Auto merge of #97697 - WaffleLapkin:no_ref_vec, r=WaffleLapkin

Replace `&Vec<_>`s with `&[_]`s

It's generally preferable to use `&[_]` since it's one less indirection and it can be created from types other that `Vec`.

I've left `&Vec` in some locals where it doesn't really matter, in cases where `TypeFoldable` is expected (`TypeFoldable: Clone` so slice can't implement it) and in cases where it's `&TypeAliasThatIsActiallyVec`. Nothing important, really, I was just a little annoyed by `visit_generic_param_vec` :D

r? `@compiler-errors`

compiler/rustc_errors/src/diagnostic.rs

@@ -827,7 +827,7 @@ impl Diagnostic {
         self
     }
 
-    pub fn styled_message(&self) -> &Vec<(DiagnosticMessage, Style)> {
+    pub fn styled_message(&self) -> &[(DiagnosticMessage, Style)] {
         &self.message
     }
 
@@ -888,11 +888,11 @@ impl Diagnostic {
         &self,
     ) -> (
         &Level,
-        &Vec<(DiagnosticMessage, Style)>,
+        &[(DiagnosticMessage, Style)],
         &Option<DiagnosticId>,
         &MultiSpan,
         &Result<Vec<CodeSuggestion>, SuggestionsDisabled>,
-        Option<&Vec<SubDiagnostic>>,
+        Option<&[SubDiagnostic]>,
     ) {
         (
             &self.level,

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -352,7 +352,7 @@ pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
 }
 
 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
-    pub fn report_region_errors(&self, errors: &Vec<RegionResolutionError<'tcx>>) {
+    pub fn report_region_errors(&self, errors: &[RegionResolutionError<'tcx>]) {
         debug!("report_region_errors(): {} errors to start", errors.len());
 
         // try to pre-process the errors, which will group some of them

compiler/rustc_middle/src/middle/region.rs

@@ -16,6 +16,7 @@ use rustc_query_system::ich::StableHashingContext;
 use rustc_span::{Span, DUMMY_SP};
 
 use std::fmt;
+use std::ops::Deref;
 
 /// Represents a statically-describable scope that can be used to
 /// bound the lifetime/region for values.
@@ -407,8 +408,8 @@ impl ScopeTree {
 
     /// Checks whether the given scope contains a `yield`. If so,
     /// returns `Some(YieldData)`. If not, returns `None`.
-    pub fn yield_in_scope(&self, scope: Scope) -> Option<&Vec<YieldData>> {
-        self.yield_in_scope.get(&scope)
+    pub fn yield_in_scope(&self, scope: Scope) -> Option<&[YieldData]> {
+        self.yield_in_scope.get(&scope).map(Deref::deref)
     }
 
     /// Gives the number of expressions visited in a body.

compiler/rustc_middle/src/mir/traversal.rs

@@ -310,7 +310,7 @@ pub fn reachable_as_bitset<'tcx>(body: &Body<'tcx>) -> BitSet<BasicBlock> {
 #[derive(Clone)]
 pub struct ReversePostorderIter<'a, 'tcx> {
     body: &'a Body<'tcx>,
-    blocks: &'a Vec<BasicBlock>,
+    blocks: &'a [BasicBlock],
     idx: usize,
 }
 
@@ -358,9 +358,9 @@ impl PostorderCache {
         self.cache = OnceCell::new();
     }
 
-    /// Returns the &Vec<BasicBlocks> represents the postorder graph for this MIR.
+    /// Returns the `&[BasicBlocks]` represents the postorder graph for this MIR.
     #[inline]
-    pub(super) fn compute(&self, body: &Body<'_>) -> &Vec<BasicBlock> {
+    pub(super) fn compute(&self, body: &Body<'_>) -> &[BasicBlock] {
         self.cache.get_or_init(|| Postorder::new(body, START_BLOCK).map(|(bb, _)| bb).collect())
     }
 }

compiler/rustc_middle/src/ty/sty.rs

@@ -1032,6 +1032,13 @@ impl<'tcx, T> Binder<'tcx, T> {
         Binder(&self.0, self.1)
     }
 
+    pub fn as_deref(&self) -> Binder<'tcx, &T::Target>
+    where
+        T: Deref,
+    {
+        Binder(&self.0, self.1)
+    }
+
     pub fn map_bound_ref_unchecked<F, U>(&self, f: F) -> Binder<'tcx, U>
     where
         F: FnOnce(&T) -> U,

compiler/rustc_mir_build/src/build/expr/as_place.rs

@@ -133,7 +133,7 @@ fn convert_to_hir_projections_and_truncate_for_capture<'tcx>(
 ///        ancestor of `foo.x.y`. It's the caller's responsibility to ensure that both projections
 ///        list are being applied to the same root variable.
 fn is_ancestor_or_same_capture(
-    proj_possible_ancestor: &Vec<HirProjectionKind>,
+    proj_possible_ancestor: &[HirProjectionKind],
     proj_capture: &[HirProjectionKind],
 ) -> bool {
     // We want to make sure `is_ancestor_or_same_capture("x.0.0", "x.0")` to return false.
@@ -187,7 +187,7 @@ fn find_capture_matching_projections<'a, 'tcx>(
     // If an ancestor is found, `idx` is the index within the list of captured places
     // for root variable `var_hir_id` and `capture` is the `ty::CapturedPlace` itself.
     let (idx, capture) = root_variable_min_captures.iter().enumerate().find(|(_, capture)| {
-        let possible_ancestor_proj_kinds =
+        let possible_ancestor_proj_kinds: Vec<_> =
             capture.place.projections.iter().map(|proj| proj.kind).collect();
         is_ancestor_or_same_capture(&possible_ancestor_proj_kinds, &hir_projections)
     })?;

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -409,7 +409,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         outer_source_info: SourceInfo,
         candidate: Candidate<'_, 'tcx>,
         guard: Option<&Guard<'tcx>>,
-        fake_borrow_temps: &Vec<(Place<'tcx>, Local)>,
+        fake_borrow_temps: &[(Place<'tcx>, Local)],
         scrutinee_span: Span,
         arm_span: Option<Span>,
         arm_scope: Option<region::Scope>,
@@ -1826,7 +1826,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         candidate: Candidate<'pat, 'tcx>,
         parent_bindings: &[(Vec<Binding<'tcx>>, Vec<Ascription<'tcx>>)],
         guard: Option<&Guard<'tcx>>,
-        fake_borrows: &Vec<(Place<'tcx>, Local)>,
+        fake_borrows: &[(Place<'tcx>, Local)],
         scrutinee_span: Span,
         arm_span: Option<Span>,
         match_scope: Option<region::Scope>,

compiler/rustc_mir_transform/src/coverage/counters.rs

@@ -43,7 +43,7 @@ impl CoverageCounters {
     pub fn make_bcb_counters(
         &mut self,
         basic_coverage_blocks: &mut CoverageGraph,
-        coverage_spans: &Vec<CoverageSpan>,
+        coverage_spans: &[CoverageSpan],
     ) -> Result<Vec<CoverageKind>, Error> {
         let mut bcb_counters = BcbCounters::new(self, basic_coverage_blocks);
         bcb_counters.make_bcb_counters(coverage_spans)
@@ -349,7 +349,7 @@ impl<'a> BcbCounters<'a> {
         // counters and/or expressions of its incoming edges. This will recursively get or create
         // counters for those incoming edges first, then call `make_expression()` to sum them up,
         // with additional intermediate expressions as needed.
-        let mut predecessors = self.bcb_predecessors(bcb).clone().into_iter();
+        let mut predecessors = self.bcb_predecessors(bcb).to_owned().into_iter();
         debug!(
             "{}{:?} has multiple incoming edges and will get an expression that sums them up...",
             NESTED_INDENT.repeat(debug_indent_level),
@@ -571,12 +571,12 @@ impl<'a> BcbCounters<'a> {
     }
 
     #[inline]
-    fn bcb_predecessors(&self, bcb: BasicCoverageBlock) -> &Vec<BasicCoverageBlock> {
+    fn bcb_predecessors(&self, bcb: BasicCoverageBlock) -> &[BasicCoverageBlock] {
         &self.basic_coverage_blocks.predecessors[bcb]
     }
 
     #[inline]
-    fn bcb_successors(&self, bcb: BasicCoverageBlock) -> &Vec<BasicCoverageBlock> {
+    fn bcb_successors(&self, bcb: BasicCoverageBlock) -> &[BasicCoverageBlock] {
         &self.basic_coverage_blocks.successors[bcb]
     }
 

compiler/rustc_mir_transform/src/coverage/debug.rs

@@ -124,6 +124,7 @@ use rustc_span::Span;
 
 use std::iter;
 use std::lazy::SyncOnceCell;
+use std::ops::Deref;
 
 pub const NESTED_INDENT: &str = "    ";
 
@@ -434,11 +435,11 @@ impl GraphvizData {
     pub fn get_bcb_coverage_spans_with_counters(
         &self,
         bcb: BasicCoverageBlock,
-    ) -> Option<&Vec<(CoverageSpan, CoverageKind)>> {
+    ) -> Option<&[(CoverageSpan, CoverageKind)]> {
         if let Some(bcb_to_coverage_spans_with_counters) =
             self.some_bcb_to_coverage_spans_with_counters.as_ref()
         {
-            bcb_to_coverage_spans_with_counters.get(&bcb)
+            bcb_to_coverage_spans_with_counters.get(&bcb).map(Deref::deref)
         } else {
             None
         }
@@ -457,12 +458,9 @@ impl GraphvizData {
         }
     }
 
-    pub fn get_bcb_dependency_counters(
-        &self,
-        bcb: BasicCoverageBlock,
-    ) -> Option<&Vec<CoverageKind>> {
+    pub fn get_bcb_dependency_counters(&self, bcb: BasicCoverageBlock) -> Option<&[CoverageKind]> {
         if let Some(bcb_to_dependency_counters) = self.some_bcb_to_dependency_counters.as_ref() {
-            bcb_to_dependency_counters.get(&bcb)
+            bcb_to_dependency_counters.get(&bcb).map(Deref::deref)
         } else {
             None
         }
@@ -571,11 +569,11 @@ impl UsedExpressions {
     /// associated with a coverage span).
     pub fn validate(
         &mut self,
-        bcb_counters_without_direct_coverage_spans: &Vec<(
+        bcb_counters_without_direct_coverage_spans: &[(
             Option<BasicCoverageBlock>,
             BasicCoverageBlock,
             CoverageKind,
-        )>,
+        )],
     ) {
         if self.is_enabled() {
             let mut not_validated = bcb_counters_without_direct_coverage_spans
@@ -634,7 +632,7 @@ pub(super) fn dump_coverage_spanview<'tcx>(
     basic_coverage_blocks: &CoverageGraph,
     pass_name: &str,
     body_span: Span,
-    coverage_spans: &Vec<CoverageSpan>,
+    coverage_spans: &[CoverageSpan],
 ) {
     let mir_source = mir_body.source;
     let def_id = mir_source.def_id();
@@ -654,7 +652,7 @@ fn span_viewables<'tcx>(
     tcx: TyCtxt<'tcx>,
     mir_body: &mir::Body<'tcx>,
     basic_coverage_blocks: &CoverageGraph,
-    coverage_spans: &Vec<CoverageSpan>,
+    coverage_spans: &[CoverageSpan],
 ) -> Vec<SpanViewable> {
     let mut span_viewables = Vec::new();
     for coverage_span in coverage_spans {
@@ -676,7 +674,7 @@ pub(super) fn dump_coverage_graphviz<'tcx>(
     basic_coverage_blocks: &CoverageGraph,
     debug_counters: &DebugCounters,
     graphviz_data: &GraphvizData,
-    intermediate_expressions: &Vec<CoverageKind>,
+    intermediate_expressions: &[CoverageKind],
     debug_used_expressions: &UsedExpressions,
 ) {
     let mir_source = mir_body.source;
@@ -753,9 +751,9 @@ fn bcb_to_string_sections<'tcx>(
     mir_body: &mir::Body<'tcx>,
     debug_counters: &DebugCounters,
     bcb_data: &BasicCoverageBlockData,
-    some_coverage_spans_with_counters: Option<&Vec<(CoverageSpan, CoverageKind)>>,
-    some_dependency_counters: Option<&Vec<CoverageKind>>,
-    some_intermediate_expressions: Option<&Vec<CoverageKind>>,
+    some_coverage_spans_with_counters: Option<&[(CoverageSpan, CoverageKind)]>,
+    some_dependency_counters: Option<&[CoverageKind]>,
+    some_intermediate_expressions: Option<&[CoverageKind]>,
 ) -> Vec<String> {
     let len = bcb_data.basic_blocks.len();
     let mut sections = Vec::new();

compiler/rustc_resolve/src/late.rs

@@ -631,7 +631,7 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
                         span,
                     },
                     |this| {
-                        this.visit_generic_param_vec(&bare_fn.generic_params, false);
+                        this.visit_generic_params(&bare_fn.generic_params, false);
                         this.with_lifetime_rib(
                             LifetimeRibKind::AnonymousPassThrough(ty.id, false),
                             |this| walk_list!(this, visit_param, &bare_fn.decl.inputs),
@@ -662,7 +662,7 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
                 span,
             },
             |this| {
-                this.visit_generic_param_vec(&tref.bound_generic_params, false);
+                this.visit_generic_params(&tref.bound_generic_params, false);
                 this.smart_resolve_path(
                     tref.trait_ref.ref_id,
                     None,
@@ -833,7 +833,7 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
     }
 
     fn visit_generics(&mut self, generics: &'ast Generics) {
-        self.visit_generic_param_vec(
+        self.visit_generic_params(
             &generics.params,
             self.diagnostic_metadata.current_self_item.is_some(),
         );
@@ -941,7 +941,7 @@ impl<'a: 'ast, 'ast> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast> {
                         span,
                     },
                     |this| {
-                        this.visit_generic_param_vec(&bound_generic_params, false);
+                        this.visit_generic_params(&bound_generic_params, false);
                         this.visit_ty(bounded_ty);
                         for bound in bounds {
                             this.visit_param_bound(bound, BoundKind::Bound)
@@ -1116,7 +1116,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         }
     }
 
-    fn visit_generic_param_vec(&mut self, params: &'ast Vec<GenericParam>, add_self_upper: bool) {
+    fn visit_generic_params(&mut self, params: &'ast [GenericParam], add_self_upper: bool) {
         // For type parameter defaults, we have to ban access
         // to following type parameters, as the InternalSubsts can only
         // provide previous type parameters as they're built. We
@@ -1870,7 +1870,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
 
     fn with_generic_param_rib<'c, F>(
         &'c mut self,
-        params: &'c Vec<GenericParam>,
+        params: &'c [GenericParam],
         kind: RibKind<'a>,
         lifetime_kind: LifetimeRibKind,
         f: F,

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -146,11 +146,13 @@ impl<'tcx, 'a> GeneratorData<'tcx, 'a> {
     /// that are live across the yield of this generator
     fn get_generator_interior_types(
         &self,
-    ) -> ty::Binder<'tcx, &Vec<GeneratorInteriorTypeCause<'tcx>>> {
+    ) -> ty::Binder<'tcx, &[GeneratorInteriorTypeCause<'tcx>]> {
         match self {
-            GeneratorData::Local(typeck_result) => typeck_result.generator_interior_types.as_ref(),
+            GeneratorData::Local(typeck_result) => {
+                typeck_result.generator_interior_types.as_deref()
+            }
             GeneratorData::Foreign(generator_diagnostic_data) => {
-                generator_diagnostic_data.generator_interior_types.as_ref()
+                generator_diagnostic_data.generator_interior_types.as_deref()
             }
         }
     }

compiler/rustc_trait_selection/src/traits/project.rs

@@ -773,7 +773,7 @@ pub struct PlaceholderReplacer<'me, 'tcx> {
     mapped_regions: BTreeMap<ty::PlaceholderRegion, ty::BoundRegion>,
     mapped_types: BTreeMap<ty::PlaceholderType, ty::BoundTy>,
     mapped_consts: BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar>,
-    universe_indices: &'me Vec<Option<ty::UniverseIndex>>,
+    universe_indices: &'me [Option<ty::UniverseIndex>],
     current_index: ty::DebruijnIndex,
 }
 
@@ -783,7 +783,7 @@ impl<'me, 'tcx> PlaceholderReplacer<'me, 'tcx> {
         mapped_regions: BTreeMap<ty::PlaceholderRegion, ty::BoundRegion>,
         mapped_types: BTreeMap<ty::PlaceholderType, ty::BoundTy>,
         mapped_consts: BTreeMap<ty::PlaceholderConst<'tcx>, ty::BoundVar>,
-        universe_indices: &'me Vec<Option<ty::UniverseIndex>>,
+        universe_indices: &'me [Option<ty::UniverseIndex>],
         value: T,
     ) -> T {
         let mut replacer = PlaceholderReplacer {

compiler/rustc_typeck/src/check/expr.rs

@@ -2448,7 +2448,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         span: Span,
         base_t: Ty<'tcx>,
-    ) -> Option<(&Vec<ty::FieldDef>, SubstsRef<'tcx>)> {
+    ) -> Option<(&[ty::FieldDef], SubstsRef<'tcx>)> {
         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_t);
 
         for (base_t, _) in self.autoderef(span, base_t) {

compiler/rustc_typeck/src/check/upvar.rs

@@ -2039,7 +2039,7 @@ fn should_do_rust_2021_incompatible_closure_captures_analysis(
 /// - s2: Comma separated names of the variables being migrated.
 fn migration_suggestion_for_2229(
     tcx: TyCtxt<'_>,
-    need_migrations: &Vec<NeededMigration>,
+    need_migrations: &[NeededMigration],
 ) -> (String, String) {
     let need_migrations_variables = need_migrations
         .iter()