make sure a < b and a >= b are considered equal by SpanlessEq

src/utils/hir.rs

@@ -75,7 +75,8 @@ impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
             }
             (&ExprBlock(ref l), &ExprBlock(ref r)) => self.eq_block(l, r),
             (&ExprBinary(l_op, ref ll, ref lr), &ExprBinary(r_op, ref rl, ref rr)) => {
-                l_op.node == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
+                l_op.node == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr) ||
+                swap_binop(l_op.node, ll, lr).map_or(false, |(l_op, ll, lr)| l_op == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr))
             }
             (&ExprBreak(li), &ExprBreak(ri)) => both(&li, &ri, |l, r| l.node.name.as_str() == r.node.name.as_str()),
             (&ExprBox(ref l), &ExprBox(ref r)) => self.eq_expr(l, r),
@@ -197,6 +198,23 @@ impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
     }
 }
 
+fn swap_binop<'a>(binop: BinOp_, lhs: &'a Expr, rhs: &'a Expr) -> Option<(BinOp_, &'a Expr, &'a Expr)> {
+    match binop {
+        BiAdd |
+        BiMul |
+        BiBitXor |
+        BiBitAnd |
+        BiEq |
+        BiNe |
+        BiBitOr => Some((binop, rhs, lhs)),
+        BiLt => Some((BiGt, rhs, lhs)),
+        BiLe => Some((BiGe, rhs, lhs)),
+        BiGe => Some((BiLe, rhs, lhs)),
+        BiGt => Some((BiLt, rhs, lhs)),
+        BiShl | BiShr | BiRem | BiSub | BiDiv | BiAnd | BiOr => None,
+    }
+}
+
 /// Check if the two `Option`s are both `None` or some equal values as per `eq_fn`.
 fn both<X, F>(l: &Option<X>, r: &Option<X>, mut eq_fn: F) -> bool
     where F: FnMut(&X, &X) -> bool

tests/compile-fail/booleans.rs

@@ -58,6 +58,9 @@ fn equality_stuff() {
     let _ = a == b && c == 5 && a == b; //~ ERROR this boolean expression can be simplified
     //|~ HELP for further information visit
     //|~ SUGGESTION let _ = c == 5 && a == b;
+    let _ = a == b && c == 5 && b == a; //~ ERROR this boolean expression can be simplified
+    //|~ HELP for further information visit
+    //|~ SUGGESTION let _ = c == 5 && a == b;
     let _ = a < b && a >= b;
     let _ = a > b && a <= b;
     let _ = a > b && a == b;

tests/compile-fail/eq_op.rs

@@ -3,7 +3,7 @@
 
 #[deny(eq_op)]
 #[allow(identity_op)]
-#[allow(no_effect)]
+#[allow(no_effect, unused_variables)]
 #[deny(nonminimal_bool)]
 fn main() {
     // simple values and comparisons
@@ -43,6 +43,18 @@ fn main() {
     true || true; //~ERROR equal expressions
     //~|ERROR this boolean expression can be simplified
 
+    let a: u32 = unimplemented!();
+    let b: u32 = unimplemented!();
+
+    a == b && b == a; //~ERROR equal expressions
+    //~|ERROR this boolean expression can be simplified
+    a != b && b != a; //~ERROR equal expressions
+    //~|ERROR this boolean expression can be simplified
+    a < b && b > a; //~ERROR equal expressions
+    //~|ERROR this boolean expression can be simplified
+    a <= b && b >= a; //~ERROR equal expressions
+    //~|ERROR this boolean expression can be simplified
+
     let mut a = vec![1];
     a == a; //~ERROR equal expressions
     2*a.len() == 2*a.len(); // ok, functions