Only warn on erroneous promoted constants

src/librustc_mir/interpret/const_eval.rs

@@ -57,7 +57,7 @@ pub fn mk_eval_cx<'a, 'tcx>(
     Ok(ecx)
 }
 
-pub fn eval_body_with_mir<'a, 'mir, 'tcx>(
+pub fn eval_promoted<'a, 'mir, 'tcx>(
     tcx: TyCtxt<'a, 'tcx, 'tcx>,
     cid: GlobalId<'tcx>,
     mir: &'mir mir::Mir<'tcx>,
@@ -67,7 +67,7 @@ pub fn eval_body_with_mir<'a, 'mir, 'tcx>(
     match res {
         Ok(val) => Some(val),
         Err(mut err) => {
-            ecx.report(&mut err, true, None);
+            ecx.report(&mut err, false, None);
             None
         }
     }

src/librustc_mir/interpret/mod.rs

@@ -19,7 +19,7 @@ pub use self::place::{Place, PlaceExtra};
 pub use self::memory::{Memory, MemoryKind, HasMemory};
 
 pub use self::const_eval::{
-    eval_body_with_mir,
+    eval_promoted,
     mk_borrowck_eval_cx,
     eval_body,
     CompileTimeEvaluator,

src/librustc_mir/monomorphize/collector.rs

@@ -1177,7 +1177,7 @@ fn collect_neighbours<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         param_substs: instance.substs,
     }.visit_mir(&mir);
     let param_env = ty::ParamEnv::reveal_all();
-    for (i, promoted) in mir.promoted.iter().enumerate() {
+    for i in 0..mir.promoted.len() {
         use rustc_data_structures::indexed_vec::Idx;
         let cid = GlobalId {
             instance,
@@ -1185,9 +1185,7 @@ fn collect_neighbours<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
         };
         match tcx.const_eval(param_env.and(cid)) {
             Ok(val) => collect_const(tcx, val, instance.substs, output),
-            Err(err) => {
+            Err(_) => {},
-                err.report(tcx, promoted.span, "promoted");
-            }
         }
     }
 }

src/librustc_mir/transform/const_prop.rs

@@ -20,7 +20,7 @@ use rustc::mir::visit::{Visitor, PlaceContext};
 use rustc::middle::const_val::ConstVal;
 use rustc::ty::{TyCtxt, self, Instance};
 use rustc::mir::interpret::{Value, PrimVal, GlobalId};
-use interpret::{eval_body_with_mir, mk_borrowck_eval_cx, ValTy};
+use interpret::{eval_promoted, mk_borrowck_eval_cx, ValTy};
 use transform::{MirPass, MirSource};
 use syntax::codemap::Span;
 use rustc::ty::subst::Substs;
@@ -161,7 +161,7 @@ impl<'b, 'a, 'tcx:'b> ConstPropagator<'b, 'a, 'tcx> {
                 };
                 // cannot use `const_eval` here, because that would require having the MIR
                 // for the current function available, but we're producing said MIR right now
-                let (value, _, ty) = eval_body_with_mir(self.tcx, cid, self.mir, self.param_env)?;
+                let (value, _, ty) = eval_promoted(self.tcx, cid, self.mir, self.param_env)?;
                 let val = (value, ty, c.span);
                 trace!("evaluated {:?} to {:?}", c, val);
                 Some(val)

src/librustc_trans/mir/operand.rs

@@ -399,7 +399,14 @@ impl<'a, 'tcx> FunctionCx<'a, 'tcx> {
                 self.mir_constant_to_miri_value(bx, constant)
                     .and_then(|c| OperandRef::from_const(bx, c, ty))
                     .unwrap_or_else(|err| {
-                        err.report(bx.tcx(), constant.span, "const operand");
+                        match constant.literal {
+                            mir::Literal::Promoted { .. } => {
+                                // don't report errors inside promoteds, just warnings.
+                            },
+                            mir::Literal::Value { .. } => {
+                                err.report(bx.tcx(), constant.span, "const operand")
+                            },
+                        }
                         // We've errored, so we don't have to produce working code.
                         let layout = bx.cx.layout_of(ty);
                         PlaceRef::new_sized(

src/test/ui/const-eval/conditional_array_execution.rs

@@ -8,11 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// compile-pass
+
 const X: u32 = 5;
 const Y: u32 = 6;
 const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
 //~^ WARN attempt to subtract with overflow
 
 fn main() {
-    println!("{}", FOO); //~ E0080
+    println!("{}", FOO);
+    //~^ WARN constant evaluation error
 }

src/test/ui/const-eval/conditional_array_execution.stderr

@@ -1,17 +1,14 @@
 warning: attempt to subtract with overflow
-  --> $DIR/conditional_array_execution.rs:13:19
+  --> $DIR/conditional_array_execution.rs:15:19
    |
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
    |                   ^^^^^
    |
    = note: #[warn(const_err)] on by default
 
-error[E0080]: constant evaluation error
+warning: constant evaluation error
-  --> $DIR/conditional_array_execution.rs:17:20
+  --> $DIR/conditional_array_execution.rs:19:20
    |
-LL |     println!("{}", FOO); //~ E0080
+LL |     println!("{}", FOO);
    |                    ^^^ referenced constant has errors
 
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0080`.

src/test/ui/const-eval/issue-43197.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// compile-pass
+
 #![feature(const_fn)]
 
 const fn foo(x: u32) -> u32 {
@@ -20,6 +22,6 @@ fn main() {
     const Y: u32 = foo(0-1);
     //~^ WARN attempt to subtract with overflow
     println!("{} {}", X, Y);
-    //~^ ERROR constant evaluation error
+    //~^ WARN constant evaluation error
-    //~| ERROR constant evaluation error
+    //~| WARN constant evaluation error
 }

src/test/ui/const-eval/issue-43197.stderr

@@ -1,29 +1,26 @@
 warning: attempt to subtract with overflow
-  --> $DIR/issue-43197.rs:18:20
+  --> $DIR/issue-43197.rs:20:20
    |
 LL |     const X: u32 = 0-1;
    |                    ^^^
    |
    = note: #[warn(const_err)] on by default
 
-error[E0080]: constant evaluation error
+warning: constant evaluation error
-  --> $DIR/issue-43197.rs:22:23
+  --> $DIR/issue-43197.rs:24:23
    |
 LL |     println!("{} {}", X, Y);
    |                       ^ referenced constant has errors
 
 warning: attempt to subtract with overflow
-  --> $DIR/issue-43197.rs:20:24
+  --> $DIR/issue-43197.rs:22:24
    |
 LL |     const Y: u32 = foo(0-1);
    |                        ^^^
 
-error[E0080]: constant evaluation error
+warning: constant evaluation error
-  --> $DIR/issue-43197.rs:22:26
+  --> $DIR/issue-43197.rs:24:26
    |
 LL |     println!("{} {}", X, Y);
    |                          ^ referenced constant has errors
 
-error: aborting due to 2 previous errors
-
-For more information about this error, try `rustc --explain E0080`.

src/test/ui/const-eval/issue-44578.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// compile-pass
+
 trait Foo {
     const AMT: usize;
 }
@@ -30,5 +32,6 @@ impl Foo for u16 {
 }
 
 fn main() {
-    println!("{}", <Bar<u16, u8> as Foo>::AMT); //~ E0080
+    println!("{}", <Bar<u16, u8> as Foo>::AMT); //~ WARN const_err
+    //~^ WARN const_err
 }

src/test/ui/const-eval/issue-44578.stderr

@@ -0,0 +1,14 @@
+warning: constant evaluation error
+  --> $DIR/issue-44578.rs:35:20
+   |
+LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT); //~ WARN const_err
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^ referenced constant has errors
+   |
+   = note: #[warn(const_err)] on by default
+
+warning: constant evaluation error
+  --> $DIR/issue-44578.rs:35:20
+   |
+LL |     println!("{}", <Bar<u16, u8> as Foo>::AMT); //~ WARN const_err
+   |                    ^^^^^^^^^^^^^^^^^^^^^^^^^^ referenced constant has errors
+

src/test/ui/const-eval/promoted_errors.rs

@@ -0,0 +1,28 @@
+// Copyright 2018 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.
+
+// compile-pass
+
+fn main() {
+    println!("{}", 0u32 - 1);
+    //~^ WARN const_err
+    //~| WARN const_err
+    let _x = 0u32 - 1;
+    //~^ WARN const_err
+    println!("{}", 1/(1-1));
+    //~^ WARN const_err
+    //~| WARN const_err
+    let _x = 1/(1-1);
+    //~^ WARN const_err
+    //~| WARN const_err
+    println!("{}", 1/(false as u32));
+    //~^ WARN const_err
+    let _x = 1/(false as u32);
+}

src/test/ui/const-eval/promoted_errors.stderr

@@ -0,0 +1,50 @@
+warning: constant evaluation error
+  --> $DIR/promoted_errors.rs:14:20
+   |
+LL |     println!("{}", 0u32 - 1);
+   |                    ^^^^^^^^ attempted to do overflowing math
+   |
+   = note: #[warn(const_err)] on by default
+
+warning: constant evaluation error
+  --> $DIR/promoted_errors.rs:14:20
+   |
+LL |     println!("{}", 0u32 - 1);
+   |                    ^^^^^^^^ attempted to do overflowing math
+
+warning: constant evaluation error
+  --> $DIR/promoted_errors.rs:17:14
+   |
+LL |     let _x = 0u32 - 1;
+   |              ^^^^^^^^ attempted to do overflowing math
+
+warning: attempt to divide by zero
+  --> $DIR/promoted_errors.rs:19:20
+   |
+LL |     println!("{}", 1/(1-1));
+   |                    ^^^^^^^
+
+warning: constant evaluation error
+  --> $DIR/promoted_errors.rs:19:20
+   |
+LL |     println!("{}", 1/(1-1));
+   |                    ^^^^^^^ attempted to do overflowing math
+
+warning: attempt to divide by zero
+  --> $DIR/promoted_errors.rs:22:14
+   |
+LL |     let _x = 1/(1-1);
+   |              ^^^^^^^
+
+warning: constant evaluation error
+  --> $DIR/promoted_errors.rs:22:14
+   |
+LL |     let _x = 1/(1-1);
+   |              ^^^^^^^ attempted to do overflowing math
+
+warning: constant evaluation error
+  --> $DIR/promoted_errors.rs:25:20
+   |
+LL |     println!("{}", 1/(false as u32));
+   |                    ^^^^^^^^^^^^^^^^ attempted to do overflowing math
+