Rollup merge of rust-lang#156021 - nnethercote:clean-up-some-traits, r=jackh726

Clean up some traits

I was looking at various traits and found some unnecessary trait bounds, and some unnecessary traits. Details in individual commits.

r? @Nadrieril

Author: GuillaumeGomez

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -47,7 +47,6 @@ use super::{DescribePlaceOpt, RegionName, RegionNameSource, UseSpans};
 use crate::borrow_set::{BorrowData, TwoPhaseActivation};
 use crate::diagnostics::conflict_errors::StorageDeadOrDrop::LocalStorageDead;
 use crate::diagnostics::{CapturedMessageOpt, call_kind, find_all_local_uses};
-use crate::prefixes::IsPrefixOf;
 use crate::{InitializationRequiringAction, MirBorrowckCtxt, WriteKind, borrowck_errors};
 
 #[derive(Debug)]

compiler/rustc_borrowck/src/prefixes.rs

@@ -8,18 +8,6 @@ use rustc_middle::mir::{PlaceRef, ProjectionElem};
 
 use super::MirBorrowckCtxt;
 
-pub(crate) trait IsPrefixOf<'tcx> {
-    fn is_prefix_of(&self, other: PlaceRef<'tcx>) -> bool;
-}
-
-impl<'tcx> IsPrefixOf<'tcx> for PlaceRef<'tcx> {
-    fn is_prefix_of(&self, other: PlaceRef<'tcx>) -> bool {
-        self.local == other.local
-            && self.projection.len() <= other.projection.len()
-            && self.projection == &other.projection[..self.projection.len()]
-    }
-}
-
 pub(super) struct Prefixes<'tcx> {
     kind: PrefixSet,
     next: Option<PlaceRef<'tcx>>,

compiler/rustc_borrowck/src/region_infer/values.rs

@@ -426,19 +426,13 @@ impl ToElementIndex<'_> for RegionVid {
 }
 
 impl<'tcx> ToElementIndex<'tcx> for ty::PlaceholderRegion<'tcx> {
-    fn add_to_row<N: Idx>(self, values: &mut RegionValues<'tcx, N>, row: N) -> bool
-    where
-        Self: Into<ty::PlaceholderRegion<'tcx>>,
-    {
+    fn add_to_row<N: Idx>(self, values: &mut RegionValues<'tcx, N>, row: N) -> bool {
         let placeholder: ty::PlaceholderRegion<'tcx> = self.into();
         let index = values.placeholder_indices.lookup_index(placeholder);
         values.placeholders.insert(row, index)
     }
 
-    fn contained_in_row<N: Idx>(self, values: &RegionValues<'tcx, N>, row: N) -> bool
-    where
-        Self: Into<ty::PlaceholderRegion<'tcx>>,
-    {
+    fn contained_in_row<N: Idx>(self, values: &RegionValues<'tcx, N>, row: N) -> bool {
         let placeholder: ty::PlaceholderRegion<'tcx> = self.into();
         let index = values.placeholder_indices.lookup_index(placeholder);
         values.placeholders.contains(row, index)

compiler/rustc_error_messages/src/lib.rs

@@ -268,10 +268,7 @@ pub fn fluent_value_from_str_list_sep_by_and(l: Vec<Cow<'_, str>>) -> FluentValu
         type Args = ();
         type Error = ();
 
-        fn construct(lang: LanguageIdentifier, _args: Self::Args) -> Result<Self, Self::Error>
-        where
-            Self: Sized,
-        {
+        fn construct(lang: LanguageIdentifier, _args: Self::Args) -> Result<Self, Self::Error> {
             let locale = icu_locale_from_unic_langid(lang)
                 .unwrap_or_else(|| rustc_baked_icu_data::supported_locales::EN);
             let list_formatter = icu_list::ListFormatter::try_new_and_unstable(

compiler/rustc_errors/src/diagnostic.rs

@@ -143,10 +143,7 @@ impl<'a, F: FnOnce(&mut Diag<'_, ()>)> Diagnostic<'a, ()> for DiagDecorator<F> {
 /// Trait implemented by error types. This should not be implemented manually. Instead, use
 /// `#[derive(Subdiagnostic)]` -- see [rustc_macros::Subdiagnostic].
 #[rustc_diagnostic_item = "Subdiagnostic"]
-pub trait Subdiagnostic
-where
-    Self: Sized,
-{
+pub trait Subdiagnostic {
     /// Add a subdiagnostic to an existing diagnostic.
     fn add_to_diag<G: EmissionGuarantee>(self, diag: &mut Diag<'_, G>);
 }

compiler/rustc_hir/src/intravisit.rs

@@ -71,11 +71,6 @@ use rustc_span::{Ident, Span, Symbol};
 
 use crate::hir::*;
 
-pub trait IntoVisitor<'hir> {
-    type Visitor: Visitor<'hir>;
-    fn into_visitor(&self) -> Self::Visitor;
-}
-
 #[derive(Copy, Clone, Debug)]
 pub enum FnKind<'a> {
     /// `#[xxx] pub async/const/extern "Abi" fn foo()`

compiler/rustc_infer/src/infer/snapshot/undo_log.rs

@@ -126,7 +126,6 @@ where
 
     fn extend<J>(&mut self, undos: J)
     where
-        Self: Sized,
         J: IntoIterator<Item = T>,
     {
         if self.in_snapshot() {

compiler/rustc_middle/src/mir/statement.rs

@@ -478,6 +478,12 @@ impl From<Local> for Place<'_> {
 }
 
 impl<'tcx> PlaceRef<'tcx> {
+    pub fn is_prefix_of(&self, other: PlaceRef<'tcx>) -> bool {
+        self.local == other.local
+            && self.projection.len() <= other.projection.len()
+            && self.projection == &other.projection[..self.projection.len()]
+    }
+
     /// Finds the innermost `Local` from this `Place`, *if* it is either a local itself or
     /// a single deref of a local.
     pub fn local_or_deref_local(&self) -> Option<Local> {

compiler/rustc_pattern_analysis/src/lib.rs

@@ -25,9 +25,6 @@ pub use rustc_index::{Idx, IndexVec}; // re-exported to avoid rustc_index versio
 use crate::constructor::{Constructor, ConstructorSet, IntRange};
 use crate::pat::DeconstructedPat;
 
-pub trait Captures<'a> {}
-impl<'a, T: ?Sized> Captures<'a> for T {}
-
 /// `bool` newtype that indicates whether this is a privately uninhabited field that we should skip
 /// during analysis.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]