mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-11-27 15:11:30 +00:00
Auto merge of #5536 - rail-rain:fix_manual_memcpy, r=phansch
Fix the bugs of `manual_memcpy`, simplify the suggestion and refactor it While I’m working on the long procrastinated work to expand `manual_memcpy`(#1670), I found a few minor bugs and probably unidiomatic or old coding style. There is a brief explanation of changes to the behaviour this PR will make below. And, I have a questoin: do I need to add tests for the first and second fixed bugs? I thought it might be too rare cases to include the tests for those. I added for the last one though. * Bug fix * It negates resulted offsets (`src/dst_offset`) when `offset` is subtraction by 0. This PR will remove any subtraction by 0 as a part of minification. ```rust for i in 0..5 { dst[i - 0] = src[i]; } ``` ```diff warning: it looks like you're manually copying between slices --> src/main.rs:2:14 | LL | for i in 0..5 { - | ^^^^ help: try replacing the loop by: `dst[..-5].clone_from_slice(&src[..5])` + | ^^^^ help: try replacing the loop by: `dst[..5].clone_from_slice(&src[..5])` | ``` * It prints `RangeTo` or `RangeFull` when both of `end` and `offset` are 0, which have different meaning. This PR will print 0. I could reject the cases `end` is 0, but I thought I won’t catch other cases `reverse_range_loop` will trigger, and it’s over to catch every such cases. ```rust for i in 0..0 { dst[i] = src[i]; } ``` ```diff warning: it looks like you're manually copying between slices --> src/main.rs:2:14 | LL | for i in 0..0 { - | ^^^^ help: try replacing the loop by: `dst.clone_from_slice(&src[..])` + | ^^^^ help: try replacing the loop by: `dst[..0].clone_from_slice(&src[..0])` | ``` * it prints four dots when `end` is `None`. This PR will ignore any `for` loops without `end` because a `for` loop that takes `RangeFrom` as its argument and contains indexing without the statements or the expressions that end loops such as `break` will definitely panic, and `manual_memcpy` should ignore the loops with such control flow. ```rust fn manual_copy(src: &[u32], dst: &mut [u32]) { for i in 0.. { dst[i] = src[i]; } } ``` ```diff -warning: it looks like you're manually copying between slices - --> src/main.rs:2:14 - | -LL | for i in 0.. { - | ^^^ help: try replacing the loop by: `dst[....].clone_from_slice(&src[....])` - | ``` * Simplification of the suggestion * It prints 0 when `start` or `end` and `offset` are same (from #3323). This PR will use `RangeTo` changelog: fixed the bugs of `manual_memcpy` and also simplify the suggestion.
This commit is contained in:
commit
e3b8c41d0d
3 changed files with 206 additions and 188 deletions
|
@ -10,7 +10,6 @@ use crate::utils::{
|
|||
};
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use crate::utils::{is_type_diagnostic_item, qpath_res, same_tys, sext, sugg};
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use if_chain::if_chain;
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use itertools::Itertools;
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use rustc_ast::ast;
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use rustc_data_structures::fx::{FxHashMap, FxHashSet};
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use rustc_errors::Applicability;
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|
@ -772,40 +771,48 @@ fn check_for_loop<'a, 'tcx>(
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|||
|
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fn same_var<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &Expr<'_>, var: HirId) -> bool {
|
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if_chain! {
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if let ExprKind::Path(ref qpath) = expr.kind;
|
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if let QPath::Resolved(None, ref path) = *qpath;
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if let ExprKind::Path(qpath) = &expr.kind;
|
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if let QPath::Resolved(None, path) = qpath;
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if path.segments.len() == 1;
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if let Res::Local(local_id) = qpath_res(cx, qpath, expr.hir_id);
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// our variable!
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if local_id == var;
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then {
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return true;
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// our variable!
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local_id == var
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} else {
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false
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}
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}
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}
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false
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#[derive(Clone, Copy)]
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enum OffsetSign {
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Positive,
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Negative,
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}
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struct Offset {
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value: String,
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negate: bool,
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sign: OffsetSign,
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}
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impl Offset {
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fn negative(s: String) -> Self {
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Self { value: s, negate: true }
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fn negative(value: String) -> Self {
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Self {
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value,
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sign: OffsetSign::Negative,
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}
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}
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fn positive(s: String) -> Self {
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fn positive(value: String) -> Self {
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Self {
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value: s,
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negate: false,
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value,
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sign: OffsetSign::Positive,
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}
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}
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}
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struct FixedOffsetVar {
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var_name: String,
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struct FixedOffsetVar<'hir> {
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var: &'hir Expr<'hir>,
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offset: Offset,
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}
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|
@ -819,10 +826,20 @@ fn is_slice_like<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ty: Ty<'_>) -> bool {
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is_slice || is_type_diagnostic_item(cx, ty, sym!(vec_type)) || is_type_diagnostic_item(cx, ty, sym!(vecdeque_type))
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}
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fn get_fixed_offset_var<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &Expr<'_>, var: HirId) -> Option<FixedOffsetVar> {
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fn fetch_cloned_expr<'tcx>(expr: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> {
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if_chain! {
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if let ExprKind::MethodCall(method, _, args) = expr.kind;
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if method.ident.name == sym!(clone);
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if args.len() == 1;
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if let Some(arg) = args.get(0);
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then { arg } else { expr }
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}
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}
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fn get_offset<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, idx: &Expr<'_>, var: HirId) -> Option<Offset> {
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fn extract_offset<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, e: &Expr<'_>, var: HirId) -> Option<String> {
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match e.kind {
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ExprKind::Lit(ref l) => match l.node {
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match &e.kind {
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ExprKind::Lit(l) => match l.node {
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ast::LitKind::Int(x, _ty) => Some(x.to_string()),
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_ => None,
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},
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|
@ -831,115 +848,139 @@ fn get_fixed_offset_var<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &Expr<'_>, v
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}
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}
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if let ExprKind::Index(ref seqexpr, ref idx) = expr.kind {
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let ty = cx.tables.expr_ty(seqexpr);
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if !is_slice_like(cx, ty) {
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return None;
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}
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let offset = match idx.kind {
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ExprKind::Binary(op, ref lhs, ref rhs) => match op.node {
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BinOpKind::Add => {
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let offset_opt = if same_var(cx, lhs, var) {
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extract_offset(cx, rhs, var)
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} else if same_var(cx, rhs, var) {
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extract_offset(cx, lhs, var)
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} else {
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None
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};
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offset_opt.map(Offset::positive)
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},
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BinOpKind::Sub if same_var(cx, lhs, var) => extract_offset(cx, rhs, var).map(Offset::negative),
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_ => None,
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},
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ExprKind::Path(..) => {
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if same_var(cx, idx, var) {
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Some(Offset::positive("0".into()))
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match idx.kind {
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ExprKind::Binary(op, lhs, rhs) => match op.node {
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BinOpKind::Add => {
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let offset_opt = if same_var(cx, lhs, var) {
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extract_offset(cx, rhs, var)
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} else if same_var(cx, rhs, var) {
|
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extract_offset(cx, lhs, var)
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} else {
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None
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}
|
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};
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offset_opt.map(Offset::positive)
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},
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BinOpKind::Sub if same_var(cx, lhs, var) => extract_offset(cx, rhs, var).map(Offset::negative),
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_ => None,
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};
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offset.map(|o| FixedOffsetVar {
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var_name: snippet_opt(cx, seqexpr.span).unwrap_or_else(|| "???".into()),
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offset: o,
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})
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} else {
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None
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},
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ExprKind::Path(..) if same_var(cx, idx, var) => Some(Offset::positive("0".into())),
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_ => None,
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}
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}
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fn fetch_cloned_fixed_offset_var<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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expr: &Expr<'_>,
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var: HirId,
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) -> Option<FixedOffsetVar> {
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if_chain! {
|
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if let ExprKind::MethodCall(ref method, _, ref args) = expr.kind;
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if method.ident.name == sym!(clone);
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if args.len() == 1;
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if let Some(arg) = args.get(0);
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then {
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return get_fixed_offset_var(cx, arg, var);
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}
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}
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get_fixed_offset_var(cx, expr, var)
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}
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fn get_indexed_assignments<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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body: &Expr<'_>,
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var: HirId,
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) -> Vec<(FixedOffsetVar, FixedOffsetVar)> {
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fn get_assignment<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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e: &Expr<'_>,
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var: HirId,
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) -> Option<(FixedOffsetVar, FixedOffsetVar)> {
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if let ExprKind::Assign(ref lhs, ref rhs, _) = e.kind {
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match (
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get_fixed_offset_var(cx, lhs, var),
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fetch_cloned_fixed_offset_var(cx, rhs, var),
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) {
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(Some(offset_left), Some(offset_right)) => {
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// Source and destination must be different
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if offset_left.var_name == offset_right.var_name {
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None
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} else {
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Some((offset_left, offset_right))
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}
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},
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_ => None,
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}
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fn get_assignments<'tcx>(body: &'tcx Expr<'tcx>) -> impl Iterator<Item = Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)>> {
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fn get_assignment<'tcx>(e: &'tcx Expr<'tcx>) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
|
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if let ExprKind::Assign(lhs, rhs, _) = e.kind {
|
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Some((lhs, rhs))
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} else {
|
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None
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}
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}
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|
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if let ExprKind::Block(ref b, _) = body.kind {
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let Block {
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ref stmts, ref expr, ..
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} = **b;
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// This is one of few ways to return different iterators
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// derived from: https://stackoverflow.com/questions/29760668/conditionally-iterate-over-one-of-several-possible-iterators/52064434#52064434
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let mut iter_a = None;
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let mut iter_b = None;
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stmts
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if let ExprKind::Block(b, _) = body.kind {
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let Block { stmts, expr, .. } = *b;
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iter_a = stmts
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.iter()
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.map(|stmt| match stmt.kind {
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.filter_map(|stmt| match stmt.kind {
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StmtKind::Local(..) | StmtKind::Item(..) => None,
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StmtKind::Expr(ref e) | StmtKind::Semi(ref e) => Some(get_assignment(cx, e, var)),
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StmtKind::Expr(e) | StmtKind::Semi(e) => Some(e),
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})
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.chain(expr.as_ref().into_iter().map(|e| Some(get_assignment(cx, &*e, var))))
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.filter_map(|op| op)
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.collect::<Option<Vec<_>>>()
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.unwrap_or_default()
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.chain(expr.into_iter())
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.map(get_assignment)
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.into()
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} else {
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get_assignment(cx, body, var).into_iter().collect()
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iter_b = Some(get_assignment(body))
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}
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iter_a.into_iter().flatten().chain(iter_b.into_iter())
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}
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fn build_manual_memcpy_suggestion<'a, 'tcx>(
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cx: &LateContext<'a, 'tcx>,
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start: &Expr<'_>,
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end: &Expr<'_>,
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limits: ast::RangeLimits,
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dst_var: FixedOffsetVar<'_>,
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src_var: FixedOffsetVar<'_>,
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) -> String {
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fn print_sum(arg1: &str, arg2: &Offset) -> String {
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match (arg1, &arg2.value[..], arg2.sign) {
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("0", "0", _) => "0".into(),
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("0", x, OffsetSign::Positive) | (x, "0", _) => x.into(),
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("0", x, OffsetSign::Negative) => format!("-{}", x),
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(x, y, OffsetSign::Positive) => format!("({} + {})", x, y),
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(x, y, OffsetSign::Negative) => {
|
||||
if x == y {
|
||||
"0".into()
|
||||
} else {
|
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format!("({} - {})", x, y)
|
||||
}
|
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},
|
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}
|
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}
|
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|
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fn print_offset(start_str: &str, inline_offset: &Offset) -> String {
|
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let offset = print_sum(start_str, inline_offset);
|
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if offset.as_str() == "0" {
|
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"".into()
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||||
} else {
|
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offset
|
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}
|
||||
}
|
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|
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let print_limit = |end: &Expr<'_>, offset: Offset, var: &Expr<'_>| {
|
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if_chain! {
|
||||
if let ExprKind::MethodCall(method, _, len_args) = end.kind;
|
||||
if method.ident.name == sym!(len);
|
||||
if len_args.len() == 1;
|
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if let Some(arg) = len_args.get(0);
|
||||
if var_def_id(cx, arg) == var_def_id(cx, var);
|
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then {
|
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match offset.sign {
|
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OffsetSign::Negative => format!("({} - {})", snippet(cx, end.span, "<src>.len()"), offset.value),
|
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OffsetSign::Positive => "".into(),
|
||||
}
|
||||
} else {
|
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let end_str = match limits {
|
||||
ast::RangeLimits::Closed => {
|
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let end = sugg::Sugg::hir(cx, end, "<count>");
|
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format!("{}", end + sugg::ONE)
|
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},
|
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ast::RangeLimits::HalfOpen => format!("{}", snippet(cx, end.span, "..")),
|
||||
};
|
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|
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print_sum(&end_str, &offset)
|
||||
}
|
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}
|
||||
};
|
||||
|
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let start_str = snippet(cx, start.span, "").to_string();
|
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let dst_offset = print_offset(&start_str, &dst_var.offset);
|
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let dst_limit = print_limit(end, dst_var.offset, dst_var.var);
|
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let src_offset = print_offset(&start_str, &src_var.offset);
|
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let src_limit = print_limit(end, src_var.offset, src_var.var);
|
||||
|
||||
let dst_var_name = snippet_opt(cx, dst_var.var.span).unwrap_or_else(|| "???".into());
|
||||
let src_var_name = snippet_opt(cx, src_var.var.span).unwrap_or_else(|| "???".into());
|
||||
|
||||
let dst = if dst_offset == "" && dst_limit == "" {
|
||||
dst_var_name
|
||||
} else {
|
||||
format!("{}[{}..{}]", dst_var_name, dst_offset, dst_limit)
|
||||
};
|
||||
|
||||
format!(
|
||||
"{}.clone_from_slice(&{}[{}..{}])",
|
||||
dst, src_var_name, src_offset, src_limit
|
||||
)
|
||||
}
|
||||
/// Checks for for loops that sequentially copy items from one slice-like
|
||||
/// object to another.
|
||||
fn detect_manual_memcpy<'a, 'tcx>(
|
||||
|
@ -951,93 +992,43 @@ fn detect_manual_memcpy<'a, 'tcx>(
|
|||
) {
|
||||
if let Some(higher::Range {
|
||||
start: Some(start),
|
||||
ref end,
|
||||
end: Some(end),
|
||||
limits,
|
||||
}) = higher::range(cx, arg)
|
||||
{
|
||||
// the var must be a single name
|
||||
if let PatKind::Binding(_, canonical_id, _, _) = pat.kind {
|
||||
let print_sum = |arg1: &Offset, arg2: &Offset| -> String {
|
||||
match (&arg1.value[..], arg1.negate, &arg2.value[..], arg2.negate) {
|
||||
("0", _, "0", _) => "".into(),
|
||||
("0", _, x, false) | (x, false, "0", false) => x.into(),
|
||||
("0", _, x, true) | (x, false, "0", true) => format!("-{}", x),
|
||||
(x, false, y, false) => format!("({} + {})", x, y),
|
||||
(x, false, y, true) => {
|
||||
if x == y {
|
||||
"0".into()
|
||||
} else {
|
||||
format!("({} - {})", x, y)
|
||||
}
|
||||
},
|
||||
(x, true, y, false) => {
|
||||
if x == y {
|
||||
"0".into()
|
||||
} else {
|
||||
format!("({} - {})", y, x)
|
||||
}
|
||||
},
|
||||
(x, true, y, true) => format!("-({} + {})", x, y),
|
||||
}
|
||||
};
|
||||
|
||||
let print_limit = |end: &Option<&Expr<'_>>, offset: Offset, var_name: &str| {
|
||||
if let Some(end) = *end {
|
||||
if_chain! {
|
||||
if let ExprKind::MethodCall(ref method, _, ref len_args) = end.kind;
|
||||
if method.ident.name == sym!(len);
|
||||
if len_args.len() == 1;
|
||||
if let Some(arg) = len_args.get(0);
|
||||
if snippet(cx, arg.span, "??") == var_name;
|
||||
then {
|
||||
return if offset.negate {
|
||||
format!("({} - {})", snippet(cx, end.span, "<src>.len()"), offset.value)
|
||||
} else {
|
||||
String::new()
|
||||
};
|
||||
}
|
||||
}
|
||||
|
||||
let end_str = match limits {
|
||||
ast::RangeLimits::Closed => {
|
||||
let end = sugg::Sugg::hir(cx, end, "<count>");
|
||||
format!("{}", end + sugg::ONE)
|
||||
},
|
||||
ast::RangeLimits::HalfOpen => format!("{}", snippet(cx, end.span, "..")),
|
||||
};
|
||||
|
||||
print_sum(&Offset::positive(end_str), &offset)
|
||||
} else {
|
||||
"..".into()
|
||||
}
|
||||
};
|
||||
|
||||
// The only statements in the for loops can be indexed assignments from
|
||||
// indexed retrievals.
|
||||
let manual_copies = get_indexed_assignments(cx, body, canonical_id);
|
||||
let big_sugg = get_assignments(body)
|
||||
.map(|o| {
|
||||
o.and_then(|(lhs, rhs)| {
|
||||
let rhs = fetch_cloned_expr(rhs);
|
||||
if_chain! {
|
||||
if let ExprKind::Index(seqexpr_left, idx_left) = lhs.kind;
|
||||
if let ExprKind::Index(seqexpr_right, idx_right) = rhs.kind;
|
||||
if is_slice_like(cx, cx.tables.expr_ty(seqexpr_left))
|
||||
&& is_slice_like(cx, cx.tables.expr_ty(seqexpr_right));
|
||||
if let Some(offset_left) = get_offset(cx, &idx_left, canonical_id);
|
||||
if let Some(offset_right) = get_offset(cx, &idx_right, canonical_id);
|
||||
|
||||
let big_sugg = manual_copies
|
||||
.into_iter()
|
||||
.map(|(dst_var, src_var)| {
|
||||
let start_str = Offset::positive(snippet(cx, start.span, "").to_string());
|
||||
let dst_offset = print_sum(&start_str, &dst_var.offset);
|
||||
let dst_limit = print_limit(end, dst_var.offset, &dst_var.var_name);
|
||||
let src_offset = print_sum(&start_str, &src_var.offset);
|
||||
let src_limit = print_limit(end, src_var.offset, &src_var.var_name);
|
||||
let dst = if dst_offset == "" && dst_limit == "" {
|
||||
dst_var.var_name
|
||||
} else {
|
||||
format!("{}[{}..{}]", dst_var.var_name, dst_offset, dst_limit)
|
||||
};
|
||||
|
||||
format!(
|
||||
"{}.clone_from_slice(&{}[{}..{}])",
|
||||
dst, src_var.var_name, src_offset, src_limit
|
||||
)
|
||||
// Source and destination must be different
|
||||
if var_def_id(cx, seqexpr_left) != var_def_id(cx, seqexpr_right);
|
||||
then {
|
||||
Some((FixedOffsetVar { var: seqexpr_left, offset: offset_left },
|
||||
FixedOffsetVar { var: seqexpr_right, offset: offset_right }))
|
||||
} else {
|
||||
None
|
||||
}
|
||||
}
|
||||
})
|
||||
})
|
||||
.join("\n ");
|
||||
.map(|o| o.map(|(dst, src)| build_manual_memcpy_suggestion(cx, start, end, limits, dst, src)))
|
||||
.collect::<Option<Vec<_>>>()
|
||||
.filter(|v| !v.is_empty())
|
||||
.map(|v| v.join("\n "));
|
||||
|
||||
if !big_sugg.is_empty() {
|
||||
if let Some(big_sugg) = big_sugg {
|
||||
span_lint_and_sugg(
|
||||
cx,
|
||||
MANUAL_MEMCPY,
|
||||
|
|
|
@ -98,6 +98,21 @@ pub fn manual_copy(src: &[i32], dst: &mut [i32], dst2: &mut [i32]) {
|
|||
for i in from..from + 3 {
|
||||
dst[i] = src[i - from];
|
||||
}
|
||||
|
||||
#[allow(clippy::identity_op)]
|
||||
for i in 0..5 {
|
||||
dst[i - 0] = src[i];
|
||||
}
|
||||
|
||||
#[allow(clippy::reverse_range_loop)]
|
||||
for i in 0..0 {
|
||||
dst[i] = src[i];
|
||||
}
|
||||
|
||||
// `RangeTo` `for` loop - don't trigger lint
|
||||
for i in 0.. {
|
||||
dst[i] = src[i];
|
||||
}
|
||||
}
|
||||
|
||||
#[warn(clippy::needless_range_loop, clippy::manual_memcpy)]
|
||||
|
|
|
@ -58,19 +58,31 @@ error: it looks like you're manually copying between slices
|
|||
--> $DIR/manual_memcpy.rs:94:14
|
||||
|
|
||||
LL | for i in from..from + src.len() {
|
||||
| ^^^^^^^^^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[from..from + src.len()].clone_from_slice(&src[0..(from + src.len() - from)])`
|
||||
| ^^^^^^^^^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[from..from + src.len()].clone_from_slice(&src[..(from + src.len() - from)])`
|
||||
|
||||
error: it looks like you're manually copying between slices
|
||||
--> $DIR/manual_memcpy.rs:98:14
|
||||
|
|
||||
LL | for i in from..from + 3 {
|
||||
| ^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[from..from + 3].clone_from_slice(&src[0..(from + 3 - from)])`
|
||||
| ^^^^^^^^^^^^^^ help: try replacing the loop by: `dst[from..from + 3].clone_from_slice(&src[..(from + 3 - from)])`
|
||||
|
||||
error: it looks like you're manually copying between slices
|
||||
--> $DIR/manual_memcpy.rs:105:14
|
||||
--> $DIR/manual_memcpy.rs:103:14
|
||||
|
|
||||
LL | for i in 0..5 {
|
||||
| ^^^^ help: try replacing the loop by: `dst[..5].clone_from_slice(&src[..5])`
|
||||
|
||||
error: it looks like you're manually copying between slices
|
||||
--> $DIR/manual_memcpy.rs:108:14
|
||||
|
|
||||
LL | for i in 0..0 {
|
||||
| ^^^^ help: try replacing the loop by: `dst[..0].clone_from_slice(&src[..0])`
|
||||
|
||||
error: it looks like you're manually copying between slices
|
||||
--> $DIR/manual_memcpy.rs:120:14
|
||||
|
|
||||
LL | for i in 0..src.len() {
|
||||
| ^^^^^^^^^^^^ help: try replacing the loop by: `dst[..src.len()].clone_from_slice(&src[..])`
|
||||
|
||||
error: aborting due to 11 previous errors
|
||||
error: aborting due to 13 previous errors
|
||||
|
||||
|
|
Loading…
Reference in a new issue