rollup merge of #23863: pnkfelix/arith-oflo-const-eval

const_eval : add overflow-checking for {`+`, `-`, `*`, `/`, `<<`, `>>`}.

One tricky detail here: There is some duplication of labor between `rustc::middle::const_eval` and `rustc_trans::trans::consts`. It might be good to explore ways to try to factor out the common structure to the two passes (by abstracting over the particular value-representation used in the compile-time interpreter).

----

Update: Rebased atop #23841

Fix #22531

Fix #23030

Fix #23221

Fix #23235

src/test/compile-fail/const-eval-overflow-2.rs

@@ -0,0 +1,30 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Evaluation of constants in refutable patterns goes through
+// different compiler control-flow paths.
+
+#![allow(unused_imports)]
+
+use std::fmt;
+use std::{i8, i16, i32, i64, isize};
+use std::{u8, u16, u32, u64, usize};
+
+const NEG_128: i8 = -128;
+const NEG_NEG_128: i8 = -NEG_128;
+//~^ ERROR constant evaluation error: attempted to negate with overflow
+//~| ERROR attempted to negate with overflow
+
+fn main() {
+    match -128i8 {
+        NEG_NEG_128 => println!("A"),
+        _ => println!("B"),
+    }
+}

src/test/compile-fail/const-eval-overflow-3.rs

@@ -0,0 +1,39 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Evaluation of constants in array-elem count goes through different
+// compiler control-flow paths.
+//
+// This test is checking the count in an array expression.
+
+// FIXME (#23926): the error output is not consistent between a
+// self-hosted and a cross-compiled setup; therefore resorting to
+// error-pattern for now.
+
+// error-pattern: expected constant integer for repeat count, but attempted to add with overflow
+
+#![allow(unused_imports)]
+
+use std::fmt;
+use std::{i8, i16, i32, i64, isize};
+use std::{u8, u16, u32, u64, usize};
+
+const A_I8_I
+    : [u32; (i8::MAX as usize) + 1]
+    = [0; (i8::MAX + 1) as usize];
+
+fn main() {
+    foo(&A_I8_I[..]);
+}
+
+fn foo<T:fmt::Debug>(x: T) {
+    println!("{:?}", x);
+}
+

src/test/compile-fail/const-eval-overflow-3b.rs

@@ -0,0 +1,43 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Evaluation of constants in array-elem count goes through different
+// compiler control-flow paths.
+//
+// This test is checking the count in an array expression.
+//
+// This is a variation of another such test, but in this case the
+// types for the left- and right-hand sides of the addition do not
+// match (as well as overflow).
+
+// FIXME (#23926): the error output is not consistent between a
+// self-hosted and a cross-compiled setup; therefore resorting to
+// error-pattern for now.
+
+// error-pattern: mismatched types
+
+#![allow(unused_imports)]
+
+use std::fmt;
+use std::{i8, i16, i32, i64, isize};
+use std::{u8, u16, u32, u64, usize};
+
+const A_I8_I
+    : [u32; (i8::MAX as usize) + 1]
+    = [0; (i8::MAX + 1u8) as usize];
+
+fn main() {
+    foo(&A_I8_I[..]);
+}
+
+fn foo<T:fmt::Debug>(x: T) {
+    println!("{:?}", x);
+}
+

src/test/compile-fail/const-eval-overflow-4.rs

@@ -0,0 +1,36 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-test this should fail to compile (#23833)
+
+// Evaluation of constants in array-elem count goes through different
+// compiler control-flow paths.
+//
+// This test is checking the count in an array type.
+
+#![allow(unused_imports)]
+
+use std::fmt;
+use std::{i8, i16, i32, i64, isize};
+use std::{u8, u16, u32, u64, usize};
+
+const A_I8_T
+    : [u32; (i8::MAX as i8 + 1i8) as usize]
+    //~^ ERROR error evaluating count: attempted to add with overflow
+    = [0; (i8::MAX as usize) + 1];
+
+fn main() {
+    foo(&A_I8_T[..]);
+}
+
+fn foo<T:fmt::Debug>(x: T) {
+    println!("{:?}", x);
+}
+

src/test/compile-fail/const-eval-overflow-4b.rs

@@ -0,0 +1,36 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Evaluation of constants in array-elem count goes through different
+// compiler control-flow paths.
+//
+// This test is checking the count in an array type.
+
+#![allow(unused_imports)]
+
+use std::fmt;
+use std::{i8, i16, i32, i64, isize};
+use std::{u8, u16, u32, u64, usize};
+
+const A_I8_T
+    : [u32; (i8::MAX as i8 + 1u8) as usize]
+    //~^ ERROR mismatched types
+    //~| the trait `core::ops::Add<u8>` is not implemented for the type `i8`
+    //~| the trait `core::ops::Add<u8>` is not implemented for the type `i8`
+    = [0; (i8::MAX as usize) + 1];
+
+fn main() {
+    foo(&A_I8_T[..]);
+}
+
+fn foo<T:fmt::Debug>(x: T) {
+    println!("{:?}", x);
+}
+

src/test/compile-fail/const-eval-overflow.rs

@@ -0,0 +1,129 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(unused_imports)]
+
+// Note: the relevant lint pass here runs before some of the constant
+// evaluation below (e.g. that performed by trans and llvm), so if you
+// change this warn to a deny, then the compiler will exit before
+// those errors are detected.
+#![warn(unsigned_negation)]
+
+use std::fmt;
+use std::{i8, i16, i32, i64, isize};
+use std::{u8, u16, u32, u64, usize};
+
+const VALS_I8: (i8, i8, i8, i8) =
+    (-i8::MIN,
+     //~^ ERROR attempted to negate with overflow
+     i8::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     i8::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     i8::MIN * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_I16: (i16, i16, i16, i16) =
+    (-i16::MIN,
+     //~^ ERROR attempted to negate with overflow
+     i16::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     i16::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     i16::MIN * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_I32: (i32, i32, i32, i32) =
+    (-i32::MIN,
+     //~^ ERROR attempted to negate with overflow
+     i32::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     i32::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     i32::MIN * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_I64: (i64, i64, i64, i64) =
+    (-i64::MIN,
+     //~^ ERROR attempted to negate with overflow
+     i64::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     i64::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     i64::MAX * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_U8: (u8, u8, u8, u8) =
+    (-u8::MIN,
+     //~^ WARNING negation of unsigned int variable may be unintentional
+     // (The above is separately linted; unsigned negation is defined to be !x+1.)
+     u8::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     u8::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     u8::MAX * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_U16: (u16, u16, u16, u16) =
+    (-u16::MIN,
+     //~^ WARNING negation of unsigned int variable may be unintentional
+     // (The above is separately linted; unsigned negation is defined to be !x+1.)
+     u16::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     u16::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     u16::MAX * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_U32: (u32, u32, u32, u32) =
+    (-u32::MIN,
+     //~^ WARNING negation of unsigned int variable may be unintentional
+     // (The above is separately linted; unsigned negation is defined to be !x+1.)
+     u32::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     u32::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     u32::MAX * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+const VALS_U64: (u64, u64, u64, u64) =
+    (-u64::MIN,
+     //~^ WARNING negation of unsigned int variable may be unintentional
+     // (The above is separately linted; unsigned negation is defined to be !x+1.)
+     u64::MIN - 1,
+     //~^ ERROR attempted to sub with overflow
+     u64::MAX + 1,
+     //~^ ERROR attempted to add with overflow
+     u64::MAX * 2,
+     //~^ ERROR attempted to mul with overflow
+     );
+
+fn main() {
+    foo(VALS_I8);
+    foo(VALS_I16);
+    foo(VALS_I32);
+    foo(VALS_I64);
+
+    foo(VALS_U8);
+    foo(VALS_U16);
+    foo(VALS_U32);
+    foo(VALS_U64);
+}
+
+fn foo<T:fmt::Debug>(x: T) {
+    println!("{:?}", x);
+}

src/test/compile-fail/discrim-ill-typed.rs

@@ -0,0 +1,118 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// When explicit discriminant value has
+// a type that does not match the representation
+// type, rustc should fail gracefully.
+
+// See also run-pass/discrim-explicit-23030.rs where the input types
+// are correct.
+
+#![allow(dead_code, unused_variables, unused_imports)]
+
+use std::{i8,u8,i16,u16,i32,u32,i64, u64};
+
+fn f_i8() {
+    #[repr(i8)]
+    enum A {
+        Ok = i8::MAX - 1,
+        Ok2,
+        OhNo = 0_u8,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u8() {
+    #[repr(u8)]
+    enum A {
+        Ok = u8::MAX - 1,
+        Ok2,
+        OhNo = 0_i8,
+        //~^  ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_i16() {
+    #[repr(i16)]
+    enum A {
+        Ok = i16::MAX - 1,
+        Ok2,
+        OhNo = 0_u16,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u16() {
+    #[repr(u16)]
+    enum A {
+        Ok = u16::MAX - 1,
+        Ok2,
+        OhNo = 0_i16,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_i32() {
+    #[repr(i32)]
+    enum A {
+        Ok = i32::MAX - 1,
+        Ok2,
+        OhNo = 0_u32,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u32() {
+    #[repr(u32)]
+    enum A {
+        Ok = u32::MAX - 1,
+        Ok2,
+        OhNo = 0_i32,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_i64() {
+    #[repr(i64)]
+    enum A {
+        Ok = i64::MAX - 1,
+        Ok2,
+        OhNo = 0_u64,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u64() {
+    #[repr(u64)]
+    enum A {
+        Ok = u64::MAX - 1,
+        Ok2,
+        OhNo = 0_i64,
+        //~^ ERROR mismatched types
+    }
+
+    let x = A::Ok;
+}
+
+fn main() { }

src/test/compile-fail/discrim-overflow-2.rs

@@ -0,0 +1,94 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-tidy-linelength
+
+// Issue 23030: Detect overflowing discriminant
+//
+// Check that we detect the overflow even if enum is not used.
+
+// See also run-pass/discrim-explicit-23030.rs where the suggested
+// workaround is tested.
+
+use std::{i8,u8,i16,u16,i32,u32,i64, u64};
+
+fn f_i8() {
+    #[repr(i8)]
+    enum A {
+        Ok = i8::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed on value after 127: i8; set explicitly via OhNo = -128 if that is desired outcome
+    }
+}
+
+fn f_u8() {
+    #[repr(u8)]
+    enum A {
+        Ok = u8::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed on value after 255: u8; set explicitly via OhNo = 0 if that is desired outcome
+    }
+}
+
+fn f_i16() {
+    #[repr(i16)]
+    enum A {
+        Ok = i16::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+}
+
+fn f_u16() {
+    #[repr(u16)]
+    enum A {
+        Ok = u16::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+}
+
+fn f_i32() {
+    #[repr(i32)]
+    enum A {
+        Ok = i32::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+}
+
+fn f_u32() {
+    #[repr(u32)]
+    enum A {
+        Ok = u32::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+}
+
+fn f_i64() {
+    #[repr(i64)]
+    enum A {
+        Ok = i64::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+}
+
+fn f_u64() {
+    #[repr(u64)]
+    enum A {
+        Ok = u64::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+}
+
+fn main() { }

src/test/compile-fail/discrim-overflow.rs

@@ -0,0 +1,108 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-tidy-linelength
+
+// Issue 23030: Detect overflowing discriminant
+
+// See also run-pass/discrim-explicit-23030.rs where the suggested
+// workaround is tested.
+
+use std::{i8,u8,i16,u16,i32,u32,i64, u64};
+
+fn f_i8() {
+    #[repr(i8)]
+    enum A {
+        Ok = i8::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed on value after 127: i8; set explicitly via OhNo = -128 if that is desired outcome
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u8() {
+    #[repr(u8)]
+    enum A {
+        Ok = u8::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed on value after 255: u8; set explicitly via OhNo = 0 if that is desired outcome
+    }
+
+    let x = A::Ok;
+}
+
+fn f_i16() {
+    #[repr(i16)]
+    enum A {
+        Ok = i16::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u16() {
+    #[repr(u16)]
+    enum A {
+        Ok = u16::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+
+    let x = A::Ok;
+}
+
+fn f_i32() {
+    #[repr(i32)]
+    enum A {
+        Ok = i32::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u32() {
+    #[repr(u32)]
+    enum A {
+        Ok = u32::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+
+    let x = A::Ok;
+}
+
+fn f_i64() {
+    #[repr(i64)]
+    enum A {
+        Ok = i64::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+
+    let x = A::Ok;
+}
+
+fn f_u64() {
+    #[repr(u64)]
+    enum A {
+        Ok = u64::MAX - 1,
+        Ok2,
+        OhNo, //~ ERROR enum discriminant overflowed
+    }
+
+    let x = A::Ok;
+}
+
+fn main() { }

src/test/compile-fail/huge-array-simple.rs

@@ -8,9 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern: too big for the current
+// FIXME (#23926): the error output is not consistent between a
+// self-hosted and a cross-compiled setup. Skipping for now.
+
+// ignore-test FIXME(#23926)
+
 #![allow(exceeding_bitshifts)]
 
 fn main() {
-   let fat : [u8; (1<<61)+(1<<31)] = [0; (1u64<<61) as usize +(1u64<<31) as usize];
+    let _fat : [u8; (1<<61)+(1<<31)] =
+        [0; (1u64<<61) as usize +(1u64<<31) as usize];
 }

src/test/compile-fail/non-constant-enum-for-vec-repeat.rs

@@ -8,9 +8,12 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// Note: This test is checking that we forbid a coding pattern that
+// Issue #5873 explicitly wants to allow.
+
 enum State { ST_NULL, ST_WHITESPACE }
 
 fn main() {
     [State::ST_NULL; (State::ST_WHITESPACE as usize)];
-    //~^ ERROR expected constant integer for repeat count, found non-constant expression
+    //~^ ERROR expected constant integer for repeat count, but non-constant path
 }

src/test/compile-fail/non-constant-expr-for-vec-repeat.rs

@@ -12,6 +12,7 @@
 
 fn main() {
     fn bar(n: usize) {
-        let _x = [0; n]; //~ ERROR expected constant integer for repeat count, found variable
+        let _x = [0; n];
+        //~^ ERROR expected constant integer for repeat count, found variable
     }
 }

src/test/run-pass/big-literals.rs

@@ -10,11 +10,16 @@
 
 // pretty-expanded FIXME #23616
 
+#![feature(core)]
+
+// Catch mistakes in the overflowing literals lint.
+#![deny(overflowing_literals)]
+
 pub fn main() {
     assert_eq!(0xffffffff, (-1 as u32));
     assert_eq!(4294967295, (-1 as u32));
     assert_eq!(0xffffffffffffffff, (-1 as u64));
     assert_eq!(18446744073709551615, (-1 as u64));
 
-    assert_eq!(-2147483648 - 1, 2147483647);
+    assert_eq!((-2147483648).wrapping_sub(1), 2147483647);
 }

src/test/run-pass/discrim-explicit-23030.rs

@@ -0,0 +1,156 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Issue 23030: Workaround overflowing discriminant
+// with explicit assignments.
+
+// See also compile-fail/overflow-discrim.rs, which shows what
+// happens if you leave the OhNo explicit cases out here.
+
+use std::{i8,u8,i16,u16,i32,u32,i64,u64,isize,usize};
+
+fn f_i8() {
+    #[repr(i8)]
+    enum A {
+        Ok = i8::MAX - 1,
+        Ok2,
+        OhNo = i8::MIN,
+        NotTheEnd = -1,
+        Zero,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+    let z = (A::NotTheEnd, A::Zero).1 as i8;
+    assert_eq!(z, 0);
+}
+
+fn f_u8() {
+    #[repr(u8)]
+    enum A {
+        Ok = u8::MAX - 1,
+        Ok2,
+        OhNo = u8::MIN,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+}
+
+fn f_i16() {
+    #[repr(i16)]
+    enum A {
+        Ok = i16::MAX - 1,
+        Ok2,
+        OhNo = i16::MIN,
+        NotTheEnd = -1,
+        Zero,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+    let z = (A::NotTheEnd, A::Zero).1 as i16;
+    assert_eq!(z, 0);
+}
+
+fn f_u16() {
+    #[repr(u16)]
+    enum A {
+        Ok = u16::MAX - 1,
+        Ok2,
+        OhNo = u16::MIN,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+}
+
+fn f_i32() {
+    #[repr(i32)]
+    enum A {
+        Ok = i32::MAX - 1,
+        Ok2,
+        OhNo = i32::MIN,
+        NotTheEnd = -1,
+        Zero,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+    let z = (A::NotTheEnd, A::Zero).1 as i32;
+    assert_eq!(z, 0);
+}
+
+fn f_u32() {
+    #[repr(u32)]
+    enum A {
+        Ok = u32::MAX - 1,
+        Ok2,
+        OhNo = u32::MIN,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+}
+
+fn f_i64() {
+    #[repr(i64)]
+    enum A {
+        Ok = i64::MAX - 1,
+        Ok2,
+        OhNo = i64::MIN,
+        NotTheEnd = -1,
+        Zero,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+    let z = (A::NotTheEnd, A::Zero).1 as i64;
+    assert_eq!(z, 0);
+}
+
+fn f_u64() {
+    #[repr(u64)]
+    enum A {
+        Ok = u64::MAX - 1,
+        Ok2,
+        OhNo = u64::MIN,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+}
+
+fn f_isize() {
+    #[repr(isize)]
+    enum A {
+        Ok = isize::MAX - 1,
+        Ok2,
+        OhNo = isize::MIN,
+        NotTheEnd = -1,
+        Zero,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+    let z = (A::NotTheEnd, A::Zero).1 as isize;
+    assert_eq!(z, 0);
+}
+
+fn f_usize() {
+    #[repr(usize)]
+    enum A {
+        Ok = usize::MAX - 1,
+        Ok2,
+        OhNo = usize::MIN,
+    }
+
+    let _x = (A::Ok, A::Ok2, A::OhNo);
+}
+
+fn main() {
+    f_i8(); f_u8();
+    f_i16(); f_u16();
+    f_i32(); f_u32();
+    f_i64(); f_u64();
+
+    f_isize(); f_usize();
+}

src/test/run-pass/small-enum-range-edge.rs

@@ -10,6 +10,9 @@
 
 // pretty-expanded FIXME #23616
 
+// this is for the wrapping_add call below.
+#![feature(core)]
+
 /*!
  * Tests the range assertion wraparound case in trans::middle::adt::load_discr.
  */
@@ -29,8 +32,8 @@ static CLs: Es = Es::Ls;
 static CHs: Es = Es::Hs;
 
 pub fn main() {
-    assert_eq!((Eu::Hu as u8) + 1, Eu::Lu as u8);
-    assert_eq!((Es::Hs as i8) + 1, Es::Ls as i8);
+    assert_eq!((Eu::Hu as u8).wrapping_add(1), Eu::Lu as u8);
+    assert_eq!((Es::Hs as i8).wrapping_add(1), Es::Ls as i8);
     assert_eq!(CLu as u8, Eu::Lu as u8);
     assert_eq!(CHu as u8, Eu::Hu as u8);
     assert_eq!(CLs as i8, Es::Ls as i8);