Fix const_err with -(-0.0)

Author: JohnTitor

src/librustc_mir/transform/const_prop.rs

@@ -6,7 +6,7 @@ use std::cell::Cell;
 use rustc::hir::def::DefKind;
 use rustc::mir::{
     AggregateKind, Constant, Location, Place, PlaceBase, Body, Operand, Rvalue,
-    Local, NullOp, UnOp, StatementKind, Statement, LocalKind, Static, StaticKind,
+    Local, NullOp, StatementKind, Statement, LocalKind, Static, StaticKind,
     TerminatorKind, Terminator,  ClearCrossCrate, SourceInfo, BinOp, ProjectionElem,
     SourceScope, SourceScopeLocalData, LocalDecl,
 };
@@ -407,18 +407,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 let arg = self.eval_operand(arg, source_info)?;
                 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)) {
-                                throw_panic!(OverflowNeg)
-                            }
-                        }
-                        UnOp::Not => {
-                            // Cannot overflow
-                        }
-                    }
                     // Now run the actual operation.
                     this.ecx.unary_op(op, prim)
                 })?;

src/test/ui/consts/const-err2.rs

@@ -13,7 +13,6 @@ fn black_box<T>(_: T) {
 
 fn main() {
     let a = -std::i8::MIN;
-    //~^ ERROR const_err
     let b = 200u8 + 200u8 + 200u8;
     //~^ ERROR const_err
     let c = 200u8 * 4;

src/test/ui/consts/const-err2.stderr

@@ -1,8 +1,8 @@
 error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:15:13
+  --> $DIR/const-err2.rs:16:13
    |
-LL |     let a = -std::i8::MIN;
-   |             ^^^^^^^^^^^^^ attempt to negate with overflow
+LL |     let b = 200u8 + 200u8 + 200u8;
+   |             ^^^^^^^^^^^^^ attempt to add with overflow
    |
 note: lint level defined here
   --> $DIR/const-err2.rs:8:9
@@ -11,28 +11,22 @@ LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
 error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:17:13
-   |
-LL |     let b = 200u8 + 200u8 + 200u8;
-   |             ^^^^^^^^^^^^^ attempt to add with overflow
-
-error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:19:13
+  --> $DIR/const-err2.rs:18:13
    |
 LL |     let c = 200u8 * 4;
    |             ^^^^^^^^^ attempt to multiply with overflow
 
 error: this expression will panic at runtime
-  --> $DIR/const-err2.rs:21:13
+  --> $DIR/const-err2.rs:20:13
    |
 LL |     let d = 42u8 - (42u8 + 1);
    |             ^^^^^^^^^^^^^^^^^ attempt to subtract with overflow
 
 error: index out of bounds: the len is 1 but the index is 1
-  --> $DIR/const-err2.rs:23:14
+  --> $DIR/const-err2.rs:22:14
    |
 LL |     let _e = [5u8][1];
    |              ^^^^^^^^
 
-error: aborting due to 5 previous errors
+error: aborting due to 4 previous errors
 

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

@@ -0,0 +1,5 @@
+// run-pass
+
+fn main() {
+    let _ = -(-0.0);
+}