Auto merge of rust-lang#6144 - rust-lang:float-cmp-ref, r=ebroto

allow refs in our constant folder

This helps with rust-lang#3804 (but won't completely fix it).

---

changelog: none

Author: bors

clippy_lints/src/consts.rs

@@ -40,6 +40,8 @@ pub enum Constant {
     Tuple(Vec<Constant>),
     /// A raw pointer.
     RawPtr(u128),
+    /// A reference
+    Ref(Box<Constant>),
     /// A literal with syntax error.
     Err(Symbol),
 }
@@ -66,6 +68,7 @@ impl PartialEq for Constant {
             (&Self::Bool(l), &Self::Bool(r)) => l == r,
             (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
             (&Self::Repeat(ref lv, ref ls), &Self::Repeat(ref rv, ref rs)) => ls == rs && lv == rv,
+            (&Self::Ref(ref lb), &Self::Ref(ref rb)) => *lb == *rb,
             // TODO: are there inter-type equalities?
             _ => false,
         }
@@ -110,6 +113,9 @@ impl Hash for Constant {
             Self::RawPtr(u) => {
                 u.hash(state);
             },
+            Self::Ref(ref r) => {
+                r.hash(state);
+            },
             Self::Err(ref s) => {
                 s.hash(state);
             },
@@ -144,6 +150,7 @@ impl Constant {
                     x => x,
                 }
             },
+            (&Self::Ref(ref lb), &Self::Ref(ref rb)) => Self::partial_cmp(tcx, cmp_type, lb, rb),
             // TODO: are there any useful inter-type orderings?
             _ => None,
         }
@@ -239,7 +246,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
             ExprKind::Unary(op, ref operand) => self.expr(operand).and_then(|o| match op {
                 UnOp::UnNot => self.constant_not(&o, self.typeck_results.expr_ty(e)),
                 UnOp::UnNeg => self.constant_negate(&o, self.typeck_results.expr_ty(e)),
-                UnOp::UnDeref => Some(o),
+                UnOp::UnDeref => Some(if let Constant::Ref(r) = o { *r } else { o }),
             }),
             ExprKind::Binary(op, ref left, ref right) => self.binop(op, left, right),
             ExprKind::Call(ref callee, ref args) => {
@@ -269,6 +276,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                 }
             },
             ExprKind::Index(ref arr, ref index) => self.index(arr, index),
+            ExprKind::AddrOf(_, _, ref inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
             // TODO: add other expressions.
             _ => None,
         }

tests/ui/float_cmp.rs

@@ -2,6 +2,7 @@
 #![allow(
     unused,
     clippy::no_effect,
+    clippy::op_ref,
     clippy::unnecessary_operation,
     clippy::cast_lossless,
     clippy::many_single_char_names
@@ -116,4 +117,8 @@ fn main() {
     1.23f64.signum() != x64.signum();
     1.23f64.signum() != -(x64.signum());
     1.23f64.signum() != 3.21f64.signum();
+
+    // the comparison should also look through references
+    &0.0 == &ZERO;
+    &&&&0.0 == &&&&ZERO;
 }

tests/ui/float_cmp.stderr

@@ -1,5 +1,5 @@
 error: strict comparison of `f32` or `f64`
-  --> $DIR/float_cmp.rs:65:5
+  --> $DIR/float_cmp.rs:66:5
    |
 LL |     ONE as f64 != 2.0;
    |     ^^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(ONE as f64 - 2.0).abs() > error_margin`
@@ -8,39 +8,39 @@ LL |     ONE as f64 != 2.0;
    = note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`
 
 error: strict comparison of `f32` or `f64`
-  --> $DIR/float_cmp.rs:70:5
+  --> $DIR/float_cmp.rs:71:5
    |
 LL |     x == 1.0;
    |     ^^^^^^^^ help: consider comparing them within some margin of error: `(x - 1.0).abs() < error_margin`
    |
    = note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`
 
 error: strict comparison of `f32` or `f64`
-  --> $DIR/float_cmp.rs:73:5
+  --> $DIR/float_cmp.rs:74:5
    |
 LL |     twice(x) != twice(ONE as f64);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(twice(x) - twice(ONE as f64)).abs() > error_margin`
    |
    = note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`
 
 error: strict comparison of `f32` or `f64`
-  --> $DIR/float_cmp.rs:93:5
+  --> $DIR/float_cmp.rs:94:5
    |
 LL |     NON_ZERO_ARRAY[i] == NON_ZERO_ARRAY[j];
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(NON_ZERO_ARRAY[i] - NON_ZERO_ARRAY[j]).abs() < error_margin`
    |
    = note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`
 
 error: strict comparison of `f32` or `f64` arrays
-  --> $DIR/float_cmp.rs:98:5
+  --> $DIR/float_cmp.rs:99:5
    |
 LL |     a1 == a2;
    |     ^^^^^^^^
    |
    = note: `f32::EPSILON` and `f64::EPSILON` are available for the `error_margin`
 
 error: strict comparison of `f32` or `f64`
-  --> $DIR/float_cmp.rs:99:5
+  --> $DIR/float_cmp.rs:100:5
    |
 LL |     a1[0] == a2[0];
    |     ^^^^^^^^^^^^^^ help: consider comparing them within some margin of error: `(a1[0] - a2[0]).abs() < error_margin`