src/tools/clippy/clippy_utils/src/usage.rs

   1 use crate::visitors::{for_each_expr, for_each_expr_with_closures, Descend, Visitable};
   2 use crate::{self as utils, get_enclosing_loop_or_multi_call_closure};
   3 use core::ops::ControlFlow;
   4 use hir::def::Res;
   5 use rustc_hir::intravisit::{self, Visitor};
   6 use rustc_hir::{self as hir, Expr, ExprKind, HirId, HirIdSet};
   7 use rustc_hir_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, Place, PlaceBase, PlaceWithHirId};
   8 use rustc_infer::infer::TyCtxtInferExt;
   9 use rustc_lint::LateContext;
  10 use rustc_middle::hir::nested_filter;
  11 use rustc_middle::mir::FakeReadCause;
  12 use rustc_middle::ty;
  13
  14 /// Returns a set of mutated local variable IDs, or `None` if mutations could not be determined.
  15 pub fn mutated_variables<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) -> Option<HirIdSet> {
  16     let mut delegate = MutVarsDelegate {
  17         used_mutably: HirIdSet::default(),
  18         skip: false,
  19     };
  20     let infcx = cx.tcx.infer_ctxt().build();
  21     ExprUseVisitor::new(
  22         &mut delegate,
  23         &infcx,
  24         expr.hir_id.owner.def_id,
  25         cx.param_env,
  26         cx.typeck_results(),
  27     )
  28     .walk_expr(expr);
  29
  30     if delegate.skip {
  31         return None;
  32     }
  33     Some(delegate.used_mutably)
  34 }
  35
  36 pub fn is_potentially_mutated<'tcx>(variable: HirId, expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) -> bool {
  37     mutated_variables(expr, cx).map_or(true, |mutated| mutated.contains(&variable))
  38 }
  39
  40 pub fn is_potentially_local_place(local_id: HirId, place: &Place<'_>) -> bool {
  41     match place.base {
  42         PlaceBase::Local(id) => id == local_id,
  43         PlaceBase::Upvar(_) => {
  44             // Conservatively assume yes.
  45             true
  46         },
  47         _ => false,
  48     }
  49 }
  50
  51 struct MutVarsDelegate {
  52     used_mutably: HirIdSet,
  53     skip: bool,
  54 }
  55
  56 impl<'tcx> MutVarsDelegate {
  57     fn update(&mut self, cat: &PlaceWithHirId<'tcx>) {
  58         match cat.place.base {
  59             PlaceBase::Local(id) => {
  60                 self.used_mutably.insert(id);
  61             },
  62             PlaceBase::Upvar(_) => {
  63                 //FIXME: This causes false negatives. We can't get the `NodeId` from
  64                 //`Categorization::Upvar(_)`. So we search for any `Upvar`s in the
  65                 //`while`-body, not just the ones in the condition.
  66                 self.skip = true;
  67             },
  68             _ => {},
  69         }
  70     }
  71 }
  72
  73 impl<'tcx> Delegate<'tcx> for MutVarsDelegate {
  74     fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
  75
  76     fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId, bk: ty::BorrowKind) {
  77         if bk == ty::BorrowKind::MutBorrow {
  78             self.update(cmt);
  79         }
  80     }
  81
  82     fn mutate(&mut self, cmt: &PlaceWithHirId<'tcx>, _: HirId) {
  83         self.update(cmt);
  84     }
  85
  86     fn fake_read(&mut self, _: &rustc_hir_typeck::expr_use_visitor::PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
  87 }
  88
  89 pub struct ParamBindingIdCollector {
  90     pub binding_hir_ids: Vec<hir::HirId>,
  91 }
  92 impl<'tcx> ParamBindingIdCollector {
  93     fn collect_binding_hir_ids(body: &'tcx hir::Body<'tcx>) -> Vec<hir::HirId> {
  94         let mut hir_ids: Vec<hir::HirId> = Vec::new();
  95         for param in body.params {
  96             let mut finder = ParamBindingIdCollector {
  97                 binding_hir_ids: Vec::new(),
  98             };
  99             finder.visit_param(param);
 100             for hir_id in &finder.binding_hir_ids {
 101                 hir_ids.push(*hir_id);
 102             }
 103         }
 104         hir_ids
 105     }
 106 }
 107 impl<'tcx> intravisit::Visitor<'tcx> for ParamBindingIdCollector {
 108     fn visit_pat(&mut self, pat: &'tcx hir::Pat<'tcx>) {
 109         if let hir::PatKind::Binding(_, hir_id, ..) = pat.kind {
 110             self.binding_hir_ids.push(hir_id);
 111         }
 112         intravisit::walk_pat(self, pat);
 113     }
 114 }
 115
 116 pub struct BindingUsageFinder<'a, 'tcx> {
 117     cx: &'a LateContext<'tcx>,
 118     binding_ids: Vec<hir::HirId>,
 119     usage_found: bool,
 120 }
 121 impl<'a, 'tcx> BindingUsageFinder<'a, 'tcx> {
 122     pub fn are_params_used(cx: &'a LateContext<'tcx>, body: &'tcx hir::Body<'tcx>) -> bool {
 123         let mut finder = BindingUsageFinder {
 124             cx,
 125             binding_ids: ParamBindingIdCollector::collect_binding_hir_ids(body),
 126             usage_found: false,
 127         };
 128         finder.visit_body(body);
 129         finder.usage_found
 130     }
 131 }
 132 impl<'a, 'tcx> intravisit::Visitor<'tcx> for BindingUsageFinder<'a, 'tcx> {
 133     type NestedFilter = nested_filter::OnlyBodies;
 134
 135     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
 136         if !self.usage_found {
 137             intravisit::walk_expr(self, expr);
 138         }
 139     }
 140
 141     fn visit_path(&mut self, path: &hir::Path<'tcx>, _: hir::HirId) {
 142         if let Res::Local(id) = path.res {
 143             if self.binding_ids.contains(&id) {
 144                 self.usage_found = true;
 145             }
 146         }
 147     }
 148
 149     fn nested_visit_map(&mut self) -> Self::Map {
 150         self.cx.tcx.hir()
 151     }
 152 }
 153
 154 pub fn contains_return_break_continue_macro(expression: &Expr<'_>) -> bool {
 155     for_each_expr(expression, |e| {
 156         match e.kind {
 157             ExprKind::Ret(..) | ExprKind::Break(..) | ExprKind::Continue(..) => ControlFlow::Break(()),
 158             // Something special could be done here to handle while or for loop
 159             // desugaring, as this will detect a break if there's a while loop
 160             // or a for loop inside the expression.
 161             _ if e.span.from_expansion() => ControlFlow::Break(()),
 162             _ => ControlFlow::Continue(()),
 163         }
 164     })
 165     .is_some()
 166 }
 167
 168 pub fn local_used_in<'tcx>(cx: &LateContext<'tcx>, local_id: HirId, v: impl Visitable<'tcx>) -> bool {
 169     for_each_expr_with_closures(cx, v, |e| {
 170         if utils::path_to_local_id(e, local_id) {
 171             ControlFlow::Break(())
 172         } else {
 173             ControlFlow::Continue(())
 174         }
 175     })
 176     .is_some()
 177 }
 178
 179 pub fn local_used_after_expr(cx: &LateContext<'_>, local_id: HirId, after: &Expr<'_>) -> bool {
 180     let Some(block) = utils::get_enclosing_block(cx, local_id) else {
 181         return false;
 182     };
 183
 184     // for _ in 1..3 {
 185     //    local
 186     // }
 187     //
 188     // let closure = || local;
 189     // closure();
 190     // closure();
 191     let loop_start = get_enclosing_loop_or_multi_call_closure(cx, after).map(|e| e.hir_id);
 192
 193     let mut past_expr = false;
 194     for_each_expr_with_closures(cx, block, |e| {
 195         if past_expr {
 196             if utils::path_to_local_id(e, local_id) {
 197                 ControlFlow::Break(())
 198             } else {
 199                 ControlFlow::Continue(Descend::Yes)
 200             }
 201         } else if e.hir_id == after.hir_id {
 202             past_expr = true;
 203             ControlFlow::Continue(Descend::No)
 204         } else {
 205             past_expr = Some(e.hir_id) == loop_start;
 206             ControlFlow::Continue(Descend::Yes)
 207         }
 208     })
 209     .is_some()
 210 }