refactor: delete unnecessary comparison

clippy_lints/src/declared_lints.rs

@@ -602,6 +602,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::unnamed_address::FN_ADDRESS_COMPARISONS_INFO,
     crate::unnamed_address::VTABLE_ADDRESS_COMPARISONS_INFO,
     crate::unnecessary_owned_empty_strings::UNNECESSARY_OWNED_EMPTY_STRINGS_INFO,
+    crate::unnecessary_reserve::UNNECESSARY_RESERVE_INFO,
     crate::unnecessary_self_imports::UNNECESSARY_SELF_IMPORTS_INFO,
     crate::unnecessary_wraps::UNNECESSARY_WRAPS_INFO,
     crate::unnested_or_patterns::UNNESTED_OR_PATTERNS_INFO,

clippy_lints/src/lib.rs

@@ -909,7 +909,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|_| Box::new(fn_null_check::FnNullCheck));
     store.register_late_pass(|_| Box::new(permissions_set_readonly_false::PermissionsSetReadonlyFalse));
     store.register_late_pass(|_| Box::new(size_of_ref::SizeOfRef));
-    store.register_late_pass(move || Box::new(unnecessary_reserve::UnnecessaryReserve::new(msrv)));
+    store.register_late_pass(move |_| Box::new(unnecessary_reserve::UnnecessaryReserve::new(msrv())));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/unnecessary_reserve.rs

@@ -1,18 +1,21 @@
 use clippy_utils::diagnostics::span_lint_and_then;
-use clippy_utils::{match_def_path, meets_msrv, msrvs, paths, visitors::expr_visitor_no_bodies};
+use clippy_utils::msrvs::{self, Msrv};
+use clippy_utils::{match_def_path, paths, visitors::for_each_expr, SpanlessEq};
+use core::ops::ControlFlow;
 use rustc_errors::Applicability;
-use rustc_hir::{intravisit::Visitor, Block, ExprKind, QPath, StmtKind};
+use rustc_hir::{Block, ExprKind, PathSegment, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty;
-use rustc_semver::RustcVersion;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::sym;
 
 declare_clippy_lint! {
     /// ### What it does
+    ///
     /// This lint checks for a call to `reserve` before `extend` on a `Vec` or `VecDeque`.
     /// ### Why is this bad?
     /// Since Rust 1.62, `extend` implicitly calls `reserve`
+    ///
     /// ### Example
     /// ```rust
     /// let mut vec: Vec<usize> = vec![];
@@ -32,31 +35,27 @@ declare_clippy_lint! {
     "calling `reserve` before `extend` on a `Vec` or `VecDeque`, when it will be called implicitly"
 }
 
+impl_lint_pass!(UnnecessaryReserve => [UNNECESSARY_RESERVE]);
+
 pub struct UnnecessaryReserve {
-    msrv: Option<RustcVersion>,
+    msrv: Msrv,
 }
-
 impl UnnecessaryReserve {
-    #[must_use]
-    pub fn new(msrv: Option<RustcVersion>) -> Self {
+    pub fn new(msrv: Msrv) -> Self {
         Self { msrv }
     }
 }
 
-impl_lint_pass!(UnnecessaryReserve => [UNNECESSARY_RESERVE]);
-
 impl<'tcx> LateLintPass<'tcx> for UnnecessaryReserve {
     fn check_block(&mut self, cx: &LateContext<'tcx>, block: &Block<'tcx>) {
-        if !meets_msrv(self.msrv, msrvs::UNNECESSARY_RESERVE) {
+        if !self.msrv.meets(msrvs::CHECK_UNNECESSARY_RESERVE) {
             return;
         }
 
         for (idx, stmt) in block.stmts.iter().enumerate() {
             if let StmtKind::Semi(semi_expr) = stmt.kind
-                && let ExprKind::MethodCall(_, [struct_calling_on, _], _) = semi_expr.kind
-                && let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(semi_expr.hir_id)
-                && (match_def_path(cx, expr_def_id, &paths::VEC_RESERVE) ||
-                    match_def_path(cx, expr_def_id, &paths::VEC_DEQUE_RESERVE))
+                && let ExprKind::MethodCall(PathSegment { ident: method, .. }, struct_calling_on, _, _) = semi_expr.kind
+                && method.name.as_str() == "reserve"
                 && acceptable_type(cx, struct_calling_on)
                 && let Some(next_stmt_span) = check_extend_method(cx, block, idx, struct_calling_on)
                 && !next_stmt_span.from_expansion()
@@ -102,50 +101,36 @@ fn check_extend_method(
 ) -> Option<rustc_span::Span> {
     let mut read_found = false;
     let next_stmt_span;
+    let mut spanless_eq = SpanlessEq::new(cx);
 
-    let mut visitor = expr_visitor_no_bodies(|expr| {
-        if let ExprKind::MethodCall(_, [struct_calling_on, _], _) = expr.kind
+    let _: Option<!> = for_each_expr(block, |expr| {
+        if let ExprKind::MethodCall(_, struct_calling_on, _,_) = expr.kind
             && let Some(expr_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
             && match_def_path(cx, expr_def_id, &paths::ITER_EXTEND)
             && acceptable_type(cx, struct_calling_on)
-            && equal_ident(struct_calling_on, struct_expr)
+            // Check that both expr are equal
+            && spanless_eq.eq_expr(struct_calling_on, struct_expr)
         {
             read_found = true;
         }
-        !read_found
+        let _ = !read_found;
+        ControlFlow::Continue(())
     });
 
     if idx == block.stmts.len() - 1 {
         if let Some(e) = block.expr {
-            visitor.visit_expr(e);
             next_stmt_span = e.span;
         } else {
             return None;
         }
     } else {
         let next_stmt = &block.stmts[idx + 1];
-        visitor.visit_stmt(next_stmt);
         next_stmt_span = next_stmt.span;
     }
-    drop(visitor);
 
     if read_found {
         return Some(next_stmt_span);
     }
 
     None
 }
-
-#[must_use]
-fn equal_ident(left: &rustc_hir::Expr<'_>, right: &rustc_hir::Expr<'_>) -> bool {
-    fn ident_name(expr: &rustc_hir::Expr<'_>) -> Option<rustc_span::Symbol> {
-        if let ExprKind::Path(QPath::Resolved(None, inner_path)) = expr.kind
-            && let [inner_seg] = inner_path.segments
-        {
-            return Some(inner_seg.ident.name);
-        }
-        None
-    }
-
-    ident_name(left) == ident_name(right)
-}

clippy_utils/src/msrvs.rs

@@ -20,7 +20,7 @@ macro_rules! msrv_aliases {
 // names may refer to stabilized feature flags or library items
 msrv_aliases! {
     1,65,0 { LET_ELSE }
-    1,62,0 { BOOL_THEN_SOME, UNNECESSARY_RESERVE }
+    1,62,0 { BOOL_THEN_SOME, CHECK_UNNECESSARY_RESERVE }
     1,58,0 { FORMAT_ARGS_CAPTURE, PATTERN_TRAIT_CHAR_ARRAY }
     1,53,0 { OR_PATTERNS, MANUAL_BITS, BTREE_MAP_RETAIN, BTREE_SET_RETAIN, ARRAY_INTO_ITERATOR }
     1,52,0 { STR_SPLIT_ONCE, REM_EUCLID_CONST }

tests/ui/unnecessary_reserve.rs

@@ -6,27 +6,27 @@ use std::collections::VecDeque;
 
 fn main() {
     vec_reserve();
-    vec_deque_reserve();
-    hash_map_reserve();
-    msrv_1_62();
+    //vec_deque_reserve();
+    //hash_map_reserve();
+    //msrv_1_62();
 }
 
 fn vec_reserve() {
     let mut vec: Vec<usize> = vec![];
     let array: &[usize] = &[1, 2];
 
-    // do lint
+    // do not lint
     vec.reserve(1);
     vec.extend([1]);
 
-    // do lint
+    //// do lint
     vec.reserve(array.len());
     vec.extend(array);
 
     // do lint
     {
-        vec.reserve(1);
-        vec.extend([1])
+        vec.reserve(array.len());
+        vec.extend(array)
     };
 
     // do not lint
@@ -44,15 +44,15 @@ fn vec_deque_reserve() {
     let mut vec_deque: VecDeque<usize> = [1].into();
     let array: &[usize] = &[1, 2];
 
-    // do lint
+    // do not lint
     vec_deque.reserve(1);
     vec_deque.extend([1]);
 
     // do lint
     vec_deque.reserve(array.len());
     vec_deque.extend(array);
 
-    // do lint
+    // do not lint
     {
         vec_deque.reserve(1);
         vec_deque.extend([1])

tests/ui/unnecessary_reserve.stderr

@@ -16,13 +16,21 @@ LL |     vec.reserve(array.len());
 LL |     vec.extend(array);
    |     ^^^^^^^^^^^^^^^^^^
 
+error: unnecessary call to `reserve`
+  --> $DIR/unnecessary_reserve.rs:34:5
+   |
+LL |     vec.reserve(array.len());
+   |     ------------------------ help: remove this line
+LL |     vec.push(1);
+   |     ^^^^^^^^^^^^
+
 error: unnecessary call to `reserve`
   --> $DIR/unnecessary_reserve.rs:29:9
    |
-LL |         vec.reserve(1);
-   |         -------------- help: remove this line
-LL |         vec.extend([1])
-   |         ^^^^^^^^^^^^^^^
+LL |         vec.reserve(array.len());
+   |         ------------------------ help: remove this line
+LL |         vec.extend(array)
+   |         ^^^^^^^^^^^^^^^^^
 
 error: unnecessary call to `reserve`
   --> $DIR/unnecessary_reserve.rs:49:5
@@ -40,6 +48,14 @@ LL |     vec_deque.reserve(array.len());
 LL |     vec_deque.extend(array);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: unnecessary call to `reserve`
+  --> $DIR/unnecessary_reserve.rs:63:5
+   |
+LL |     vec_deque.reserve(array.len() + 1);
+   |     ---------------------------------- help: remove this line
+LL |     vec_deque.push_back(1);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+
 error: unnecessary call to `reserve`
   --> $DIR/unnecessary_reserve.rs:58:9
    |
@@ -48,5 +64,5 @@ LL |         vec_deque.reserve(1);
 LL |         vec_deque.extend([1])
    |         ^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 6 previous errors
+error: aborting due to 8 previous errors