Rollup merge of #92432 - fee1-dead:constck-impl-constness, r=oli-obk

Error when selected impl is not const in constck

Catches bad things when checking a `default_method_body_is_const` body, such as:

```rust
self.map(/* .. */).is_sorted();
```

When `Map` does not yet have a `const` `impl` for `Iterator`.

r? ```@oli-obk```

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -810,7 +810,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         param_env,
                         Binder::dummy(TraitPredicate {
                             trait_ref,
-                            constness: ty::BoundConstness::ConstIfConst,
+                            constness: ty::BoundConstness::NotConst,
                             polarity: ty::ImplPolarity::Positive,
                         }),
                     );
@@ -829,6 +829,10 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             return;
                         }
                         Ok(Some(ImplSource::UserDefined(data))) => {
+                            if let hir::Constness::NotConst = tcx.impl_constness(data.impl_def_id) {
+                                self.check_op(ops::FnCallNonConst(None));
+                                return;
+                            }
                             let callee_name = tcx.item_name(callee);
                             if let Some(&did) = tcx
                                 .associated_item_def_ids(data.impl_def_id)

src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.rs

@@ -0,0 +1,17 @@
+#![feature(const_fn_trait_bound)]
+#![feature(const_trait_impl)]
+
+pub trait Tr {
+    #[default_method_body_is_const]
+    fn a(&self) {}
+
+    #[default_method_body_is_const]
+    fn b(&self) {
+        ().a()
+        //~^ ERROR calls in constant functions are limited
+    }
+}
+
+impl Tr for () {}
+
+fn main() {}

src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr

@@ -0,0 +1,9 @@
+error[E0015]: calls in constant functions are limited to constant functions, tuple structs and tuple variants
+  --> $DIR/default-method-body-is-const-same-trait-ck.rs:10:9
+   |
+LL |         ().a()
+   |         ^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0015`.