ElidedLifetimeResolution::Static => {
-                    ElidedNamedLifetime { span, kind, name: kw::StaticLifetime, declaration: None }
-                }
-                ElidedLifetimeResolution::Param(name, declaration) => {
-                    ElidedNamedLifetime { span, kind, name, declaration: Some(declaration) }
-                }
-            }
-            .decorate_lint(diag)
-        }
     }
 }

compiler/rustc_lint/src/lib.rs

@@ -356,6 +356,7 @@ fn register_builtins(store: &mut LintStore) {
     store.register_renamed("unused_tuple_struct_fields", "dead_code");
     store.register_renamed("static_mut_ref", "static_mut_refs");
     store.register_renamed("temporary_cstring_as_ptr", "dangling_pointers_from_temporaries");
+    store.register_renamed("elided_named_lifetimes", "mismatched_lifetime_syntaxes");
 
     // These were moved to tool lints, but rustc still sees them when compiling normally, before
     // tool lints are registered, so `check_tool_name_for_backwards_compat` doesn't work. Use

compiler/rustc_lint/src/lifetime_style.rs

@@ -62,7 +62,7 @@ declare_lint! {
     /// In certain `unsafe` code, lifetime elision combined with
     /// inconsistent lifetime syntax may result in unsound code.
     pub MISMATCHED_LIFETIME_SYNTAXES,
-    Allow,
+    Warn,
     "detects when an elided lifetime uses different syntax between arguments and return values"
 }
 

compiler/rustc_lint/src/lints.rs

@@ -8,17 +8,17 @@ use rustc_errors::{
     Applicability, Diag, DiagArgValue, DiagMessage, DiagStyledString, ElidedLifetimeInPathSubdiag,
     EmissionGuarantee, LintDiagnostic, MultiSpan, Subdiagnostic, SuggestionStyle,
 };
+use rustc_hir as hir;
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::VisitorExt;
-use rustc_hir::{self as hir, MissingLifetimeKind};
 use rustc_macros::{LintDiagnostic, Subdiagnostic};
 use rustc_middle::ty::inhabitedness::InhabitedPredicate;
 use rustc_middle::ty::{Clause, PolyExistentialTraitRef, Ty, TyCtxt};
 use rustc_session::Session;
 use rustc_session::lint::AmbiguityErrorDiag;
 use rustc_span::edition::Edition;
-use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, kw, sym};
+use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, sym};
 
 use crate::builtin::{InitError, ShorthandAssocTyCollector, TypeAliasBounds};
 use crate::errors::{OverruledAttributeSub, RequestedLevel};
@@ -2689,58 +2689,6 @@ pub(crate) struct ElidedLifetimesInPaths {
     pub subdiag: ElidedLifetimeInPathSubdiag,
 }
 
-pub(crate) struct ElidedNamedLifetime {
-    pub span: Span,
-    pub kind: MissingLifetimeKind,
-    pub name: Symbol,
-    pub declaration: Option<Span>,
-}
-
-impl<G: EmissionGuarantee> LintDiagnostic<'_, G> for ElidedNamedLifetime {
-    fn decorate_lint(self, diag: &mut rustc_errors::Diag<'_, G>) {
-        let Self { span, kind, name, declaration } = self;
-        diag.primary_message(fluent::lint_elided_named_lifetime);
-        diag.arg("name", name);
-        diag.span_label(span, fluent::lint_label_elided);
-        if let Some(declaration) = declaration {
-            diag.span_label(declaration, fluent::lint_label_named);
-        }
-        // FIXME(GrigorenkoPV): this `if` and `return` should be removed,
-        //  but currently this lint's suggestions can conflict with those of `clippy::needless_lifetimes`:
-        //  https://github.com/rust-lang/rust/pull/129840#issuecomment-2323349119
-        // HACK: `'static` suggestions will never sonflict, emit only those for now.
-        if name != kw::StaticLifetime {
-            return;
-        }
-        match kind {
-            MissingLifetimeKind::Underscore => diag.span_suggestion_verbose(
-                span,
-                fluent::lint_suggestion,
-                format!("{name}"),
-                Applicability::MachineApplicable,
-            ),
-            MissingLifetimeKind::Ampersand => diag.span_suggestion_verbose(
-                span.shrink_to_hi(),
-                fluent::lint_suggestion,
-                format!("{name} "),
-                Applicability::MachineApplicable,
-            ),
-            MissingLifetimeKind::Comma => diag.span_suggestion_verbose(
-                span.shrink_to_hi(),
-                fluent::lint_suggestion,
-                format!("{name}, "),
-                Applicability::MachineApplicable,
-            ),
-            MissingLifetimeKind::Brackets => diag.span_suggestion_verbose(
-                span.shrink_to_hi(),
-                fluent::lint_suggestion,
-                format!("<{name}>"),
-                Applicability::MachineApplicable,
-            ),
-        };
-    }
-}
-
 #[derive(LintDiagnostic)]
 #[diag(lint_invalid_crate_type_value)]
 pub(crate) struct UnknownCrateTypes {

compiler/rustc_lint_defs/src/builtin.rs

@@ -39,7 +39,6 @@ declare_lint_pass! {
         DUPLICATE_MACRO_ATTRIBUTES,
         ELIDED_LIFETIMES_IN_ASSOCIATED_CONSTANT,
         ELIDED_LIFETIMES_IN_PATHS,
-        ELIDED_NAMED_LIFETIMES,
         EXPLICIT_BUILTIN_CFGS_IN_FLAGS,
         EXPORTED_PRIVATE_DEPENDENCIES,
         FFI_UNWIND_CALLS,
@@ -1827,38 +1826,6 @@ declare_lint! {
     "hidden lifetime parameters in types are deprecated"
 }
 
-declare_lint! {
-    /// The `elided_named_lifetimes` lint detects when an elided
-    /// lifetime ends up being a named lifetime, such as `'static`
-    /// or some lifetime parameter `'a`.
-    ///
-    /// ### Example
-    ///
-    /// ```rust,compile_fail
-    /// #![deny(elided_named_lifetimes)]
-    /// struct Foo;
-    /// impl Foo {
-    ///     pub fn get_mut(&'static self, x: &mut u8) -> &mut u8 {
-    ///         unsafe { &mut *(x as *mut _) }
-    ///     }
-    /// }
-    /// ```
-    ///
-    /// {{produces}}
-    ///
-    /// ### Explanation
-    ///
-    /// Lifetime elision is quite useful, because it frees you from having
-    /// to give each lifetime its own name, but sometimes it can produce
-    /// somewhat surprising resolutions. In safe code, it is mostly okay,
-    /// because the borrow checker prevents any unsoundness, so the worst
-    /// case scenario is you get a confusing error message in some other place.
-    /// But with `unsafe` code, such unexpected resolutions may lead to unsound code.
-    pub ELIDED_NAMED_LIFETIMES,
-    Warn,
-    "detects when an elided lifetime gets resolved to be `'static` or some named parameter"
-}
-
 declare_lint! {
     /// The `bare_trait_objects` lint suggests using `dyn Trait` for trait
     /// objects.

compiler/rustc_lint_defs/src/lib.rs

@@ -9,7 +9,7 @@ use rustc_data_structures::stable_hasher::{
 use rustc_error_messages::{DiagMessage, MultiSpan};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefPathHash;
-use rustc_hir::{HashStableContext, HirId, ItemLocalId, MissingLifetimeKind};
+use rustc_hir::{HashStableContext, HirId, ItemLocalId};
 use rustc_macros::{Decodable, Encodable, HashStable_Generic};
 pub use rustc_span::edition::Edition;
 use rustc_span::{Ident, MacroRulesNormalizedIdent, Span, Symbol, sym};
@@ -635,12 +635,6 @@ pub enum DeprecatedSinceKind {
     InVersion(String),
 }
 
-#[derive(Debug)]
-pub enum ElidedLifetimeResolution {
-    Static,
-    Param(Symbol, Span),
-}
-
 // This could be a closure, but then implementing derive trait
 // becomes hacky (and it gets allocated).
 #[derive(Debug)]
@@ -653,10 +647,6 @@ pub enum BuiltinLintDiag {
     },
     MacroExpandedMacroExportsAccessedByAbsolutePaths(Span),
     ElidedLifetimesInPaths(usize, Span, bool, Span),
-    ElidedNamedLifetimes {
-        elided: (Span, MissingLifetimeKind),
-        resolution: ElidedLifetimeResolution,
-    },
     UnknownCrateTypes {
         span: Span,
         candidate: Option<Symbol>,

compiler/rustc_resolve/src/late.rs

@@ -1706,7 +1706,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         if ident.name == kw::StaticLifetime {
             self.record_lifetime_res(
                 lifetime.id,
-                LifetimeRes::Static { suppress_elision_warning: false },
+                LifetimeRes::Static,
                 LifetimeElisionCandidate::Named,
             );
             return;
@@ -1854,8 +1854,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                     if lifetimes_in_scope.is_empty() {
                         self.record_lifetime_res(
                             lifetime.id,
-                            // We are inside a const item, so do not warn.
-                            LifetimeRes::Static { suppress_elision_warning: true },
+                            LifetimeRes::Static,
                             elision_candidate,
                         );
                         return;
@@ -2202,47 +2201,6 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             panic!("lifetime {id:?} resolved multiple times ({prev_res:?} before, {res:?} now)")
         }
 
-        match candidate {
-            LifetimeElisionCandidate::Missing(missing @ MissingLifetime { .. }) => {
-                debug_assert_eq!(id, missing.id);
-                match res {
-                    LifetimeRes::Static { suppress_elision_warning } => {
-                        if !suppress_elision_warning {
-                            self.r.lint_buffer.buffer_lint(
-                                lint::builtin::ELIDED_NAMED_LIFETIMES,
-                                missing.id_for_lint,
-                                missing.span,
-                                BuiltinLintDiag::ElidedNamedLifetimes {
-                                    elided: (missing.span, missing.kind),
-                                    resolution: lint::ElidedLifetimeResolution::Static,
-                                },
-                            );
-                        }
-                    }
-                    LifetimeRes::Param { param, binder: _ } => {
-                        let tcx = self.r.tcx();
-                        self.r.lint_buffer.buffer_lint(
-                            lint::builtin::ELIDED_NAMED_LIFETIMES,
-                            missing.id_for_lint,
-                            missing.span,
-                            BuiltinLintDiag::ElidedNamedLifetimes {
-                                elided: (missing.span, missing.kind),
-                                resolution: lint::ElidedLifetimeResolution::Param(
-                                    tcx.item_name(param.into()),
-                                    tcx.source_span(param),
-                                ),
-                            },
-                        );
-                    }
-                    LifetimeRes::Fresh { .. }
-                    | LifetimeRes::Infer
-                    | LifetimeRes::Error
-                    | LifetimeRes::ElidedAnchor { .. } => {}
-                }
-            }
-            LifetimeElisionCandidate::Ignore | LifetimeElisionCandidate::Named => {}
-        }
-
         match res {
             LifetimeRes::Param { .. } | LifetimeRes::Fresh { .. } | LifetimeRes::Static { .. } => {
                 if let Some(ref mut candidates) = self.lifetime_elision_candidates {
@@ -2760,14 +2718,9 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                 ..
             }) => {
                 self.with_static_rib(def_kind, |this| {
-                    this.with_lifetime_rib(
-                        LifetimeRibKind::Elided(LifetimeRes::Static {
-                            suppress_elision_warning: true,
-                        }),
-                        |this| {
-                            this.visit_ty(ty);
-                        },
-                    );
+                    this.with_lifetime_rib(LifetimeRibKind::Elided(LifetimeRes::Static), |this| {
+                        this.visit_ty(ty);
+                    });
                     if let Some(expr) = expr {
                         // We already forbid generic params because of the above item rib,
                         // so it doesn't matter whether this is a trivial constant.
@@ -2804,9 +2757,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         this.visit_generics(generics);
 
                         this.with_lifetime_rib(
-                            LifetimeRibKind::Elided(LifetimeRes::Static {
-                                suppress_elision_warning: true,
-                            }),
+                            LifetimeRibKind::Elided(LifetimeRes::Static),
                             |this| this.visit_ty(ty),
                         );
 

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -3276,7 +3276,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     maybe_static = true;
                     in_scope_lifetimes = vec![(
                         Ident::with_dummy_span(kw::StaticLifetime),
-                        (DUMMY_NODE_ID, LifetimeRes::Static { suppress_elision_warning: false }),
+                        (DUMMY_NODE_ID, LifetimeRes::Static),
                     )];
                 }
             } else if elided_len == 0 {
@@ -3288,7 +3288,7 @@ impl<'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'_, 'ast, 'ra, 'tcx> {
                     maybe_static = true;
                     in_scope_lifetimes = vec![(
                         Ident::with_dummy_span(kw::StaticLifetime),
-                        (DUMMY_NODE_ID, LifetimeRes::Static { suppress_elision_warning: false }),
+                        (DUMMY_NODE_ID, LifetimeRes::Static),
                     )];
                 }
             } else if num_params == 1 {

src/tools/clippy/tests/ui/needless_lifetimes.fixed

@@ -10,7 +10,7 @@
     clippy::unnecessary_wraps,
     dyn_drop,
     clippy::get_first,
-    elided_named_lifetimes
+    mismatched_lifetime_syntaxes,
 )]
 
 extern crate proc_macros;

src/tools/clippy/tests/ui/needless_lifetimes.rs

@@ -10,7 +10,7 @@
     clippy::unnecessary_wraps,
     dyn_drop,
     clippy::get_first,
-    elided_named_lifetimes
+    mismatched_lifetime_syntaxes,
 )]
 
 extern crate proc_macros;

src/tools/clippy/tests/ui/ptr_arg.rs

@@ -312,7 +312,7 @@ mod issue_9218 {
 
     // Inferred to be `&'a str`, afaik.
     fn cow_good_ret_ty<'a>(input: &'a Cow<'a, str>) -> &str {
-        //~^ ERROR: elided lifetime has a name
+        //~^ ERROR: lifetime flowing from input to output with different syntax
         todo!()
     }
 }