Auto merge of #8487 - dswij:8478, r=giraffate

[rust.git] / clippy_lints / src / bytecount.rs

diff --git a/clippy_lints/src/bytecount.rs b/clippy_lints/src/bytecount.rs
index 877ae002d36e9de67bb360716112cf266929ae4d..02d97bf43df83d50587d50b9669ee205230766a4 100644 (file)
--- a/clippy_lints/src/bytecount.rs
+++ b/clippy_lints/src/bytecount.rs
@@ -1,33 +1,36 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::match_type;
-use clippy_utils::{contains_name, get_pat_name, paths, single_segment_path};
+use clippy_utils::visitors::is_local_used;
+use clippy_utils::{path_to_local_id, paths, peel_blocks, peel_ref_operators, strip_pat_refs};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, UnOp};
+use rustc_hir::{BinOpKind, Expr, ExprKind, PatKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self, UintTy};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::sym;
-use rustc_span::Symbol;
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for naive byte counts
+    /// ### What it does
+    /// Checks for naive byte counts
     ///
-    /// **Why is this bad?** The [`bytecount`](https://crates.io/crates/bytecount)
+    /// ### Why is this bad?
+    /// The [`bytecount`](https://crates.io/crates/bytecount)
     /// crate has methods to count your bytes faster, especially for large slices.
     ///
-    /// **Known problems:** If you have predominantly small slices, the
+    /// ### Known problems
+    /// If you have predominantly small slices, the
     /// `bytecount::count(..)` method may actually be slower. However, if you can
     /// ensure that less than 2³²-1 matches arise, the `naive_count_32(..)` can be
     /// faster in those cases.
     ///
-    /// **Example:**
-    ///
+    /// ### Example
     /// ```rust
     /// # let vec = vec![1_u8];
     /// &vec.iter().filter(|x| **x == 0u8).count(); // use bytecount::count instead
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub NAIVE_BYTECOUNT,
     pedantic,
     "use of naive `<slice>.filter(|&x| x == y).count()` to count byte values"
@@ -38,42 +41,43 @@
 impl<'tcx> LateLintPass<'tcx> for ByteCount {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
         if_chain! {
-            if let ExprKind::MethodCall(count, _, count_args, _) = expr.kind;
-            if count.ident.name == sym!(count);
-            if count_args.len() == 1;
-            if let ExprKind::MethodCall(filter, _, filter_args, _) = count_args[0].kind;
+            if let ExprKind::MethodCall(count, [count_recv], _) = expr.kind;
+            if count.ident.name == sym::count;
+            if let ExprKind::MethodCall(filter, [filter_recv, filter_arg], _) = count_recv.kind;
             if filter.ident.name == sym!(filter);
-            if filter_args.len() == 2;
-            if let ExprKind::Closure(_, _, body_id, _, _) = filter_args[1].kind;
+            if let ExprKind::Closure(_, _, body_id, _, _) = filter_arg.kind;
             let body = cx.tcx.hir().body(body_id);
-            if body.params.len() == 1;
-            if let Some(argname) = get_pat_name(body.params[0].pat);
+            if let [param] = body.params;
+            if let PatKind::Binding(_, arg_id, _, _) = strip_pat_refs(param.pat).kind;
             if let ExprKind::Binary(ref op, l, r) = body.value.kind;
             if op.node == BinOpKind::Eq;
             if match_type(cx,
-                       cx.typeck_results().expr_ty(&filter_args[0]).peel_refs(),
+                       cx.typeck_results().expr_ty(filter_recv).peel_refs(),
                        &paths::SLICE_ITER);
+            let operand_is_arg = |expr| {
+                let expr = peel_ref_operators(cx, peel_blocks(expr));
+                path_to_local_id(expr, arg_id)
+            };
+            let needle = if operand_is_arg(l) {
+                r
+            } else if operand_is_arg(r) {
+                l
+            } else {
+                return;
+            };
+            if ty::Uint(UintTy::U8) == *cx.typeck_results().expr_ty(needle).peel_refs().kind();
+            if !is_local_used(cx, needle, arg_id);
             then {
-                let needle = match get_path_name(l) {
-                    Some(name) if check_arg(name, argname, r) => r,
-                    _ => match get_path_name(r) {
-                        Some(name) if check_arg(name, argname, l) => l,
-                        _ => { return; }
-                    }
-                };
-                if ty::Uint(UintTy::U8) != *cx.typeck_results().expr_ty(needle).peel_refs().kind() {
-                    return;
-                }
-                let haystack = if let ExprKind::MethodCall(path, _, args, _) =
-                        filter_args[0].kind {
+                let haystack = if let ExprKind::MethodCall(path, args, _) =
+                        filter_recv.kind {
                     let p = path.ident.name;
                     if (p == sym::iter || p == sym!(iter_mut)) && args.len() == 1 {
                         &args[0]
                     } else {
-                        &filter_args[0]
+                        filter_recv
                     }
                 } else {
-                    &filter_args[0]
+                    filter_recv
                 };
                 let mut applicability = Applicability::MaybeIncorrect;
                 span_lint_and_sugg(
@@ -91,24 +95,3 @@ fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
         };
     }
 }
-
-fn check_arg(name: Symbol, arg: Symbol, needle: &Expr<'_>) -> bool {
-    name == arg && !contains_name(name, needle)
-}
-
-fn get_path_name(expr: &Expr<'_>) -> Option<Symbol> {
-    match expr.kind {
-        ExprKind::Box(e) | ExprKind::AddrOf(BorrowKind::Ref, _, e) | ExprKind::Unary(UnOp::Deref, e) => {
-            get_path_name(e)
-        },
-        ExprKind::Block(b, _) => {
-            if b.stmts.is_empty() {
-                b.expr.as_ref().and_then(|p| get_path_name(p))
-            } else {
-                None
-            }
-        },
-        ExprKind::Path(ref qpath) => single_segment_path(qpath).map(|ps| ps.ident.name),
-        _ => None,
-    }
-}