Linting classical overflow checks

README.md

@@ -8,7 +8,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
 [Jump to usage instructions](#usage)
 
 ##Lints
-There are 130 lints included in this crate:
+There are 131 lints included in this crate:
 
 name                                                                                                                 | default | meaning
 ---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@@ -92,6 +92,7 @@ name
 [option_unwrap_used](https://github.com/Manishearth/rust-clippy/wiki#option_unwrap_used)                             | allow   | using `Option.unwrap()`, which should at least get a better message using `expect()`
 [or_fun_call](https://github.com/Manishearth/rust-clippy/wiki#or_fun_call)                                           | warn    | using any `*or` method when the `*or_else` would do
 [out_of_bounds_indexing](https://github.com/Manishearth/rust-clippy/wiki#out_of_bounds_indexing)                     | deny    | out of bound constant indexing
+[overflow_check_conditional](https://github.com/Manishearth/rust-clippy/wiki#overflow_check_conditional)             | warn    | Using overflow checks which are likely to panic
 [panic_params](https://github.com/Manishearth/rust-clippy/wiki#panic_params)                                         | warn    | missing parameters in `panic!`
 [precedence](https://github.com/Manishearth/rust-clippy/wiki#precedence)                                             | warn    | catches operations where precedence may be unclear. See the wiki for a list of cases caught
 [print_stdout](https://github.com/Manishearth/rust-clippy/wiki#print_stdout)                                         | allow   | printing on stdout

src/lib.rs

@@ -79,6 +79,7 @@ pub mod needless_features;
 pub mod needless_update;
 pub mod no_effect;
 pub mod open_options;
+pub mod overflow_check_conditional;
 pub mod panic;
 pub mod precedence;
 pub mod print;
@@ -173,6 +174,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_early_lint_pass(box formatting::Formatting);
     reg.register_late_lint_pass(box swap::Swap);
     reg.register_early_lint_pass(box if_not_else::IfNotElse);
+    reg.register_late_lint_pass(box overflow_check_conditional::OverflowCheckConditional);
 
     reg.register_lint_group("clippy_pedantic", vec![
         enum_glob_use::ENUM_GLOB_USE,
@@ -283,6 +285,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
         needless_update::NEEDLESS_UPDATE,
         no_effect::NO_EFFECT,
         open_options::NONSENSICAL_OPEN_OPTIONS,
+        overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL,
         panic::PANIC_PARAMS,
         precedence::PRECEDENCE,
         ptr_arg::PTR_ARG,

src/overflow_check_conditional.rs

@@ -0,0 +1,73 @@
+#![allow(cyclomatic_complexity)]
+use rustc::lint::*;
+use rustc_front::hir::*;
+use utils::{span_lint};
+
+/// **What it does:** This lint finds classic underflow / overflow checks.
+///
+/// **Why is this bad?** Most classic C underflow / overflow checks will fail in Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead.
+///
+/// **Known problems:** None.
+///
+/// **Example:** `a + b < a`
+
+declare_lint!(pub OVERFLOW_CHECK_CONDITIONAL, Warn,
+              "Using overflow checks which are likely to panic");
+
+#[derive(Copy, Clone)]
+pub struct OverflowCheckConditional;
+
+impl LintPass for OverflowCheckConditional {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(OVERFLOW_CHECK_CONDITIONAL)
+    }
+}
+
+impl LateLintPass for OverflowCheckConditional {
+    // a + b < a, a > a + b, a < a - b, a - b > a
+    fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
+        if_let_chain! {[
+        let Expr_::ExprBinary(ref op, ref first, ref second) = expr.node,
+        let Expr_::ExprBinary(ref op2, ref ident1, ref ident2) = first.node,
+        let Expr_::ExprPath(_,ref path1) = ident1.node,
+        let Expr_::ExprPath(_, ref path2) = ident2.node,
+        let Expr_::ExprPath(_, ref path3) = second.node,
+        (&path1.segments[0]).identifier == (&path3.segments[0]).identifier || (&path2.segments[0]).identifier == (&path3.segments[0]).identifier,
+        cx.tcx.expr_ty(ident1).is_integral(),
+        cx.tcx.expr_ty(ident2).is_integral()
+        ], {
+            if let BinOp_::BiLt = op.node {
+                if let BinOp_::BiAdd = op2.node {
+                    span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C overflow conditons that will fail in Rust.");
+                }
+            }
+            if let BinOp_::BiGt = op.node {
+                if let BinOp_::BiSub = op2.node {
+                    span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C underflow conditons that will fail in Rust.");
+                }
+            }
+        }}
+
+        if_let_chain! {[
+        let Expr_::ExprBinary(ref op, ref first, ref second) = expr.node,
+        let Expr_::ExprBinary(ref op2, ref ident1, ref ident2) = second.node,
+        let Expr_::ExprPath(_,ref path1) = ident1.node,
+        let Expr_::ExprPath(_, ref path2) = ident2.node,
+        let Expr_::ExprPath(_, ref path3) = first.node,
+        (&path1.segments[0]).identifier == (&path3.segments[0]).identifier || (&path2.segments[0]).identifier == (&path3.segments[0]).identifier,
+        cx.tcx.expr_ty(ident1).is_integral(),
+        cx.tcx.expr_ty(ident2).is_integral()
+        ], {
+            if let BinOp_::BiGt = op.node {
+                if let BinOp_::BiAdd = op2.node {
+                    span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C overflow conditons that will fail in Rust.");
+                }
+            }
+            if let BinOp_::BiLt = op.node {
+                if let BinOp_::BiSub = op2.node {
+                    span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C underflow conditons that will fail in Rust.");
+                }
+            }
+        }}
+    }
+}

tests/compile-fail/overflow_check_conditional.rs

@@ -0,0 +1,61 @@
+#![feature(plugin)]
+#![plugin(clippy)]
+
+#![deny(overflow_check_conditional)]
+
+fn main() {
+	let a: u32 = 1;
+	let b: u32 = 2;
+	let c: u32 = 3;
+	if a + b < a { //~ERROR You are trying to use classic C overflow conditons that will fail in Rust.
+
+	}
+	if a > a + b { //~ERROR You are trying to use classic C overflow conditons that will fail in Rust.
+
+	}
+	if a + b < b { //~ERROR You are trying to use classic C overflow conditons that will fail in Rust.
+
+	}
+	if b > a + b { //~ERROR You are trying to use classic C overflow conditons that will fail in Rust.
+
+	}
+	if a - b > b { //~ERROR You are trying to use classic C underflow conditons that will fail in Rust.
+
+	}
+	if b < a - b { //~ERROR You are trying to use classic C underflow conditons that will fail in Rust.
+
+	}
+	if a - b > a { //~ERROR You are trying to use classic C underflow conditons that will fail in Rust.
+
+	}
+	if a < a - b { //~ERROR You are trying to use classic C underflow conditons that will fail in Rust.
+
+	}
+	if a + b < c {
+
+	}
+	if c > a + b {
+
+	}
+	if a - b < c {
+
+	}
+	if c > a - b {
+
+	}
+	let i = 1.1;
+	let j = 2.2;
+	if i + j < i {
+
+	}
+	if i - j < i {
+
+	}
+	if i > i + j {
+
+	}
+	if i - j < i {
+
+	}
+}
+