Auto merge of rust-lang#3677 - daxpedda:integer_arithmetic, r=oli-obk

Remove negative integer literal checks.

Fixes rust-lang#3678.

clippy_lints/src/arithmetic.rs

@@ -1,3 +1,4 @@
+use crate::consts::constant_simple;
 use crate::utils::span_lint;
 use rustc::hir;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
@@ -94,8 +95,10 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
             hir::ExprKind::Unary(hir::UnOp::UnNeg, arg) => {
                 let ty = cx.tables.expr_ty(arg);
                 if ty.is_integral() {
-                    span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
-                    self.expr_span = Some(expr.span);
+                    if constant_simple(cx, cx.tables, expr).is_none() {
+                        span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
+                        self.expr_span = Some(expr.span);
+                    }
                 } else if ty.is_floating_point() {
                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
                     self.expr_span = Some(expr.span);

tests/ui/arithmetic.rs

@@ -17,6 +17,10 @@ fn main() {
     i - 2 + 2 - i;
     -i;
 
+    // no error, overflows are checked by `overflowing_literals`
+    -1;
+    -(-1);
+
     i & 1; // no wrapping
     i | 1;
     i ^ 1;

tests/ui/arithmetic.stderr

@@ -32,39 +32,39 @@ LL |     -i;
    |     ^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:28:5
+  --> $DIR/arithmetic.rs:32:5
    |
 LL |     f * 2.0;
    |     ^^^^^^^
    |
    = note: `-D clippy::float-arithmetic` implied by `-D warnings`
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:30:5
+  --> $DIR/arithmetic.rs:34:5
    |
 LL |     1.0 + f;
    |     ^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:31:5
+  --> $DIR/arithmetic.rs:35:5
    |
 LL |     f * 2.0;
    |     ^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:32:5
+  --> $DIR/arithmetic.rs:36:5
    |
 LL |     f / 2.0;
    |     ^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:33:5
+  --> $DIR/arithmetic.rs:37:5
    |
 LL |     f - 2.0 * 4.2;
    |     ^^^^^^^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:34:5
+  --> $DIR/arithmetic.rs:38:5
    |
 LL |     -f;
    |     ^^