diff --git a/src/lib.rs b/src/lib.rs index 7d29d96637d..80ba04031fa 100755 --- a/src/lib.rs +++ b/src/lib.rs @@ -51,6 +51,7 @@ pub fn plugin_registrar(reg: &mut Registry) { reg.register_lint_pass(box misc::CmpOwned as LintPassObject); reg.register_lint_pass(box attrs::AttrPass as LintPassObject); reg.register_lint_pass(box collapsible_if::CollapsibleIf as LintPassObject); + reg.register_lint_pass(box misc::ModuloOne as LintPassObject); reg.register_lint_pass(box unicode::Unicode as LintPassObject); reg.register_lint_pass(box strings::StringAdd as LintPassObject); reg.register_lint_pass(box misc::NeedlessReturn as LintPassObject); @@ -75,5 +76,6 @@ pub fn plugin_registrar(reg: &mut Registry) { unicode::ZERO_WIDTH_SPACE, strings::STRING_ADD_ASSIGN, misc::NEEDLESS_RETURN, + misc::MODULO_ONE, ]); } diff --git a/src/misc.rs b/src/misc.rs index b3a74194552..53bf73de35a 100644 --- a/src/misc.rs +++ b/src/misc.rs @@ -337,3 +337,34 @@ impl LintPass for NeedlessReturn { self.check_block_return(cx, block); } } + + +declare_lint!(pub MODULO_ONE, Warn, "Warn on expressions that include % 1, which is always 0"); + +#[derive(Copy,Clone)] +pub struct ModuloOne; + +impl LintPass for ModuloOne { + fn get_lints(&self) -> LintArray { + lint_array!(MODULO_ONE) + } + + fn check_expr(&mut self, cx: &Context, expr: &Expr) { + if let ExprBinary(ref cmp, _, ref right) = expr.node { + if let &Spanned {node: BinOp_::BiRem, ..} = cmp { + if is_lit_one(right) { + cx.span_lint(MODULO_ONE, expr.span, "Any number modulo 1 will be 0"); + } + } + } + } +} + +fn is_lit_one(expr: &Expr) -> bool { + if let ExprLit(ref spanned) = expr.node { + if let LitInt(1, _) = spanned.node { + return true; + } + } + false +} diff --git a/tests/compile-fail/modulo_one.rs b/tests/compile-fail/modulo_one.rs new file mode 100644 index 00000000000..26c7de855e5 --- /dev/null +++ b/tests/compile-fail/modulo_one.rs @@ -0,0 +1,8 @@ +#![feature(plugin)] +#![plugin(clippy)] +#![deny(modulo_one)] + +fn main() { + 10 % 1; //~ERROR Any number modulo 1 will be 0 + 10 % 2; +}