Add note back to conditionally-const error message

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -92,7 +92,7 @@ impl<'tcx> NonConstOp<'tcx> for ConditionallyConstCall<'tcx> {
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        ccx.tcx.sess.create_feature_err(
+        let mut err = ccx.tcx.sess.create_feature_err(
             errors::ConditionallyConstCall {
                 span,
                 def_path_str: ccx.tcx.def_path_str_with_args(self.callee, self.args),
@@ -100,7 +100,15 @@ impl<'tcx> NonConstOp<'tcx> for ConditionallyConstCall<'tcx> {
                 kind: ccx.const_kind(),
             },
             sym::const_trait_impl,
-        )
+        );
+
+        err.note(format!(
+            "calls in {}s are limited to constant functions, \
+             tuple structs and tuple variants",
+            ccx.const_kind(),
+        ));
+
+        err
     }
 }
 

tests/ui/issues/issue-25901.stderr

@@ -7,6 +7,7 @@ LL | static S: &'static B = &A;
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in statics are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 1 previous error
 

tests/ui/self/arbitrary-self-from-method-substs-ice.stderr

@@ -7,6 +7,7 @@ LL |         self.0
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error[E0493]: destructor of `R` cannot be evaluated at compile-time
   --> $DIR/arbitrary-self-from-method-substs-ice.rs:10:43

tests/ui/traits/const-traits/cross-crate.stock.stderr

@@ -7,6 +7,7 @@ LL |     Const.func();
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 1 previous error
 

tests/ui/traits/const-traits/cross-crate.stocknc.stderr

@@ -7,6 +7,7 @@ LL |     NonConst.func();
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error[E0658]: cannot call conditionally-const method `<cross_crate::Const as cross_crate::MyTrait>::func` in constant functions
   --> $DIR/cross-crate.rs:22:5
@@ -17,6 +18,7 @@ LL |     Const.func();
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 2 previous errors
 

tests/ui/traits/const-traits/staged-api-user-crate.stderr

@@ -7,6 +7,7 @@ LL |     Unstable::func();
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 1 previous error
 

tests/ui/traits/const-traits/super-traits-fail-3.nyn.stderr

@@ -47,6 +47,7 @@ LL |     x.a();
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 5 previous errors
 

tests/ui/traits/const-traits/super-traits-fail-3.nyy.stderr

@@ -47,6 +47,7 @@ LL |     x.a();
    = note: see issue #67792 <https://github.com/rust-lang/rust/issues/67792> for more information
    = help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
 
 error: aborting due to 5 previous errors