Fix const_err with -(-0.0)

src/librustc_mir/transform/const_prop.rs

@@ -405,13 +405,15 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 }
 
                 let arg = self.eval_operand(arg, source_info)?;
+                let oflo_check = self.tcx.sess.overflow_checks();
                 let val = self.use_ecx(source_info, |this| {
                     let prim = this.ecx.read_immediate(arg)?;
                     match op {
                         UnOp::Neg => {
-                            // Need to do overflow check here: For actual CTFE, MIR
-                            // generation emits code that does this before calling the op.
-                            if prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
+                            // We check overflow in debug mode already
+                            // so should only check in release mode.
+                            if !oflo_check
+                            && prim.to_bits()? == (1 << (prim.layout.size.bits() - 1)) {
                                 throw_panic!(OverflowNeg)
                             }
                         }
@@ -485,7 +487,9 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                         Scalar::from_bool(overflow).into(),
                     )
                 } else {
-                    if overflow {
+                    // We check overflow in debug mode already
+                    // so should only check in release mode.
+                    if !self.tcx.sess.overflow_checks() && overflow {
                         let err = err_panic!(Overflow(op)).into();
                         let _: Option<()> = self.use_ecx(source_info, |_| Err(err));
                         return None;

src/test/ui/consts/issue-64059.rs

@@ -0,0 +1,4 @@
+fn main() {
+    let _ = -(-0.0);
+    //~^ ERROR: this expression will panic at runtime
+}

src/test/ui/consts/issue-64059.stderr

@@ -0,0 +1,10 @@
+error: this expression will panic at runtime
+  --> $DIR/issue-64059.rs:2:13
+   |
+LL |     let _ = -(-0.0);
+   |             ^^^^^^^ attempt to negate with overflow
+   |
+   = note: `#[deny(const_err)]` on by default
+
+error: aborting due to previous error
+