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Evaluate the return expression of a block

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This commit is contained in:
Caio 2023-02-18 09:14:41 -03:00
parent e1da00210a
commit 7518969501
4 changed files with 95 additions and 14 deletions
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37
clippy_lints/src/significant_drop_tightening.rs
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@ -61,10 +61,26 @@ pub struct SignificantDropTightening<'tcx> {
}
impl<'tcx> SignificantDropTightening<'tcx> {
/// Unifies the statements of a block with its return expression.
fn all_block_stmts<'ret, 'rslt, 'stmts>(
block_stmts: &'stmts [hir::Stmt<'tcx>],
dummy_ret_stmt: Option<&'ret hir::Stmt<'tcx>>,
) -> impl Iterator<Item = &'rslt hir::Stmt<'tcx>>
where
'ret: 'rslt,
'stmts: 'rslt,
{
block_stmts.iter().chain(dummy_ret_stmt)
}
/// Searches for at least one statement that could slow down the release of a significant drop.
fn at_least_one_stmt_is_expensive(stmts: &[hir::Stmt<'_>]) -> bool {
fn at_least_one_stmt_is_expensive<'stmt>(stmts: impl Iterator<Item = &'stmt hir::Stmt<'tcx>>) -> bool
where
'tcx: 'stmt,
{
for stmt in stmts {
match stmt.kind {
hir::StmtKind::Expr(expr) if let hir::ExprKind::Path(_) = expr.kind => {}
hir::StmtKind::Local(local) if let Some(expr) = local.init
&& let hir::ExprKind::Path(_) = expr.kind => {},
_ => return true
@ -99,7 +115,7 @@ impl<'tcx> SignificantDropTightening<'tcx> {
expr: &'tcx hir::Expr<'_>,
idx: usize,
sdap: &mut SigDropAuxParams,
stmt: &'tcx hir::Stmt<'_>,
stmt: &hir::Stmt<'_>,
cb: impl Fn(&mut SigDropAuxParams),
) {
let mut sig_drop_finder = SigDropFinder::new(cx, &mut self.seen_types);
@ -117,7 +133,7 @@ impl<'tcx> SignificantDropTightening<'tcx> {
}
}
/// Shows a generic overall message as well as specialized messages depending on the usage.
/// Shows generic overall messages as well as specialized messages depending on the usage.
fn set_suggestions(cx: &LateContext<'tcx>, block_span: Span, diag: &mut Diagnostic, sdap: &SigDropAuxParams) {
match sdap.number_of_stmts {
0 | 1 => {},
@ -172,8 +188,13 @@ impl<'tcx> SignificantDropTightening<'tcx> {
impl<'tcx> LateLintPass<'tcx> for SignificantDropTightening<'tcx> {
fn check_block(&mut self, cx: &LateContext<'tcx>, block: &'tcx hir::Block<'_>) {
let dummy_ret_stmt = block.expr.map(|expr| hir::Stmt {
hir_id: hir::HirId::INVALID,
kind: hir::StmtKind::Expr(expr),
span: DUMMY_SP,
});
let mut sdap = SigDropAuxParams::default();
for (idx, stmt) in block.stmts.iter().enumerate() {
for (idx, stmt) in Self::all_block_stmts(block.stmts, dummy_ret_stmt.as_ref()).enumerate() {
match stmt.kind {
hir::StmtKind::Expr(expr) => self.modify_sdap_if_sig_drop_exists(
cx,
@ -213,11 +234,9 @@ impl<'tcx> LateLintPass<'tcx> for SignificantDropTightening<'tcx> {
_ => {}
};
}
let stmts_after_last_use = sdap
.last_use_stmt_idx
.checked_add(1)
.and_then(|idx| block.stmts.get(idx..))
.unwrap_or_default();
let idx = sdap.last_use_stmt_idx.wrapping_add(1);
let stmts_after_last_use = Self::all_block_stmts(block.stmts, dummy_ret_stmt.as_ref()).skip(idx);
if sdap.number_of_stmts > 1 && Self::at_least_one_stmt_is_expensive(stmts_after_last_use) {
span_lint_and_then(
cx,