diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs index 3410341a1e3c..7f998c63f497 100644 --- a/clippy_lints/src/loops.rs +++ b/clippy_lints/src/loops.rs @@ -2134,7 +2134,7 @@ enum VarState { DontWarn, } -/// Scan a for loop for variables that are incremented exactly once. +/// Scan a for loop for variables that are incremented exactly once and not used after that. struct IncrementVisitor<'a, 'tcx> { cx: &'a LateContext<'tcx>, // context reference states: FxHashMap, // incremented variables @@ -2154,6 +2154,10 @@ impl<'a, 'tcx> Visitor<'tcx> for IncrementVisitor<'a, 'tcx> { if let Some(def_id) = var_def_id(self.cx, expr) { if let Some(parent) = get_parent_expr(self.cx, expr) { let state = self.states.entry(def_id).or_insert(VarState::Initial); + if *state == VarState::IncrOnce { + *state = VarState::DontWarn; + return; + } match parent.kind { ExprKind::AssignOp(op, ref lhs, ref rhs) => { diff --git a/tests/ui/explicit_counter_loop.rs b/tests/ui/explicit_counter_loop.rs index aa6ef162fe40..81d8221bd13e 100644 --- a/tests/ui/explicit_counter_loop.rs +++ b/tests/ui/explicit_counter_loop.rs @@ -38,54 +38,54 @@ mod issue_1219 { let text = "banana"; let mut count = 0; for ch in text.chars() { + println!("{}", count); if ch == 'a' { continue; } count += 1; - println!("{}", count); } // should not trigger the lint because the count is conditional let text = "banana"; let mut count = 0; for ch in text.chars() { + println!("{}", count); if ch == 'a' { count += 1; } - println!("{}", count); } // should trigger the lint because the count is not conditional let text = "banana"; let mut count = 0; for ch in text.chars() { + println!("{}", count); count += 1; if ch == 'a' { continue; } - println!("{}", count); } // should trigger the lint because the count is not conditional let text = "banana"; let mut count = 0; for ch in text.chars() { + println!("{}", count); count += 1; for i in 0..2 { let _ = 123; } - println!("{}", count); } // should not trigger the lint because the count is incremented multiple times let text = "banana"; let mut count = 0; for ch in text.chars() { + println!("{}", count); count += 1; for i in 0..2 { count += 1; } - println!("{}", count); } } } @@ -96,30 +96,30 @@ mod issue_3308 { let mut skips = 0; let erasures = vec![]; for i in 0..10 { + println!("{}", skips); while erasures.contains(&(i + skips)) { skips += 1; } - println!("{}", skips); } // should not trigger the lint because the count is incremented multiple times let mut skips = 0; for i in 0..10 { + println!("{}", skips); let mut j = 0; while j < 5 { skips += 1; j += 1; } - println!("{}", skips); } // should not trigger the lint because the count is incremented multiple times let mut skips = 0; for i in 0..10 { + println!("{}", skips); for j in 0..5 { skips += 1; } - println!("{}", skips); } } } @@ -145,3 +145,16 @@ mod issue_4732 { let _closure = || println!("index: {}", index); } } + +mod issue_4677 { + pub fn test() { + let slice = &[1, 2, 3]; + + // should not trigger the lint because the count is used after incremented + let mut count = 0; + for _i in slice { + count += 1; + println!("{}", count); + } + } +}