Always evaluate constant operands in const-prop

.github/workflows/ci.yml

@@ -46,6 +46,9 @@ jobs:
           - name: x86_64-gnu-llvm-12
             os: ubuntu-20.04-xl
             env: {}
+          - name: dist-i586-gnu-i586-i686-musl
+            os: ubuntu-20.04-xl
+            env: {}
           - name: x86_64-gnu-tools
             env:
               CI_ONLY_WHEN_SUBMODULES_CHANGED: 1

compiler/rustc_mir_transform/src/const_prop.rs

@@ -468,11 +468,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
 
     /// Returns the value, if any, of evaluating `c`.
     fn eval_constant(&mut self, c: &Constant<'tcx>) -> Option<OpTy<'tcx>> {
-        // FIXME we need to revisit this for #67176
-        if c.needs_subst() {
-            return None;
-        }
-
         self.ecx.mir_const_to_op(&c.literal, None).ok()
     }
 

compiler/rustc_mir_transform/src/const_prop_lint.rs

@@ -514,11 +514,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             | Rvalue::NullaryOp(..) => {}
         }
 
-        // FIXME we need to revisit this for #67176
-        if rvalue.needs_subst() {
-            return None;
-        }
-
         self.use_ecx(source_info, |this| this.ecx.eval_rvalue_into_place(rvalue, place))
     }
 }

src/ci/github-actions/ci.yml

@@ -286,7 +286,10 @@ jobs:
 
           - name: x86_64-gnu-llvm-12
             <<: *job-linux-xl
-
+
+          - name: dist-i586-gnu-i586-i686-musl
+            <<: *job-linux-xl
+
           - name: x86_64-gnu-tools
             env:
               CI_ONLY_WHEN_SUBMODULES_CHANGED: 1

src/test/ui/consts/const-eval/erroneous-const.rs

@@ -6,6 +6,8 @@ impl<T> PrintName<T> {
     const VOID: () = [()][2]; //~WARN any use of this value will cause an error
     //~^ WARN this operation will panic at runtime
     //~| WARN this was previously accepted by the compiler but is being phased out
+    //~| WARN this was previously accepted by the compiler but is being phased out
+    //~| WARN any use of this value will cause an error
 }
 
 const fn no_codegen<T>() {

src/test/ui/consts/const-eval/erroneous-const.stderr

@@ -24,19 +24,28 @@ LL | #![warn(const_err, unconditional_panic)]
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
+warning: any use of this value will cause an error
+  --> $DIR/erroneous-const.rs:6:22
+   |
+LL |     const VOID: () = [()][2];
+   |     --------------   ^^^^^^^ index out of bounds: the length is 1 but the index is 2
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
 error[E0080]: could not evaluate static initializer
-  --> $DIR/erroneous-const.rs:15:17
+  --> $DIR/erroneous-const.rs:17:17
    |
 LL |         let _ = PrintName::<T>::VOID;
    |                 ^^^^^^^^^^^^^^^^^^^^
    |                 |
    |                 referenced constant has errors
-   |                 inside `no_codegen::<i32>` at $DIR/erroneous-const.rs:15:17
+   |                 inside `no_codegen::<i32>` at $DIR/erroneous-const.rs:17:17
 ...
 LL | pub static FOO: () = no_codegen::<i32>();
-   |                      ------------------- inside `FOO` at $DIR/erroneous-const.rs:19:22
+   |                      ------------------- inside `FOO` at $DIR/erroneous-const.rs:21:22
 
-error: aborting due to previous error; 2 warnings emitted
+error: aborting due to previous error; 3 warnings emitted
 
 For more information about this error, try `rustc --explain E0080`.
 Future incompatibility report: Future breakage diagnostic:
@@ -54,3 +63,18 @@ LL | #![warn(const_err, unconditional_panic)]
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
+Future breakage diagnostic:
+warning: any use of this value will cause an error
+  --> $DIR/erroneous-const.rs:6:22
+   |
+LL |     const VOID: () = [()][2];
+   |     --------------   ^^^^^^^ index out of bounds: the length is 1 but the index is 2
+   |
+note: the lint level is defined here
+  --> $DIR/erroneous-const.rs:2:9
+   |
+LL | #![warn(const_err, unconditional_panic)]
+   |         ^^^^^^^^^
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+

src/test/ui/consts/const-eval/issue-50814.rs

@@ -14,12 +14,15 @@ struct Sum<A,B>(A,B);
 impl<A: Unsigned, B: Unsigned> Unsigned for Sum<A,B> {
     const MAX: u8 = A::MAX + B::MAX;
     //~^ ERROR any use of this value will cause an error [const_err]
+    //~| ERROR any use of this value will cause an error
+    //~| WARN this was previously accepted by the compiler but is being phased out
     //~| WARN this was previously accepted by the compiler but is being phased out
 }
 
 fn foo<T>(_: T) -> &'static u8 {
     &Sum::<U8,U8>::MAX
     //~^ ERROR E0080
+    //~| ERROR evaluation of `foo::<i32>` failed
 }
 
 fn main() {

src/test/ui/consts/const-eval/issue-50814.stderr

@@ -8,19 +8,34 @@ LL |     const MAX: u8 = A::MAX + B::MAX;
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
+error[E0080]: evaluation of `foo::<T>` failed
+  --> $DIR/issue-50814.rs:23:6
+   |
+LL |     &Sum::<U8,U8>::MAX
+   |      ^^^^^^^^^^^^^^^^^ referenced constant has errors
+
+error: any use of this value will cause an error
+  --> $DIR/issue-50814.rs:15:21
+   |
+LL |     const MAX: u8 = A::MAX + B::MAX;
+   |     -------------   ^^^^^^^^^^^^^^^ attempt to compute `u8::MAX + u8::MAX`, which would overflow
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+
 error[E0080]: evaluation of `foo::<i32>` failed
-  --> $DIR/issue-50814.rs:21:6
+  --> $DIR/issue-50814.rs:23:6
    |
 LL |     &Sum::<U8,U8>::MAX
    |      ^^^^^^^^^^^^^^^^^ referenced constant has errors
 
 note: the above error was encountered while instantiating `fn foo::<i32>`
-  --> $DIR/issue-50814.rs:26:5
+  --> $DIR/issue-50814.rs:29:5
    |
 LL |     foo(0);
    |     ^^^^^^
 
-error: aborting due to 2 previous errors
+error: aborting due to 4 previous errors
 
 For more information about this error, try `rustc --explain E0080`.
 Future incompatibility report: Future breakage diagnostic:
@@ -34,3 +49,14 @@ LL |     const MAX: u8 = A::MAX + B::MAX;
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
 
+Future breakage diagnostic:
+error: any use of this value will cause an error
+  --> $DIR/issue-50814.rs:15:21
+   |
+LL |     const MAX: u8 = A::MAX + B::MAX;
+   |     -------------   ^^^^^^^^^^^^^^^ attempt to compute `u8::MAX + u8::MAX`, which would overflow
+   |
+   = note: `#[deny(const_err)]` on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
+