user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Auto merge of #9496 - yotamofek:never_loop_let_else, r=Jarcho

Browse source 
[`never_loop`]: Fix FP with let..else statements.

Fixes #9356

This has been bugging me for a while, so I thought I'd take a stab at it! I'm completely uncertain about the quality of my code, but I think it's an alright start, so opening this PR to get some feedback from more experienced clippy people :)

changelog: [`never_loop`]: Fix FP with let..else statements
This commit is contained in:
bors 2022-09-23 16:06:49 +00:00
commit ff65eec801
3 changed files with 71 additions and 20 deletions
Download patch file Download diff file Expand all files Collapse all files

31
clippy_lints/src/loops/never_loop.rs
View file

@ -42,6 +42,7 @@ pub(super) fn check(
}
}
#[derive(Copy, Clone)]
enum NeverLoopResult {
// A break/return always get triggered but not necessarily for the main loop.
AlwaysBreak,
@ -51,8 +52,8 @@ enum NeverLoopResult {
}
#[must_use]
fn absorb_break(arg: &NeverLoopResult) -> NeverLoopResult {
match *arg {
fn absorb_break(arg: NeverLoopResult) -> NeverLoopResult {
match arg {
NeverLoopResult::AlwaysBreak | NeverLoopResult::Otherwise => NeverLoopResult::Otherwise,
NeverLoopResult::MayContinueMainLoop => NeverLoopResult::MayContinueMainLoop,
}
@ -92,19 +93,29 @@ fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult
}
fn never_loop_block(block: &Block<'_>, main_loop_id: HirId) -> NeverLoopResult {
let mut iter = block.stmts.iter().filter_map(stmt_to_expr).chain(block.expr);
let mut iter = block
.stmts
.iter()
.filter_map(stmt_to_expr)
.chain(block.expr.map(|expr| (expr, None)));
never_loop_expr_seq(&mut iter, main_loop_id)
}
fn never_loop_expr_seq<'a, T: Iterator<Item = &'a Expr<'a>>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult {
es.map(|e| never_loop_expr(e, main_loop_id))
.fold(NeverLoopResult::Otherwise, combine_seq)
fn never_loop_expr_seq<'a, T: Iterator<Item = (&'a Expr<'a>, Option<&'a Block<'a>>)>>(
es: &mut T,
main_loop_id: HirId,
) -> NeverLoopResult {
es.map(|(e, els)| {
let e = never_loop_expr(e, main_loop_id);
els.map_or(e, |els| combine_branches(e, never_loop_block(els, main_loop_id)))
})
.fold(NeverLoopResult::Otherwise, combine_seq)
}
fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<&'tcx Expr<'tcx>> {
fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<(&'tcx Expr<'tcx>, Option<&'tcx Block<'tcx>>)> {
match stmt.kind {
StmtKind::Semi(e, ..) | StmtKind::Expr(e, ..) => Some(e),
StmtKind::Local(local) => local.init,
StmtKind::Semi(e, ..) | StmtKind::Expr(e, ..) => Some((e, None)),
StmtKind::Local(local) => local.init.map(|init| (init, local.els)),
StmtKind::Item(..) => None,
}
}
@ -139,7 +150,7 @@ fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult {
| ExprKind::Index(e1, e2) => never_loop_expr_all(&mut [e1, e2].iter().copied(), main_loop_id),
ExprKind::Loop(b, _, _, _) => {
// Break can come from the inner loop so remove them.
absorb_break(&never_loop_block(b, main_loop_id))
absorb_break(never_loop_block(b, main_loop_id))
},
ExprKind::If(e, e2, e3) => {
let e1 = never_loop_expr(e, main_loop_id);